砂姜黑土农田土壤异养呼吸与可溶性有机碳淋失的关联效应研究

Soil heterotrophic respiration and dissolved organic carbon leaching are considered to play important in soil organic carbon loss processes in agro-ecosystems, which is greatly crucial to enhance soil organic carbon sequestration. There is an obvious synergy between soil heterotrophic respiration and dissolved organic carbon leaching, and dissolved organic carbon leaching is a potential regulating factor of soil heterotrophic respiration. However, few studies link soil heterotrophic respiration and dissolved organic carbon leaching loss on cropland due to no field experiment conducting the monitoring on both processes simultaneously. Coupling effect between soil heterotrophic respiration and dissolved organic carbon leaching has not been very clearly clarified. Therefore, according to the characteristics of rainfall concentrate and leaching development on cropland in lime concretion black soil, we simultaneously observe soil heterotrophic respiration rate and dissolved organic carbon leaching flux in different rainfall events through soil respiration instrument and field lysimeter under long-term different fertilization practices in the rainy season. Moreover, we also simultaneously analyze dissolved organic carbon, microbial biomass carbon contents and soil enzymatic activities. It is aimed to examining coupling effect between soil heterotrophic respirations and dissolved organic carbon leaching completely. It is great helpful to regulate soil organic carbon loss processes on cropland in lime concretion black soil, which is also greatly important to further understand soil organic carbon sequestration mechanism on cropland in agro-ecosystems.

土壤异养呼吸和可溶性有机碳淋失是农田土壤有机碳损失的关键过程，二者之间存在明显的协同作用，可溶性有机碳淋失势必会影响土壤异养呼吸速率。然而，以往关于农田土壤异养呼吸和可溶性有机碳淋失的研究相对孤立，对二者的同步观测试验和研究极为缺乏，它们的关联效应尚不清楚。因此，本项目拟以砂姜黑土农田为研究对象，根据该地区降雨集中，淋溶水发育的特点，以长期定位施肥试验为基础，通过野外试验同步测定不同降雨条件下土壤异养呼吸速率和可溶性有机碳淋失通量，并以土壤微生量碳和土壤酶活性为纽带，弄清土壤异养呼吸和可溶性有机碳淋失的数量变化关系和内在联系，查明二者的数量关联性和内在关联机制，揭示关联效应。项目研究成果可为调控砂姜黑土农田土壤有机碳的损失过程提供理论支撑，进而为深入解析农田土壤固碳机制奠定基础。

土壤异养呼吸和可溶性有机碳淋失是农田土壤有机碳损失的关键过程，二者之间存在明显的协同作用，可溶性有机碳淋失势必会影响土壤异养呼吸速率。然而，目前的研究多将土壤异养呼吸和可溶性有机碳淋失割裂开来，很少在同一田块对二者进行同步观测研究，研究相对孤立，忽略了二者的协同作用，关联效应尚不清楚。针对上述问题，在本项目的支持下，课题组成员利用长期定位施肥试验，通过野外试验同步测定了不同降雨条件下土壤异养呼吸速率和可溶性有机碳淋失通量，并辅以测定土壤微生量碳和土壤酶活性。研究结果表明，当可溶性有机碳的淋失量较高时，表层土壤可溶性有机碳和为微生物碳含量均较低。次降雨事件可溶性有机碳淋失通量与次降雨的土壤可溶性有机碳和微生物碳含量均呈显著指数负相关（-0.69和-0.77，p < 0.01），这说明土壤可溶性有机碳在降雨的作用下产生了强烈淋溶，降低了表层土壤可溶性有机碳含量和微生物活性。因此，当可溶性有机碳淋失通量升高时，土壤异养呼吸速率(雨前、雨中和雨后的平均值)呈现降低的趋势，二者间存在明显的数量关联性，符合指数衰减方程(R =-0.61, p < 0.05)，关联机制在于可溶性有机碳淋失降低了表层土壤可溶性有机碳与微生物量碳的含量，导致土壤微生物活性的降低，降低土壤有机碳的分解过程，从而降低土壤异养呼吸速率。研究结果可为调控该区域农田土壤有机碳损失过程提供理论支持，进而为深入解析农田土壤固碳机制奠定基础。