长江下游支流水阳江小流域土壤侵蚀与土地覆被变化研究

Study on Soil Erosion Rates and Land Cover Changes in a Small Catchment on Shuiyangjiang River, a Tributary in the Lower Reaches of Yangtze River

长江下游地区人类活动频繁,土地覆被变化强烈致使土壤侵蚀相对严重。本研究以长江下游支流水阳江–郎川河流域为研究对象,首先确定该区域土壤中137Cs的背景值为1275 Bq m−2,并结合相关侵蚀模型,对该区域的土壤侵蚀速率进行了定量估算。同时基于1985~2015年8期高分辨率遥感影像,在ENVI 5.2支持下,对研究区的土地覆被变化进行了遥感定量解译。结果表明:该区域水稻田占主导的耕作土土壤侵蚀速率小于非耕作土。非耕作土中土壤侵蚀速率大小依次为:林地(非马尾松) 】马尾松 】板栗树 】樟树 】竹林 】稀疏林。过去30余年间,该研究区建设用地面积呈增加趋势,耕地面积呈下降趋势,林草地以2000年为转折点呈现先下降后上升趋势,这与不同时期的土地利用政策密切相关。对比新老茶园的土壤侵蚀速率大小,其结果反映了农耕地退耕转变为茶园加速了土壤侵蚀。从水土保持角度考虑,保持当前的土地利用方式可以有效降低该区域的土壤侵蚀。

Serious soil erosion was occurred in the lower reaches of the Yangtze River of China due to land cover destroyed by frequent human activities. Taking the Langchuan catchment of Shuiyangjiang River, a tributary in the lower Reaches of Yangtze River as the study area, the objects of this study were to determine the 137Cs reference inventory in a 70-year old paddy field, to estimate the soil erosion rates in uncultivated/cultivated lands, and to interpret the land cover changes based on the remote sensing images of 1985~2015. Results indicated that soil erosion rates in cultivated land dominated by paddy were lower than that in uncultivated land. Soil erosion rates in uncultivated land were in order: Woodland >Pinus massoniana >Camphor trees >Castanea mollissima >Bam-boo >Sparse trees. In the past 30 years, the changed area of constructed land showed an increasing trend, but a decreasing trend in cultivated land. At the meanwhile, the area of forest and grassland was transformed from decrease to increase in late 1990s, which is in accordance with the policy of returning farmland to forest. Compared with soil erosion rates of new and old tea-trees, soil erosion was accelerated by frequent human disturbance. To reduce soil erosion in the study area, it is very necessary to maintain the current land use types in the long run.