根据咸阳庞西村苹果林地、梧桐林地和草地土壤含水量测定,研究了0~6m土壤含水量的变化和土壤干层特点与分布。结果显示, 咸阳人工林地从表层向下含水量呈现由高到低再到低的变化;10龄苹果林地2~4m深处土壤含水量平均为8.3%,12龄梧桐林2~4m深处土壤含水量平均为8.6%,均发育了明显的土壤干层;4龄苹果林下土层有干化显示,但无干层发育;草地土层含水量明显较苹果林地高,无土壤干化的显示。研究表明,土壤干层形成的具体原因一是降水量少决定的薄膜水带埋藏深度小,二是薄膜水的运移速度缓慢和含水量低。为保持人工林基本正常的生长和土壤水的正常运移,应避免严重的土壤干层出现。咸阳附近土壤干层的出现表明土壤干层在黄土高原广泛分布,该区的植被恢复首先应以疏林或森林草原为主,待土壤水分改善后再考虑恢复森林植被。
According to soil moisture content determination of apple forest land and the Chinese parasol forest land at Pangxi and Dongshi villages in Xianyang, the change of 0-6-m soil moisture content and the characteristic and the distribution of dry soil layers were studied in this paper. The result shows that the soil moisture content in 6-m soil profile under artificial forest in Xianyang is high in the upper layer and becomes low in the middle and then become high in the lower layer; mean soil moisture content is 13.2% in 0-1-m earth layer under 10-year apple forest, 8.3% in 2-4-m earth layer, and 10.8% in the 4-6-m earth layer. Mean soil moisture content under Chinese parasol trees forest grown for 12 years is 12.8% in 0-1-m earth, 8.6% in 2-4-m earth layer, and 12.2% in the 4-6-m deep earth layer. Mean soil moisture content is 12.4% in 0-1-m earth layer under 4-year apple forest, 11.9% in 1-4-m earth layer, and 13.6% in the 4-6-m earth layer. Mean soil moisture content is 12.3% in 0-1-m earth layer under grassland, 13.2% in 1-4-m earth layer, and 14.5% in the 4-6-m earth layer. The change of the above mentioned indicates that, dried soil layer develops in 2-4-m earth layer under 10-year apple forest and 12-year Chinese parasol trees forest; soil drying also occurs in 2-4-m under 4-year apples forest, but has no the development of dry soil layer. The soil moisture content is obviously higher in grassland than in the apple forest land, soil drying does not occur in grassland. The research result indicated that one of development causes of dry soil layer is that burial depth of film water belt is small, which is decided by the a little precipitation; anthor is slowly moving speed of the film water and low moisture content. In order to maintain normal growth of the artificial forest and the normal circulation of soil water, we should avoid the development of serious dry soil layer. The development of the obvious dry soil layer nearby Xianyang indicates that the soil drying layer is distributed widespread in the Loess Plateau, and the vegetation reconstruction in this area should first develop the thin forest or the forest-steppe, then restore the forest vegetation after the soil moisture improvement. Taking the project measure and improving soil structure, enhancing soil permeability, also can increase burial depth of film water belt and reduces the development intensity of dry soil layer.
[1] 姜逢清,朱 诚,穆桂金,等.新疆当代人地关系紧张情势与缓解途径[J].地理科学,2003, 23(2): 157~163.
[2] 蒙吉军,李正国.河西走廊张掖绿洲LUCC的驱动力分析[J].地理科学,2003, 23(4): 467~470.
[3] 李香云,王立新,章予舒,等.西北干旱区土地荒漠化中人类 活动作用及其指标选择[J].地理科学, 2004, 24(1):68~ 75.
[4] 杨维西. 试论我国北方地区人工植被的土壤干化问题[J]. 林业科学,1996, 32 (1): 78~85.
[5] 侯庆春. 黄土高原地区小老树成因及其改造途径的研究[J]. 水土保持学报,1991, 5(2):76~83.
[6] 赵景波, 侯甬坚, 黄春长. 黄土高原土壤干化原因及防治[J]. 中国沙漠, 2003, 23 (6): 612~615.
[7] 李玉山. 黄土区土壤水循环特征及其对陆地水循环的影响[J]. 生态学报, 1983, 3(2): 91~101.
[8] Ole Wendroth. Observations of measured soil hydraulic properites from laboratory tension disc infiltrometer experiments[J]. Water Resource Research, 1998, 34 (9): 2191-2202.
[9] Yuin E. An infiltration model to predict suction changes in the soil profile[J]. Water Resource Research, 1998, 34 (7): 1617-1622.
[10] Nassar I N. Thermally induced water movement in uniform clay soil[J]. Soil Science, 1996, 161(8): 471-479.
[11] Rapp I. Evaporation and crust imperdance role in seeding emergence[J]. Soil Science, 2000, 165 (4): 354-364.
[12] 王孟本. 黄土区土壤水分循环水平研究[J]. 水土保持学报,1995, 9 (4) : 106~108.
[13] 陈云明, 侯喜禄, 刘文兆. 黄土丘陵半干旱区不同类型植被水保生态效益研究[J]. 水土保持学报, 2000, 14 (3): 57~62.
[14] 黄明斌, 样新民, 李玉山. 黄土区渭北旱塬苹果基地对区域水循环的影响[J]. 地理学报, 2001, 56 (1): 7~13.
[15] 王 力, 邵明安, 侯庆春. 土壤干层量化指标初探[J]. 水土保持学报, 2000, 14 (4): 87~ 90.
[16] 杨文治, 邵明安. 黄土高原土壤水分研究[M]. 北京: 科学出版社, 2000. 86~114.
[17] 王义风. 黄土高原地区植被资源及其合理利用[M]. 北京: 中国科学技术出版社,1991.
[18] 延军平, 黄春长, 陈 瑛. 跨世纪全球环境问题及行为对策[M]. 北京: 科学出版社, 1999. 49~60.
[19] 赵景波. 淀积理论与黄土高原环境演变[M]. 北京: 科学出版社, 2002.165~178.
[20] 熊 毅, 李庆逵. 中国土壤[M]. 北京: 科学出版社, 1987.70~75.
[21] 赵景波.西安和宝鸡第5层古土壤铁质粘土结核的发现与研究[J].地理科学,2002, 22(4): 420~425.