紫色土坡地土壤有机碳土-气交换与土-水迁移协同过程与通量

Sloping croplands of purple soil widely distributed in the upper Yangtze River play an important role in the local agriculture. Soil-atmosphere gas exchange are affected by seriously soil organic carbon especially dissolved organic carbon loss in this area because of concentrative rainfall. However, the mechanisms and fluxes of the reactive soil organic carbon loss via hydrological and gaseous exchange (CO2 and CH4) have not been well documented because of isolated study on separate losing pathway. It is crucial important to conduct coupling researches on hydrological and gaseous loss of soil organic carbon so as to understand mechanisms on manipulation of gaseous and aqueous carbon loss jointly. Thus, we proposed to conduct this coupling research on processes and fluxes of carbon loss via hydrological and gaseous pathways in sloping cropland of purple soil. In this proposal, synchronous monitoring on processes of both soil-atmosphere gas exchange and carbon loss will be conducted in the free-drain lysimeter of purple soil. Impacts of rainfall intensities, slope gradients and fertilization regimes on both aqueous and gaseous carbon loss will be studied by rainfall simulation experiments. Therefore, basic scientific supports will be provided for both management strategy of soil organic carbon and sustainable agriculture.

长江上游紫色土坡耕地土层浅薄，加之该地区降雨集中导致坡地土壤有机碳径流损失严重。表层土壤有机碳特别是土壤中可溶性有机碳等养分的流失势必会影响土壤有机碳土-气交换过程。但以往农田土壤有机碳气体排放（CO2和CH4）与径流流失过程的研究相对孤立，对土壤有机碳土-气交换和土-水迁移过程的同步观测与试验研究极为缺乏，二者之间的协同过程与关联机制不清楚。针对上述问题，利用紫色土坡地lysimeter装置，结合小区定位观测和人工模拟降雨试验，开展紫色土坡地土壤有机碳随地表径流、壤中流和泥沙迁移损失与气体排放的同步观测试验，研究紫色土坡地农田土壤有机碳气体交换与有机碳径流流失的协同过程特征及影响因素，查明二者之间的关联机制和通量变化关系，为紫色土坡地农田土壤有机碳管理和温室气体减排提供科学依据。

本文利用紫色土坡耕地Lysimeter装置开展土壤有机碳气体排放（CH4和CO2）与其随径流迁移损失的同步观测试验。论文比较了OM（单施粪肥）、OMNPK（粪肥配施氮磷钾肥）、RSDNPK（秸秆还田配施氮磷钾肥）、NPK（常规氮磷钾肥）、N（单施氮肥）及CK（无肥对照）等6种处理下土壤有机碳气态损失和径流损失特征，获得了紫色土坡耕地土壤有机碳的损失途径、通量及其相互关系，主要研究结果与结论如下：.（1）施肥处理对紫色土坡耕地土壤的CH4和CO2排放均有显著影响，施肥显著抑制紫色土坡耕地土壤吸收大气CH4的能力，但促进CO2的排放。.（2）土壤可溶性有机碳（DOC）含量是紫色土坡耕地土壤CH4排放的主要影响因子，而影响CO2排放环境因子除DOC外，还包括土壤温度、湿度及NO3--N含量。.（3）壤中流是紫色土坡耕地土壤DOC的主要径流损失途径，壤中流DOC损失通量占径流DOC损失总量的70%以上。.（4）紫色土坡耕地土壤有机碳损失途径主要包括气态损失途径（包括CO2和CH4排放）和径流损失途径（包括泥沙和DOC的径流迁移）。气态损失途径尤其是CO2的排放是土壤有机碳损失的主要途径。.（5）土壤有机碳的气态损失和径流损失间存在一个负相关关系，可能与土壤有机碳活性组分含量有关。