三峡库区苔藓生物结皮对土壤水分入渗的影响

在三峡库区王家桥小流域选取以苔藓为优势种的生物结皮样地,以附近无结皮发育的裸地为对照,设计5个盖度水平(1%～20%、20%～40%、40%～60%、60%～80%和80%～100%),采用环刀法测定土壤入渗过程,研究生物结皮盖度对入渗过程的影响。结果表明: 与裸地相比,生物结皮发育可显著提高表层土壤粘结力、孔隙度、黏粒含量、水稳性团聚体和有机碳含量,显著降低土壤容重和砂粒含量。生物结皮促进了土壤水分入渗,初始入渗率、稳定入渗率、平均入渗率和累积入渗量可达裸地的2.0倍及以上,土壤入渗性能随结皮盖度的增大呈先增加后减小的变化规律,在40%～60%盖度下最大。通径分析显示,土壤初始入渗率主要受结皮盖度、土壤容重和有机碳含量的影响,稳定入渗率主要受结皮盖度和土壤容重的影响。Horton模型对三峡库区生物结皮覆盖土壤的水分入渗过程拟合效果最佳。

Effects of moss biocrust on soil water infiltration in the Three Gorges Reservoir Area,China

We examined the effects of moss-dominated biocrusts on soil infiltration properties in Wangjiaqiao watershed of the Three Gorges Reservoir Area. Five levels of coverage (1%-20%, 20%-40%, 40%-60%, 60%-80% and 80%-100%) were set, with a nearby bare land as the control. We collected soil samples and conducted infiltration process observation by double cutting ring method. The results showed that biocrusts could appreciably increase soil cohesion, porosity, clay content, water-stable aggregates and organic carbon of topsoil, but significantly reduce soil bulk density and sand content. Biocrusts promoted soil water infiltration, with the initial infiltration rate (I_i), stable infiltration rate (I_f), average infiltration rate and cumulative infiltration amount being two times or more of that in bare land. Withbiocrust coverage increasing, soil infiltration properties firstly increased and then decreased, and peaked at 40%-60% coverage level. Results of path analysis indicated that I_i was mainly affected by biocrust coverage, soil bulk density, and organic carbon content, while I_f was mainly affected by biocrust coverage and soil bulk density. The simulation results of four infiltration models demonstrated that Horton model was the best fitting on the water infiltration process of biocrusted soil in the Three Gorges Reservoir Area.