期 刊 ：生态学报 2008年 28卷 5期 页码：2389~2389～2394
Keywords:Qilian Mountain, precipitation, vegetation types, soil moisture, temporal heterogeneity,
摘 要 ：资源供给的时间异质性与环境异质性对植被群落动态甚至景观格局的形成有着同等重要的意义。干旱区山地生态系统植被通常具有明显的空间自组织特征，土壤水分时间异质性可能在这种自组织格局的形成和稳定过程中扮演了重要角色。以祁连山排露沟小流域林草复合景观为例，通过连续监测林线附近草地、灌丛及林地对应的土壤水分状况，比较不同植被类型降水截留以及植物根系提水作用对土壤水分的影响，发现在生长季内典型月时间尺度上草地、灌丛及林地之间土壤水分时间异质性(变异系数CV)具有显著差异（5cm深度，F2,27 =11.25，P <0.01；20cm深度，F 2,27 =5.51，P<0.01），草地与灌丛5cm深度土壤水分时间异质性（CV=0.65、0.61）明显高于林地（0.52），灌丛与林地20cm深度土壤水分时间异质性（CV=0.84、0.84）明显高于草地（0.72）。灌丛5cm深度土壤水分具有较高的时间异质性是因为其较高的冠层截留率，而草地表层5cm深度具有相对较高的时间异质性是因为强烈的土壤蒸发；20cm深度土壤水分时间异质性差异则主要由植被截留差异所致。不同植被类型5cm深度土壤水分时间异质性均明显低于20cm深度（P<0.01），土壤湿度变异系数最大值并不一定发生在表层。
Abstract:Temporal heterogeneity of resources supply is as important a factor as environmental heterogeneity (spatial) to vegetation dynamics and landscape evolution. Mountain ecosystems in arid and semiarid regions are frequently characterized by significant spatial self-organization, and temporal heterogeneity of soil moisture maybe an important driver factor in the vegetation pattern formation and maintenance. A series of observations and experiments were conducted near the forest boundary in Qilian Mountain to test the differences in daily variability of soil moisture between grassland, shrubland and forest habitats, and to examine the contributions of canopy interception and plant uptake to any observed differences. The results show that: daily measurements of soil moisture during a month of growing season showed strong interactions between habitat and time(F2,27 =11.25，P <0.01 for 5cm depth; F 2,27 =5.51，P<0.01 for 20 cm). The coefficient of variation (CV) of soil moisture content of 5cm depth over time during the growing season was significantly higher in grassland and shrubland (0.65,0.61) than in forest(0.52), while the CV of 20cm was significantly higher in shrubland and forest (084,0.84)than in grassland(0.72). We found much more interception of rainfall in shrubs (44%) than in forest (27%) and grassland (12%), and believe that the higher interception of rainfall should be responsible for the higher temporal variability of soil moisture content of 5cm depth in shrubland, while the intense soil moisture evaporation may be the major mechanism that contributes to higher temporal variability of soil moisture content of 5cm depth in grassland. Also we find that the net effect of vegetation on soil moisture was significantly greater in grassland than in forest and shrubland, but continuing analysis suggested that water uptake ability provide little contribution to the differences of CV of soil moisture content in both 5cm and 20cm depth. Another interesting finding in this field experiment is that the CV in depth of 20cm was significantly higher than in 5cm, suggesting that the most active area of soil moisture not necessarily happed in the surface.
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