黄土区典型乡土草本植物对土壤侵蚀动力学过程的调控机理研究

The grass vegetation played an important role in control soil water erosion due to its effect on runoff hydraulics and soil anti-erodibility. The grassland soil water erosion is an important part of international soil erosion research. However, in the previous studies, the synchronization contribution of the effect of grass vegetation reduce runoff hydraulics and increase soil anti-erodibility on grass vegetation control soil erosion were limited reported. The lack of these studies were not benefit to totally and accurately understanding the kinetic mechanism of grass vegetation controlling soil erosion, as well as to promote the development of grassland soil erosion modelling. In order to compensate these problem which exist in the current studies, based on laboratory simulated rainfall experiments and sampling analysis, the effect of typically native grasses （Bothriochloa ischaemum）on soil water erosion will be studied in the Loess Plateau in this project. The effectiveness of native grasses on controlling soil erosion would be studied. As well as the effectiveness and mechanism of native grasses on reducing flow hydraulics and increasing soil anti-erodibility were also would be analyzed. Based on these, the contribution rate of grasses impact on reducing flow hydraulics and increasing soil anti-erodibility to its controlling soil erosion would be quantified. These can clarify the mechanism of grasses on controlling soil erosion, and also to realize the mechanism of typically native grasses on controlling soil water erosion dynamics process. The results of this study can benefit to development of international grassland soil erosion modelling, and also provide a basis theory for soil and water conservation, and also ecological construction in the Chinese Loess Plateau.

草地植被通过影响侵蚀水动力和土壤抗侵蚀性而调控土壤侵蚀，草地侵蚀是国际土壤侵蚀研究的重要对象之一。但在以往研究中，缺乏对草地植被调控侵蚀水动力、土壤抗侵蚀性和侵蚀量的同步系统研究，不明确侵蚀动力、土壤抗侵蚀性调控对侵蚀调控的同步贡献率，极大制约了草地植被对土壤侵蚀动力学过程调控机理的全面、准确认识，以及草地侵蚀过程研究的深入。本项目针对黄土区植被自然修复形成的典型乡土草本植物(白羊草)对土壤侵蚀的调控，采用草坡地与裸坡地模拟降雨与恒流量放水试验，研究草本植物对土壤侵蚀的阻控效应，分析草本植物削减侵蚀水动力、增强土壤抗侵蚀性效应与机理，界定草本植物侵蚀水动力削减效应与土壤抗侵蚀性增强效应对土壤侵蚀阻控效应的同步影响贡献，阐明草本植物阻控土壤侵蚀效应机理，实现黄土区典型乡土草本植物对土壤侵蚀动力学过程调控机理的研究揭示，促进草地侵蚀过程研究进一步发展，为黄土高原水土保持与生态建设提供科学依据。

草地植被通过影响侵蚀水动力和土壤抗侵蚀性而调控土壤侵蚀，尤以退耕恢复地最为明显。本项目以黄土丘陵区典型乡土草本植物对土壤侵蚀的调控为主题，以黄土丘陵区退耕草地为研究对象，并以农耕地为对照，通过野外采样分析、放水冲刷、室内模拟试验等方式，分别研究了土壤理化性质、降雨入渗特征在不同退耕年限及其植被类型之间的差异；黄土丘陵区坡面径流含沙量及其泥沙颗粒组成特征对土壤分离速率的影响；草本植物根系强化土壤抗分离能力的效应与机制；草本植物对坡面流侵蚀动力的削减效应与机制，探讨植被恢复对土壤侵蚀的调控效应与机制。.研究发现，植被恢复能够有效的改善土壤理化性质，并增加土壤的入渗速率，土壤理化性质及其入渗速率与植物根系参数密度密切相关；黄土丘陵区土壤分离速率与径流水流功率密切相关，径流泥沙含量及其泥沙颗粒粒级组成对土壤分离速率具有负反馈效应，随径流泥沙含量的增加及其泥沙颗粒中值粒径增大，土壤分离速率降低；植物根系参数在土壤内部呈垂直衰减分布规律，且这种空间分布特征在植被恢复达12年后达到稳定；植物根长密度（RLD）是预测细沟分离和细沟可蚀性的最佳参数，土壤分离速率随根长密度增加呈指数递减；自然恢复植被的根系在减少细沟侵蚀效应上比人工种植单一植被更有效；植被覆盖具有较好的减水减沙效应，其强度与覆盖度呈正相关关系；坡面植被分布格局对减水减沙效应具有较大的影响，植被集中于坡面中部是，其减水减沙效益最大。.通过项目的研究，构建了基于根系参数的土壤可蚀性定量转化方程（K_r=K_b×e^(-0.411RLD)），该方程适用于人工和自然恢复植被对土壤分离的影响描述与转化，可以快速计算根土复合体土壤细沟可蚀性，对发展根土复合体抗侵蚀动力学及其模型模拟具有重要的科学意义；揭示了泥沙粒径对细沟分离能力的影响，建立了输沙量和输沙粒径对分离速率的多元线性响应关系，研究结果丰富了国际著名土壤侵蚀过程模型（WEPP模型）中土壤分离的影响因素。