黄土丘陵沟壑区坡面径流侵蚀产沙过程的环境解释

Environmental Interpretation on Slope Runoff-Erosion-Sediment Process in Loess Hilly and Gully Region

应用数量分类(TWINSPAN)和排序(DCCA)方法对陕北吴起县典型坡面侵蚀产沙过程进行了环境解释。结果表明:环境因子对土样侵蚀产沙量的解释量达83%,其中DCCA排序轴前4轴的解释量占总排序轴解释量的69%,且分别与坡位、土壤质量、海拔、干根重显著相关。坡面径流侵蚀产沙量随冲刷时间呈波浪式变化,环境因子对侵蚀产沙过程影响甚微。坡面径流侵蚀产沙量按地形部位表现为梁峁顶<梁峁坡<沟坡<沟底,按地类则表现为灌木林<针阔混交林<针叶纯林<阔叶纯林。

Loess Plateau is the world＇s most serious soil erosion region. Slope runoff erosion, as the main type of soil erosion, has been priorities and hotspots of soil and water conservation disciplinary about its relation with environmental factors. 23 soil samples under slope runoff erosion during 12 periods were collected as the objects around Wuqi County in the northem Shaanxi, China. The methods of TWINSPAN and DCCA were ap- plied to interpret the relation between environmental factors and slope runoff-erosion-sediment. Results indicat- ed that soil samples in same topography positions and vegetation factors gathered. Eigenvalues of all sorts axis is 0.313, accounting for 83% of environmental interpretation. The cumulative explaining amount of the first 4 axis is 57.5% for runoff erosion and 56.9% for the relationship between runoff erosion and environmental fac- tors. Meanwhile, interpretation of the first two axis accounted for 65% of all sorts axis which indicates the first two axis reflecting the most information of runoff erosion-environment relationship. First axis reflected the in- fluence of soil pH and slope position on runoff erosion, and second axis manifested influence of soil bulk den- sity on runoff erosion. The third and fourth axis reflected, respectively, influences of altitude and dry root weight. Among environmental factors, correlation coefficients of slope position were-0.46, 0.61 and 0.64 to soil pH, elevation, capillary porosity respectively. The correlation coefficients were-0.63 and-0.81 between slope and soil bulk density, plant cover, and the correlation coefficients were-0.37 and-0.57 between soil bulk density and soil organic matter, root dry weight. Sediment content of runoff erosion presented as hilly top 〈hilly slope 〈gully slope 〈gully bottom according to the topography positions. And also presented as shrub forest〈mixed wood〈pure needless forest〈pure broadleaf forest according to forest types, which is similar as the result of clustering analyses. Human activities including site preparation and road construction have great impact on runoff-erosion-sediment. The erosion was stronger in level-terrace than that in scale pit. And the ero- sion near paths was weaker than others. Sediment concentration followed by form of wave with periods and be divided into 5 periods which were from 0 minutes to 8 minutes, from 8 minutes to 13 minutes, from 13 min- utes to 19 minutes, from 19 minutes to 26 minutes and from 26 minutes to 34 minutes. Although environmen- tal factors played a minor role on Runoff-erosion-sediment process according to DCCA analysis, periods of sediment yield can be reasonably divided by DCCA which illustrate sorting method of DCCA also played an important role describing runoff erosion process.