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    黄土丘陵区水蚀坡面土壤有机碳矿化动态模拟

    Modelling the dynamics of soil organic carbon mineralization on water-eroded sloping land in the Loess Hilly Region

    • 摘要: 为了深入理解侵蚀影响下的碳排放机制,本文以黄土丘陵区不同有机碳背景的水蚀坡面土壤为研究对象,采用3因素(土壤有机碳水平、温度和土壤含水量)4水平的正交试验设计,通过对坡面不同部位土壤的室内矿化培 养实验,分析水蚀坡面土壤有机碳矿化特征,并模拟土壤有机碳矿化动态。 结果表明:土壤有机碳质量分数是影响水蚀坡面有机碳矿化的主要因素,不同有机碳背景下,水蚀坡面表现出不同有机碳矿化特征。 当土壤有机碳水平 较低时,坡面侵蚀促进了沉积区土壤有机碳矿化;当土壤有机碳水平较高时,沉积区土壤有机碳矿化受到抑制。 一 级动力学方程较好的描述土壤有机碳矿化累积动态(R>0.98),有机碳矿化潜力(Cp 值)能综合反映土壤有机碳水平、温度和含水量对有机碳矿化的影响。 通过 C p 值修正,得到的土壤有机碳矿化多因素方程拟合度较高(R2 > 0.95),能够很好地拟合不同有机碳水平下土壤有机碳矿化动态。

       

      Abstract: Background In order to understand the mechanism of soil carbon emission under soil erosion, we chose the study area located in Ansai County of Shaanxi Province. It is a typical loess hilly and gully region where annual precipitation distribution is not even, precipitation on July-September accounts for about 60% of annual rainfall, and most are heavy rainstorms. The zonal soil is dark loessial one that lost completely due to serious soil erosion, thus soil is mainly loessial one (calcareous ustic cambisols) developed from parent-soil loess. As one of the most serious water erosion area all over the world, the selected area is suitable for exploring erosion induced carbon emission. Methods Based on the orthogonal experiment design with three factors (soil organic carbon (SOC) level, soil temperature, and water content) and four levels of the factors, incubation experiment for soil mineralization was conducted with soil sampled at different slope positions of a water-eroded sloping land under different soil organic carbon background in the Loess Hilly Region. Random sampling method was used to collect samples in the positions of water-eroded sloping land (control area, eroded area and deposition area). The dynamic characteristics of SOC mineralization were analyzed and modelled. Results 1) SOC level, soil temperature and soil water content affected significantly the mineralization rate and accumulated mineralization amount of SOC (P <0.05). The primary and secondary relation of the three variables was: SOC level > soil temperature > soil water content. 2) Based on the first-order kinetic equation, which could well describe the accumulation dynamics of soil organic carbon mineralization, a multi-factor equation with high fitting degree was obtained by modifying the Cp value (R2 > 0.95). Conclusions 1) Soil organic carbon content was one of the main factors affecting the soil organic carbon mineralization at different slope positions. The response of soil organic carbon mineralization to soil erosion on the eroded slope varied with the soil organic carbon background of the sloping land. The mineralization of soil organic carbon was stimulated at sediment area of the slope with a lower content of soil organic carbon, whereas it was depressed with higher organic carbon content. 2) The first-order kinetic equation well described the accumulation dynamics of soil organic carbon mineralization (r > 0.98), its Cp value (organic carbon mineralization potential) reflected the influence of soil organic carbon, soil temperature, and water content on organic carbon mineralization. 3) Through modifying the Cp value, a multi-factor equation for describing the dynamics of soil organic carbon mineralization was obtained. This equation presented a solid fitting effect on predicting the dynamics of soil organic carbon mineralization under different soil organic carbon levels.

       

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