中亚热带地区常绿阔叶林地表径流和产沙影响机制

为探究中亚热带地区常绿阔叶林地的地表径流和侵蚀产沙的影响机制,于2016年和2017年的5—9月在天然降雨条件下,采用野外定位观测结合室内试验分析方法,得到磨盘山常绿阔叶林林外降雨和林内穿透雨及其雨滴特性数据,采用RDA排序及CANOCO的Forward分析筛选出主导环境影响因子。结果表明:(1)产沙量与林外降雨量和林内穿透雨量存在正相关关系。当径流量0.064mm时,研究区内形成的地表径流才开始携带泥沙;林冠层对降雨动能的缓冲作用在降雨强度小的情况下较明显。(2)林冠缓冲动能、叶面积指数和树干茎流量与径流量产沙量存在负相关关系,降雨历时、林外降雨量、林内降雨量、平均雨强、雨滴个数、雨滴直径、雨滴速度、林内降雨动能、降雨总动能对径流量产沙量产生正相关影响。(3)对12个环境因子进行主导因子筛选,降雨总动能、林外降雨量、平均雨强、林冠缓冲动能、降雨历时对径流量产沙量的影响效果较为显著。从典范特征值分析结果显示,仅选择这5个主环境影响变量可解释环境影响因子与径流量产沙关系73.2%的信息量,比12个变量所解释的信息量仅少16.8%。

The Mechanism of Surface Runoff and Sediment Yield of Evergreen Broad-leaved Forest in the Middle Subtropical Region

To explore the mechanism of surface runoff and sediment yield of evergreen broad-leaved forest in the middle subtropical region, the natural rainfall and raindrop characteristics from May to September in 2016 and 2017 were observed by field observation and indoor test analysis Also, the leading environmental factors were selected by RDA sequencing and the Forward analysis of CANOCO. The results showed that:(1) Sediment yield was positively correlated with rainfall outside forest and throughfall in forest area. When runoff was greater than 0.064 mm in the study area, sediment occurred. The buffer effect of canopy layer on rainfall kinetic energy was more obvious when rainfall intensity was small. (2) Canopy buffering energy, leaf area index and stemflow and sediment yield had a negative correlation, rainfall duration, rainfall outside the forest, forest rainfall, average rainfall intensity, raindrop number, raindrop diameter, raindrop velocity, rainfall kinetic energy and rainfall kinetic energy on runoff sediment produced positive influence. (3) Through the screening of the leading factors of 12 environmental factors, we got the most significant influences of total rainfall, total rainfall, average rainfall intensity, canopy buffer kinetic energy and rainfall duration on the runoff and sediment yield of 12 environmental factors. The results from canonical eigenvalues analysis showed that choosing only 5 main environmental variables could explain 73.2% of the information content of the relationship between environmental factors and runoff and sediment yield, which was only 16.8% less than that explained by 12 variables.