黄土丘陵区环境因子对土壤水分的的贡献率及其尺度效应

Soil water is the primary limiting factor for vegetation growth and rehabilitation in the semiarid loess hilly region. It has nonlinear characteristics and obvious scale effects. Aiming at the contradiction between vegetation construction and water shortage, the goal of this subject is to realize the coordinated development of rational allocation of vegetation and sustainable utilizatian of soil water. The soil water amount and structural feature in Yanhe watershed were studied on typical area, slope surface, small watershed, and regional scales. Soil water distribution and its heterogeneity were studied, which proved the key scale of soil water variability. Furthermore, how environmental factors affect soil water and its trans-scale correlation, contribution rate, scaling effects in different scale were analyzed. After that, we studied key factors and their weights in soil water variability in different scales and clarified how main environmental factors affected soil water and which was the key scale. At the end of the study, we could reveal the interaction process and its mechanism between soil water and environmental factors. The research is of importance for further understanding the interaction process and its mechanism between soil water and environmental factors, which provides scientific basis for more effective plan and design for vegetation pattern and restoration models in the semiarid loess hilly region.

土壤水分是半干旱黄土丘陵区植物生长和恢复的主要限制因子，而土壤水具有非线性特征和明显尺度效应。本项目针对黄土高原地区植被建设与水资源短缺的矛盾，以实现与有限水土资源相协调的植被合理配置与土壤水分可持续利用为目标，以黄土丘陵区延河流域为对象，通过对典型地块到坡面、小流域和区域四种尺度水平下土壤水分数量和结构特征的调查，研究土壤水分空间分布及其异质性特征，探明土壤水分变异的关键尺度；分析不同尺度水平下环境因子对土壤水分的影响程度及其跨尺度关联，评估各环境因子对土壤水分影响的贡献率及其尺度效应，考察不同尺度影响土壤水分变化的主导因子及其权重，阐明环境因子对土壤水分影响的主导因子和关键尺度，揭示不同尺度下土壤水分与环境因子之间相互作用的过程和机理。本项目的开展可以进一步认识土壤水分与环境因子之间相互作用的过程和机理，从而为更有效地规划和设计半干旱黄土丘陵区植被格局和重建的植被恢复模式提供科学依据。

环境因子对土壤水分重大影响。尽管环境因子对土壤水分的空间分布和变异有巨大贡献，但它们是如何随尺度变化而变化的仍然知之甚少。我们在四个尺度（地块尺度、坡度尺度、小流域尺度、和区域尺度）上研究了黄土高原年均降雨量、年均温度、年均蒸发量、坡向、坡度、坡位和土地利用等8个环境因子对土壤水分的贡献。研究表明，从地块到区域尺度，随着尺度的增加气候因素的贡献逐渐增加，而地形因素逐渐下降，随着尺度的增加，坡向、坡位、坡度等地形承担的信息量逐渐流向蒸散、降水、温度等气象因子，而土地利用类型承担的信息量变化比较平稳。研究中主控因子信息的转移也与不同尺度的决定因素和主要限制因素的变化有关。这些结果表明了随时间和空间的变化，土壤水分的时空变异及其主导因素是不同的，环境因子影响土壤水分的的尺度效应所决定的。