不同农业模式下水土流失的生态学特征研究

Ecological property of soil erosion under different agricultural systems

利用径流小区及Eu定位土芯中子活化示踪技术,对不同区域多年、多种生态农业模式下土壤侵蚀及空间分布特征进行研究。结果表明:当坡度<10°时,林、农林、作物、作物+工程这4种模式的土壤侵蚀模数、径流系数无明显差异;坡度为15°时其侵蚀模数分别达1 707.46 t.km-2.a-1、2 127.3 t.km-2.a-1、2 144.81t.km-2.a-1、1 847.06 t.km-2.a-1,是坡度<10°时土壤侵蚀模数的10.78倍、11.33倍、8.55倍、9.41倍。不同农业模式在不同时期水土流失的程度不同,但所有农业模式在发展前期,水土流失较严重,农林复合模式到中期土壤侵蚀趋于稳定。纯林和农林模式后期能明显减少水土流失。流域内不同农业模式下土壤侵蚀表现为侵蚀与沉积交错出现的趋势,侵蚀与沉积量的大小取决于植被覆盖率、坡度、农业活动的强弱等因素。复合结构的农业模式优于单一结构的农业模式,农业模式的水土保持效果与其本身群落、物种结构有密切关系。

Soil erosion and its spatial distribution under different eco-agricultural systems were studied in the red-soil hills of South China, using the runoff plot method and neutron activation analysis of fixed core soil Eu tracer. The results show that soil erosion modules and runoff coefficient have no significant difference under the four eco-agricultural systems（ forest system, agro-forest system,crop system and crop and engineering system） at 〈 10° slope. Soil erosion module can reach 1 707.46 t·km^-1·a^-1, 2 127.3 t·km^-2·a^-1 ,2 144.81 t·km^-2·a^-1and 1 847.06 t·km^-2·a^-1 ,at 15° slope,which are 10.78,11.33,8.55 and 9.41 times the values at 〈 10° slope for four systems respectively. The amount of soil erosion is different for the four eco-agricuhural systems during different developmental stages. However, soil erosion is serious in the early stage of the eco-agricuhural systems,but gradually decreases in the middle stage, down to the agro-forest system levels. The amount of soil and water loss obviously decreases in the finial stage in the forest and agro-forest systems. There is a wave-like relationship between soil erosion and sediment distribution ; soil erosion and sediment is determined by vegetation mantle, slope gradient and frequency of agricultural activity. Soil and water loss under complex eco-agricuhural systems is less than that of mono-ecological systems. A tight relationship exists between the effect of soil and water conservation, and species and community structure under different agriculture models.