地理科学  2018 , 38 (5): 800-807 https://doi.org/10.13249/j.cnki.sgs.2018.05.018

Orginal Article

盐度对滨海湿地土壤碳库组分及稳定性的影响

王纯1, 刘兴土1, 仝川23

1.中国科学院东北地理与农业生态研究所湿地生态与环境重点实验室,吉林 长春 130102
2.福建师范大学地理科学学院,福建 福州 350007
3.福建师范大学亚热带湿地研究中心,福建 福州 350007

Effects of Salinity on Characteristics and Stability of Soil Carbon Pool in Coastal Wetland

Wang Chun1, Liu Xingtu1, Tong Chuan23

1.Key Laboratory of Wetland Ecology and Environment, Northeast Institute of Geography and Agroecology, Chinese Academy of Sciences, Changchun 130102, Jilin,China
2. College of Geographical Sciences, Fujian Normal University, Fuzhou 350007, Fujian,China
3. Key Labratory of Humid Subtropical Eco-geographical Process, Ministry of Education, Fujian Normal University, Fuzhou 350007, Fujian, China

中图分类号:  P95

文献标识码:  A

文章编号:  1000-0690(2018)05-0800-08

通讯作者:  通讯作者:刘兴土,研究员。E-mail:lxtmxh@163.com

收稿日期: 2017-04-10

修回日期:  2017-07-20

网络出版日期:  2018-05-10

版权声明:  2018 《地理科学》编辑部 本文是开放获取期刊文献,在以下情况下可以自由使用:学术研究、学术交流、科研教学等,但不允许用于商业目的.

基金资助:  国家重点基础研究发展计划课题(2013CB430401)、中国博士后科学基金(2017M611337)资助

作者简介:

作者简介:王纯(1982-),女,湖南益阳人,博士,主要从事湿地元素生物地球化学循环研究。E-mail:wangchun821314@163.com

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摘要

从土壤有机碳含量和活性组分出发,分析了湿地土壤碳库组分对盐度变化的响应特征。同时分析了土壤有机碳3种稳定机制,评述了土壤碳稳定性与盐分中主要离子的博弈。并在基于研究滨海湿地碳固定与稳定的基础上,提出了土壤碳稳定与营养元素循环的相互作用机制研究、土壤碳稳定与微生物及酶学机制的关系研究、借助稳定同位素技术多要素多过程耦合研究等科学问题展望。以期为了解未来中国海平面上升背景下湿地碳截获潜力的可能演变趋势及其应对策略,为发展和完善中国湿地土壤碳循环理论奠定科学基础。

关键词: 盐度 ; 土壤碳库 ; 土壤活性组分 ; 滨海湿地

Abstract

Soil carbon sequestration and stability in coastal wetland are of great significance in maintaining primary productivity of wetland and mitigating global warming. Current studies about soil carbon stability mainly focused on the inland ecosystems while lack on the coastal wetland. Based on the content and active fractions of soil organic carbon, the responses of soil carbon fractions to varied salinity were analyzed. Meanwhile, three stabilization mechanisms of soil organic carbon were reviewed, and the game of soil carbon stability and main ions in salt was in depth explored. Furthermore, based on the study of carbon sequestration and stabilization of coastal wetland, three scientific issues have been suggested, including the interaction mechanism of soil carbon stabilization and nutrient cycling, and the relationship between soil carbon stability and microbial and enzymatic mechanisms, as well as the coupling research of multi-factor and multi-process, in order to understand the possible evolution trend of carbon sequestration, and for strategies making aiming at sustainable carbon sequestration in coastal wetland under the rising sea level, as well as to provide sound knowledge base for the development and improvement of carbon cycling theory in wetland soil of China.

Keywords: salinity ; soil carbon pool ; soil active fractions ; coastal wetland

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王纯, 刘兴土, 仝川. 盐度对滨海湿地土壤碳库组分及稳定性的影响 [J]. 地理科学, 2018, 38(5): 800-807 https://doi.org/10.13249/j.cnki.sgs.2018.05.018

Wang Chun, Liu Xingtu, Tong Chuan. Effects of Salinity on Characteristics and Stability of Soil Carbon Pool in Coastal Wetland[J]. Scientia Geographica Sinica, 2018, 38(5): 800-807 https://doi.org/10.13249/j.cnki.sgs.2018.05.018

随着全球气候变化问题日益增多,有关土壤碳在调节中所起作用的研究已引起越来越多科学家的关注。土壤是陆地生态系统中最大的碳库,土壤有机碳(Soil organic carbon, SOC)库为1 550 Pg,约为陆地植物碳库(610 Pg)的2.5倍和大气碳库(760 Pg)的2倍[1]。土壤碳库变化反映了陆地生态系统碳输入和输出之间的平衡关系[2,3],控制土壤碳循环过程的微小变化都将对大气中CO2等温室气体浓度产生显著影响[1]。湿地是地球陆地表面碳密度最高的生态系统[4,5]。滨海湿地,由于同时受到海水和陆地径流的相互作用,被认为是全球环境变化的“驱动器”和“自然记录”,成为对全球气候变化响应最敏感的生态系统[6]

全球气候变化导致的海平面上升已成为威胁滨海湿地的主要因素[7]。据政府间气候变化专业委员会(IPCC)第四次评估报告指出,20世纪全球海平面上升约0.17 m[8]。海平面上升增加了滨海湿地风暴潮和极端潮汐事件发生的频率和强度,从而强化海水上溯[9],形成明显的海水入侵梯度。在全球气候变化背景下,目前有关海水入侵对河口湿地生态系统水-土-气-生物连续体碳氮循环的研究已引起了国内外学者的广泛关注[10,11,12,13]。而就海水入侵对土壤碳库组分及土壤碳库稳定性的影响机理认识还很匮乏。本文主要从盐度对土壤碳库组分及其稳定性的影响两方面进行综述,并提出今后应加强研究的几个方面。

1 土壤碳库组分

根据SOC库功能和周转周期不同, SOC库可分为活性碳库、慢性碳库和惰性碳库3个部分[14]。目前,SOC库分组方法多样,包括化学分组(如浸提法、氧化法和裂解法)、物理分组(如团聚体分组、密度分组、颗粒分组和磁分离法等)以及多种分组方法结合使用。而物理分组方法可避免化学分组过程中酸、碱或氧化物等对SOC化学结构的破坏[14]。其中,团聚体分组和密度分组相结合的分组方法被广泛应用于SOC组分和稳定性的研究中[15]

2 盐度对土壤碳库组分的影响

2.1 盐度对SOC含量的影响

盐度是滨海湿地常见的环境胁迫因子之一,海水入侵过程携带大量氯化钠和硫酸根等主要通过以下3种途径影响湿地土壤元素生物地球化学循环:① 海水入侵引起的过高离子强度,影响土壤微生物群落结构和活性[16,17];②大量的硫酸盐输入,改变土壤碳代谢的主要途径[10,18,19];③ 通过离子交换以及水文条件的变化影响湿地土壤营养盐有效性[20,21]。近年来,有关盐度对湿地生态系统SOC含量的影响已开展了一些工作。美国Delaware河及Waccamaw 河流域潮汐淡水湿地,由于外源盐分添加的同时伴随大量硫酸盐的输入,硫酸盐电子受体通过硫酸盐还原,显著促进了淡水湿地SOC的亏损[11,19]。但同时,随着盐度增加,盐析作用增强,微生物的新陈代谢能力减弱[20,21,22],从而使得高盐环境下SOC的分解速率减慢,有利于SOC的积累与贮存。此外,盐度也是影响滨海湿地植被类型的重要参数之一,盐度通过调节湿地植被光合固碳以及植物残体的归还与分解作用对土壤碳输入和输出过程产生深刻影响。研究表明,植物生长期可通过根系分泌作用将光合产物的10%~40%输入土壤,而大部分光合作用固定的碳则以枯落物的形式进入土壤碳库[23]。植被类型对土壤碳库也产生显著影响[24]。张耀鸿等[25]研究发现真盐生植物互花米草(C4植物)入侵增加了盐沼SOC含量。同时,湿地植被的地下碳分配模式可通过改变土壤微生物群落结构与丰度,从而改变湿地生态系统地下碳代谢的诸多过程[26],进而影响湿地SOC含量。并且,植物体不同结构和器官由于其物理特征和化学成分的不同,使其碳分解速率、碳浸出和碳存留时间各异,如木本植物支撑器官的碳含量高且难分解,形成分解速率慢、滞留时间长的慢性或惰性碳库[27]

2.2 盐度对SOC活性组分的影响

通常,SOC总量的变化对外界环境干扰的响应并不灵敏,且不能准确全面地反应SOC的变化特点。因而识别SOC库的特征组分并了解其形成与周转机制对探索SOC的动态变化至关重要[28]。土壤活性碳在土壤中迁移快、稳定性差且易矿化,对植物和土壤微生物来说有效性较高,包含微生物生物量碳(Microbial biomass carbon, MBC)、可溶性有机碳(Dissolved organic carbon, DOC)和易氧化有机碳(Easily oxidized organic carbon, EOC)等。

土壤MBC是土壤有机质中最活跃最易变化的部分[29],是土壤有效C的源和汇,限制土壤营养元素循环和有机质分解等土壤系统过程[30]。土壤MBC对盐度变化的响应十分敏感,Kiehn 等[31]通过室内模拟实验发现寡盐沼湿地历经一次盐度脉冲后,表层土壤MBC含量增加一倍。海水入侵可通过离子交换过程将NH4+-N 从土壤中解析出来,从而为微生物生长提高了营养元素的可获得性[32]。并且,盐度上升提高了土壤有机质的溶解性[33],为微生物生长提供了更多可矿化的碳源。但Mahajan 等[34]在印度Goa 滨海酸性盐沼湿地发现土壤MBC含量与土壤盐度负相关,这与土壤中过高的盐度会通过低渗透势作用或离子毒害等方式对植物和土壤生物造成盐害有关[35]

土壤DOC 作为微生物可直接利用的有机碳源[36],是SOC 中迁移最快最易被分解的活性组分,是SOC损失的主要方式[37]。SOC、DOC和碳矿化之间的关系可用一级动力学概念模型较好的解释(图1[38,39]。该模型假定土壤碳矿化遵循一级动力学反应,土壤微生物可以分别利用SOC和DOC作为基质矿化产生CO2,微生物也可利用SOC转化为DOC。土壤碳矿化速率与DOC浓度之间的关系取决于KDOC(DOC矿化产生CO2的反应速率)与KSOC(SOC矿化产生CO2的反应速率)的大小。假如DOC比SOC包含更多能被微生物利用的活性碳,则KDOC大于KSOC,土壤碳矿化速率与DOC浓度正相关,DOC控制土壤碳矿化。反之,若SOC比DOC包含更多能被微生物利用的活性碳,则KDOC小于KSOC,土壤碳矿化速率与DOC浓度负相关。如前所述,盐度增加对SOC矿化的影响主要通过离子强度影响土壤微生物群落结构和活性[16,17],进而影响SOC矿化;或者盐分中的硫酸盐电子受体,可通过硫酸盐还原过程,促进SOC矿化[10,18,19]。同时盐度还可通过离子交换等方式影响湿地土壤底物和营养盐的有效性 [20,21],进而间接影响SOC矿化。而土壤DOC浓度对盐度变化的响应也因湿地类型而异。Chambers 等[21]通过室内模拟实验发现,淡水湿地土壤经历半咸水脉冲,显著抑制土壤DOC释放,提高了土壤DOC的固持能力,而盐沼湿地土壤经历淡水脉冲,DOC释放能力显著提高,加速了土壤DOC的损失。Wang 等[40]在中国南部英罗湾红树林湿地的研究中发现土壤DOC含量随盐度增加而增加。

图 1   土壤碳矿化一级动力学概念模型[38] KSOC:SOC矿化产生CO2的反应速率; KDOC:DOC矿化产生CO2的反应速率;KSD:SOC转化为DOC的反应速率

Fig.1   A first-order kinetic conceptual model describing carbon mineralization in soil[38]

土壤EOC是指能被333 mmol/L的KMnO4 氧化且活性较高的有机碳[41],可在较短的生长季内给土壤微生物提供能量[42]。Wang 等[40]在中国南部英罗湾红树林湿地的研究中发现土壤EOC的含量与盐度显著正相关。高灯州等[43]在中国东南沿海闽江河口潮汐湿地的研究中发现土壤EOC含量与盐度相关性不显著。这种研究结论的差异可能归因于湿地类型的不同,Wang等[40]研究的红树林湿地由于其独特的环境梯度,导致土壤盐度和营养物质(N和P等)随土壤高程增加。低盐表征着更高的水淹频率和时长(即低潮滩区),强烈的潮水冲刷作用不利于有机质的滞留和较细的土壤颗粒的沉降[44],减少了有机质来源。并且,较高的淹水频率和时长以及营养物质匮乏等生存环境使得低潮滩区初级生产者少且生长缓慢,不利于植物枯落物和根系分泌物的产生与输入,进一步减少了有机质来源[45]

可见,在探讨盐度对滨海湿地SOC含量及其活性组分的影响时,不同研究者由于实验方法、湿地类型和研究区域等的不同而结果有所差别。因此,今后应在更为广泛的区域尺度探讨土壤碳库动态对于盐度的响应,并尝试梳理这种区域差异的内在机理,对于科学评价与预测未来全球范围内湿地碳源汇功能变化具有重要意义。

3 土壤碳库稳定机制

SOC库的稳定性是评价土壤长期固碳潜力的重要指标。土壤固碳研究是近些年土壤学研究的重要前沿,而可持续的土壤碳库管理是当前应对气候变化和全球土壤退化的重大需求。从表1中不难发现,国内外学者已从不同的研究对象或调控因子对不同土地类型的SOC稳定机制开展了大量研究,但大多数研究主要集中于内陆生态系统,而对滨海湿地生态系统的研究相对较少。特别是以往研究主要针对某一种或两种SOC稳定机制进行探讨,鲜有对3种稳定机制同时探讨与系统分析。过去几十年,SOC分子结构的稳定性被视为SOC稳定的主要指标,但最近一些研究发现许多稳定碳库中包含大量易分解的碳组分[57,58]。还有研究发现土壤矿质吸附的表层有机碳较土体中有机碳的周转速率更慢,且在含有大量易分解有机碳组分的情况下先分解掉一些芳香族有机碳组分[59,60]。这些研究表明即使有较高稳定性的有机碳输入也不一定在土壤中长期固存,分子结构的稳定并不表征土壤碳库的稳定[61]。SOC稳定机制主要有3种:分子生物学稳定机制、物理稳定机制以及化学结合稳定机制[62,63]。分子生物学稳定机制是指由于SOC化学组成具有难降解性,或SOC经过一系列化学耦合等过程使分子结构稳定性增强,可以抵抗微生物的分解作用。物理稳定机制是SOC通过形成土壤团聚体结构或被包裹在团聚体内部,形成团聚体结合态有机碳,不利于微生物或酶的接近,从而减少矿化分解,提高其稳定性。化学结合稳定机制是指SOC与土壤矿物之间通过化学或物理化学的键合作用,形成土壤有机-矿质复合体,土壤黏粒、粉粒结合有机碳通过离子交换、氢键和范德华力被吸附在黏土矿物表面,从而降低了矿物分解。

表1   SOC稳定机制研究现状总结

Table 1   The summary of current studies on SOC stabilization mechanisms

土地类型研究对象SOC稳定机制参考
文献
分子生物学稳定团聚体物理稳定化学结合稳定
农田(美国)干湿交替干湿交替初期大团聚体周转快,SOC稳定性差,后期固碳增加[46]
水稻田(中国)疏水性有机质木质素和脂类等疏水性SOC被选择性保护氧化铁含量高和土壤pH较低的水稻土保护疏水性SOC[47]
沙土(澳大利亚)作物残茬vs 土壤pH分子结构稳定顺序:烷基碳>芳基碳>氧烷基碳[48]
无草休闲地
(法国)
钙盐土壤结构vs钾盐土壤结构钙盐样地大团聚稳定性高,短时间以团聚体固碳为主长时间尺度钙盐样地主要以黏粒和粉砂固碳为主[49]
亚北极草地
(冰岛)
土壤增温增温时分子结构稳定不是固碳的主要机理增温降低团聚体稳定性,导致团聚体保护的SOC大量亏损[50]
黄土丘陵区
(中国)
退耕还林53~250 µm粒级土壤微团聚体物理保护SOC组分的比例较小退耕还林后主要通过粉砂和黏粒内矿物表面吸附固定SOC[51]
森林土壤
(西班牙)
生物炭生物炭、层状硅酸盐和铁铝氧化物等在黏粒尺度固碳[52]
高山和亚高山土
壤(比利牛斯山)
土壤矿物弱晶质氧化铁和水铁矿固定SOC较硅铝矿物更重要[53]
森林土壤
(中国)
不同树种阔叶林较马尾松林低烷基碳,高氧烷基碳,稳定性差[54]
黏土和沙土
(捷克)
蚯蚓蚯蚓处理下SOC的芳香族成分和酚类含量无显著变化蚯蚓吸收有机残体进入土壤产生新的团聚体而保护SOC[55]
河口湿地
(中国)
时间尺度和土地利用变化旱地农田土壤微团聚体闭蓄SOC与输入的植物残茬有关未开垦的湿地SOC主要被水合氧化铁和铝稳定[56]

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4 盐度对SOC稳定机制的影响

盐度对SOC稳定性的影响主要体现为盐度变化引起的离子浓度变化影响了土壤颗粒对有机碳的固持能力。目前有关盐度对滨海湿地土壤碳库稳定机制影响的报道十分匮乏,本文主要基于上述3个稳定机制来探讨盐度对SOC稳定性的影响。

盐溶液中含有大量的Na+和K+可通过离子交换作用对SOC降解过程产生深刻影响。特别是Na+,由于其较短的离子半径,使得Na+具有更强的偏振能力[64,65],更容易与水分子结合而水解SOC。Thurman[33]的研究也发现SOC的溶解性随盐度升高而升高。并且,若盐溶液中的单价Na+和K+等离子与土壤中的多价离子发生离子交换,会松散SOC的分子结构[66],从而有利于土壤微生物降解SOC。反之,盐溶液中的多价离子(如Ca2+等)也可与土壤中单价离子(如Na+等)发生离子交换,使得SOC的分子结构变得更加紧实,从而不利用土壤微生物降解SOC。

土壤团聚体是通过SOC、动植物、离子桥、黏粒和碳酸盐等胶结物质的作用,对土壤颗粒重新排列、胶结而形成[67]。Zhang等[68]的研究中发现盐度对土壤不同粒级水稳性团聚体的影响不同,表现为与大团聚体(>2 mm)和微团聚体(0.25~0.053 mm)的水稳性团聚体呈负相关,而对于小团聚体(2~0.25 mm)之间各粒级水稳性团聚体呈正相关,特别是2~0.5 mm粒级间的水稳性团聚体与土壤盐度的相关性显著。盐溶液中的大量离子,特别是Na+、Ca2+和Mg2+,可通过离子交换或阳离子桥作用深刻地影响土壤团聚体的形成。Na+饱和能促进土壤黏粒级有机碳组分直接解聚[69],或通过降低植物生产力间接影响土壤团聚体。Mg2+对土壤颗粒团聚也有负效应,这种负效应的程度取决于土壤中黏粒的类型和电解质的浓度[70]。并且,Mg2+还可引起黏粒膨胀,破坏土壤团聚体。而土壤团聚体一旦破坏,吸附在团聚体表面或包裹在团聚体内部的SOC就会释放出来,遭受淋溶流失或被微生物分解矿化。但同时,Ca2+可通过阳离子桥作用使黏粒和SOC紧密结合,促进土壤颗粒团聚[67],从而减少SOC的矿化分解,提高其稳定性。

盐度对土壤颗粒吸附有机碳的影响还受土壤矿物组分的化学特征,特别是非晶质的氧化铁或氧化铝含量的控制[71]。土壤中三价的铁和铝可通过阳离子桥形成有机-金属复合体,促进土壤团聚[72],但铁和铝阳离子的溶解性和移动性取决于土壤pH,在pH较低的环境中,铁和铝离子的溶解性较高。土壤盐度与土壤pH之间的关系受控于气候、土壤、水文、地貌、生物以及人类干扰等各种环境变量及相互作用过程的影响,二者之间并无明确的关系。Wang等[73]在半干旱的干草原生态系统中发现土壤盐度与pH呈极显著正相关,高灯州等[43]在亚热带滨海湿地的研究发现土壤盐度与pH呈极显著负相关,Wang等[40]在红树林潮滩湿地的研究中发现土壤盐度与pH之间相关性不显著。

5 展望

土壤是地球表层系统的重要组成部分,集中了物理、化学、生物及人文多种反应过程。且各种反应过程彼此间既相互影响和作用,又与周围环境存在依存和反馈关系[39]。土壤生态系统的碳固定和稳定取决于关键养分元素输入和需求之间的平衡。Sinsabaugh 等[74]研究认为,如果养分供应不足,土壤微生物将消耗更多的能量用于生产所缺元素生态酶,进而影响土壤有机质分解速率。并且,土壤碳循环与营养元素循环间相互作用较为复杂,但耦合机制的认识十分有限。因此,今后应将土壤固碳与营养元素循环研究相结合,特别是土壤碳稳定与关键养分元素循环(如N、P和S)的相互作用机制研究,通过采用土壤学、生态学和地球化学等多学科领域的理论与方法,阐明土壤系统的固碳功能与可持续机制。

土壤微生物利用SOC作为代谢基质,维持自身生命活动的同时进行着元素转化和能量代谢。微生物通过其分泌的酶参与和调控各种反应过程,土壤酶活性被认为是微生物功能活性的代表[75]。因此,今后研究应进一步从微观尺度探索微生物及酶学机制与SOC稳定机制之间的关系,表征其土壤学过程与机理,诠释SOC稳定与微生物活性的本质。

SOC的分解、转化、保护和矿化过程是SOC固定的基本过程。从上述3种SOC稳定机制可以看出,SOC的固存和稳定不是分子属性问题,而是生态系统属性问题[76]。在全球气候变暖背景下,海水入侵叠加周期性的潮汐涨落,将对滨海湿地生态系统碳源汇功能产生深刻影响。海水入侵不仅通过盐度影响滨海湿地土壤碳循环过程,大量海水入侵引起的水分环境变化也对湿地生态系统产生深远影响。Ström 和 Christensen[77]研究发现水分条件的变化会影响湿地土壤-植物-大气连续体之间碳元素生物地球化学诸过程的方向与强度。但海水入侵伴随的盐度和水文协同变化对湿地生态系统碳截获能力产生怎样的影响,目前这方面研究仍十分匮乏。因此,今后湿地土壤固碳研究应从分子尺度向生态系统尺度,从单要素、单过程的研究向多要素、多过程耦合方向发展,探索多界面、多过程交互作用下土壤碳固定与生态系统结构和功能之间的内在联系与机理。同时可借助稳定同位素技术,溯源并计算不同来源有机碳在碳稳定诸过程的分配比率,示踪滨海湿地土壤活性碳库和惰性碳库的来源与归趋,为了解未来海平面上升背景下湿地碳截获潜力的演变趋势及其应对策略,为发展和完善中国湿地土壤碳循环理论奠定科学基础。

The authors have declared that no competing interests exist.


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Tidal freshwater marshes exist in a dynamic environment where plant productivity, subsurface biogeochemical processes, and soil elevation respond to hydrological fluctuations over tidal to multi-decadal time scales. The objective of this study was to determine ecosystem responses to elevated salinity and increased water inputs, which are likely as sea level rise accelerates and saltwater intrudes into freshwater habitats. Since June 2008, in situ manipulations in a Zizaniopsis miliacea (giant cutgrass)-dominated tidal freshwater marsh in South Carolina have raised porewater salinities from freshwater to oligohaline levels and/or subtly increased the amount of water flowing through the system. Ecosystem-level fluxes of CO2 and CH4 have been measured to quantify rates of production and respiration. During the first 20 months of the experiment, the major impact of elevated salinity was a depression of plant productivity, whereas increasing freshwater inputs had a greater effect on rates of ecosystem CO2 emissions, primarily due to changes in soil processes. Net ecosystem production, the balance between gross ecosystem production and ecosystem respiration, decreased by 55% due to elevated salinity, increased by 75% when freshwater inputs were increased, and did not change when salinity and hydrology were both manipulated. These changes in net ecosystem production may impact the ability of marshes to keep up with rising sea levels since the accumulation of organic matter is critical in allowing tidal freshwater marshes to build soil volume. Thus, it is necessary to have regional-scale predictions of saltwater intrusion and water level changes relative to the marsh surface in order to accurately forecast the long-term sustainability of tidal freshwater marshes to future environmental change.
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Environmental perturbations in wetlands affect the integrated plant-microbial-soil system, causing biogeochemical responses that can manifest at local to global scales. The objective of this study was to determine how saltwater intrusion affects carbon mineralization and greenhouse gas production in coastal wetlands. Working with tidal freshwater marsh soils that had experienced similar to 3.5 yr of in situ saltwater additions, we quantified changes in soil properties, measured extracellular enzyme activity associated with organic matter breakdown, and determined potential rates of anaerobic carbon dioxide (CO2) and methane (CH4) production. Soils from the field plots treated with brackish water had lower carbon content and higher C : N ratios than soils from freshwater plots, indicating that saltwater intrusion reduced carbon availability and increased organic matter recalcitrance. This was reflected in reduced activities of enzymes associated with the hydrolysis of cellulose and the oxidation of lignin, leading to reduced rates of soil CO2 and CH4 production. The effects of long-term saltwater additions contrasted with the effects of short-term exposure to brackish water during three-day laboratory incubations, which increased rates of CO2 production but lowered rates of CH4 production. Collectively, our data suggest that the long-term effect of saltwater intrusion on soil CO2 production is indirect, mediated through the effects of elevated salinity on the quantity and quality of autochthonous organic matter inputs to the soil. In contrast, salinity, organic matter content, and enzyme activities directly influence CH4 production. Our analyses demonstrate that saltwater intrusion into tidal freshwater marshes affects the entire process of carbon mineralization, from the availability of organic carbon through its terminal metabolism to CO2 and/or CH4, and illustrate that long-term shifts in biogeochemical functioning are not necessarily consistent with short-term disturbance-type responses.
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Climate change-associated sea level rise is expected to cause saltwater intrusion into many historically freshwater ecosystems. Of particular concern are tidal freshwater wetlands, which perform several important ecological functions including carbon sequestration. To predict the impact of saltwater intrusion in these environments, we must first gain a better understanding of how salinity regulates decomposition in natural systems. This study sampled eight tidal wetlands ranging from freshwater to oligohaline (0 2 ppt) in four rivers near the Chesapeake Bay (Virginia). To help isolate salinity effects, sites were selected to be highly similar in terms of plant community composition and tidal influence. Overall, salinity was found to be strongly negatively correlated with soil organic matter content (OM%) and C : N, but unrelated to the other studied environmental parameters (pH, redox, and above- and below-ground plant biomass). Partial correlation analysis, controlling for these environmental covariates, supported direct effects of salinity on the activity of carbon-degrading extracellular enzymes (-1, 4-glucosidase, 1, 4--cellobiosidase, -D-xylosidase, and phenol oxidase) as well as alkaline phosphatase, using a per unit OM basis. As enzyme activity is the putative rate-limiting step in decomposition, enhanced activity due to salinity increases could dramatically affect soil OM accumulation. Salinity was also found to be positively related to bacterial abundance (qPCR of the 16S rRNA gene) and tightly linked with community composition (T-RFLP). Furthermore, strong relationships were found between bacterial abundance and/or composition with the activity of specific enzymes (1, 4--cellobiosidase, arylsulfatase, alkaline phosphatase, and phenol oxidase) suggesting salinity's impact on decomposition could be due, at least in part, to its effect on the bacterial community. Together, these results indicate that salinity increases microbial decomposition rates in low salinity wetlands, and suggests that these ecosystems may experience decreased soil OM accumulation, accretion, and carbon sequestration rates even with modest levels of saltwater intrusion.
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Soil organic matter (SOM) consists of various functional pools that are stabilized by specific mechanisms and have certain turnover rates. For the development of mechanistic models that predict changes in SOM storage, these pools have to be quantified and characterized. In the past, numerous fractionation schemes have been developed to separate and analyse such SOM fractions. In this review, the SOM fractions obtained with such operational fractionation procedures are described in terms of their pool sizes, chemical properties, and turnover rates. The main objective of this review is to evaluate these operationally defined fractions with respect to their suitability to describe functional SOM pools that could be used to parameterize SOM turnover models. Fractionation procedures include (1) physical separation of SOM into aggregate, particle size, and density fractions and fractions according to their magnetic susceptibility, and (2) various wet chemical procedures that fractionate SOM according to solubility, hydrolysability, and resistance to oxidation or by destruction of the mineral phase. Furthermore, combinations of fractionation methods are evaluated. The active SOM pool with turnover rates <10 years may best be represented by the soil microbial biomass and the light fraction (<1.6 2 g cm 3) obtained by density fractionation (if black carbon contents are considered). Most chemical and physical fractionations as well as combinations of methods yield SOM fractions that are not homogeneous in terms of turnover rates. It has proven to be particularly difficult to isolate functional fractions that represent the passive model pools in which the majority of soil SOM is stabilized. The available fractionation methods do not correspond to specific stabilization mechanisms and hence do not describe functional SOM pools. Another problem is that comprehensive data for turnover rates and data for whole soil profiles are only now becoming available, especially for new fractionation methods. Such information as well as the use of specific markers and compound-specific isotope analysis may be important for future differentiation and evaluation of functional SOM fractions.
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[J]. Geoderma, 2005,128(1-2): 63-79.

https://doi.org/10.1016/j.geoderma.2004.12.013      URL      [本文引用: 1]      摘要

The type of land use and soil cultivation are important factors controlling organic carbon storage in soils and they may also change the relative importance of different mechanisms of soil organic matter stabilization. Our objectives were: i) to quantify the soil organic carbon (SOC) and nitrogen (N) storage in silty soils under wheat, maize, grassland and spruce, ii) to determine the SOC and N storage in water-stable aggregates of different size (<53 μm, 53–250 μm, 250–1000 μm, 1000–2000 μm, >2000 μm) and in density fractions (Mineral-associated soil organic matter >2 g cm 613 (Mineral-SOM), free particulate organic matter <1.6 g cm 613 (free POM), light occluded particulate organic matter <1.6 g cm 613 (occluded POM <1.6) and dense occluded particulate organic matter 1.6 to 2.0 g cm 613 (occluded POM 1.6–2.0)) and iii) to analyse the stability and turnover of these SOC fractions in the maize soil on the basis of the δ 13C values. Total SOC stocks down to a depth of 60 cm and including the humus layer were larger at the spruce site (10.3 kg C m 612) as compared with the grassland, wheat and maize (7 to 8 C kg m 612). However, SOC stocks in the mineral soil were smaller in the forest soil than in the agricultural soils. In the arable soils, the aggregate fractions 53–250 μm and 250–1000 μm were the most abundant size fractions, whereas aggregates >1000 μm were most abundant in the grassland and forest soil. The SOC concentration and the C/N ratio were greater for macroaggregates (>250 μm) than microaggregates (<250 μm) in the field and grassland soils. At the maize site the percentage of maize-derived C was smallest in the fraction <53 μm with 24% and steadily increased with increasing aggregate size to 47% in the fraction >1000 μm. The major part (86–91%) of the SOC was associated with the heavy mineral fraction at the grassland, maize and wheat site. In the A horizon of the spruce stand, the particulate organic matter accounted for 52% of the total SOC content. The C/N ratios of density fractions decreased in the order free POM <1.6>occluded POM>Mineral-SOM for all soils and depths. The mean age of organic carbon in the water-stable aggregates in the Ap horizon of the maize site increased with decreasing aggregate size from 35 yr (>1000 μm) to 86 yr (<53 μm). For the density fractions the order was free POM (22 yr)<dense occluded POM 1.6–2.0 (49 yr)<Mineral-SOM (63 yr)<light occluded POM <1.6 (83 yr). The results showed that the type of land use affected the distribution pattern of litter carbon to functionally different SOM pools and that increasing SOC concentrations were closely associated with the formation of macroaggregates.
[16] Van Ryckegem G, Verbeken A.

Fungal diversity and community structure on Phragmites australis (Poaceae) along a salinity gradient in the Scheldt estuary (Belgium)

[J]. Nova Hedwigia, 2005, 80(1-2):173-197.

https://doi.org/10.1127/0029-5035/2005/0080-0173      URL      [本文引用: 2]      摘要

@article{301592, author = {Van Ryckegem, Gunther and Verbeken, Annemieke}, issn = {0029-5035}, journal = {NOVA HEDWIGIA}, language = {eng}, number = {1-2}, pages = {173--197}, publisher = {GEBRUDER BORNTRAEGER}, title = {Fungal diversity and community structure on Phragmites australis (Poaceae) along a salinity gradient in the Scheldt estuary (Belgium)}, volume = {80}, year = {2005}, }
[17] Chambers L G, Guevara R, Boyer J N et al.

Effects of salinity and inundation on microbial community structure and function in a mangrove peat soi

[J]. Wetlands, 2016, 36(2):361-371.

https://doi.org/10.1007/s13157-016-0745-8      URL      [本文引用: 2]      摘要

Shifts in microbial community function and structure can be indicators of environmental stress and ecosystem change in wetland soils. This study evaluated the effects of increased salinity, increased inundation, and their combination, on soil microbial function (enzyme activity) and structure (phospholipid fatty acid (PLFA) signatures and terminal restriction fragment length polymorphisms (T-RFLP) profiles) in a brackish mangrove peat soil using tidal mesocosms (Everglades, Florida, USA). Increased tidal inundation resulted in reduced soil enzyme activity, especially alkaline phosphatase, an increase in the abundance and diversity of prokaryotes, and a decline in number of eukaryotes. The community composition of less abundant bacteria (T-RFLPs comprising 0.3 1 % of total fluorescence) also shifted as a result of increased inundation under ambient salinity. Several key biogeochemical indicators (oxidation-reduction potential, CO2 flux, porewater NH4+, and dissolved organic carbon) correlated with measured microbial parameters and differed with inundation level. This study indicates microbial function and composition in brackish soil is more strongly impacted by increased inundation than increased salinity. The observed divergence of microbial indicators within a short time span (10-weeks) demonstrates their usefulness as an early warning signal for shifts in coastal wetland ecosystems due to sea level rise stressors.
[18] Edmonds J W, Weston N B, Joye S B et al.

Microbial community response to seawater amendment in low-salinity tidal sediments

[J]. Microbial Ecology, 2009, 58(3): 558-568.

https://doi.org/10.1007/s00248-009-9556-2      URL      PMID: 19629578      Magsci      [本文引用: 2]      摘要

Rising sea levels and excessive water withdrawals upstream are making previously freshwater coastal ecosystems saline. Plant and animal responses to variation in the freshwater–saline interface have been well studied in the coastal zone; however, microbial community structure and functional response to seawater intrusion remains relatively unexplored. Here, we used molecular approaches to evaluate the response of the prokaryotic community to controlled changes in porewater salinity levels in freshwater sediments from the Altamaha River, Georgia, USA. This work is a companion to a previously published study describing results from an experiment using laboratory flow-through sediment core bioreactors to document biogeochemical changes as porewater salinity was increased from 0 to 10 over 35days. As reported in Weston et al. ( Biogeochemistry , 77:375–408, 62 ), porewater chemistry was monitored, and cores were sacrificed at 0, 9, 15, and 35days, at which time we completed terminal restriction fragment length polymorphism and 16S rRNA clone library analyses of sediment microbial communities. The biogeochemical study documented changes in mineralization pathways in response to artificial seawater additions, with a decline in methanogenesis, a transient increase in iron reduction, and finally a dominance of sulfate reduction. Here, we report that, despite these dramatic and significant changes in microbial activity at the biogeochemical level, no significant differences were found between microbial community composition of control vs. seawater-amended treatments for either Bacterial or Archaeal members. Further, taxa in the seawater-amended treatment community did not become more “marine-like” through time. Our experiment suggests that, as seawater intrudes into freshwater sediments, observed changes in metabolic activity and carbon mineralization on the time scale of weeks are driven more by shifts in gene expression and regulation than by changes in the composition of the microbial community.
[19] Weston N B, Vile M A, Neubauer S C et al.

Accelerated microbial organic matter mineralization following salt-water intrusion into tidal freshwater marsh soil

[J]. Biogeochemistry, 2011, 102(1):135-151.

https://doi.org/10.1007/s10533-010-9427-4      URL      [本文引用: 3]      摘要

AbstractThe impact of salt-water intrusion on microbial organic carbon (C) mineralization in tidal freshwater marsh (TFM) soils was investigated in a year-long laboratory experiment in which intact soils were exposed to a simulated tidal cycle of freshwater or dilute salt-water. Gas fluxes [carbon dioxide (CO) and methane (CH)], rates of microbial processes (sulfate reduction and methanogenesis), and porewater and solid phase biogeochemistry were measured throughout the experiment. Flux rates of CO and, surprisingly, CH increased significantly following salt-water intrusion, and remained elevated relative to freshwater cores for 6 and 502months, respectively. Following salt-water intrusion, rates of sulfate reduction increased significantly and remained higher than rates in the freshwater controls throughout the experiment. Rates of acetoclastic methanogenesis were higher than rates of hydrogenotrophic methanogenesis, but the rates did not differ by salinity treatment. Soil organic C content decreased significantly in soils experiencing salt-water intrusion. Estimates of total organic C mineralized in freshwater and salt-water amended soils over the 1-year experiment using gas flux measurements (18.2 and 24.902mol02C02m, respectively) were similar to estimates obtained from microbial rates (37.8 and 56.202mol02C02m, respectively), and to losses in soil organic C content (0 and 44.102mol02C02m, respectively). These findings indicate that salt-water intrusion stimulates microbial decomposition, accelerates the loss of organic C from TFM soils, and may put TFMs at risk of permanent inundation.
[20] Portnoy J W, Giblin A E.

Biogeochemical effects of seawater restoration to diked salt marshes

[J]. Ecological Applications, 1997, 7(3):1054-1063.

https://doi.org/10.2307/2269455      URL      [本文引用: 3]      摘要

We conducted greenhouse microcosm experiments to examine the biogeochemical effects of restoring seawater to historically diked Cape Cod salt marshes. Peat cores from both seasonally flooded and drained diked marshes were waterlogged with seawater, and porewater chemistry was subsequently monitored for 21 mo. The addition of seawater to highly organic, seasonally flooded peat caused the death of freshwater wetland plants, 6-8 cm of sediment subsidence, and increased N and P mineralization. Also, sulfides and alkalinity increased 10-fold, suggesting accelerated decomposition by sulfate reduction. Addition of seawater to the low-organic-content acidic peat from the drained marsh increased porewater pH, alkalinity, PO$_4$-P, and Fe(II), which we attribute to the reestablishment of SO$_4$ and Fe(III) mineral reduction. Increased cation exchange contributed to 6-fold increases in dissolved Fe(II) and A1 and 60-fold increases in NH$_4$-N within 6 mo of salination. Seawater reintroductions to seasonally flooded diked marshes will cause porewater sulfides to increase, likely reducing the success of revegetation efforts. Sulfide toxicity is of less concern in resalinated drained peats because of the abundance of Fe(II) to precipitate sulfides, and of NH$_4$-H to offset sulfide inhibition of N uptake. Restoration of either seasonally flooded or drained diked marshes could stimulate potentially large nutrient and Fe(II) releases, which could in turn increase primary production and lower oxygen in receiving waters. These findings suggest that tidal restoration be gradual and carefully monitored.
[21] Chambers L G, Osborne T Z, Reddy K R.

Effect of salinity pulsing events on soil organic carbon loss across an intertidal wetland gradient: A laboratory experiment

[J]. Biogeochemistry, 2013, 115(1):363-383.

https://doi.org/10.1007/s10533-013-9841-5      URL      [本文引用: 4]      摘要

Salinity changes resulting from storm surge, tides, precipitation, and stormwater run-off are common in coastal wetlands. Soil microbial communities respond quickly to salinity changes, altering the rate of soil organic carbon (SOC) loss and associated biogeochemical processes. This study quantified the impact of salinity-altering pulses on SOC loss, defined as microbial respiration (CO2 flux) at high and low tide, CH4 flux, and dissolved OC (DOC) release, in 3 intertidal wetlands (Jacksonville, FL, USA). Intact soil cores from a freshwater tidal, brackish, and salt marsh were exposed to simulated tides and 3 salinity pulsing events during a 53-day laboratory experiment. Soil and water physio-chemical properties, nutrient release, and microbial indicators were measured. Microbial respiration was the dominate pathway of SOC loss (> 97 %). Soil hydraulic conductivity was greater in brackish and salt marshes and was critical to overall soil respiration. High tide CO2 flux was greatest in the freshwater marsh (58 % of SOC loss) and positively correlated with DOC concentration; low tide CO2 flux was greatest in brackish and salt marshes (62 and 70 % of SOC loss, respectively) and correlated with NH4 (+) and microbial biomass. The freshwater marsh was sensitive to brackish pulses, causing a 112 % increase in respiration, presumably from accelerated sulfate reduction and N-cycling. SOC loss increased in the salt marsh pulsed with freshwater, suggesting freshwater run-off may reduce a salt marsh's ability to keep-pace with sea level rise. Increased inundation from storm surges could accelerate SOC loss in freshwater marshes, while decreasing SOC loss in brackish and salt marshes.
[22] Thottathil S D, Balachandran K K, Jayalakshmy K V et al.

Tidal switch on metabolic activity: Salinity induced responses on bacterioplankton metabolic capabilities in a tropical estuary

[J]. Estuarine, Coastal and Shelf Science, 2008, 78(4): 665-673.

https://doi.org/10.1016/j.ecss.2008.02.002      URL      [本文引用: 1]      摘要

“Biolog” plates were used to study the changes in the metabolic capabilities of bacterioplankton over a complete tidal cycle in a tropical ecosystem (Cochin Estuary) along southwest coast of India. The pattern of utilization of carbon sources showed a definite shift in the community metabolism along a salinity gradient. Multivariate statistical analysis revealed two communities, namely allochthonous bacterioplankton sensitive to salinity and autochthonous bacterioplankton, which are tolerant to wide salinity fluctuations. Regression analysis showed salinity as the most important parameter influencing the physiological profile of bacterioplankton, irrespective of tide. Apart from salinity, limno-tolerant retrievable counts and halo-tolerant retrievable counts also accounted for the metabolic variation of bacterioplankton during low and high tides, respectively. The shift in the substrate utilization from carbohydrates to amino acids appears to be due to the physiological adaptation or nitrogen limitation of bacterial community with increasing salinity.
[23] Kaštovská E, Šantrůčková H.

Fate and dynamics of recently fixed C in pasture plant-soil system under field conditions

[J]. Plant and Soil, 2007, 300(1-2): 61-69.

https://doi.org/10.1007/s11104-007-9388-0      URL      Magsci      [本文引用: 1]      摘要

The flow of photosynthetically fixed C from plants to selected soil C pools was studied after 13CO2 pulse labeling of pasture plants under field conditions, dynamics of root-derived C in soil was assessed and turnover times of the soil C pools were estimated. The transport of the fixed C from shoots to the roots and into the soil was very fast. During 27 h, net C belowground allocation reached more than 10% of the fixed C and most of the C was already found in soil. Soil microbial biomass (CMIC) was the major sink of the fixed C within soil C pools (ca 40 70% of soil 13C depending on sampling time). Significant amounts of 13C were also found in other labile soil C pools connected with microbial activity, in soluble organic C and C associated with microbial biomass (hot-water extract from the soil residue after chloroform fumigation-extraction) and the 13C dynamics of all these pools followed that of the shoots. When the labelling (2 h) finished, the fixed 13C was exponentially lost from the plant oil system. The loss had two phases; the first rapid phase corresponded to the immediate respiration of 13C during the first 24 h and the second slower loss was attributable to the turnover of 13C assimilated in CMIC. The corresponding turnover times for CMIC were 1.1 days and 3.4 days respectively. Such short turnover times are comparable to those measured by growth kinetics after the substrate amendment in other studies, which indicates that microbial growth in the rhizosphere is probably not limited by substrate availability. Our results further confirmed the main role of the soil microbial community in the transformation of recently fixed C, short turnover time of the easily degradable C in the rhizosphere, and its negligible contribution to more stable soil C storage.
[24] 张林海, 曾从盛, 仝川.

闽江河口湿地芦苇和互花米草生物量季节动态研究

[J]. 亚热带资源与环境学报, 2008, 3(2): 25-33.

[本文引用: 1]     

[Zhang Linhai, Zeng Congsheng, Tong Chuan.

Study on biomass dynamics of Phragmites australis and Spartina alterniflora in the wetlands of Min jiang River Estuary

. Journal of Subtropical Resources and Environment, 2008, 3(2): 25-33.]

[本文引用: 1]     

[25] 张耀鸿, 张富存, 周晓冬, .

互花米草对苏北滨海湿地表土有机碳更新的影响

[J]. 中国环境科学, 2011, 31(2): 271-276.

Magsci      [本文引用: 1]      摘要

自互花米草引入苏北滨海湿地后,逐渐替代本土植物盐蒿并形成单一植被的互花米草湿地.选择苏北地区盐蒿湿地及不同生长年限的互花米草湿地,采集其表层土壤样品,分别测定全土和分离的土壤粒径组分中总有机碳及δ13C值,分析湿地土壤有机碳浓度及其同位素组成的变化.结果表明,互花米草引入盐蒿湿地后,表层土壤有机碳浓度显著增加(增量达70%),且随着互花米草生长时间延长而明显增加.与盐蒿湿地相比,互花米草湿地土壤中大团聚体(>250mm)和微团聚体组分(53~250mm)有机碳浓度均显著增加,而粉粒组分(2~53mm)则无明显变化.互花米草湿地土壤原状土及各粒径组分的δ13C值均明显高于盐蒿土壤,源于互花米草的新碳在各粒径组分中均有分布,但主要富集在大团聚体组分中,占该组分总碳的31%~43%,说明互花米草生长对土壤有机碳浓度增加主要反映在粗粒径组分中,而对粉、黏粒组分则影响较小.

[Zhang Yaohong, Zhang Fucun, Zhou Xiaodong et al.

Effects of plant invasion along a Spartina alterniflora chronosequence on organic carbon dynamics in coastal wetland in north Jiangsu

. China Environmental Science, 2011, 31(2):271-276.]

Magsci      [本文引用: 1]      摘要

自互花米草引入苏北滨海湿地后,逐渐替代本土植物盐蒿并形成单一植被的互花米草湿地.选择苏北地区盐蒿湿地及不同生长年限的互花米草湿地,采集其表层土壤样品,分别测定全土和分离的土壤粒径组分中总有机碳及δ13C值,分析湿地土壤有机碳浓度及其同位素组成的变化.结果表明,互花米草引入盐蒿湿地后,表层土壤有机碳浓度显著增加(增量达70%),且随着互花米草生长时间延长而明显增加.与盐蒿湿地相比,互花米草湿地土壤中大团聚体(>250mm)和微团聚体组分(53~250mm)有机碳浓度均显著增加,而粉粒组分(2~53mm)则无明显变化.互花米草湿地土壤原状土及各粒径组分的δ13C值均明显高于盐蒿土壤,源于互花米草的新碳在各粒径组分中均有分布,但主要富集在大团聚体组分中,占该组分总碳的31%~43%,说明互花米草生长对土壤有机碳浓度增加主要反映在粗粒径组分中,而对粉、黏粒组分则影响较小.
[26] Cheng X, Chen J, Luo Y et al.

Assessing the effects of short-term Spartina alterniflora invasion on labile and recalcitrant C and N pools by means of soil fractionation and stable C and N isotopes

[J]. Geoderma, 2008, 145(3): 177-184.

https://doi.org/10.1016/j.geoderma.2008.02.013      URL      [本文引用: 1]      摘要

An exotic grass Spartina alterniflora was intentionally introduced to Jiuduansha wetlands in Yangtze River estuary in 1997, and since then it had rapidly replaced native plant Scirpus mariqueter that used to dominate the estuarine salt marshes. We investigated consequences of S. alterniflora invasion to soil labile and recalcitrant C and N compared to the native S. mariqueter using soil fractionation and stable C and N isotopes. Results showed that S. alterniflora increased soil labile carbon (LC), recalcitrant carbon (RC), and soil recalcitrant nitrogen (RN) contents significantly ( P < 0.05) in the upper soil layers (0–6002cm) compared to the S. mariqueter soil. Soil labile nitrogen (LN) in the S. alterniflora soil, however, remained lower than that in the S. mariqueter soil ( P < 0.01), except for the surface soil layer (0–2002cm). The LC accounted for, on average, 36–38% of soil organic matter (SOM) in both communities, while labile N accounted for 32% of SOM in S. alterniflora soil and 48% in S. mariqueter soil. The δ 13C values in S. alterniflora soil showed that S. alterniflora contributed on average 8.6% and 3.3% to the LC and RC pools, respectively, within the 0–100-cm soil layer. The greatest labile C contribution derived from S. alterniflora was found at the 40-cm soil whereas the proportion of recalcitrant C originating from S. alterniflora showed a decreasing trend with soil depth. These changes appeared to be associated with vertical distributions of roots and rhizodeposition. We also found that the δ 15N values of SOM were more enriched in S. alterniflora soil compared to S. mariqueter soil, suggesting that greater SOM input by S. alterniflora residues would stimulate microbial activity rates that could lead to increased N turnover rates in S. alterniflora soil.
[27] Sitch S, Smith B, Prentice I C et al.

Evaluation of ecosystem dynamics, plant geography and terrestrial carbon cycling in the LPJ dynamic global vegetation model

[J]. Global Change Biology, 2003, 9(2): 161-185.

https://doi.org/10.1046/j.1365-2486.2003.00569.x      URL      [本文引用: 1]      摘要

The Lund–Potsdam–Jena Dynamic Global Vegetation Model (LPJ) combines process-based, large-scale representations of terrestrial vegetation dynamics and land-atmosphere carbon and water exchanges in a modular framework. Features include feedback through canopy conductance between photosynthesis and transpiration and interactive coupling between these 'fast' processes and other ecosystem processes including resource competition, tissue turnover, population dynamics, soil organic matter and litter dynamics and fire disturbance. Ten plants functional types (PFTs) are differentiated by physiological, morphological, phenological, bioclimatic and fire-response attributes. Resource competition and differential responses to fire between PFTs influence their relative fractional cover from year to year. Photosynthesis, evapotranspiration and soil water dynamics are modelled on a daily time step, while vegetation structure and PFT population densities are updated annually.
[28] Denef K, Six J, Merckx R et al.

Carbon sequestration in microaggregates of no-tillage soils with different clay mineralogy

[J]. Soil Science Society of America Journal, 2004, 68(6):1935-1944.

https://doi.org/10.2136/sssaj2004.1935      URL      [本文引用: 1]      摘要

This study compares the soil organic carbon (SOC) sequestration of three different soil types under no-tillage and conventional tillage. In all three soil types, soils under no-tillage had greater total SOC and greater C in microaggregates. More than 90% of the difference in total SOC between no-tillage and conventional tillage was attributable to the difference in microaggregate-associated C, regardless of clay mineralogy differences.
[29] Anderson T H, Domsch K H.

Application of eco-physiological quotients (qCO2 and qD) on microbial biomass from soils of different cropping histories

[J]. Soil Biology and Biochemistry, 1990, 22(2): 251-255.

https://doi.org/10.1016/0038-0717(90)90094-G      URL      [本文引用: 1]      摘要

Metabolic quotients for CO 2C ( qCO 2C) and microbial-C-loss ( qD) were studied on soil microbial communities under long-term monoculture (M) or continuous crop rotations (CR). Under defined laboratory conditions the mean qCO 2C (unit CO 2C unit 611 C mic h 611) of different microbial biomasses from 17 M systems amounted to 1.097 μg CO 2 qCO 2CC as compared to 0.645 μg CO 2C of microbial biomasses from 19 CR systems. The 1.7 times higher CO 2C release per unit biomass and time of microbial biomasses from M systems was significantly different at the P =0.001 level. In addition, microbial C-loss in samples from M or CR plots was followed for 5 weeks. Again, mean qD per unit microbial biomass and time was 1.6 times higher ( P = 0.01) for microbial biomasses from M systems (0.301 μg C, 14 soils) when compared with CR systems (0.188μg C, 14 soils). These differences were not related to soil texture, C org or pH of these soils. The effects of environmental influences (soil management) on the microbial pool in terms of a changing energy demand are discussed.
[30] Jia G M, Liu X.

Soil microbial biomass and metabolic quotient across a gradient of the duration of annually cyclic drainage of hillslope riparian zone in the three gorges reservoir area

[J]. Ecological Engineering, 2017, 99: 366-373.

https://doi.org/10.1016/j.ecoleng.2016.11.063      URL      [本文引用: 1]      摘要

Hydrological alteration caused by dam operation and river modification has affected the habitat of microorganisms by directly changing soil physical and chemical environment in the hillslope riparian zone. However, the changes in the hillslope riparian zone’s soil microbial biomass and qCO 2 caused by a range of annual cyclic water-level fluctuations over time have received considerably less attention. Three subsites with different durations of annual cyclic drainage in riparian zone were chosen for soil microbial biomass carbon, microbial biomass nitrogen and qCO 2 measurement during the drainage across a hillslope riparian elevation in Three Gorges Reservoir Area for two years from 2011 to 2012. The studied subsites included shorter drainage (SD) at 145–15502m above sea level, middle drainage (MD) at 155–16502m above sea level, and longer drainage (LD) at 165–17502m above sea level. One adjacent upland site that was never inundation (NI) at 175–18502m above sea level was used as a control. The analysis of covariance (ANCOVA) indicated that the elevation gradient and the time of sampling significantly affected soil microbial biomass carbon and soil qCO 2 . Soil microbial biomass carbon and microbial biomass nitrogen were lower in the riparian zone than the upland site. In the riparian zone, microbial biomass carbon was lower in SD (126.6302mg02kg 611 ) than those of MD (217.3302mg 611 ) and LD (220.9902mg02kg 611 ), both of which exhibited no significant difference in May 2011. However, in July 2012, the microbial biomass carbon values followed the order: MD02>02LD02>02SD. Microbial biomass nitrogen had no significant difference among three riparian zone subsites in May 2011. In July 2012, microbial biomass nitrogen was lower in SD (22.1702mg02kg 611 ) than MD (29.1702mg02kg 611 ) and LD (29.702mg02kg 611 ), both of which had no significant difference. Soil qCO 2 was higher in SD than those of MD, LD, and NI in both May 2011 and July 2012. Microbial biomass carbon was higher in July 2012 than in May 2011, whereas soil qCO 2 was lower in July 2012 than in May 2011. Overall, soil microbial biomass showed a significantly positive relationship with organic carbon and total nitrogen. Soil qCO 2 showed a negative relationship with organic carbon, microbial biomass carbon, and microbial biomass nitrogen. Therefore, the results suggested that soil microbial biomass and metabolic quotient were sensitive indicators of hydrological alteration in hillslope riparian zone as a consequence of dam operation.
[31] Kiehn W M, Mendelssohn I A, White J R.

Biogeochemical recovery of oligohaline wetland soils experiencing a salinity pulse

[J]. Soil Science Society of America Journal, 2013, 77(6): 2205-2215.

https://doi.org/10.2136/sssaj2013.05.0202      URL      [本文引用: 1]      摘要

ABSTRACT Oligohaline wetlands exist at a dynamic interface along a river-to-estuary gradient where salinity changes frequently due to fluctuating tidal cycles and weather events. Large storms can cause short-term saltwater intrusion into these low-lying coastal areas, exposing oligohaline wetland plants and soils to above-normal salinities and severe stress on wetland organisms. The objective of this study was to determine how oligohaline wetland soils respond to a single pulse saltwater intrusion, similar to what may occur during hurricane-associated storm surge. Soil response variables were measured in intrusion-Impacted and Reference soils before, during, and after a 6-wk saltwater intrusion event to determine potential impacts on microbial biomass and activity and associated nutrient dynamics. We observed no significant change in basal CO2 or CH4 production in oligohaline soils (interstitial salinity = 1.3 卤 0.1 practical salinity units [psu]; mean 卤 1 SD) exposed to 20 psu saltwater, while substrate-induced methanogenesis was negatively correlated with salinity. Microbial biomass C (MBC) responded positively to saltwater intrusion by doubling in concentration at the 0- to 5-cm depth interval. Saltwater intrusion had no impact on porewater nutrient concentrations; however, extractable NH4 increased. Although some significant changes in microbial activity, abundance, and nutrient availability occurred due to saltwater intrusion, these impacts were generally transient, with post-intrusion conditions resembling pre-intrusion conditions. These results suggest that short-term and transient saltwater intrusion may have little longer-term effect on wetland soil biogeochemistry. However, compounding effects of frequent saltwater intrusion pulses due to strong, regularly occurring storm events could cause longer-lasting shifts in biogeochemical functioning of these wetlands.
[32] Weston N B, Giblin A E, Banta G T et al.

The effects of varying salinity on ammonium exchange in estuarine sediments of the Parker River, Massachusetts

[J]. Estuaries and Coasts, 2010, 33(4): 985-1003.

https://doi.org/10.1007/s12237-010-9282-5      URL      Magsci      [本文引用: 1]      摘要

We examined the effects of seasonal salinity changes on sediment ammonium (NH6262 ) adsorption and exchange across the sediment-water interface in the Parker River Estuary, by means of seasonal field sampling, laboratory adsorption experiments, and modeling. The fraction of dissolved NH6262 relative to adsorbed NH6262 in oligohaline sediments rose significantly with increased pore water salinity over the season. Laboratory experiments demonstrated that small (~ 3) increases in salinity from freshwater conditions had the greatest effect on NH6262 adsorption by reducing the exchangeable pool from 69% to 14% of the total NH6262 in the upper estuary sediments that experience large (0-20) seasonal salinity shifts. NH6262 dynamics did not appear to be significantly affected by salinity in sediments of the lower estuary where salinities under 10 were not measured. We further assessed the importance of salinity-mediated desorption by constructing a simple mechanistic numerical model for pore water chloride and NH6262 diffusion for sediments of the upper estuary. The model predicted pore water salinity and NH6262 profiles that fit measured profiles very well and described a seasonal pattern of NH6262 flux from the sediment that was significantly affected by salinity. The model demonstrated that changes in salinity on several timescales (tidally, seasonally, and annually) can significantly alter the magnitude and timing of NH6262 release from the sediments.Salinity-mediated desorption and fluxes of NH6262 from sediments in the upper estuary can be of similar magnitude to rates of organic nitrogen mineralization and may therefore be important in supporting estuarine productivity when watershed inputs of N are low.
[33] Thurman E M.

Organic geochemistry of natural waters (Vol. 2)

[M]. New York: Springer Science and Business Media, 2012.

[本文引用: 2]     

[34] Mahajan G R, Manjunath B L, Latare A M et al.

Microbial and enzyme activities and carbon stock in unique coastal acid saline soils of Goa

[J]. Proceedings of the National Academy of Sciences, India Section B: Biological Sciences, 2015, 86(4):961-971.

https://doi.org/10.1007/s40011-015-0552-7      URL      [本文引用: 1]      摘要

Abstract The aim of the present investigation was to study the effects of salinity under low soil pH conditions on soil microbial and enzyme activities and to quantify soil organic carbon (SOC) stocks in coastal saline soils of Goa, India. Global positioning system based replicated soil samples collected from fifteen different locations showed characteristic variations in electrical conductivity (0.09–6.29 dS m6301), soil pH (4.11–6.57), exchangeable sodium (Na) (7.40–23.2 meq 100 g6301) and exchangeable sodium percentage (48.3–85.7 %). Exchangeable Na was the most dominant cation among all the cations analyzed at all the sites. The total SOC stock of the study sites varied significantly (p < 0.05) and ranged from 4.27–24.3 Mg C ha6301. The soil microbial activity measured in terms of basal soil respiration, soil microbial biomass carbon (Cmb), Cmb as a fraction of SOC and enzyme activities related to dehydrogenase, phosphatase and urease showed a decline with increasing salinity levels. On the contrary, metabolic quotient increased with increasing salinity. The results of the study suggest that salinity under low soil pH has a depressive effect on the soil microbial and enzyme activity. Alleviation of the depressive effect of salinity on microbial activity needs to be addressed through suitable interventions and countermeasures for sustainable crop production in coastal acid saline soils of Goa.
[35] Yan N, Marschner P.

Response of soil respiration and microbial biomass to changing EC in saline soils

[J]. Soil Biology and Biochemistry, 2013, 65: 322-328.

https://doi.org/10.1016/j.soilbio.2013.06.008      URL      [本文引用: 1]      摘要

61In the field, salinity changes but little is known about how this affects soil microbes.61Every 5 days, C was added as glucose and salinity was changed or maintained.61Respiration rate responded within one day to changes in EC: increasing when EC was reduced.61A large initial microbial biomass was more resilient to changes in EC than a small initial biomass.61The effect of high EC was similar if the salinity was increased gradually or abruptly.
[36] 万忠梅, 郭岳, 郭跃东.

土地利用对湿地土壤活性有机碳的影响研究进展

[J]. 生态环境学报, 2011, 20(3): 567-570.

[本文引用: 1]     

[Wan Zhongmei, Guo Yue, Guo Yuedong.

Research progress on influence of land use on wetland soil active organic carbon

. Ecology and Environmental Sciences, 2011, 20(3): 567-570.]

[本文引用: 1]     

[37] Tian J, Fan M, Guo J et al.

Effects of land use intensity on dissolved organic carbon properties and microbial community structure

[J]. European Journal Soil Biology, 2012, 52:67-72

https://doi.org/10.1016/j.ejsobi.2012.07.002      URL      [本文引用: 1]      摘要

In the last three decades there has been a major shift in China's agriculture with the conversion from cereal fields to vegetable production, however little is known about the impact of this land use change on labile soil carbon and microbial community structure. We conducted a study to characterize dissolved organic carbon (DOC) and soil microbial community by comparing greenhouse vegetable fields with contrasting management intensity and adjacent cereal fields (wheat aize rotation) in Shouguang and Quzhou in North China. Compared with cereal fields, greenhouse vegetable cultivation increased soil organic carbon (SOC) and total nitrogen (TN), while it decreased the soil pH, particularly at the high-intensity site. The DOC concentration was significantly higher in greenhouse vegetable fields than in cereal fields, whereas DOC composition differed between greenhouse vegetable fields and cereal fields only at high management intensity. Chemical fractionation indicated that DOC from greenhouse vegetable fields with high management intensity was less decomposed than DOC from cereal fields, because the percentage of hydrophobic acid (HOA) as DOC was higher in vegetable fields. Vegetable production significantly changed the microbial community structure in comparison to cereal fields: high-intensity management increased total bacteria, G (+) bacteria and fungi, while low-intensity decreased fungi and increased bacteria-to-fungi ratio. The main factor affecting microbial community structure was soil pH in this study, accounting for 24% of the differences.
[38] Chow A T, Tanji K K, Gao S.

Temperature, water content and wet-dry cycle effects on DOC production and carbon mineralization in agricultural peat soils

[J]. Soil Biology and Biochemistry, 2006, 38(3): 477-488.

https://doi.org/10.1016/j.soilbio.2005.06.005      URL      [本文引用: 3]      摘要

Agricultural peat soils in the Sacramento-San Joaquin Delta, California have been identified as an important source of dissolved organic carbon (DOC) and trihalomethane precursors in waters exported for drinking. The objectives of this study were to examine the primary sources of DOC from soil profiles (surface vs. subsurface), factors (temperature, soil water content and wet–dry cycles) controlling DOC production, and the relationship between C mineralization and DOC concentration in cultivated peat soils. Surface and subsurface peat soils were incubated for 60 d under a range of temperature (10, 20, and 30 °C) and soil water contents (0.3–10.0 g-water g-soil 611). Both CO 2–C and DOC were monitored during the incubation period. Results showed that significant amount of DOC was produced only in the surface soil under constantly flooded conditions or flooding/non-flooding cycles. The DOC production was independent of temperature and soil water content under non-flooded condition, although CO 2 evolution was highly correlated with these parameters. Aromatic carbon and hydrophobic acid contents in surface DOC were increased with wetter incubation treatments. In addition, positive linear correlations ( r 2=0.87) between CO 2–C mineralization rate and DOC concentration were observed in the surface soil, but negative linear correlations ( r 2=0.70) were observed in the subsurface soil. Results imply that mineralization of soil organic carbon by microbes prevailed in the subsurface soil. A conceptual model using a kinetic approach is proposed to describe the relationships between CO 2–C mineralization rate and DOC concentration in these soils.
[39] 吴金水, 葛体达, 祝贞科.

稻田土壤碳循环关键微生物过程的计量学调控机制探讨

[J]. 地球科学进展, 2015, 30(9):1006-1017.

https://doi.org/10.11867/j.issn.1001-8166.2015.09.1006      Magsci      [本文引用: 2]      摘要

<p>稻田生态系统碳循环是我国陆地生态系统碳循环的重要组成部分,微生物驱动的稻田土壤碳循环(输入、分配、稳定等过程)的生物地球化学过程是土壤碳循环过程研究的核心。目前,对稻田土壤碳循环过程及其机制的认识缺乏基于生态化学计量学层面的研究。因此,系统解析耦合化学&mdash;生物&mdash;环境要素的稻田土壤碳循环的关键过程是深入研究当前面临的诸多土壤生物化学问题(如土壤碳循环与土壤肥力、温室气体减排等)的科学瓶颈。在综合分析计量学的基本内涵与土壤计量学发展需求的基础上,论述了稻田土壤有明显区别于其他土壤类型的土壤发生学和生物化学特点,重点评述了稻田土壤碳循环的3个主要过程的研究进展,包括:①稻田土壤新鲜有机质转化、矿化的关键微生物过程计量;②典型水稻土CH<sub>4</sub>产生的关键微生物过程计量;③典型水稻土微生物CO<sub>2</sub>光合同化功能的计量。在此基础上,探讨了土壤生物化学过程统计学和数学模型在土壤计量学研究中的应用,并提出了稻田土壤碳循环关键微生物过程的计量学特征研究的发展趋势和科学问题展望。期望能够通过这些探讨对推动我国该研究领域的基础理论建设和新技术发展有所贡献。</p>

[Wu Jinshui, Ge Tida, Zhu Zhenke.

Discussion on the key microbial process of carbon cycle and stoichiometric regulation mechanisms in paddy soils

. Advances in Earth Science, 2015, 30(9):1006-1017.]

https://doi.org/10.11867/j.issn.1001-8166.2015.09.1006      Magsci      [本文引用: 2]      摘要

<p>稻田生态系统碳循环是我国陆地生态系统碳循环的重要组成部分,微生物驱动的稻田土壤碳循环(输入、分配、稳定等过程)的生物地球化学过程是土壤碳循环过程研究的核心。目前,对稻田土壤碳循环过程及其机制的认识缺乏基于生态化学计量学层面的研究。因此,系统解析耦合化学&mdash;生物&mdash;环境要素的稻田土壤碳循环的关键过程是深入研究当前面临的诸多土壤生物化学问题(如土壤碳循环与土壤肥力、温室气体减排等)的科学瓶颈。在综合分析计量学的基本内涵与土壤计量学发展需求的基础上,论述了稻田土壤有明显区别于其他土壤类型的土壤发生学和生物化学特点,重点评述了稻田土壤碳循环的3个主要过程的研究进展,包括:①稻田土壤新鲜有机质转化、矿化的关键微生物过程计量;②典型水稻土CH<sub>4</sub>产生的关键微生物过程计量;③典型水稻土微生物CO<sub>2</sub>光合同化功能的计量。在此基础上,探讨了土壤生物化学过程统计学和数学模型在土壤计量学研究中的应用,并提出了稻田土壤碳循环关键微生物过程的计量学特征研究的发展趋势和科学问题展望。期望能够通过这些探讨对推动我国该研究领域的基础理论建设和新技术发展有所贡献。</p>
[40] Wang G, Guan D, Zhang Q et al.

Distribution of dissolved organic carbon and KMnO4-oxidizable carbon along the low-to-high intertidal gradient in a mangrove forest

[J]. Journal of Soils and Sediments, 2015, 15(11):2199-2209.

https://doi.org/10.1007/s11368-015-1150-2      URL      [本文引用: 4]      摘要

Purpose Research on soil organic carbon (SOC) fractions is needed in order to improve the understanding of natural processes that take place in mangroves. This study aimed to evaluate the variation of...
[41] Shrestha R K, Ladha J K, Gami S K.

Total and organic soil carbon in cropping systems of Nepal

[J]. Nutrient Cycling in Agroecosystems, 2006, 75(1): 257-269.

https://doi.org/10.1007/s10705-006-9032-z      URL      [本文引用: 1]      摘要

The significance of soil organic matter (SOM) in sustaining agriculture has long been recognized. The rate of change depends on climate, cropping system, cropping practice, and soil moisture. A 3-yr on-farm study was conducted in two major agro-ecologies (hills with warm-temperate climate and plains with subtropical climate) of Nepal. The soils in warm-temperate climate are Lithic subgroups of Ustorthents with well-drained loamy texture, and in subtropical climate are Haplaquepts with imperfectly drained loamy texture. Farmers’ predominant cropping systems were selected from different cultivation length in addition to a reference sample collected from adjacent virgin forest. The objectives were to examine the effect of cultivation length and cropping system on total carbon, KMnO 4 -oxidizable soil C, C storage, and C/N ratio in two climatic scenarios: warm-temperate and subtropical. A large difference in KMnO 4 -oxidizable soil organic C was observed due to the effect of cultivation length and cropping system. However, TC remained similar during the 3-year study. The decrease in KMnO 4 -oxidizable C due to cultivation was more in the surface layer (43–56%) than in the subsurface layer (20–30%). Total C in uncultivated, 50-year cultivated soil was 22, 13, and 1002g02kg 611 in warm-temperate climate and 10, 6, and 502g02kg 611 in subtropical climate, respectively. During the 3-year study period in both climates, large changes in soil C were observed for KMnO 4 -oxidizable C but not for TC, confirming our earlier work on the usefulness of the KMnO 4 oxidized fraction for detecting a relatively short-term increase or decrease in soil C pool. The TC storage in uncultivated, 50-year cultivated soil was 38, 25, and 1902Mg02ha 611 in warm-temperate climate and 22, 15, and 1202Mg02ha 611 in subtropical climate, respectively. The rice–wheat and maize–potato cropping systems were good in storing soil C of 30 and 2002Mg02ha 611 for 0–15-cm soil depth in warm-temperate climate. The rice–wheat cropping system was also good in storing soil C in subtropical climate (1902Mg02ha 611 ) compared with other cropping systems studied.
[42] Zhang M, Zhang X, Liang W et al.

Distribution of soil organic carbon fractions along the altitudinal gradient in Changbai Mountain, China

[J]. Pedosphere, 2011, 21(5):615-620.

https://doi.org/10.1016/S1002-0160(11)60163-X      URL      Magsci      [本文引用: 1]      摘要

Understanding the responses of soil organic carbon (SOC) fractions to altitudinal gradient variation is important for understanding changes in the carbon balance of forest ecosystems. In our study the SOC and its fractions of readily oxidizable carbon (ROC), water-soluble carbon (WSC) and microbial biomass carbon (MBC) in the soil organic and mineral horizons were investigated for four typical forest types, including mixed coniferous broad-leaved forest (MCB), dark coniferous spruce-fir forest (DCSF), dark coniferous spruce forest (DCS), and Ermans birch forest (EB), along an altitudinal gradient in the Changbai Mountain Nature Reserve in Northeast China. The results showed that there was no obvious altitudinal pattern in the SOC. Similar variation trends of SOC with altitude were observed between the organic and mineral horizons. Significant differences in the contents of SOC, WSC, MBC and ROC were found among the four forest types and between horizons. The contents of ROC in the mineral horizon, WSC in the organic horizon and MBC in both horizons in the MCB and EB forests were significantly greater than those in either DCSF or DCS forest. The proportion of soil WSC to SOC was the lowest among the three main fractions. The contents of WSC, MBC and ROC were significantly correlated ( P < 0.05) with SOC content. It can be concluded that vegetation types and climate were crucial factors in regulating the distribution of soil organic carbon fractions in Changbai Mountain.
[43] 高灯州, 曾从盛, 章文龙, .

闽江口湿地土壤有机碳及其活性组分沿水文梯度分布特征

[J]. 水土保持学报, 2014, 28(6): 216-221.

[本文引用: 2]     

[Gao Dengzhou, Zeng Congsheng, Zhang Wenlong et al.

Spatial distributions of soil organic carbon and active composition along a hydrologic gradient in Min River estuarine wetland

. Journal of soil and water conservation, 2014, 28(6): 216-221

[本文引用: 2]     

[44] Sebastian R, Chacko J.

Distribution of organic carbon in tropical mangrove sediments (Cochin, India)

[J]. International Journal Environmental Studies, 2006, 63(3):303-311.

https://doi.org/10.1080/00207230600720498      URL      [本文引用: 1]      摘要

Surficial sediments were sampled every month from three mangrove regions around the metropolis of Cochin (India). Sedimentary organic carbon content exhibited wide seasonal fluctuations. The hydrology of the mangrove system is regulated mainly by high rainfall during the monsoon and by tidal inundation. The results indicated the role of tidal activity and sediment texture in the preservation and retention of organic matter.
[45] Ren H, Chen H, Li Z A.

Biomass accumulation and carbon storage of four different aged Sonneratia apetala plantations in Southern China

[J]. Plant and Soil, 2010, 327(1):279-291.

https://doi.org/10.1007/s11104-009-0053-7      URL      [本文引用: 1]      摘要

The objectives of this study were to examine plant biomass accumulation and carbon (C) storage in four different aged Sonneratia apetala plantations in the Leizhou Bay in South China. The allometric equations using diameter at breast height (DBH) and height (H) were developed to quantify plant biomass. The total forest biomass (TFB) of S. apetala plantation at 4, 5, 8, and 10 years old was 47.9, 71.7, 95.9, and 108.1 Mg ha-1, respectively. The forest biomass C storage in aboveground (AGB) and roots at 4, 5, 8, and 10-year plantation was 19.9, 32.6, 42.0, 49.0 Mg ha-1, respectively. Soil organic C (SOC) on the top 20 cm of sediments increased by 0.3, 6.8, 27.4, and 35.0 Mg ha-1 after 4, 5, 8, and 10 years of reforestation, respectively. The average annual rate of total carbon storage (TCS) accumulation at 4, 5, 8, and 10-year S. apetala plantation was 5.0, 7.9, 8.7, and 8.4 Mg ha-1 yr-1, respectively. The TCS values in this study were underestimated because we only estimated SOC storage on the top 20-cm sediments in these plantations. This study suggests these young S. apetala plantations have the characteristics of fast growth, high biomass accumulation, and high C storage capacity, especially in sediments. They sequestrated C at a high but varying rate over time. The large-scale reforestation of S. apetala plantations in the open coastal mudflats in southern China has great potential to sequestrate more C as well as restore the degraded coastal land. The potential ecological issues associated with the increasing monoculture plantations were discussed. More long-term monitoring and research are needed to further evaluate biomass and C accumulation of S. apetala plantations over time as well as how the increasing distribution of this monoculture plantation will influence the few native mangrove remnants.
[46] Denef K, Six J, Paustian K et al.

Importance of macroaggregate dynamics in controlling soil carbon stabilization: short-term effects of physical disturbance induced by dry-wet cycles

[J]. Soil Biology and Biochemistry, 2001, 33(15): 2145-2153.

https://doi.org/10.1016/S0038-0717(01)00153-5      URL      摘要

Physical protection of soil organic matter by aggregates is considered to be an important mechanism for soil carbon stabilization. In this study, we evaluated the effect of drying and wetting on the interrelationships between macroaggregate formation and degradation (i.e. macroaggregate turnover), microaggregate formation within macroaggregates, and aggregate-associated carbon dynamics. Dry–wet (DW) cycles were used to simulate one of the soil aggregate disruptive effects induced by tillage. A conceptual model developed from long-term no-till (NT) and conventional tilled (CT) field experiments was then used to interpret our results. Sieved (250 μm) air-dried soil samples were taken from Weld silt loam soil (Aridic Paleustoll) that had been cultivated continuously. The samples were mixed with 13C-labeled wheat and incubated for 74 days. One set of soil samples was subjected to four DW cycles, while the other set was kept at field capacity (control). At days 14, 44 and 74, water-stable microaggregates (53–250 μm) held within large macroaggregates (>2000 μm) were isolated. Inter-and intra-microaggregate particulate organic matter (POM) fractions were separated and analyzed for total and wheat-derived C. After two DW cycles (day 44), we observed a significantly lower proportion of water-stable microaggregates within DW macroaggregates compared to control macroaggregates (9 versus 13% of the macroaggregate weight). Simultaneously, DW macroaggregates had significantly lower intra-microaggregate POM-C concentrations compared to control macroaggregates. This difference in intra-microaggregate POM-C between DW and control was more significant for native intra-microaggregate POM-C (0.73 versus 1.03 g kg 611 macroaggregates) ( P<0.05) than for wheat-derived intra-microaggregate POM-C (41 versus 49 mg C kg 611 macroaggregates) ( P<0.1). After two DW cycles (day 44), drying and wetting no longer caused macroaggregate disruption. From day 44 to day 74, both the proportion of microaggregates and the concentration of intra-microaggregate POM-C significantly increased in DW macroaggregates. We conclude that POM-C in new microaggregates within macroaggregates is inhibited by an enhanced macroaggregate turnover, which is only in the short term enhanced by drying and wetting. Furthermore, we suggest that besides a release of total (i.e. native and wheat-derived) POM upon macroaggregate breakdown, drying and wetting induced a fast reformation of macroaggregates with preferential incorporation of wheat-derived POM, resulting in a relative decline of native POM-C in DW macroaggregates.
[47] Song X Y, Spaccini R, Pan G et al.

Stabilization by hydrophobic protection as a molecular mechanism for organic carbon sequestration in maize-amended rice paddy soils

[J]. Science of the Total Environment, 2013, 458:319-330.

https://doi.org/10.1016/j.scitotenv.2013.04.052      URL      PMID: 23669578      摘要

61Four paddy soils were incubated for 180days with and without maize straw addition.61The SOM characterization showed a selective preservation of hydrophobic molecules.61The presence of iron oxyhydrates slackened the decomposition of lignin and lipids.61The amounts of lignin and lipids were closely correlated to the increase of TOC.61Hydrophobic compounds may have a basic role in the OC sequestration in paddy soils.
[48] Wang X, Butterly C R, Baldock et al.

Long-term stabilization of crop residues and soil organic carbon affected by residue quality and initial soil pH

[J]. Science of the Total Environment, 2017, 587:502-509.

https://doi.org/10.1016/j.scitotenv.2017.02.199      URL      摘要

Residues differing in quality and carbon (C) chemistry are presumed to contribute differently to soil pH change and long-term soil organic carbon (SOC) pools. This study examined the liming effect of different crop residues (canola, chickpea and wheat) down the soil profile (0–3002cm) in two sandy soils differing in initial pH as well as the long-term stability of SOC at the amended layer (0–1002cm) using mid-infrared (MIR) and solid-state 13 C nuclear magnetic resonance (NMR) spectroscopy. A field column experiment was conducted for 4802months. Chickpea- and canola-residue amendments increased soil pH at 0–1002cm in the Podzol by up to 0.47 and 0.3602units, and in the Cambisol by 0.31 and 0.1802units, respectively, at 4802months when compared with the non-residue-amended control. The decomposition of crop residues was greatly retarded in the Podzol with lower initial soil pH during the first 902months. The MIR-predicted particulate organic C (POC) acted as the major C sink for residue-derived C in the Podzol. In contrast, depletion of POC and recovery of residue C in MIR-predicted humic organic C (HOC) were detected in the Cambisol within 302months. Residue types showed little impact on total SOC and its chemical composition in the Cambisol at 4802months, in contrast to the Podzol. The final HOC and resistant organic C (ROC) pools in the Podzol amended with canola and chickpea residues were about 25% lower than the control. This apparent priming effect might be related to the greater liming effect of these two residues in the Podzol.
[49] Paradelo R, van Oort F, Barré P et al.

Soil organic matter stabilization at the pluri-decadal scale: Insight from bare fallow soils with contrasting physicochemical properties and macrostructures

[J]. Geoderma, 2016, 275:48-54.

https://doi.org/10.1016/j.geoderma.2016.04.009      URL      摘要

61Physical protection of C was studied in soils from a long-term bare fallow experiment.61Soils with a more stable macrostructure had higher organic matter contents and stocks.61Higher SOM contents are not due to better physical protection at the mm scale.61Differences are due to physicochemical protection in silt- and clay-size fractions.
[50] Poeplau C, Kätterer T, Leblans N I et al.

Sensitivity of soil carbon fractions and their specific stabilization mechanisms to extreme soil warming in a subarctic grassland

[J]. Global Change Biology, 2016, 23(3):1316-1327.

https://doi.org/10.1111/gcb.13491      URL      PMID: 27591579      摘要

Abstract Terrestrial carbon cycle feedbacks to global warming are major uncertainties in climate models. For in-depth understanding of changes in soil organic carbon (SOC) after soil warming, long-term responses of SOC stabilisation mechanisms such as aggregation, organo-mineral interactions and chemical recalcitrance need to be addressed. This study investigated the effect of six years of geothermal soil warming on different SOC fractions in an unmanaged grassland in Iceland. Along an extreme warming gradient of +0 to ~+40°C, we isolated five fractions of SOC that varied conceptually in turnover rate from active to passive in the following order: particulate organic matter (POM), dissolved organic carbon (DOC), SOC in sand and stable aggregates (SA), SOC in silt and clay (SC-rSOC) and resistant SOC (rSOC). Soil warming of 0.6°C increased bulk SOC by 22±43% (0-10 cm soil layer) and 27±54% (20-30 cm), while further warming led to exponential SOC depletion of up to 79±14% (0-10 cm) and 74±8% (20-30) in the most warmed plots (~+40°C). Only the SA fraction was more sensitive than the bulk soil, with 93±6% (0-10 cm) and 86±13% (20-30 cm) SOC losses and the highest relative enrichment in (13) C as an indicator for the degree of decomposition (+1.6±1.5 ‰ in 0-10 cm and +1.3±0.8 ‰ in 20-30 cm). The SA fraction mass also declined along the warming gradient, while the SC fraction mass increased. This was explained by deactivation of aggregate-binding mechanisms. There was no difference between the responses of SC-rSOC (slow-cycling) and rSOC (passive) to warming, and (13) C enrichment in rSOC was equal to that in bulk soil. We concluded that the sensitivity of SOC to warming was not a function of age or chemical recalcitrance, but triggered by changes in bio-physical stabilisation mechanisms, such as aggregation. This article is protected by copyright. All rights reserved.
[51] Han X, Zhao F, Tong X et al.

Understanding soil carbon sequestration following the afforestation of former arable land by physical fractionation

[J]. Catena, 2017, 150:317-327.

https://doi.org/10.1016/j.catena.2016.11.027      URL      摘要

To determine soil organic carbon (SOC) sequestration and storage mechanisms following the afforestation of arable land, soil samples were collected from a depth of 0–10002cm from cropland as well as six hippophae ( Hippophae rhamnoides ) and robinia ( Robinia pseudoacacia ) stands, which represented two afforestation chronosequences that were converted from arable land 13 and 3902yrs ago, respectively, in the Loess Hilly Region of China. The SOC in the whole soil profile was separated into four specific size/density fractions: coarse free (cf) particulate organic carbon (POC) inter-macroaggregates (>0225002μm), fine free POC (ffPOC) inter-microaggregates ?thyc=5?> (53–25002μm), intra–microaggregate POC (iPOC) and mineral–associated organic carbon (MOC) in silt02+02clay (022502yrs02>021302yrs, whereas under the hippophae stands, the order was 3802yrs02=022802yrs02>021302yrs. The concentrations of SOC in all of the fractions in each soil layer were significantly higher under afforested stands relative to cropland, especially in the topsoil layer (0–1002cm). At a soil depth of 0–10002cm, the SOC sequestration rates in the fractions under robinia over 3902yrs were ranked on the order of MOC (0.9402Mg02C02ha 61021 02yr 61021 )02>02iPOC (0.4102Mg02C02ha 61021 02yr 61021 )02>02cfPOC (0.3502Mg02C02ha 61021 02yr 61021 )02>02ffPOC (0.1202Mg02C02ha 61021 02yr 61021 ), whereas the order under hippophae over 3802yrs was MOC (0.2702Mg02C02ha 61021 02yr 61021 )02>02cfPOC (0.1802Mg02C02ha 61021 02yr 61021 )02>02ffPOC (0.0902Mg02C02ha 61021 02yr 61021 )02=02iPOC (0.0702Mg02C02ha 61021 02yr 61021 ). Furthermore, MOC accounted for 47.0% and 52.1% of SOC sequestration under hippophae 3802yrs after afforestation and under robinia 3902yrs after afforestation, respectively. Our results indicate that the afforestation of former arable land with robinia and hippophae in the loess hilly gully region could greatly increase SOC sequestration in all four fractions, especially the MOC.
[52] Fernández-Ugalde O, Gartzia-Bengoetxea N, Arostegi J et al.

Storage and stability of biochar-derived carbon and total organic carbon in relation to minerals in an acid forest soil of the Spanish Atlantic area

[J]. Science of the Total Environment, 2017, 587:204-213.

https://doi.org/10.1016/j.scitotenv.2017.02.121      URL      PMID: 28237467      摘要

61Mineral control on storage of biochar-C and total OC was studied in a forest soil.61A particle-size fractionation was used to separate various silt and clay fractions.61Vermiculitic phases and metallic oxides increased with decreasing clay-size.61Similarly, biochar-C increased with decreasing clay size.61Biochar application reduced total OC in the finest clay fraction.
[53] Jiménez J J, Villar L.

Mineral controls on soil organic C stabilization in alpine and subalpine soils in the Central Pyrenees: Insights from wet oxidation methods, mineral dissolution treatment and radiocarbon dating

[J]. Catena, 2017, 149(1):363-373.

https://doi.org/10.1016/j.catena.2016.10.011      URL      摘要

61Data on SOC concentration, stabilization and radiocarbon age in Central Pyrenees61Old C not preferentially removed by Na2S2O8or H2O2treatments6114C age from 825 at 2200ma.s.l. to 15,700yr BP in higher summit (2800m a.s.l)61Positive association between stable C compounds and mineral phases was demonstrated
[54] Wang H, Liu S R, Mo J M et al.

Soil organic carbon stock and chemical composition in four plantations of indigenous tree species in subtropical China

[J]. Ecological Research, 2010, 25(6):1071-1079.

https://doi.org/10.1007/s11284-010-0730-2      URL      Magsci      摘要

Subtropical China has more than 60% of the total plantation area in China and over 70% of these subtropical plantations are composed of pure coniferous species. In view of low ecosystem services and ecological instability of pure coniferous plantations, indigenous broadleaf plantations are being advocated as a prospective silvicultural management for substituting in place of large coniferous plantations in subtropical China. However, little information is known about the effects of tree species conversion on stock and stability of soil organic carbon (SOC). The four adjacent monospecific plantations were selected to examine the effects of tree species on the stock and chemical composition of SOC using elemental analysis and solid-state 13 C nuclear magnetic resonance (NMR) spectroscopy. One coniferous plantation was composed of Pinus massoniana (PM), and the three broadleaf plantations were Castanopsis hystrix (CH), Michelia macclurei (MM), and Mytilaria laosensis (ML). We found that SOC stock differed significantly among the four plantations in the upper (0–1002cm) layer, but not in the underneath (10–3002cm) layer. SOC stocks in the upper (0–1002cm) layer were 11, 19, and 18% higher in the CH, MM, and ML plantations than in the PM plantation. The differences in SOC stock among the four plantations were largely attributed to fine root rather than aboveground litterfall input. However, the soils in the broadleaf plantations contained more decomposable C proportion, indicated by lower percentage of alkyl C, higher percentage of O -alkyl C and lower alkyl C/ O -alkyl C ratio compared to those in the PM plantation. Our findings highlight that future strategy of tree species selection for substituting in place of large coniferous plantations in subtropical China needs to consider the potential effects of tree species on the chemical composition in addition to the quantity of SOC stock.
[55] Angst Š, Mueller C W, Cajthaml T et al.

Stabilization of soil organic matter by earthworms is connected with physical protection rather than with chemical changes of organic matter

[J]. Geoderma, 2017, 289:29-35.

https://doi.org/10.1016/j.geoderma.2016.11.017      URL      摘要

61Earthworms supported a higher C stock in treatments with clay.61Earthworm and mechanically mixed treatments did not differ in chemical composition.61Stabilization of SOM in earthworm treatments is connected with physical protection.
[56] Cui J, Li Z, Liu Z et al.

Physical and chemical stabilization of soil organic carbon along a 500-year cultived soil chronosequence originating from estuarine wetlands: Temporal patterns and land use effects

[J]. Agriculture, Ecosystems and Environment, 2014, 196:10-20.

https://doi.org/10.1016/j.agee.2014.06.013      URL      摘要

How soil carbon is stabilized during centuries of cultivation and how this would be influenced by land use largely remain unclear. Here the relative role of physical and chemical stabilization mechanisms in agricultural soil organic carbon (SOC) accumulation were studied by fractionation of paddy/upland cropland soils along a 500-year soil chronosequence created by intermittent reclamation of estuarine wetlands. In unreclaimed wetlands, about 50% of SOC was chemically-stabilized by binding to Fe/Al oxyhydrates (mainly amorphous Fe) and 30% by unknown forms of chemical association with silt/clay particles. Physical stabilization of SOC by soil aggregation was negligible in wetlands. After conversion of wetlands to croplands, SOC rapidly declined within the first 16 years and then recovered slowly with cultivation time. Chemical mechanisms still dominated SOC stabilization processes during 500 years of cultivation, but the contribution of Fe/Al-bound and Ca-bound carbon to total SOC decreased with time. The contribution of physically stabilized carbon (i.e. microaggregate-occluded particulate organic carbon, iPOM) to SOC kept around 16% in croplands even when microaggregate contents increased from 8.83% to 30.52% between 16 and 500 years. The iPOM fraction was not closely related to microaggregate formation but to free coarse particulate organic matter, a carbon fraction indicative of inputs of plant materials. Consistently higher SOC density in paddy soils than in upland soils was observed along the chronosequence, which could be accounted for by higher contents of physical and chemical carbon fractions in paddy fields. The higher physically-stabilized carbon of paddy soils probably resulted from larger stubble return rather than from stronger soil aggregation given similar contents of microaggregates between the two cropland types. Notably, in both paddy and upland soils, carbon concentrations of intra-microaggregate silt/clay particles were consistently higher than those of free silt/clay particles. An implication was that despite the small proportion (<20% here) of physically-stabilized carbon to total SOC in croplands, soil aggregation could promote chemical SOC stabilization by creating intimate interactions between occluded carbon and soil minerals within aggregates. To conclude, during five centuries of soil cultivation, chemical carbon stabilization was the dominant mechanism controlling SOC accumulation of paddy/upland croplands but physical occlusion of carbon by aggregation might have promoted chemical stabilization of SOC.
[57] Gleixner G, Poirier N, Bol R et al.

Molecular dynamics of organic matter in a cultivated soil

[J]. Organic Geochemistry, 2002, 33(3): 357-366.

https://doi.org/10.1016/S0146-6380(01)00166-8      URL      [本文引用: 1]      摘要

The dynamics of soil organic carbon are included in global carbon (C) cycle scenarios using different, but generally arbitrary defined, kinetic pools. To improve global C models, better relationships between the chemical structure of soil organic matter (SOM) and its kinetic pools are needed. To assess the molecular residence time of SOM and the relation with plant inputs, pyrolysis–GC/MS–C–IRMS was performed on maize plants and on two samples from the same soil that had undergone a vegetation change from the C3 plant wheat to the C4 plant maize. This vegetation change has added naturally 13C-enriched material to the soil. Most pyrolysis products from the maize were derived from polysaccharides and lignins, and were not detected in soils. However, polysaccharide-derived products were also major pyrolysis products in soils, N-containing or unspecific pyrolysis products were also detected. The residence times (based on 13C natural labelling) revealed a continuum of values, that was independent of chemical structure, with only two pyrolysis products presenting a relatively long residence time (ca. 100 years). An unexpected long life-time for N-containing (6549 years) and polysaccharide-derived (6554 years) pyrolysis products was found. Our results suggest that mainly recycling of carbon in carbohydrates and N-containing materials in addition to physical and chemical protection is responsible for SOM stabilization in the slow carbon pool.
[58] Knicker H.

Stabilization of N-compounds in soil and organic-matter-rich sediments--what is the difference?

[J] Marine Chemistry, 2004, 92(1):167-195.

https://doi.org/10.1016/j.marchem.2004.06.025      URL      [本文引用: 1]      摘要

Most of the organic nitrogen in soils and sediments ultimately derives from living organisms where it is mainly present as peptides and amino acids. These biomolecules are considered to have a biologically labile chemical structure and are expected to be quickly mineralized during early stages of organic matter stabilization. In spite of this, nitrogen is still found in aged soils, recent and even fossilized sediments. To elucidate the nature of this recalcitrant nitrogen and the processes that are involved in its formation, solid-state 15N nuclear magnetic resonance (NMR) spectroscopy was recently introduced into geosciences and applied to various environments differing in the origin of their organic matter precursors as well as in chemical and physical conditions of the environment. Results obtained with this approach indicate that survival of peptide-like structures is a ubiquitous phenomenon, although the mechanisms for their stabilization may differ in different ecological systems. However, a conspicuous change in organic nitrogen composition is observed in fossilized sediments and for organic matter formed by vegetation fires. Cyclization and rearrangement of peptide structures result in the formation of heteroaromatic N during fossilization, which was not detected for recent sediments and soils. From this, it may be concluded that such compounds are only formed in environments in which abiotic transformation of biogenic precursors dominates over biotic degradation.
[59] Wattel-Koekkoek E J W, Buurman P, Van Der Plicht J et al.

Mean residence time of soil organic matter associated with kaolinite and smectite

[J]. European Journal of Soil Science, 2003, 54(2):269-278.

https://doi.org/10.1046/j.1365-2389.2003.00512.x      URL      [本文引用: 1]      摘要

To gain insight into the effect of clay mineralogy on the turnover of organic matter, we analysed the 14 C activity of soil organic matter associated with clay in soils dominated by kaolinite and smectite in natural savanna systems in seven countries. Assuming that carbon inputs and outputs are in equilibrium in such soils, we took the 14 C age as mean residence time of the organic matter. We corrected the 14 C activity for the Suess effect, Bomb effect and difference between date of sampling and date of 14 C measurement. Organic matter associated with kaolinite turned over fast (360 years on average). Organic matter associated with smectite turned over relatively slowly, with an average mean residence time for the whole clay-size fraction of 1100 years. Multiple linear regression indicates that clay mineralogy is the main factor explaining differences in the mean residence time of the organic matter extracted.
[60] Kleber M, Mikutta R, Torn M S et al.

Poorly crystalline mineral phases protect organic matter in acid subsoil horizons

[J]. European Journal of Soil Science, 2005, 56(6):717-725.

https://doi.org/10.1111/j.1365-2389.2005.00706.x      URL      [本文引用: 1]      摘要

Soil minerals are known to influence the biological stability of soil organic matter (SOM). Our study aimed to relate properties of the mineral matrix to its ability to protect organic C against decomposition in acid soils. We used the amount of hydroxyl ions released after exposure to NaF solution to establish a reactivity gradient spanning 12 subsoil horizons collected from 10 different locations. The subsoil horizons represent six soil orders and diverse geological parent materials. Phyllosilicates were characterized by X-ray diffraction and pedogenic oxides by selective dissolution procedures. The organic carbon (C) remaining after chemical removal of an oxidizable fraction of SOM with NaOCl solution was taken to represent a stable organic carbon pool. Stable organic carbon was confirmed as older than bulk organic carbon by a smaller radiocarbon ( 14 C) content after oxidation in all 12 soils. The amount of stable organic C did not depend on clay content or the content of dithionite itrate-extractable Fe. The combination of oxalate-extractable Fe and Al explained the greatest amount of variation in stable organic C ( R 2 = 0.78). Our results suggest that in acid soils, organic matter is preferentially protected by interaction with poorly crystalline minerals represented by the oxalate-soluble Fe and Al fraction. This evidence suggests that ligand exchange between mineral surface hydroxyl groups and negatively charged organic functional groups is a quantitatively important mechanism in the stabilization of SOM in acid soils. The results imply a finite stabilization capacity of soil minerals for organic matter, limited by the area density of reactive surface sites.
[61] Han L, Sun K, Jin J et al.

Some concepts of soil organic carbon characteristics and mineral interaction from a review of literature

[J]. Soil Biology and Biochemistry, 2016, 94:107-121.

https://doi.org/10.1016/j.soilbio.2015.11.023      URL      [本文引用: 1]      摘要

61We identified the uncertainties in examining dynamics of specific SOC fractions.61Mineralogy, SOC species and soil condition affect organo-mineral complex formation.61Different-sized minerals possibly protect different SOC species.61Limitations of13C and14C-dating techniques were identified.
[62] Six J, Conant R T, Paul E A et al.

Stabilization mechanisms of soil organic matter: implications for C-saturation of soils

[J]. Plant and Soil, 2002, 241(2):155-176.

https://doi.org/10.1023/A:1016125726789      URL      Magsci      [本文引用: 1]      摘要

The relationship between soil structure and the ability of soil to stabilize soil organic matter (SOM) is a key element in soil C dynamics that has either been overlooked or treated in a cursory fashion when developing SOM models. The purpose of this paper is to review current knowledge of SOM dynamics within the framework of a newly proposed soil C saturation concept. Initially, we distinguish SOM that is protected against decomposition by various mechanisms from that which is not protected from decomposition. Methods of quantification and characteristics of three SOM pools defined as protected are discussed. Soil organic matter can be: (1) physically stabilized, or protected from decomposition, through microaggregation, or (2) intimate association with silt and clay particles, and (3) can be biochemically stabilized through the formation of recalcitrant SOM compounds. In addition to behavior of each SOM pool, we discuss implications of changes in land management on processes by which SOM compounds undergo protection and release. The characteristics and responses to changes in land use or land management are described for the light fraction (LF) and particulate organic matter (POM). We defined the LF and POM not occluded within microaggregates (53 250 m sized aggregates as unprotected. Our conclusions are illustrated in a new conceptual SOM model that differs from most SOM models in that the model state variables are measurable SOM pools. We suggest that physicochemical characteristics inherent to soils define the maximum protective capacity of these pools, which limits increases in SOM (i.e. C sequestration) with increased organic residue inputs.
[63] Lützow M V, Kögel-Knabner I, Ekschmitt K et al.

Stabilization of organic matter in temperate soils: mechanisms and their relevance under different soil conditions-a review

[J]. European Journal of Soil Science, 2006, 57(4):426-445.

https://doi.org/10.1111/j.1365-2389.2006.00809.x      URL      [本文引用: 1]      摘要

Mechanisms for C stabilization in soils have received much interest recently due to their relevance in the global C cycle. Here we review the mechanisms that are currently, but often contradictorily or inconsistently, considered to contribute to organic matter (OM) protection against decomposition in temperate soils: (i) selective preservation due to recalcitrance of OM, including plant litter, rhizodeposits, microbial products, humic polymers, and charred OM; (ii) spatial inaccessibility of OM against decomposer organisms due to occlusion, intercalation, hydrophobicity and encapsulation; and (iii) stabilization by interaction with mineral surfaces (Fe-, Al-, Mn-oxides, phyllosilicates) and metal ions. Our goal is to assess the relevance of these mechanisms to the formation of soil OM during different stages of decomposition and under different soil conditions. The view that OM stabilization is dominated by the selective preservation of recalcitrant organic components that accumulate in proportion to their chemical properties can no longer be accepted. In contrast, our analysis of mechanisms shows that: (i) the soil biotic community is able to disintegrate any OM of natural origin; (ii) molecular recalcitrance of OM is relative, rather than absolute; (iii) recalcitrance is only important during early decomposition and in active surface soils; while (iv) during late decomposition and in the subsoil, the relevance of spatial inaccessibility and organo-mineral interactions for SOM stabilization increases. We conclude that major difficulties in the understanding and prediction of SOM dynamics originate from the simultaneous operation of several mechanisms. We discuss knowledge gaps and promising directions of future research.
[64] Kang Y, Zhang Z, Shi H et al.

Na+ and K+ ion selectivity by size-controlled biomimetic graphene nanopores

[J]. Nanoscale, 2014, 6(18), 10666-10672.

https://doi.org/10.1039/c4nr01383b      URL      PMID: 25089590      Magsci      [本文引用: 1]      摘要

Because biological ionic channels play a key role in cellular transport phenomena, they have attracted extensive research interest for the design of biomimetic nanopores with high permeability and selectivity in a variety of technical applications. Inspired by the structure of K+channel proteins, we designed a series of oxygen doped graphene nanopores of different sizes by molecular dynamics simulations to discriminate between K+and Na+channel transport. The results from free energy calculations indicate that the ion selectivity of such biomimetic graphene nanopores can be simply controlled by the size of the nanopore; compared to K+, the smaller radius of Na+leads to a significantly higher free energy barrier in the nanopore of a certain size. Our results suggest that graphene nanopores with a distance of about 3.9 between two neighboring oxygen atoms could constitute a promising candidate to obtain excellent ion selectivity for Na+and K+ions.
[65] Lim C, Dudev T.

Potassium versus sodium selectivity in monovalent ion channel selectivity filters

[M]//In the alkali metal ions: Their role for life. Springer International Publishing, 2016: 325-347.

[本文引用: 1]     

[66] Zhang X, Huang C, Jin X.

Influence of K+ and Na+ ions on the degradation of wet-spun alginate fibers for tissue engineering

[J]. Journal of Applied Polymer Science, 2017, 134(2):1-8.

https://doi.org/10.1002/app.44396      URL      [本文引用: 1]      摘要

A synthetic type of wet‐spun alginate fibers were immersed in simulated body fluid(SBF) composed of K, Na, and Cacations with various concentrations. Experimental measurements revealed that Nahad a greater impact on degradability than that of Kion. The finding was further confirmed by the characterization of mass loss, ICP, XRD, and theoretical analyses. The degradation process and mechanism were demonstrated through the research on swelling behavior and mass loss. Besides, the wet‐spun alginate fibers were characterized by FT‐IR, XRD, and SEM. The results showed that the degradation mechanism could be attributed to the ion‐exchange between Caof the synthetic alginate fibers and Na, Kof the solutions under the osmotic pressure. The synthetic fibers were swelled and then degraded faster with the presence of Naion presented greater influence on degradability compared with Kion. The degradation results of a mechanical rupture of fibers due to excessive water uptake without the occurrence of any chemical changes in the spun alginates structure. 08 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 133, 44396.
[67] Bronick C J, Lal R.

Soil structure and management: a review

[J]. Geoderma, 2005, 124(1): 3-22.

https://doi.org/10.1016/j.geoderma.2004.03.005      URL      [本文引用: 2]      摘要

Soil structure exerts important influences on the edaphic conditions and the environment. It is often expressed as the degree of stability of aggregates. Aggregation results from the rearrangement, flocculation and cementation of particles. It is mediated by soil organic carbon (SOC), biota, ionic bridging, clay and carbonates. The complex interactions of these aggregants can be synergistic or disruptive to aggregation. Clay-sized particles are commonly associated with aggregation by rearrangement and flocculation, although swelling clay can disrupt aggregates. Organo-metallic compounds and cations form bridges between particles. The SOC originates from plants, animals and microorganisms, and their exudates. It enhances aggregation through the bonding of primary soil particles. The effectiveness of SOC in forming stable aggregates is related to its decomposition rate, which in turn is influenced by its physical and chemical protection from microbial action. Soil inorganic carbon (SIC) increases aggregation in arid and semi-arid environments, and the formation of secondary carbonates is influenced by the presence of SOC and Ca 2+ and Mg 2+. Soil biota release CO 2 and form SOC which increase dissolution of primary carbonates while cations increase precipitation of secondary carbonates. The precipitation of (hydr)oxides, phosphates and carbonates enhances aggregation. Cations such as Si 4+, Fe 3+, Al 3+ and Ca 2+ stimulate the precipitation of compounds that act as bonding agents for primary particles. Roots and hyphae can enmesh particles together while realigning them and releasing organic compounds that hold particles together, a process with a positive impact on soil C sequestration. Soil structure can be significantly modified through management practices and environmental changes. Practices that increase productivity and decrease soil disruption enhance aggregation and structural development.
[68] Zhang S, Wang R, Yang X et al.

Soil aggregation and aggregating agents as affected by long term contrasting management of an Anthrosol

[J]. Scientific Reports, 2016, 6:1-11.

https://doi.org/10.1038/srep39107      URL      PMID: 27958366      [本文引用: 1]      摘要

Abstract Soil aggregation was studied in a 21-year experiment conducted on an Anthrosol. The soil management regimes consisted of cropland abandonment, bare fallow without vegetation and cropping system. The cropping system was combined with the following nutrient management treatments: control (CONTROL, no nutrient input); nitrogen, phosphorus and potassium (NPK); straw plus NPK (SNPK); and manure (M) plus NPK (MNPK). Compared with the CONTROL treatment, the abandonment treatment significantly increased the formation of large soil macroaggregates (>265mm) and consequently improved the stability of aggregates in the surface soil layer due to enhancement of hyphal length and of soil organic matter content. However, in response to long-term bare fallow treatment aggregate stability was low, as were the levels of aggregating agents. Long term fertilization significantly redistributed macroaggregates; this could be mainly ascribed to soil organic matter contributing to the formation of 0.5-265mm classes of aggregates and a decrease in the formation of the >265mm class of aggregates, especially in the MNPK treatment. Overall, hyphae represented a major aggregating agent in both of the systems tested, while soil organic compounds played significantly different roles in stabilizing aggregates in Anthrosol when the cropping system and the soil management regimes were compared.
[69] Asano M, Wagai R.

Evidence of aggregate hierarchy at micro-to submicron scales in an allophanic Andisol

[J]. Geoderma, 2014, 216: 62-74.

https://doi.org/10.1016/j.geoderma.2013.10.005      URL      [本文引用: 1]      摘要

61Strong evidence of aggregate hierarchy in Andisol was shown for the first time.61Clay-sized particles accounted for roughly half of total C and soil solid volume.61Amorphous clay, N-rich OM and organo-metal complex were enriched in these particles.61These organo-mineral particles contributed to both micro- and macro-aggregation.61A conceptual model of aggregate hierarchy for Andisol was proposed.
[70] Zhang X C, Norton L D.

Effect of exchangeable Mg on saturated hydraulic conductivity, disaggregation and clay dispersion of disturbed soils

[J]. Journal of Hydrology, 2002, 260(1):194-205.

https://doi.org/10.1016/S0022-1694(01)00612-6      URL      [本文引用: 1]      摘要

Different opinions exist regarding the specific effect of Mg on soil physical and chemical properties. We hypothesized that Mg 2+, compared with Ca 2+, reduces saturated hydraulic conductivity ( K s) via promoting clay swelling, disaggregation, and clay dispersion. Two soils (mixed, mesic Typic Hapludalfs) in packed soil columns were leached with either Ca- or Mg-containing solutions at the successive concentrations of 250, 10, 2, 0.5, and 0 mM. Critical flocculation concentration (CFC) in either Ca or Mg systems was determined with flocculation series tests. Aggregate stability and mean weight diameter (MWD) were assessed by wet-sieving. The CFCs were higher in Mg than in Ca for both soils, indicating that Mg is more dispersive than Ca. The MWDs measured using 1–2 mm aggregates of both soils were significantly larger for Ca-soils than for Mg-soils ( P=0.05). The K sr (normalized with initial K s) started to decline at higher concentrations for Mg than for Ca, and the reduction was much greater in Mg than in Ca above 0.5 mM. The K sr and percent transmittance (inversely related to turbidity) of leachate at a given eluted pore volume following ‘steady state’ were higher in Ca than in Mg for both soils ( P=0.1), indicating lower permeability and more clay dispersion with the Mg treatment. Swelling and disaggregation, which reduced large pores, appeared to be the dominant process causing the rapid initial decline of K sr. Clay dispersion and subsequent pore plugging became progressively important when electrolyte concentration was reduced to below CFCs.
[71] Mavi M S, Sanderman J, Chittleborough D J et al.

Sorption of dissolved organic matter in salt-affected soils: Effect of salinity, sodicity and texture

[J]. Science of the Total Environment, 2012, 435: 337-344.

https://doi.org/10.1016/j.scitotenv.2012.07.009      URL      PMID: 22863809      [本文引用: 1]      摘要

78 We studied the interactive effect of salinity and sodicity on DOC sorption in soils varying in texture. 78 DOC losses from saline–sodic soils will be lower than sodic soils due to cation bridging at high electrolyte concentration. 78 DOC sorption in salt-affected soils is more strongly controlled by CEC and Fe/Al concentration than by clay concentration.
[72] Amezketa E.

Soil aggregate stability: a review

[J]. Journal of Sustainable Agriculture, 1999, 14(2-3): 83-151.

https://doi.org/10.1300/J064v14n02_08      URL      [本文引用: 1]      摘要

Soil aggregate stability is a crucial soil property affecting soil sustainability and crop production. A broad outline of the processes and agents of aggregate formation and aggregate stabilization are presented and discussed in this review. Aggregate stability is difficult to quantify and interpret. The aim of aggregate stability tests is to give a reliable description and ranking of the behavior of soils under the effect of water, wind and management. Numerous methods have been used to determine aggregate stability with varying success. The different methodologies complicate the comparison among aggregate stability data. It is also difficult to obtain a consistent correlation between aggregate stability and other important soil properties such as soil erodibility or crusting potential. This paper reviews the different methods of measurement of soil aggregate stability used in the literature, paying attention to the conditions of sample collection in the field and sample preparation and treatments in the laboratory. A unified methodological framework including the most interesting aspects of existing methods is suggested. The possibility of using aggregate stability data as an estimation of soil erodibility is also discussed.
[73] Wang R, Dungait J A, Buss H L et al.

Base cations and micronutrients in soil aggregates as affected by enhanced nitrogen and water inputs in a semi-arid steppe grassland

[J]. Science of the Total Environment, 2017, 575:564-572.

https://doi.org/10.1016/j.scitotenv.2016.09.018      URL      PMID: 27613671      [本文引用: 1]      摘要

61Higher base cations were detected in microaggregates compared to macroaggregates.61Nitrogen addition decreased effective cation exchange capacity in macroaggregates.61Nitrogen addition decreased Ca and Mg but increased extractable Fe, Mn and Cu.61Water addition increased exchangeable Na while decreased available Fe and Mn.
[74] Sinsabaugh R L, Manzoni S, Moorhead D L et al.

Carbon use efficiency of microbial communities: stoichiometry, methodology and modelling

[J]. Ecology Letters, 2013, 16(7): 930-939.

https://doi.org/10.1111/ele.12113      URL      PMID: 23627730      Magsci      [本文引用: 1]      摘要

Carbon use efficiency (CUE) is a fundamental parameter for ecological models based on the physiology of microorganisms. CUE determines energy and material flows to higher trophic levels, conversion of plant-produced carbon into microbial products and rates of ecosystem carbon storage. Thermodynamic calculations support a maximum CUE value of ~ 0.60 (CUE max). Kinetic and stoichiometric constraints on microbial growth suggest that CUE in multi-resource limited natural systems should approach ~ 0.3 (CUE max/2). However, the mean CUE values reported for aquatic and terrestrial ecosystems differ by twofold (~ 0.26 vs. ~ 0.55) because the methods used to estimate CUE in aquatic and terrestrial systems generally differ and soil estimates are less likely to capture the full maintenance costs of community metabolism given the difficulty of measurements in water-limited environments. Moreover, many simulation models lack adequate representation of energy spilling pathways and stoichiometric constraints on metabolism, which can also lead to overestimates of CUE. We recommend that broad-scale models use a CUE value of 0.30, unless there is evidence for lower values as a result of pervasive nutrient limitations. Ecosystem models operating at finer scales should consider resource composition, stoichiometric constraints and biomass composition, as well as environmental drivers, to predict the CUE of microbial communities.
[75] Bandick A K, Dick R P.

Field management effects on soil enzyme activities

[J]. Soil biology and biochemistry, 1999, 31(11):1471-1479.

https://doi.org/10.1016/S0038-0717(99)00051-6      URL      [本文引用: 1]      摘要

There is growing recognition for the need to develop sensitive indicators of soil quality that reflect the effects of land management on soil and assist land managers in promoting long-term sustainability of terrestrial ecosystems. Eleven soil enzymes assays were investigated relative to soil management and soil quality at two study sites. Soils were sampled from the Vegetable Crop Rotation Plots (VRP) (established in 1989 in humid western Oregon) which compared continuous fescue (Festuca arundinacea) and four winter cover crop treatments in annual rotation with a summer vegetable crop. The second site was the Residue Utilization Plots (RUP) (initiated in 1931 in semi-arid Eastern Oregon) which is under a winter wheat-summer fallow and compared inorganic N, green manure and beef manure treatments. Soil also was sampled at the research center from a nearby grass pasture that is on the same soil type. The enzymes were - and -glucosidase, - and -galactosidase, amidase, arylsulfatase, deaminase, fluorescein diacetate hydrolysis, invertase, cellulase and urease. At both sites there was a significant treatment effect for each enzyme tested (P<0.05). Enzyme activities (except - and -glucosidase and - and -galactosidase) were generally higher in continuous grass fields than in cultivated fields. In cultivated systems, activity was higher where cover crops or organic residues were added as compared to treatments without organic amendments. It was found that use of air-dried soil samples provided the same ranking of treatments by a number of enzyme assays and would facilitate adoption of these assays for practical or commercial applications. Deaminase was not a good indicator of soil quality, while -glucosidase was suggested as an assay that reflects soil management effects and has microbial ecological significance because of its role in the C cycle.
[76] Schmidt M W, Torn M S, Abiven S et al.

Persistence of soil organic matter as an ecosystem property

[J]. Nature, 2011, 478(7367):49-56.

https://doi.org/10.1038/nature10386      URL      PMID: 21979045      [本文引用: 1]      摘要

Abstract Globally, soil organic matter (SOM) contains more than three times as much carbon as either the atmosphere or terrestrial vegetation. Yet it remains largely unknown why some SOM persists for millennia whereas other SOM decomposes readily--and this limits our ability to predict how soils will respond to climate change. Recent analytical and experimental advances have demonstrated that molecular structure alone does not control SOM stability: in fact, environmental and biological controls predominate. Here we propose ways to include this understanding in a new generation of experiments and soil carbon models, thereby improving predictions of the SOM response to global warming.
[77] Ström L, Christensen T R.

Below ground carbon turnover and greenhouse gas exchanges in a sub-arctic wetland

[J]. Soil Biology and Biochemistry, 2007, 39(7): 1689-1698.

https://doi.org/10.1016/j.soilbio.2007.01.019      URL      [本文引用: 1]      摘要

Here we present results from a field experiment in a sub-arctic wetland near Abisko, northern Sweden, where the permafrost is currently disintegrating with significant vegetation changes as a result. During one growing season we investigated the fluxes of CO 2 and CH 4 and how they were affected by ecosystem properties, i.e., composition of species that are currently expanding in the area ( Carex rotundata, Eriophorum vaginatum and Eriophorum angustifolium), dissolved CH 4 in the pore water, substrate availability for methane producing bacteria, water table depth, active layer, temperature, etc. We found that the measured gas fluxes over the season ranged between: CH 4 0.2 and 36.1 mg CH 4 m 612 h 611, Net Ecosystem Exchange (NEE) 611000 and 1250 mg CO 2 m 612 h 611 (negative values meaning a sink of atmospheric CO 2) and dark respiration 110 and 1700 mg CO 2 m 612 h 611. We found that NEE, photosynthetic rate and CH 4 emission were affected by the species composition. Multiple stepwise regressions indicated that the primary explanatory variables for NEE was photosynthetic rate and for respiration and photosynthesis biomass of green leaves. The primary explanatory variables for CH 4 emissions were depth of the water table, concentration of organic acid carbon and biomass of green leaves. The negative correlations between pore water concentration and emission of CH 4 and the concentrations of organic acid, amino acid and carbohydrate carbon indicated that these compounds or their fermentation by-products were substrates for CH 4 formation. Furthermore, calculation of the radiative forcing of the species expanding in the area as a direct result of permafrost degradation and a change in hydrology indicate that the studied mire may act as an increasing source of radiative forcing in future.

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