黄土区坡面径流产沙对草地植物群落功能参数季节变化的响应

Investigation of the mechanisms of vegetation impacts on soil and water loss (SWL) is critical for incisive revelation of soil and water conservation functions of plants and appropriate design of plant measurements for the purpose of soil and water conservation. In the past, many vegetation factors measured at individual plant scale, such as vegetation coverage and species composition, have been investigated in previous studies on the effects of vegetation on SWL at slope scale. Recently, the concept of community functional parameters has been raised in this research area in order to break through the limitations of traditional vegetation factors at individual plant scale. Since the significant effects of seasonal change on vegetation is usually ignored in precious studies, plant functional traits in different seasons will be measured, and SWL from experiment plots of different plant community types located in small watershed of loess hilly region will be observed in this project. Based on the biomass ratio hypothesis, the measured plant functional trait parameters at plant scale will be extrapolated to community functional parameters. Rainfall event based runoff and sediment generation models will be developed on the basis of runoff, sediment yield, community functional parameters, and other impact factors on community scale. The impacts of community functional parameters on slope SWL in different seasons and with different rainfall intensity conditions will be further analyzed. The expected results of this study could be helpful to the revelation of the mechanism of SWL, and also provide valuable reference for designs of soil and water conservation plant measurements.

掌握植被对水土流失的影响规律，是揭示植物水土保持功能机理和合理设计植物措施的重要基础。以往在群落尺度研究植被因子影响坡面水土流失时，常考虑盖度及物种组成等以植物个体为计量单位的植被因子。植物群落功能参数的提出，打破了以往研究中应用植物因子的局限，为揭示坡面尺度植物群落抑制水土流失的机理提供了新思路。鉴于季节因素对植被因子影响巨大但却往往疏于考虑，本项目拟测度黄土丘陵小流域常见植物不同季节的植物功能性状，根据生物量假说，利用个体尺度的植物功能性状推算群落尺度的植物群落功能参数；通过搭建不同植物群落类型的径流小区，常年监测小区产流产沙结果；针对每一次侵蚀性降雨，构建包括植物群落功能参数在内的群落尺度各影响因子与产流产沙之间的模型。分析不同季节，植物群落功能参数对坡面产流、产沙的作用强度随雨强的不同而变化的特征。预期结果无论对于侵蚀机理的阐释还是对于坡面水土保持措施的优化，都具有重要价值。

本项目通过测度黄土丘陵小流域常见植物不同季节的植物功能性状，根据生物量比例假说，利用个体尺度的植物功能性状推算群落尺度的植物群落功能组成指数；通过搭建不同植物群落类型的径流小区，常年监测小区产流产沙结果；针对每一次侵蚀性降雨，构建包括植物群落功能组成指数在内的群落尺度各影响因子与产流产沙之间的模型。分析不同季节，植物群落功能参数对坡面产流、产沙的作用强度随雨强的不同而变化的特征。对于坡面径流而言，研究发现，在代表研究区生长季节初期的六月中旬，根系特征对坡面径流的影响随降雨强度的增加而降低。在代表研究区域生长季节中期的七月下旬，坡面径流受各种植物功能性状的综合影响。而在生长季后期，坡面径流主要受到植物群落地上部分的影响。对于土壤流失而言，在生长季早期和中期，FRic和FEve在低降雨强度下限制土壤侵蚀方面起着重要作用。在生长季初期的中、高降雨强度下，植物抗拉强度对土壤侵蚀有很大影响。然而，在生长季中期的中高降雨强度条件下，植物地上部分对土壤侵蚀的影响最大。在生长季节末期，无论什么降雨强度条件下，植物生态位的分化程度都是土壤侵蚀的最大限制因素。本项研究深入挖掘了土壤侵蚀的机制，并能够为水土保持的植物措施提供借鉴。