滇池流域土壤侵蚀与氮流失的同位素示踪研究

The recent research of global changes is focused on the terrestrial ecosystems which are closely related to human activies. In recent years, the nitrogen loss from the soil erosion has attemped many attentions. In this study, Dianchi watershed is selected as the target region. The 137Cs and 210Pbex will be studied to calculate the sand yield and soil erosion rate according to the mixed model for estimating the total amount of soil erosion in the forest and cultivated land with different age, slope and slopelength. The molecular combination characteristics of normal alkanes 13C and advanced isotope 15N will be employed to investigate the proportion of the organic carbon and nitrogen in the soil profile. The variation of nitrogen concentration will be obtained. Accordingly, the nitrogen source of different land use patterns and deposition of sediments will be analyzed. The equation between soil erosion and nitrogen loss will be constructed to predict nitrogen loss from soil erosion in different land use patterns in Dianchi watershed.Based on the four-dimensional nonlinear dynamical model of nirogen established in the terrestrial ecosystem,2009, the new nitrogen loss models with arable and non-arable lands will be constructed according to the observed values to evaluate different land use patterns and rainfall effects on the nitrogen loss in Dianchi watershed.

与人类活动密切相关的陆地生态系统是目前全球变化的研究热点。本项目紧密跟踪国际上近年来关于土壤侵蚀导致的氮流失问题，针对我国滇池流域日益严峻的土壤侵蚀现状，通过泥沙沉积和土壤中137Cs 和210Pbex的测定，根据混合模型分别求算出不同源地的产沙量和土壤侵蚀速率，确定不同树龄、坡度、坡长的林地及耕地土壤中总的侵蚀量。利用氮稳定性同位素和正构烷烃单体碳同位素组成在土壤剖面的分布规律探讨土壤有机物中碳氮比重的时空特征，得出氮含量的变化趋势。据此，综合分析不同源地土壤中氮的来源，进而分析沉积泥沙的来源，建立不同源地土壤侵蚀量与氮流失量之间的定量关系，预测滇池流域不同源地氮的侵蚀损失。以申请者前期研究中建立的陆地生态系统氮迁移转化四维非线性动力系统模型为基础，以实际观测值为依据，构建基于同位素示踪的耕地氮流失模型和非耕地氮流失模型，评估不同的土地利用方式及降雨对滇池流域土壤氮流失的影响。

本项目紧密跟踪国际上近年来关于土壤侵蚀导致的氮流失问题，针对我国滇池流域严峻的土壤侵蚀现状，通过泥沙沉积和不同土地利用方式下土壤中137Cs 和210Pbex比活度的对比分析，利用混合模型求算出不同源地的相对产沙量和土壤侵蚀速率。结合正构烷烃单体碳同位素和氮稳定性同位素在沉积剖面的分布规律，反演人类活动对滇池流域有机质迁移的影响。构建基于同位素示踪的耕地氮流失模型和非耕地氮流失模型，估算氮的侵蚀损失，评估不同的土地利用方式及季节转化对滇池流域氮流失的影响。迄今已发表相关研究论文23篇(其中SCI收录10篇)，完成预期目标。