我国典型旱地农田土壤活性有机碳转化特征及驱动机制

Active soil organic carbon can not only maintain the stability of soil aggregate, but also evaluate the potential productivity of the soil. The indicators such as carbon pool activity, the carbon effectiveness, hexose / pentose ratio of neutral sugar often characterized the conversion of soil active carbon pool, which are providing the basis for study the transforming and driving mechanism of the active carbon pool. Therefore, this project aims to solve scientific problem which the conversion of activated carbon and the driving mechanism is not clear in the typical upland of China. We select representative 3 long-term soil fertilizer experiments with 4 treatments among three typical upland regions of China, and collecting soil samples with 0-20cm. We use carbon pool activity and the carbon effectiveness to evaluate the characteristics of active soil organic carbon pool; using hexose / pentose ratio of neutral sugar to evaluate the proportion of soil active carbon pools from the plant and microbial sources of carbohydrates.we quantify contributions of main and interactive effects of climate and edaphical factors in regulating the transforming of soil active carbon pool at different regions by employing canonical correspondence analysis (CCA)-based variation partitioning analysis (VPA). Research results are of significance for better understanding soil organic carbon transforming in agroecosystem, and will also, in practice, provide scientific basis for efficiently increasing soil organic carbon content in typical regions of China.

土壤活性有机碳不仅维持土壤团粒结构的稳定性，还可评价土壤潜在生产力。土壤活性有机碳库的转化常以碳库活度、碳素有效率、中性糖中六碳糖/五碳糖的比例等表征，这均为我们研究活性碳库的转化和驱动机制提供了基础。故本项目针对我国旱地农田土壤中活性碳库的转化特征、驱动机制尚不明确的科学问题，选择分布于我国不同土壤类型的肥料长期试验点3个，不同种类外源碳投入的4个处理，采集0-20cm的土壤样品等，利用碳库活度、碳素有效率评价我国农田土壤活性碳库转化的差异特征，进一步评价其稳定性及周转速度；利用六碳糖/五碳糖的比例来评价土壤活性碳库中植物和微生物源碳水化合物的主导作用；通过测定土壤性质及气象因素等指标，利用CCA-VPA多元统计方法确定碳库活度、碳素有效率对土壤活性碳库转化的驱动机制。研究结果将深化认识农田系统碳转化机制，为我国典型区域旱地土壤有机碳的高效提升技术提供科学依据。

本项目针对我国旱地及水田土壤中活性碳库的转化特征、驱动因素尚不明确的科学问题，选择分布于我国不同土壤类型的长期定位试验3-4个及江西省长期种植水稻的水稻土，采集0-20cm/0-40cm/0-100cm的土壤样品，通过测定不同深度的有机碳储量、不同氧化方式（高锰酸钾/硫酸氧化）的活性有机碳及相关土壤性质，评价我国农田土壤活性碳库转化的差异特征及驱动因素。结果表明：（1）相较于初始值，CK处理0-20cm及20-60cm的SOC储量均降低，而所有处理下公主岭点位表层及深层的碳储量均升高。NPK及NPKM处理使高肥力土壤（公主岭和重庆）深层土壤碳储量增加，使低肥力土壤（郑州和祁阳）深层土壤碳储量保持不变或降低。相较于表层土壤，高肥力使土壤剖面的CSE升高，低肥力使剖面CSE受到抑制。土壤性质是深层土壤CSE转化的关键驱动因素。（2）郑州、祁阳、公主岭三点位能被不同浓度KMnO4氧化的三种活性有机碳储量均为0-20cm > 20-40cm > 40-60cm > 60-80cm > 80-100cm。NPKM处理下三点位土壤剖面中有机碳，低、中、高活性有机碳的储量增幅最大。郑州、公主岭土壤活性有机碳来自于植物与微生物源的近似。土壤性质（可解释60.7%的变异）是不同活性有机碳转化的关键驱动因素。（3）长期施用化肥或化肥有机肥配施提高了土壤有机碳的储量，其中约有50%左右的相对贡献来自于可氧化态有机碳，而稳定性有机碳的相对贡献也为50%左右。（4）江西省赣北、赣中、赣南的总活性有机碳含量在5.21~7.12g/kg之间；中活性有机碳含量在3.09~5.33g/kg之间；高活性有机碳含量在2.04~2.89g/kg之间。三种活性有机碳组分的含量均为赣北＞赣中＞赣南。研究结果将深化认识农田系统碳转化机制，为我国典型区域农田土壤有机碳的高效提升技术提供科学依据。