内源性土壤可利用性有机质对激发效应的影响机制

Priming effects are a common phenomenon in natural ecosystems. Most of previous priming studies considered how inputs of exogenous organics affect priming effects based on its definition. However, so far very few studies have examined effects of native soil labile organic matter on priming effects. To answer the above question, in this project we used two mineral soils (0-10 cm) collected from a subtropical montane evergreen broad-leaved forest of Ailaoshan Mountain in Yunnan Province and a subtropical China fir plantation of Qianyanzhou in Jiangxi Province. Contents of native labile organic matter will be adjusted through adding soil solution extracted with the vacuum technology or shading plants. Meanwhile, active microbial biomass will be measured by substrate-induced growth respiration, while different active microbial groups will be measured by 13C-PLFA. Fluorogenic methylumbelliferone-based substrates are used to measure the enzyme activities of ß-cellobiohydrolase, ß-glucosidase, protease and ß-xylosidase as well as urease. 13C-labeled glucose (or 13CO2 continuous labeling) is used to quantify priming of soil organic carbon decomposition. Finally, we aim to clarify the mechanisms of native soil labile organic matter affecting priming effects and thus improve our knowledge about priming effects.

激发效应是自然界中普遍存在的现象，先前大多数激发效应研究仅基于其定义考虑了外源性的可利用性有机质的输入对激发效应的影响，但到目前尚未考虑内源性的土壤可利用性有机质库对激发效应产生与维持的影响。基于此，本项目利用真空土壤溶液抽提技术及植物遮阴方式调节内源性的土壤可利用性有机质含量，用底物诱导生长呼吸测定活性土壤微生物量，用13C-PLFA(磷脂脂肪酸)区分不同微生物类群的活性，借助于荧光标记技术测定胞外酶活性(纤维素二糖水解酶、木聚糖酶、ß-葡萄糖苷酶、蛋白酶和脲酶)，用13C标记葡萄糖(或13CO2连续标记)量化土壤激发效应，揭示内源性的土壤可利用性有机质含量对土壤激发效应的影响机制，进而完善对土壤激发效应理论的认知。

本项目采用真空土壤溶液抽提技术及植物遮阴方式调节内源性的土壤可利用性有机质含量，通过底物诱导生长呼吸测定活性土壤微生物量，借助13C-PLFA区分不同微生物类群的活性，利用荧光标记技术测定胞外酶活性，以13C标记葡萄糖量化土壤激发效应，揭示内源性的土壤可利用性有机质含量对土壤激发效应的影响机制。获取如下研究结果：1）发现内源性的土壤可利用性有机物质跟外源性的可利用性物质相互作用可改变土壤激发效应的强度和方向。2）利用有机质分解连续体，阐明了哀牢山亚热带森林土壤激发效应对外源性碳氮输入的响应模式。3）利用次生演替序列，解析了内源性碳氮可利用性对土壤激发效应的影响。4）借助于种植方式种，发现邻居物种可通过根系间的互作影响目标物种的氮素获取。