增温背景下冻土区泥炭地植物根输入变化及其对土壤活性碳组分的影响研究

The mid-high latitude permafrost regions act as important carbon sinks in terrestrial ecosystem and are sensitive to climate change. Soil organic carbon (SOC) pool in these regions would be significantly affected by climate warming, which will feed back to regional and global climate change. Root input is an important source of SOC. Warming climate influences the process of plant root carbon input to the soil, which acts on soil carbon balance. Labile organic carbon fractions are early indicators of changes in SOC, and are affected by temperature and root input. However, changes in labile organic carbon fractions of permafrost regions under warming and how they are affected by root input prove to be not clear now, which are essential to estimate the ability of carbon sequestration. Based on the field warming experiment simulating warming climate, this project investigates the main vegetation Eriophorum vaginatum in the peat land of permafrost region, aiming to disclose the effects of warming on fine root decomposition, root exudates, SOC and its labile fractions, analyzing the coupling relation between root decomposition, root exudates and SOC and its labile fractions, clarifying the influences of plant root input on the stability of SOC pool in peat land in permafrost regions. Based on aforementioned work, the present study hopes to provide scientific basis for scientific assessment of carbon sink capacity and response to climate change in permafrost regions.

中高纬冻土区是陆地生态系统重要的碳汇，也是气候变化的敏感区。气候变暖将对区内有机碳库产生重要影响，继而反馈于区域及全球变化。根输入是土壤有机碳的重要来源，气候变暖会影响植物根系向土壤输入碳的过程，作用于土壤碳平衡。活性碳组分是土壤有机碳变化的早期指标，受温度和根输入等因素影响，然而，增温背景下冻土区土壤活性碳组分的变化及其受根输入的影响尚不清楚，这些问题是评估碳固持能力的关键。本研究以冻土区泥炭地主要植被白毛羊胡子草为研究对象，通过野外原位增温控制实验模拟气候变暖，揭示增温对细根分解、根系分泌物、土壤有机碳及其活性碳组分的影响，分析细根分解和根系分泌物与土壤有机碳和活性碳组分之间的耦合关系，阐明增温背景下植物根输入对冻土区泥炭地土壤碳库稳定性的影响，为科学评估冻土区碳汇能力和应对气候变暖提供科学依据。

中高纬冻土区是陆地生态系统重要的碳汇，也是气候变化的敏感区。气候变暖将对区内有机碳库产生重要影响，继而反馈于区域及全球变化。植物细根是土壤有机碳库大小与稳定性的重要影响因素。细根可以通过根际沉积和死亡增加土壤有机质的来源，而根系分泌物也会通过影响微生物的群落结构与活性调节有机质的分解速度，即根际激发效应效应。冻土区泥炭地植被根系向更深层的分布必然导致其碳库的变化，而根际激发效应的方向与强度是影响和控制生态系统尺度土壤碳氮生物地球化学循环的重要根际生态过程。增温背景下冻土区泥炭地细根分布和根际碳效应尚不清楚，这些问题是评估碳固持能力的关键。本项目主要研究了增温背景下冻土区泥炭地白毛衣胡子草细根周转动态；根际和非根际土壤有机碳组分的剖面分布；根系分泌物和细根分解的变化；根际激发效应的方向与强度。增温通过增加融深使白毛羊胡子草细根向更深层生长。自然条件下，白毛羊胡子草细根的分布深度最大为32 cm，而增温条件下为37 cm。增温条件下，30-40 cm深度白毛羊胡子草细根总长度、总面积和总体积分别增加了152.14%、163.85%和208.72%。增温时间的延长降低了白毛羊胡子草负根际激发效应的强度。自然条件下白毛衣胡子草对CO2释放的根际激发效应效应方向为负，说明白毛衣胡子草活根的存在降低了有机质的分解速度。对照条件下（CK），九月初RPE的强度比八月初低13.5%，说明RPE的强度随植物的生长发育和环境因素的变化而变化。增温约一个月并未显著影响RPE的方向与强度，而增温两个月之后RPE的强度比对照低30%。本研究对于深刻认知冻土区泥炭地土壤碳库对全球增温的响应具有重要的理论意义，也可为“双碳”背景下估算与预测冻土区泥炭地土壤碳汇功能提供重要的科学基础数据。