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【目的】对比研究河段尺度土地利用方式与水文地貌单元不同组合模式下土壤氮分布的差异性。【方法】选取长江中游下荆江段7种典型组合模式下的15个样地,0~20 cm土层每隔5 cm环刀采样,然后测定土壤的全氮含量(TN)及容重,并计算土壤氮密度(ND)和储量(NS)。【结果】0~20 cm土层的土壤TN及NS在芦苇地中较在薏杨林地中高,且在江心洲人工芦苇地中最大,在堤岸薏杨林地最小;不同地貌单元0~20 cm土壤TN及NS的对比则是,同为芦苇地以在江心洲最高,然后依次是河漫滩、堤岸,同为薏杨林地以在故道中最高,然后依次是河漫滩、堤岸;在土壤TN及ND的垂向分布上,农林活动增强了0~10 cm土层土壤氮的相对富集、加大了垂向变异,江心洲人工芦苇地的垂向分布特征体现了大洪水间歇期土壤氮的阶段性累积过程,不同组合模式下土壤氮的差异性在0~10 cm土层较大、>10~20 cm土层较小。【结论】河流漫滩系统土壤氮不仅受到土地利用的影响,还与水文地貌性质如洪水脉冲、侵蚀与堆积特性等有关。
【Objective】 The aim of this study is to compare the differences of soil nitrogen distribution under different combinations of land use and hydrographic units in river sections. 【Method】 15 samples from 7 typical combinations of Jingjiang section in the middle reaches of the Yangtze River were sampled. Soil samples were collected at 5 cm intervals in 0 ~ 20 cm soil layer. Total nitrogen (TN) and bulk density were measured and calculated Soil nitrogen density (ND) and stock (NS). 【Result】 The results showed that TN and soil TN in 0-20 cm soil layer were higher in reeds than in Pleurotus ostreatus, and were the largest in artificial reed fields in Jiangxin Island and the smallest in Pleurotus ostreatus on banks. Soil TN And NS are the same as the reeds to the highest in the heart of Xinzhou, followed by floodplain, embankment, with the same larchwood in order to be the highest in the old course, followed by floodplain, embankment; TN and ND vertical distribution of soil On the other hand, the activities of agriculture and forestry enhanced the relative enrichment of soil nitrogen in 0 ~ 10 cm soil layer and increased the vertical variation. The vertical distribution of artificial reed land in Jiangxin Island reflected the stage of accumulation of soil nitrogen in flood intermission period. The soil nitrogen difference under combination mode was larger in 0 ~ 10 cm soil layer and smaller in> 10 ~ 20 cm soil layer. 【Conclusion】 The soil nitrogen in floodplain system is not only affected by land use, but also related to hydrogeological features such as flood pulse, erosion and accumulation characteristics.