丹江口库区典型小流域生物结皮驱动土壤性质变化及分离响应

Soil Properties Change and Soil Detachment Response Driven by Biocrusts in Typical Small Watershed of DanJiangkou Reservoir Area

为探究生物结皮发育驱动下土壤水蚀特征及机理,选取苔藓发育为优势种的退耕样地,设计5个盖度等级(1%~20%,20%~40%,40%~60%,60%~80%,80%~100%),以裸地为对照,在不同水流剪切力(6.12~19.64 Pa)下进行冲刷试验。结果表明:结皮发育显著影响土壤养分含量,且高盖度结皮覆盖下养分表聚效应更加明显。生物结皮发育显著影响土壤分离能力,裸地土壤分离能力[1.4656 kg/(m^(2)·s)]为生物结皮[0.0042~0.4682 kg/(m^(2)·s)]的3.58~348.95倍,裸地细沟可蚀性(0.2935 s/m)为生物结皮(0.0010~0.0822 s/m)的3.57~293.50倍。相对土壤分离能力及细沟可蚀性均随结皮盖度增加呈指数函数衰减,结皮冲破时间随结皮盖度增加呈指数函数增长;非线性回归分析表明,土壤分离能力可用水流剪切力、生物结皮盖度和土壤黏结力进行模拟(NSE=0.749)。综上,生物结皮发育显著提升土壤抗侵蚀性能,研究结果可为半湿润区水土流失防治及生物结皮管理利用提供理论参考。

In order to explore the characteristics and mechanism of soil water erosion driven by biological crust development,five coverage grades(1%~20%,20%~40%,40%~60%,60%~80%,80%~100%)were designed for the abandoned farmland plots with moss development as the dominant species in Wulongchi small watershed in Danjiangkou Reservoir area,and the bare soil was used as the control to collect samples.Soil detachment text was studied under different flow shear forces(6.12~19.64 Pa).The results showed that:The development of biocrusts significantly affected soil nutrient content,and nutrient surface aggregation was more obvious under the high coverage of crust;The development of biocrusts significantly affected the soil detachment capacity.The soil detachment capacity of bare soil[1.4656 kg/(m^(2)·s)]was 3.58~348.95 times that of biological crust[0.0042~0.4682 kg/(m^(2)·s)].The rill erodibility of bare soil(0.2935 s/m)was 3.57~293.50 times that of biological crust(0.0010~0.0822 s/m).The relative soil detachment ability and rill erodibility decreased exponentially with the increase of crust coverage,and the crust breaking time increased exponentially with the increase of crust coverage.Nonlinear regression analysis showed that the soil detachment ability could be simulated by water flow shear force,biological crust coverage and soil bonding force(NSE=0.749).In conclusion,the development of biocrusts significantly improved soil erosion resistance.The results can provide scientific basis and theoretical reference for soil and water loss control and biocrusts management and utilization in subhumid area.