种植多年生作物土壤固碳效应的驱动机制

Perennial cropping has been proposed as an alternative practice to increase soil C sequestration, as its higher C sequestration potential relative to the annual crop-soil ecosystems. However, the process and the underpinning mechanism of soil C sequestration within perennial cropping ecosystems are still unclear. Here, we hypothesize that higher biomass (especially in roots) of perennial crops results in higher organic C input and the concomitant changes in soil conditions, the corresponding enzymatic activities and microbial C catabolic function, consequently lower C mineralization ratio and higher C sequestration potential, and thus more C accumulation in soils. The corresponding project is proposed and will be conducted in perennial ramie and pasture lands through the synthetical research approach of Chronosequences associated with field survey， mineralization experimemts in situ and seasonal soil samplings and determinations. In the proposed project, we are planning to: 1) quantify changes in organic C input and C sequestration of soils; 2) study changes in mineralization output of soil organic C, and their responses to the fluctuations of soil water content and temperature; 3) study long-term and seasonal changes in soil physico-chemical conditions, components of soil organic C and their distributions within aggregates, key enzymatic activities and microbial C catabolic function; and 4) further explore key factors influencing the accumulation and mineralization of soil organic C, and interactions among organic C, soil conditions and microbial communities, and disscuss the mechanism on the transformation and stability of organic C in soils. Finally, integrative studies will be taken to elucidat soil C sequestration potential of perennial croping ecosystems, and to reveal their underpinning mechanism. Results from this project will strengthen our knowledge on C cycling of perennial crop-soil ecosystems, and provide new sights and theory basis for enhancing soil C sequestration.

种植多年生作物因具有较强固碳能力而被认为是增加土壤碳库的新举措，然而其涉及的土壤固碳过程及其驱动机制不清楚。本项目以"多年生作物-高生物量（尤其根系）-土壤环境、土壤酶和微生物活性-低矿化率/高截获率-土壤强固碳能力"为科学假设，拟以多年生作物苎麻和牧草为研究对象，采用时空替代方法和野外调查、田间原位矿化试验及定期综合监测等试验手段，研究多年生作物土壤中有机碳输入与积累的演变特征，有机碳矿化输出的演变特征及其对水温变化的响应，有机碳组分及其在团聚体内的分布、土壤环境、碳转化关键酶与微生物碳代谢功能的长期/季节演变规律；探寻影响土壤有机碳积累与矿化的关键因子以及土壤有机碳与土壤环境、微生物之间的相互作用关系，探讨种植多年生作物土壤有机碳的转化与稳定机制，初步揭示种植多年生作物土壤固碳效应的驱动机制，为深化对多年生作物土壤碳循环过程的认识和促进土壤固碳增汇提供新思路和理论依据。

种植多年生作物具有强土壤固碳能力，被认为是增加土壤固碳的新举措，然而其土壤有机碳累积过程及其驱动机制仍不清楚。本项目重点研究长期种植多年生作物过程中土壤有机碳储量、有机碳输入与矿化、有机碳组分及其分布、土壤理化性质、碳转化关键酶以及微生物碳代谢功能的演变规律，阐明多年生作物土壤的固碳效应，揭示多年生作物-土壤系统中土壤强碳截获能力的驱动机制。主要研究结果如下：.（1）不同利用方式区域调查与多年生作物不同种植年限典型样地调查研究结果显示，种植多年生作物苎麻可显著增加表层土壤有机碳、活性有机碳、全氮，其效果略低于长期林地；农田改种多年生作物苎麻显著增加1 m土壤有机碳氮储量，年均增量在均在10–15年达到最大；利用表层20cm土壤有机碳氮储量和对数模型可有效预测改种多年生作物苎麻后剖面土壤有机碳氮储量的变化。.（2）不同种植年限苎麻典型样地土壤有机碳原位矿化试验研究结果显示，种植多年生苎麻显著增加了土壤的固碳量和CH4平均氧化速率、降低了N2O平均排放速率， “净碳汇”随种植年限的增加而增大，年均增幅在改植多年生苎麻后10–15年间达到最大。.（3）典型样地土壤有机碳分布与土壤环境特征的演变规律研究结果显示，种植多年生作物苎麻增强了土壤的团聚作用，增加了土壤团聚体包裹态和矿质结合态有机碳氮的含量和比例，增强了土壤β葡萄糖酶、纤维素酶、几丁质酶等酶的活性，增加了土壤微生物碳代谢功能多样性，调节了土壤微生物碳源利用效率。.（4）综合研究结果显示，多年生作物苎麻生长、土壤理化性质、土壤酶活性、微生物功能多样性间存在复杂的相互作用；细根等有机质输入量的增加、土壤团聚的保护作用、土壤酶活性与微生物碳代谢功能多样性的增加增强生态系统持续性与稳定性是种植多年生作物苎麻固碳效应持续增加的三大驱动机制，且三者间存在一定的相互作用。.本项目的研究为深化对多年生作物-土壤系统碳循环过程的认识和促进土壤固碳增汇提供了新思路和理论依据。