重构松散堆积体径流侵蚀对植物群落结构的响应机制

Runoff erosion control by vegetation community structure over reconstructed loose deposits slopes is an important scientific issue in vegetation restoration and runoff erosion control field. Most available information is focused on those factors which reflect restoration effect such as coverage and diversity when investigating the benefits of vegetation protection effect. The runoff-sediment-yield process of various layers over loose deposits within multi factors, multilevel and multi scenarios would be investigated in this study. This approach applies a new way to reveal the control mechanism of soil and water loss over slopes formed by different size fraction loose deposits. Study on runoff erosion process simulating in different layers and plant community conformation would be conducted as follow. (1)Confirming the composition of loose slope via field investigation and grading the loose deposits and then reconstructing 5 kinds of loose deposits with different composition. (2) Dividing plant community conformation through field investigation and describing the community distribution pattern quantificationally. (3)Finding out the process of soil and water loss over loose slopes within multi factors, multilevel and multi scenarios and building comprehensive contribution models of runoff, sediment and community scale factors including distribution patterns by indoor artificial simulation of rainfall and confirm the control effects of reconstruction patterns and plant community structure on slope erosion. These results provide theoretical reference for vegetation restoration and soil and water losing prediction on loose residue slopes.

重构松散堆积体边坡植物群落结构对径流侵蚀的抑制机理是植被恢复与径流侵蚀防治领域的重要科学问题。以往研究多集中在矿区植被防护功效方面，常选取盖度、多样性等体现恢复效果的植被指标，而本研究从多因素-多水平-多情景的角度研究松散堆积体的多层产流产沙过程，为揭示松散堆积体边坡径流侵蚀的抑制机理提供了新思路。基于构建植物群落结构与分层模拟径流侵蚀过程等关键技术，拟开展以下研究：采用野外调查取样法（1）确定松散堆积边坡的物质组成，筛分矿渣粒级，重构5类松散堆积物；（2）划分植物群落配置方式，定量描述植物群落分布格局；模拟室内人工降雨实验（3）明晰多因素-多水平-多情景松散堆积体边坡水土流失过程，构建植物群落配置及其空间分布格局在内的群落尺度各影响因子与产流产沙的关联度模型，明确重构方式及植物群落结构对边坡径流侵蚀的抑制效果。预期结果可为松散堆积体边坡恢复植被设计、水土流失量的预测提供理论参考。

松散堆积体是一种特殊的立地类型，人类不合理的开发建设活动使其原本稳定健康的生态系统遭受严重破坏，植被恢复生境极其脆弱，是公认的特殊困难立地环境。项目以松散堆积体边坡为研究对象，以植物空间布局分析为切入点，揭示和量化植被分布对产流产沙变化的影响。研究得出以下主要结论：. 1）松散堆积体具有土壤级配差、养分含量低的特点，在无人为干预的情况下，6-10年内很难实现植被自然恢复。为探究重构堆积体的水分运移过程，人为配置20种混合土体开展水分入渗实验，研究表明随着砾石含量的增加，稳定入渗率、平均渗透速率、稳定渗透率、饱和导水率、渗透系数均增大，60%砾石含量下入渗速率最快。人工降雨1小时内，随着砾石含量的增加，累计产流量和累计产沙量均逐渐降低，砾石含量与累计产沙量呈显著负相关关系。. 2）松散堆积体边坡植被斑块数量多、景观形状指数大，其中阴坡和半阴半阳坡具有较大的斑块面积和最大斑块指数，最大值分别为22.37m2和11.57%，说明植被分布相对分散，生长过程受环境的空间异质性强，与阳坡相比，阴坡和半阴半阳坡更利于植物聚集生长。在一定自然恢复周期内，阳坡植被群落尚不稳定，优势种地位突出；阴坡和半阴半阳坡的植被丰富度指数高且分布更为均匀。经研究推荐土石边坡适宜恢复植物20种，构建适宜不同微地形条件的群落配置5种。. 3）为了探究松散堆积体边坡植被恢复与产流产沙的响应关系，选取减流效益、减沙效益构建综合贡献度模型，解析植被恢复对坡面产流产沙的抑制效果。同时构建边坡植被—土壤系统耦合协调综合评价模型，阐述植被系统与土壤系统的耦合协调程度。研究发现植物群落配合生态袋和椰纤植生毯措施具有较高的减流效益和减沙效益，综合贡献度达到0.47和0.53，耦合协调度Cd值分别为0.82和0.76，属于良好协调发展模式。多情景坡面植被恢复模拟研究揭示了坡顶—均匀分布的植被格局可达到最佳的植被恢复效果。. 以上研究结果可为松散堆积体水土流失治理和坡面植被恢复提供科学依据。