神祥金
, 周道玮, 李飞
SHEN Xiang-jin, ZHOU Dao-wei, LI Fei
中图分类号: TP79
文献标识码: A
文章编号: 1000-0690(2015)05-0622-08
通讯作者:
收稿日期: 2014-01-12
修回日期: 2014-03-20
网络出版日期: 2015-05-20
版权声明: 2015 《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.
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作者简介:
作者简介：神祥金（1987-）,男,山东沂水人,博士研究生,主要从事生态气候研究。E-mail:shenxiangjin@iga.ac.cn
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摘要
利用1982~2006年GIMMS NDVI和气象数据,探究中国草原区植被变化及对气候的响应。结果表明,近25 a中国草原区植被覆盖总体呈上升趋势,但季节变化空间差异明显。春季温度对温带典型草原、高寒草甸草原和高寒典型草原植被生长有重要影响,而夏季和秋季温度同样对高寒草甸草原影响显著;夏季降水增多能明显促进夏季温带荒漠草原植被生长。除8月份以外,温带草原5~9月NDVI均与前一个月降水显著正相关;在生长季内,高寒草原NDVI与同期温度显著正相关,但8月份除外。此外高寒草原植被在生长最旺盛时期对降水变化存在1~3个月滞后期。
关键词：
Abstract
This study analyzed the variation trend of vegetation NDVI and its response to climate change in grassland region of China by employing MODIS NDVI and meteorological data from1982 to 2006. Trend analysis, correlation analysis and spatial statistical analysis were carried out to investigate variation characteristics and spatial distribution pattern of vegetation NDVI, and analyze the relations between vegetation NDVI and meteorological factors. For temperate grassland region of China, growing season NDVI decreased gradually from northeast to southwest, and the grassland types from northeast to southwest are temperate meadow, temperate typical grassland and temperate desert grassland. For alpine grassland region of China, growing season NDVI was smaller overall than that of temperate grassland region, and it decreased on the whole from east to west, with the largest values concentrating in the east alpine meadow grassland. The results indicated that growing season NDVI increased on the whole in recent 25 years, but the spatial differences of seasonal changes were obvious. The largest increase of monthly NDVI occurred in August for temperate grassland region and in July for alpine grassland region. In the aspect of climate change, temperature showed obvious increase trend in the whole grassland region of China, while precipitation changes were not significant. For temperate grassland, spring temperature played an important impact on the vegetation growth of temperate typical grassland. The increase of summer precipitation could obviously promote the vegetation growth of temperate desert grassland. Monthly correlation analyses results showed that temperate grassland vegetation NDVI was significantly positively correlated with temperature in April, and May NDVI was significantly positively correlated with temperature in March and April. By contrast, the increase of June temperature could inhibit the growth of temperate grassland plants during the same period. In terms of precipitation, temperate grassland vegetation NDVI was significantly positively correlated with the previous month's precipitation (except August). April NDVI was significantly negatively correlated with precipitation in February, indicating that the low temperature in February could limit the growth of temperate grassland at the beginning of the growing season. Precipitation in June and July was significant for temperate grassland vegetation growth during the same time period, and the effect of August precipitation on vegetation growth was remarkable in September and October. For alpine grassland, spring temperature played an important impact on the vegetation growth of alpine meadow grassland and alpine typical grassland; summer and autumn temperatures had significant effect on alpine meadow grassland vegetation growth. Monthly correlation analyses results showed that monthly (April to October ) alpine grassland vegetation NDVI was significantly positively related to the air temperature during the same time period (except August), and temperature in August could affect alpine grassland vegetation growth in September. In addition, during the most vigorous growth period, alpine grassland vegetation had a time lag of 1-3 months for precipitation.
Keywords：
全球变化与陆地生态系统（GCTE）是全球变化研究中的重要内容,气候变化对陆地生态系统的影响及其反馈是目前科学领域研究的重点问题[1]。植被作为生态系统重要组成部分,能在一定程度上代表土地覆盖的变化,并对全球变化起到指示作用[2]。归一化植被指数(NDVI)作为反映地表植被生长状况与覆盖变化的敏感度量参数,是公认的可以定量表征植被生长状态的有效指标[3]。
草地是地球上主要的生物群落之一,覆盖了陆地表面近1/5的区域,草地植被对气候变化响应敏感[4],在全球变化研究中有重要的地位。根据中国植被区划,中国草原区包括温带草原区和高寒草原区。前者连续分布于松辽平原、内蒙高原和黄土高原,小部分在新疆阿尔泰山区,植被类型主要包括温带草甸草原、典型草原和荒漠化草原。后者主要位于青藏高原,主要包括高寒草甸草原、典型草原。以往关于中国草地植被变化及对气候响应的研究多局限在温带或高寒草原区某一区域范围,或某一植被类型,对整个温带和高寒草原区研究较少,而将两个草原区结合在一起来探究中国草原区植被变化的研究,目前尚未见类似报道。
本文通过利用1982~2006年GIMMS NDVI数据和气象数据,分别在生长季尺度,季节尺度和月尺度上,分析了中国草原区NDVI变化及与气象因子的关系,以期为中国草原区植被变化研究,草地生态系统对气候变化响应研究提供科学依据,并进一步为中国草原区生态环境建设、生物多样性保护及中国草地资源可持续利用提供决策支持。
本文NDVI数据,是由美国GLCF(Global Land Cover Facility)研究组生产的1982~2006年GIMMS NDVI半月数据,空间分辨率8 km×8 km。气象数据是由国家气象中心提供的草原区108个气象站点及其附近11个气象站点的1982~2006年逐月平均气温,降水观测数据。
本文的植被数据来自中国科学院中国植被图编辑委员会2001年编制的1∶100万中国植被图和1∶600万中国植被区划图,在数字化和属性添加基础上,制作成中国草原植被区分布及植被类型图（图1）。以气象站所在位置为中心,选取站点周边10 km×10 km区域的平均NDVI值代表各气象站点对应的NDVI值,将植被类型图与气象站点图进行叠加,对站点进行半径为10 km的缓冲区分析,选取缓冲区中所占面积较大者作为该站点对应草原植被类型。
图1 中国草原植被区分布及植被类型
Fig. 1 Spatial distribution and vegetation types of grassland region in China
本文将温带草原生长季定义为4~10月,将高寒草原生长季定义为5~9月。为便于分析比较,将月尺度研究选在4~10月,并将4~5月作为春季,6~8月作为夏季,9~10月作为秋季[5]。本文采用相关分析法研究植被NDVI与气候因子之间的关系;利用基于像元的一元线性回归分析[6,7],通过回归方程的斜率来表示植被NDVI的变化,斜率为正值表示植被NDVI随时间变化而升高,负值表示下降,绝对值越大表明变化幅度越大;在空间相关分析时,首先对气象数据进行普通克里格插值,得到与NDVI影像相同分辨率的栅格图层,再对NDVI与气象因子进行逐像元相关分析[8],以相关系数大小来反映植被NDVI与气象因子相关程度。
从草原区生长季NDVI与气象因子变化结果（图2）可以看出,近25 a温带草原区与高寒草原区生长季NDVI呈现增长趋势,变化均达到显著水平（p值分别为0.018和0.022）,表明中国草原区植被生长状况总体变好。在生长季尺度,中国草原区气温呈现明显上升趋势（p=0.000）,其中温带草原区气温升幅为0.586℃/10 a,高寒草原区升幅为0.427℃/10 a,这可作为北半球升温的又一例证;降水在温带草原区呈现下降趋势（p=0.155）,而在高寒草原区为上升趋势（p=0.588）,但两者变化均不显著。
从草原区生长季平均NDVI空间分布（图3a）可以看出,温带草原区生长季平均NDVI由东北向西南逐渐降低,植被类型依次为温带草甸草原、典型草原和荒漠草原,这与许旭等[9]得出内蒙古地区温带草原植被平均盖度大小的空间分布相一致。
图2 草原区生长季NDVI、气温和降水变化
Fig.2 Changes of NDVI, temperature and precipitation in grassland region of China in growing season
图3 草原区植被生长季NDVI平均值及季节变化
Fig.3 Spatial pattern of average NDVI in growing season and seasonal variation in grassland region of China
此外,高寒草原区生长季NDVI较温带草原区整体偏小,总体由东向西逐渐降低,最高值集中在东部高寒草甸草原。
植被空间变化方面,草原区植被NDVI季节变化空间差异明显（图3b~e）。在整个生长季,除了高寒草原区中西部及温带草原区东北局部出现轻微下降以外,草原区NDVI总体呈现增长趋势。在不同季节,松嫩平原春季NDVI明显下降,而在秋季呈现明显上升趋势,这可能与该地区大面积草地被开垦成农田有关[10]。在呼伦贝尔草原区,春季NDVI呈现上升趋势,而在夏秋季节呈现下降趋势,从而使得整个生长季平均NDVI变化不明显,这与之前许多研究相一致[11,12]。高寒草原区各季节NDVI明显上升处集中在青海省与四川省交界的高寒草甸草原地区,且只在春季位于青藏高原中部高寒典型草原与高寒草甸草原交汇地区出现明显下降（图3c）,这与Piao等[13]研究发现青藏高原中部春季NDVI明显下降的结果相一致。
1） 整个区域相关性分析。温带草原生长季NDVI与降水显著正相关,而高寒草原生长季NDVI与生长季温度和降水相关性均不显著（表1）。春季温度与两个草原区春季NDVI显著正相关,表明温度是影响春季草原植被生长的关键因素,此外秋季温度还会显著影响秋季高寒草原植被生长。降水方面,温带草原夏季NDVI与降水呈显著正相关,表明夏季降水增多能够明显促进夏季温带草原植被的生长。李霞等[14]利用像元分析发现降水,尤其是夏季降水对北方草原植被生长影响显著;杨元合等[15]研究发现青藏高原草地植被NDVI与降水无显著相关性,而春、秋季NDVI与温度显著正相关;本文研究结果与以上结论相一致。
表1 生长季和各季节NDVI与气候因子相关系数
Table 1 Correlation coefficient between growing season or seasonal NDVI and climate variables
| 生长季温度 | 生长季降水 | 春季温度 | 春季降水 | 夏季温度 | 夏季降水 | 秋季温度 | 秋季降水 | |
|---|---|---|---|---|---|---|---|---|
| 温带草原 | 0.177 | 0.513** | 0.573** | 0.303 | -0.025 | 0.473* | 0.309 | 0.022 |
| 高寒草原 | 0.120 | -0.324 | 0.467* | -0.360 | 0.357 | -0.313 | 0.607** | 0.166 |
2） 空间相关性分析。不同季节植被NDVI与温度、降水相关性空间结果（图4）表明,春季温度对高寒草原植被影响的区域差异较小,而对温带草原植被影响最显著地区集中在松嫩平原以西的温带典型草原地区（图4a）;秋季温度与高寒草原秋季NDVI正相关分布较为均匀,相关系数较大值位于青海省高寒草甸草原地区（图4e）;夏季降水对温带草原植被生长影响显著区集中在西部温带荒漠草原地区（图4d）,表明夏季降水能显著促进温带荒漠草原植被夏季生长。尽管在整个温带草原区相关性不显著（表1）,但春季降水与高寒草原NDVI总体呈现负相关,与温带典型草原NDVI呈现明显正相关（图4b）;夏季温度与温带草原NDVI总体呈现负相关,而与高寒草原NDVI总体呈现正相关,负相关区域集中在西藏那曲县,日喀则市与拉萨市境内（图4c）;秋季降水与两个草原区秋季NDVI的正负相关比例接近,且相关系数值较小,使得秋季降水对草原植被生长总体影响较弱（图4f）。
图4 草原区各季节NDVI与温度、降水相关系数的空间分布
a、b. 春季; c、d. 夏季; e、f. 秋季
Fig.4 Spatial pattern of correlation coefficient between seasonal NDVI and temperature, precipitation in grassland region of China
3） 不同植被类型对相关性影响。为避免气象数据插值对相关性带来的不确定影响,本文基于气象站点及其对应的植被类型,来对草原区不同类型植被生长季、季节（春、夏、秋）NDVI与气象因子相关性进行了分析。分析结果（表2）表明,温带典型草原春季NDVI与温度显著正相关,这一结果与逐像元空间相关分析结果（图4a）相吻合,在一定程度上证明了本文通过气象数据插值来运算相关性的可信性;在整个区域相关分析中,我们已发现生长季内降水尤其是夏季降水对温带草原植被生长产生重要影响（表1）,通过基于站点的不同类型植被分析,进一步发现温带典型草原与温带荒漠草原夏季降水对夏季植被生长产生重要影响（表2）,其中温带荒漠草原植被与降水的相关性最强,这说明水分是干旱的荒漠草原地区植被生长重要的限制因子,而温带草甸草原区由于降水充足,水分条件不足以成为植被生长的限制性因子,水分过多甚至可能对植被生长产生抑制作用[9]。
与整个区域分析结果（表1）一致,降水对高寒草原植被生长影响不大,而春季和秋季温度对高寒草原植被生长产生重要影响,但高寒典型草原秋季NDVI与温度相关性不显著（表2）。此外高寒草甸草原夏季NDVI还与夏季温度显著正相关,表明在整个生长季节内,温度一直作为高寒草甸草原生长的关键因素,较高的温度更利于高寒草甸草原植被的生长。
表2 不同类型植被NDVI与气候因子的相关系数
Table 2 Correlation coefficient between NDVI and climate variables for different vegetation types
| 生长季温度 | 生长季降水 | 春季温度 | 春季降水 | 夏季温度 | 夏季降水 | 秋季温度 | 秋季降水 | |
|---|---|---|---|---|---|---|---|---|
| 温带典型草原 | 0.052 | 0.650** | 0.644** | 0.368 | -0.157 | 0.411* | 0.282 | 0.166 |
| 温带草甸草原 | -0.070 | -0.036 | 0.286 | 0.011 | -0.140 | -0.217 | 0.069 | -0.345 |
| 温带荒漠草原 | -0.046 | 0.676** | -0.343 | 0.212 | -0.013 | 0.529** | -0.210 | 0.083 |
| 高寒典型草原 | 0.255 | -0.330 | 0.408* | 0.372 | 0.309 | -0.387 | 0.324 | -0.148 |
| 高寒草甸草原 | 0.461** | -0.180 | 0.623** | -0.335 | 0.580** | -0.301 | 0.615** | 0.331 |
基于月尺度分析结果（图5）表明,草原区NDVI均在8月达到最大,月均NDVI只在温带草原区的6月及在高寒草原区5月和10月呈现轻微下降趋势,其余逐月NDVI均呈现上升趋势;温带草原NDVI在8月升幅（2.5×10-3/a）最大,而高寒草原在7月升幅（1.1×10-3/a）最大。气温方面,两个草原区温度均在7月达到最大,与生长季尺度气温变化一致,两个草原区逐月气温均呈现上升趋势;温带草原区气温上升率在9月（0.089℃/a）最大,而高寒草原区在4月（0.062℃/a）最大,上述结果表明中国草原区气温升高已是不争的事实,这与以往研究相一致[1]。降水方面,两个草原区降水量均在7月达到最大,但降水变化差异明显：温带草原区逐月（4~10月）降水均呈现下降趋势,但并不显著（p>0.05）;高寒草原区降水在7、9月呈现下降趋势,在其他月呈现上升趋势,但只有5月变化达到显著水平（p=0.03）。
图5 草原区植被逐月NDVI、气温和降水变化
Fig.5 Changes of monthly NDVI, temperature and precipitation in grassland region of China
气温、降水不仅能影响植被当前生长状况,还可能存在一定的时滞性[16,17,18]。本文将逐月（4~10月）NDVI分别与同期、前1个月、前2个月、前3个月温度和降水进行相关分析。
在气温影响方面（表3）,温带草原4月NDVI与同期温度显著正相关,而5月NDVI对气温存在时滞性,分别与前一个月和前两个月温度显著正相关,表明温带草原生长季初期气温对植被生长产生较大影响,这与之前对呼伦贝尔草地植被变化研究结论相一致[11];此外温带草原6月NDVI与同期温度显著负相关,表明6月气温升高会阻碍植被生长,这与许旭[9]等发现内蒙古温带草原6月植被盖度与当月气温呈显著负相关相吻合。与温带草原不同,高寒草原逐月NDVI均与同期温度呈显著正相关（8月份除外）,9月植被对温度存在一个月的时滞性,使得8月温度仍会对9月植被生长产生影响（表3）。高寒草原区位于青藏高原,海拔较高,气温较低,温度成为制约高寒草原植被生长的关键因素;8月高寒草原区气温较高,草原植被生长最为旺盛,植被绿度达到最大（图5）,气温变化对同期植被生长影响较小,又由于温度驱动下的热量累积同样会对植物生长产生影响,8月温度仍对9月植被生长产生了影响。
表3 草原区植被逐月NDVI与气象因子的相关性分析
Table 3 Correlation between monthly NDVI and climate variables in grassland region of China
| 温带草原区 | 4月 | 5月 | 6月 | 7月 | 8月 | 9月 | 10月 |
|---|---|---|---|---|---|---|---|
| 同期温度 | 0.423* | 0.205 | -0.454* | 0.025 | 0.013 | 0.118 | 0.239 |
| 前1个月温度 | 0.065 | 0.492* | -0.371 | -0.040 | 0.213 | -0.154 | 0.161 |
| 前2个月温度 | 0.205 | 0.517** | -0.077 | -0.078 | 0.291 | -0.007 | -0.217 |
| 前3个月温度 | 0.173 | 0.311 | -0.114 | 0.056 | 0.080 | 0.131 | -0.091 |
| 同期降水 | -0.056 | 0.141 | 0.422* | 0.490* | -0.067 | -0.133 | 0.322 |
| 前1个月降水 | -0.169 | 0.428* | 0.431* | 0.412* | 0.340 | 0.408* | 0.102 |
| 前2个月降水 | -0.448** | 0.310 | 0.162 | 0.304 | 0.169 | 0.131 | 0.485* |
| 前3个月降水 | -0.206 | -0.008 | 0.359 | 0.155 | 0.013 | -0.001 | 0.368 |
| 高寒草原区 | 4月 | 5月 | 6月 | 7月 | 8月 | 9月 | 10月 |
| 同期温度 | 0.501* | 0.493* | 0.438* | 0.466* | 0.120 | 0.524** | 0.485* |
| 前1个月温度 | 0.214 | 0.140 | 0.226 | -0.014 | 0.298 | 0.437* | 0.272 |
| 前2个月温度 | 0.212 | -0.136 | 0.240 | -0.066 | -0.319 | 0.163 | -0.168 |
| 前3个月温度 | 0.056 | -0.014 | -0.210 | 0.163 | -0.350 | -0.086 | 0.045 |
| 同期降水 | -0.317 | -0.302 | -0.058 | -0.303 | -0.324 | 0.097 | -0.297 |
| 前1个月降水 | 0.106 | -0.303 | 0.015 | 0.115 | -0.221 | 0.500* | 0.164 |
| 前2个月降水 | -0.137 | 0.204 | -0.158 | 0.494* | 0.011 | -0.078 | 0.259 |
| 前3个月降水 | 0.049 | 0.175 | -0.063 | 0.199 | 0.451* | 0.013 | -0.163 |
在降水影响方面（表3）,温带草原区4月NDVI与2月降水呈显著负相关,这可能由于2月降水量增多意味着草原区降雪增多,温度偏低,4月正值温带草本植物萌芽期,积温对该阶段植被生长意义重大[11],2月较低的温度可能影响到植物萌芽所需积温,从而对植被生长产生不利影响。本文发现,温带草原5~9月NDVI均与前一个月降水显著正相关,但8月份除外,这可能是由于8月温带草原生长最为旺盛,绿度已达到峰值（图5）,此时降水的变化对植被生长影响不大[19]。本文结果与张戈丽等[11]研究得出呼伦贝尔草原5~8月植被生长分别与前一月降水关系密切略有不同,这可能是由于本文研究范围是整个温带草原区的缘故。除了存在时滞性,6、7月植被NDVI还与同期降水显著正相关,表明在6、7月的温带草原植被生长对同期降水量需求较高;此外8月降水还影响到9、10月温带草原植被的生长,这与李霞等[16]研究得出在北方温带草原生长季中后期,当月和前1、2个月降水对植被生长具有重要影响的结论相吻合。在高寒草原区,尽管在整个生长季和季
节尺度上植被NDVI与降水无明显相关性（表1,2）,但7、8月NDVI与5月降水,9月NDVI与8月降水均呈现明显正相关,表明高寒草原植被在生长最旺盛的3个月份（图5）对降水存在1~3个月的滞后期。由于高寒草原植被在5月进入生长初期[15],5月降水必然会对植物后期生长产生重要的影响;在8月份高寒草原植物生长最为旺盛,同期降水对植被生长影响不大,但对9月植被生长影响显著。
1） 草原区植被状况方面,温带草原区生长季平均NDVI由东北向西南逐渐降低,植被类型依次为温带草甸草原、典型草原和荒漠草原。高寒草原区生长季NDVI总体由东向西逐渐降低,最高值集中在东部高寒草甸草原。
2） 草原区植被变化方面,近25 a中国草原区植被覆盖总体呈上升趋势,但季节变化空间差异明显;松嫩平原NDVI在春季呈明显下降趋势,而在秋季呈上升趋势。呼伦贝尔草原区春季NDVI呈上升趋势,而夏季和秋季NDVI呈下降趋势。高寒草原NDVI只在春季位于青藏高原中部地区出现明显下降。
3） 气温对草原植被影响方面,温带草原生长季初期温度对植被生长影响较大,但6月气温的升高会阻碍植被生长。在整个生长季内,温度一直作为高寒草甸草原生长的关键因素,较高的温度更利于高寒草甸草原植被的生长。而在高寒草原植物生长最为旺盛的8月,气温对同期植被生长影响不大,但8月气温会对9月植被生长产生影响。
4） 降水对草原植被影响方面,夏季降水对温带荒漠草原植被生长有明显促进作用。温带草原2月降水对4月植被生长有抑制作用,5~9月NDVI均与前一个月降水显著正相关（8月除外）,8月降水能够影响9和10月植被生长。除了存在时滞性,温带草原植被6、7月生长对同期降水需求较高。此外高寒草原植被在生长最旺盛的时期对降水变化存在1~3个月的滞后期。
The authors have declared that no competing interests exist.
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气候变化对中国北方荒漠草原植被的影响 [J].https://doi.org/10.3321/j.issn:1001-8166.2002.02.015 URL Magsci [本文引用: 2] 摘要
气候变化对陆地生态系统的影响及其反馈是全球变化研究的焦点之 一.利用气候变量实现对遥感植被指数所表示的植被绿度信息的模拟,可以尝试作为表达生物圈过去和未来状态的一种途径.利用1961-2000年的气温、降 水和1983-1999年的NOAA/AVHRR资料,分析了中国北方地带性植被类型荒漠草原植被分布区的短尺度气候的年际和季节变化,及其对植被的影 响.结果表明,过去40年中该区域年际气候变化表现为增温和降水波动.年NDVI的最大值(NDVImax)可以较好地反映气候的变化,过去17年中 NDVImax出现的时间略有提前.综合分析NDVI、植被盖度、NPP、区域蒸散量、土壤含水量及其气候的年际变化,表明增温加剧了土壤干旱化,降水和 土壤含水量仍是制约本区植被生长的根本原因.
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多时相AVHRR-NDVI数据的时间序列分析及其在土地覆盖分类中的应用[D] . |
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The relationship between NDVI and precipitation on the Tibetan Plateau [J].https://doi.org/10.1007/s11442-007-0259-7 URL Magsci [本文引用: 1] 摘要
The temporal and spatial changes of NDVI on the Tibetan Plateau, as well as the relationship between NDVI and precipitation, were discussed in this paper, by using 8-km resolution multi-temporal NOAA AVHRR-NDVI data from 1982 to 1999. Monthly maximum NDVI and monthly rainfall were used to analyze the seasonal changes, and annual maximum NDVI, annual effective precipitation and growing season precipitation (from April to August) were used to discuss the interannual changes. The dynamic change of NDVI and the correlation coefficients between NDVI and rainfall were computed for each pixel. The results are as follows: (1) The NDVI reached the peak in growing season (from July to September) on the Tibetan Plateau. In the northern and western parts of the plateau, the growing season was very short (about two or three months); but in the southern, vegetation grew almost all the year round. The correlation of monthly maximum NDVI and monthly rainfall varied in different areas. It was weak in the western, northern and southern parts, but strong in the central and eastern parts. (2) The spatial distribution of NDVI interannual dynamic change was different too. The increase areas were mainly distributed in southern Tibet montane shrub-steppe zone, western part of western Sichuan-eastern Tibet montane coniferous forest zone, western part of northern slopes of Kunlun montane desert zone and southeastern part of southern slopes of Himalaya montane evergreen broad-leaved forest zone; the decrease areas were mainly distributed in the Qaidam montane desert zone, the western and northern parts of eastern Qinghai-Qilian montane steppe zone, southern Qinghai high cold meadow steppe zone and Ngari montane desert-steppe and desert zone. The spatial distribution of correlation coefficient between annual effective rainfall and annual maximum NDVI was similar to the growing season rainfall and annual maximum NDVI, and there was good relationship between NDVI and rainfall in the meadow and grassland with medium vegetation cover, and the effect of rainfall on vegetation was small in the forest and desert area.
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Grassland responses to three years of elevated temperature,CO2,precipitation,and N deposition [J].https://doi.org/10.1890/02-4053 URL [本文引用: 1] 摘要
Global climate and atmospheric changes may interact in their effects on the diversity and composition of natural communities. We followed responses of an annual grassland to three years of all possible combinations of experimentally elevated CO(2) (+300, muL/L), warming (+80 W/m(2), + similar to1degreesC), nitrogen deposition (+7 g N.m(-2).yr(-1)),and precipitation (+50%). Responses of the 10 most common plant species to global changes and to interannual variability were weak but sufficiently consistent within functional groups to drive clearer responses at the functional group level. The dominant functional groups (annual grasses and forbs) showed distinct production and abundance responses to individual global changes. After three years, N deposition suppressed plant diversity, forb production, and forb abundance in association with enhanced grass production. Elevated precipitation enhanced plant diversity, forb production, and forb abundance but affected grasses little. Warming increased forb production and abundance but did not strongly affect diversity or grass response. Elevated CO(2) reduced diversity with little effect on relative abundance or production of forbs and grasses. Realistic combinations of global changes had small diversity effects but more marked effects on the relative dominance of forbs and grasses. The largest change in relative functional group abundance (+50% forbs) occurred under the combination of elevated CO(2) + warming + precipitation, which will likely affect much of California in the future. Strong interannual variability in diversity, individual. species abundances, and functional group abundances indicated that in our system, (1) responses after three years were not constrained by lags in community response, (2) individual species were more sensitive to interannual variability and extremes than to mean changes in environmental and resource conditions, and (3) simulated global changes interacted with interannual variability to produce responses of varying magnitude and even direction among years. Relative abundance of forbs, the most speciose group in the community, ranged after three years from >30% under elevated CO(2) + warming + precipitation to <12% under N deposition: While opposing production responses at the ecosystem level by different functional groups may buffet responses such as net primary production (NPP) change, these shifts in relative dominance could influence ecosystem processes such as nutrient cycling and,NPP via differences between grasses and forbs in tissue chemistry, allocation, phenology, and productivity.
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NDVI-based increase in growth of temperate grasslands and its responses to climate changes in China [J].https://doi.org/10.1016/j.gloenvcha.2006.02.002 URL [本文引用: 1] 摘要
This study analyzes the temporal change of Normalized Difference Vegetation Index (NDVI) for temperate grasslands in China and its correlation with climatic variables over the period of 1982–1999. Average NDVI of the study area increased at rates of 0.5%02yr 611 for the growing season (April–October), 0.61%02yr 611 for spring (April and May), 0.49%02yr 611 for summer (June–August), and 0.6%02yr 611 for autumn (September and October) over the study period. The humped-shape pattern between coefficient of correlation ( R ) of the growing season NDVI to precipitation and growing season precipitation documents various responses of grassland growth to changing precipitation, while the decreased R values of NDVI to temperature with increase of temperature implies that increased temperature declines sensitivity of plant growth to changing temperature. The results also suggest that the NDVI trends induced by climate changes varied between different vegetation types and seasons.
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1982~2010 年中国东北地区植被 NPP 时空格局及驱动因子分析 [J].
<p>应用逐像元线性回归模型方法, 整合应用MODIS和AVHRR NDVI数据集, 构建1982~2010 年覆盖东北地区的8 km 空间分辨率的NDVI 数据集, 进而应用CASA模型估算得到东北地区29 a NPP 数据集, 模拟精度在75%以上。29 a 平均的东北地区植被NPP总量为6.5×10<sup>8</sup> tC/a。植被NPP的分布受植被类型、气候、地形因素的综合影响。NPP地域差异明显, 山地区植被>平原区植被>高原区植被,变化最大的植被类型为草地植被。过去29 a间, 植被NPP呈显著上升趋势(<em>P</em><0.01)。气候变化和土地利用变化均是影响植被时空格局的重要因素。</p>
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青藏高原植被覆盖变化的地域分异特征 [J].https://doi.org/10.11820/dlkxjz.2009.03.010 URL Magsci [本文引用: 1] 摘要
植被的空间分布及其变化都具有明显的地域分异特征。本研究以1981-2006年间的GIMMS/NDVI产品为主要数据源,在地理信息系统技术的支持下,分别从植被空间分布、植被波动和植被变化等方面,探讨了青藏高原植被覆盖变化的水平地域分异特征。研究结果显示,1981-2006年间,雅鲁藏布江河谷区、错那县和墨脱县的西北部、柴达木盆地南缘、三江源地区的顶端和青海南山北麓等区域地表植被年际波动较大。反映区域植被盖度时间变化趋势的SLOPE值以及植被盖度,具有从南部、东南部向北、西北部"下降—上升—不变"的规律。植被盖度下降显著的区域主要分布在喜马拉雅山南麓和青海湖南部,其次是三江源中南部地区;植被没有明显变化的区域主要分布在藏北高原和柴达木盆地。植被指数显著上升的区域集中在雅鲁藏布江河谷区,植被指数明显上升区域主要分布在人迹罕至的唐古拉山和念青唐古拉山等山间盆地区,轻微上升的区域分散在明显改善区的周围。依据SLOPE值的空间分异特征将整个高原划分为4个一级区:帕米尔高原植被指数上升区、藏北高原—阿里高原—柴达木盆地植被指数稳定区、高原中部—雅鲁藏布江中上游河谷植被指数上升区和三江源—横断山区植被指数下降区。
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| [8] |
近10年蒙古高原植被覆盖变化及其对气候的季节响应 [J].
利用2001~2010年间 MODIS NDVI数据、同期气象数据和MODIS土地覆盖分类产品,探讨蒙古高原植被覆盖变化趋势及其对气温和降水量的季节响应特征。结果表明,10 a来,蒙古高原植被覆盖度呈增加趋势和呈下降趋势的面积基本持平;春季和夏季植被覆盖度呈下降趋势,而秋季呈上升趋势,降水量是最主要的影响因子;在秋季 5种植被类型均呈增加趋势,而在春季和夏季不同植被类型的增减趋势因植被类型而异。
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| [9] |
内蒙古温带草原区植被盖度变化及其与气象因子的关系 [J].
利用1982-1999年内蒙 古地区NOAA/AVHRR的NDVI数字遥感影像,对内蒙古温带草原区植被盖度进行了反演,探讨了近20a来温带草原植被盖度的变化情况,并对植被盖度 与不同组合方式的降水及气温数据进行了相关分析,探讨了植被盖度与气象因子的关系。结果表明:①近20a来温带草原植被盖度呈上升趋势,占总面积72%的 草原植被盖度发生了增长,3种不同草原类型中典型草原盖度上升趋势最为明显;②温带草原生长季平均盖度、逐月盖度与降水成正相关关系,与气温呈负相关关 系,其中降水对盖度的影响存在着时滞及累积效应;③3种草原类型植被盖度对气象因子的敏感性不同,荒漠草原植被盖度与气温和降水相关性最强,其次为典型草 原与草甸草原。
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| [10] |
Shrinkage and fragmentation of grasslands in the West Songnen Plain,China [J].https://doi.org/10.1016/j.agee.2008.10.009 URL [本文引用: 1] 摘要
In the past century, especially the past five decades, the grasslands of the West Songnen Plain, Northeast China, were rapidly converted into croplands and salinized wasteland, and experienced a fragmentation process that is still ongoing. Almost no information is available on the spatial-temporal changes of grasslands in this area. In this study, grassland cover change, agricultural reclamation and salinized wasteland expansion were investigated during the past five decades. Grassland fragmentation was studied based on four landscape metrics. The grassland cover change was detected from a time series of topographic maps from 1954, satellite images of Landsat TM in 1986, 1995, and 2000 using remote sensing and geographic information systems (GIS). In addition, the land use changes were analyzed using a transition matrix of land use types, while the driving forces were explored according to climatic changes and socioeconomic developments. The results indicated a significant decrease in grassland area. Of the 1418945ha of native grassland in 1954, approximately 64% was removed by 2000, while the number of patches (NP) increased from 865 to 2035 and the mean patch size (MPS) decreased from 1640ha to 252ha. During the whole study period, the average annual decrease rate of grassland was 34894ha/year. Cropland and salinized wasteland were the two main land use types into which grassland converted. During the past decades, obvious climatic changes occurred, which supplied a favorable potential environment for agricultural development but damaged grassland productivity. On the other hand, population, GDP and livestock number increased significantly as grassland quality decreased. According to the results, the shrinkage and fragmentation of grasslands may well be explained by socioeconomic development and aided by changing climatic conditions.
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| [11] |
近30 年来呼伦贝尔地区草地植被变化对气候变化的响应 [J].
基于1981-2006 年的GIMMS NDVI数据和2000-2009 年的MODIS NDVI数据反演呼伦贝尔地区草地变化，结合1981-2009 年该地区7 个气象站点的气温和降水数据，分别从年际变化、季节变化和月变化角度分析该地区草地变化对气候变化的响应。结果表明，从年际变化来看，降水是驱动草地植被年际变化的主要因素；从季节变化来看，草地植被生长在不同季节对水热条件变化的敏感性不同，春季草地植被生长对气温变化的敏感性较降水变化高，夏季和秋季草地植被的生长对降水变化的敏感性则高于对气温变化的敏感性，其中以夏季最为显著；从月变化来看，4 月和5 月草地植被变化受气温变化影响较明显；5-8 月与前一月降水变化关系密切，说明植被生长对降水变化具有一定的滞后性；4 月正值草本植物萌芽期，而4 月份草地生长与年气温变化关系最为密切，一定程度上说明4 月份表征植被生长的NDVI值增加可能是由于气候变暖引起的草地植被生长季提前产生的。综上所述，通过植被与气候要素月变化的关系可以具体地揭示气温和降水对草地植被生长的季节韵律控制。
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| [12] |
基于生态分区的内蒙古地区植被覆盖变化及其影响因素研究 [J].
基于GIMMS数据和MODIS数据反演1982～2011年内蒙古生长季NDVI，分析内蒙古不同生态区内NDVI变化时空特征，探讨自然和人为因素对NDVI的影响。结果表明：30a来内蒙古生长季平均NDVI整体呈增加趋势，分布在呼伦贝尔、锡林郭勒典型草原的部分地区NDVI有下降趋势。大部分地区NDVI与年降水量呈显著相关，与温度的相关性不显著；近30a人类活动对植被NDVI的影响程度逐渐增强，其中人类活动在西辽河平原、大兴安岭南端草原区以及华北山地落叶阔叶林区促进植被生长，在内蒙古东北部草原区抑制植被生长。
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| [13] |
Interannual variations of monthly and seasonal normalized difference vegetation index (NDVI) in China from 1982 to 1999 [J].https://doi.org/10.1029/2002JD002848 URL [本文引用: 1] 摘要
ABSTRACT 1] In this paper, we analyzed interannual variations of normalized difference vegetation index (NDVI) and their relationships with climatic variables (temperature and precipitation) and human activity in China between 1982 and 1999. Monthly and seasonal NDVI increased significantly at both the country and biome scales over the study period. NDVI shows the largest increase (14.4% during the 18 years and a trend of 0.0018 yr À1) over 85.9% of the total study area in spring and the smallest increase (5.2% with a trend of 0.0012 yr À1) over 72.2% of the area in summer. The NDVI trends show a marked heterogeneity corresponding to regional and seasonal variations in climates. There is about a 3-month lag for the period between the maximum trend in temperature (February) and that in NDVI (April or May) at the country and biome scales. Human activity (urbanization and agricultural practices) also played an important role in influencing the NDVI trends over some regions. Rapid urbanization resulted in a sharp decrease in NDVI in the Yangtze River and Pearl River deltas, while irrigation and fertilization may have contributed to the increased NDVI in the North China plain.
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气候变化对中国北方温带草原植被的影响 [J].https://doi.org/10.3321/j.issn:0476-0301.2006.06.019 URL [本文引用: 1] 摘要
在月、季节、生长季和年4个时间尺度上,采用Krigging空 间插值方法对1982-1999年的降水、气温数据插值生成栅格影像,将其与1982-1999年的NOAA/AVHRR NDVI影像进行相关分析.同时,综合分析了归一化差值植被指数(normalized differential vegetation index,NDVI)、降水、气温、区域潜在蒸散量、区域实际蒸散量的年际季节变化.结果表明,降水是制约本区植被生长的根本原因,夏季降水量对植被生 长的影响最为显著,7-8月份的降水对下月植被的生长有重要的影响.同时得出中国北方温带草原植被与气象因子相关性的空间分布图.
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青藏高原草地植被覆盖变化及其与气候因子的关系 [J].https://doi.org/10.17521/cjpe.2006.0001 URL Magsci [本文引用: 2] 摘要
？为揭示气候变化对青藏高原草地生态系统的影响及其生态适应机制，利用1982～1999年间的NOAA/AVHRR？NDVI数据和对应的气候资料，研究了近20年来青藏高原草地植被覆盖变化及其与气候因子的关系。结果表明，18年来研究区生长季NDVI显著增加(p=0.015)，其增加率和增加量分别为0.41%a－1和0.0010a－1。生长季提前和生长季生长加速是青藏高原草地植被生长季NDVI增加的主要原因。春季为NDVI增加率和增加量最大的季节，其增加率和增加量分别为0.92%a－1和0.0014a－1；夏季NDVI的增加对生长季NDVI增加的贡献相对较小，其增加率和增加量分别为0.37%a－1和0.0010a－1。3种草地(高寒草甸、高寒草原、温性草原)春季NDVI均显著增加(p<0.01;p=0.001;p=0.002);高寒草甸夏季NDVI显著增加(p=0.027)，而高寒草原和温性草原夏季NDVI呈增加趋势，但都不显著(p=0.106;p=0.087)；3种草地秋季NDVI则没有明显的变化趋势(p=0.585;p=0.461;p=0.143)。3种草地春季NDVI的增加是由春季温度上升所致。高寒草地(高寒草甸和高寒草原)夏季NDVI的增加是夏季温度和春季降水共同作用的结果。温性草原夏季NDVI变化与气候因子并没有表现出显著的相关关系。高寒草地植被生长对气候变化的响应存在滞后效应。
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中国北方草原植被对气象因子的时滞响应 [J].https://doi.org/10.17521/cjpe.2007.0133 URL Magsci [本文引用: 2] 摘要
利用1982~1997年的气 温、降水和1983~1997年生长季的NOAA/AVHRR的归一化植被指数(Normalized differential vegetationindex,NDVI)遥感数据,分析了中国北方温带草原植被生长对气象因子的时滞响应。根据4个时间尺度(1~4个月)和4个时滞 期(前0~3个月)将降水数据进行16种组合方式,计算了植被的NDVI与同期及前期(前1~6个月)降水之间的相关系数。同时,计算了植被的NDVI与 同期和前一个月气温之间的相关系数。结果表明:1)中国北方温带草原植被的NDVI与同期降水和气温的显著相关。2)植被的NDVI对前一个月降水的时滞 响应最强烈,植被的NDVI与当月降水和前两个月降水的累积量相关性最强。3)在生长季的起始阶段,去冬、今春的降水总量对草甸草原植被的生长有重要的作 用。在生长季的中期和后期,当月和前一、二个月的降水对典型草原和荒漠草原的植被有显著影响。4)在草甸草原、典型草原区,生长季早期的气温均对植被生长 的影响较为显著。在荒漠草原区,气温不仅在生长季初期与植被的NDVI呈现正相关,而且在生长季的中后期,气温与植被的NDVI呈现负相关性。
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中国东部植被NDVI对气温和降水的旬响应特征 [J].
<p>利用中国东部SPOT VGT-NDVI数据和气象站点的日平均气温和降水资料，分析了1998-2007年中国东部植被NDVI在全年、春季、夏季和秋季对气温和降水变化的旬时空响应特征。结果表明，中国东部植被总体上对气温变化的响应大于降水，植被对气温变化的最大响应滞后1旬左右，对降水变化的最大响应滞后3旬左右。秋季植被NDVI对气温和降水变化响应最大，夏季NDVI对气温和降水响应的滞后期较长。在空间上，植被对气温变化的最大响应总体表现为北部和中部大于南部，对降水变化的最大响应表现为北部大于中部和南部。植被对气温变化最大响应的滞后期呈现出北部较长—中部短—南部最长的空间分布，对降水变化最大响应的滞后期则随着纬度降低由北到南逐渐延长。</p>
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青藏高原春季植被变化特征及其对夏季气温的影响 [J].https://doi.org/10.3969/j.issn.1000-0690.2008.02.023 URL Magsci [本文引用: 1] 摘要
分析1982～2001年NDVI和青藏高原地区台站气温资料,得到结论：近20年来春季高原植被总体呈明显的增加趋势,其中以高原北部、西北部和南部日喀则附近地区的植被增加最明显。高原NDVI与季节同期和滞后的气温以正相关为主。春季NDVI与滞后0～3季气温都表现为正相关,尤以高原春季NDVI与夏季气温的相关更为显著。高原春季NDVI如果处于异常偏小（或偏大）状态,同时高原的北部和中西部是较明显的NDVI负距平（或正距平）分布时,则高原地区夏季气温具有整体上（或大部分地区）偏低（或偏高）的倾向,平均气温和最高气温在高原西部和北部表现明显,对最低气温的影响的关键区位于高原的中南部和东南部。
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中国北方草原对气候干旱的响应 [J].https://doi.org/10.3321/j.issn:1000-0933.2008.01.020 URL Magsci [本文引用: 1] 摘要
草原生长动态受气候条件的影响和制约，在很大程度上取决于水分条件。为了较好阐明草原生长与干旱气候关系，利用表征草原生长变化的ndvi（normalized？difference？vegetation？index）指数和表征干旱的spi（standardized？precipitation？index）指数研究了荒漠草原、典型草原、草甸草原与干旱气候的线性关系，表明荒漠草原的生长动态受季节性干旱影响很大，短期、中长期和长期干旱对荒漠草原影响较小。典型草原对季节性干旱响应较强，而对短期、中长期和长期的干旱响应较弱。草甸草原对季节性和长期干旱响应较强。并且草原对降雨量的响应具有时滞效应，水分盈亏对草原的影响是累积效应。利用基于虚拟变量的回归模型和简单回归模型模拟了草原ndvi对spi指数的响应关系，基于虚拟变量的回归模型显示出对草原ndvi与spi关系的较优拟合度。表明了草原生长动态对干旱气候响应具有季节性效应。
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