木本植物对土壤碳氮矿化的根际激发效应及其影响机制

The effect of living roots on soil organic matter (SOM) decomposition, or rhizosphere priming effect (RPE), plays a crucial role in the carbon cycling of terrestrial ecosystems. However, our understanding of RPE is mostly based on greenhouse studies of herbaceous plants and tree seedlings, and the mechanisms of RPE remain elusive. Therefore, in-depth studies on dynamics and mechanisms of RPE for woody plants are urgently needed to better predict SOM dynamics under global change. In this study, we will choose two important woody plants (Larix principis-rupprechtii and Pinus sylvestris var. mongolica) in the temperate and boreal forests of Northern China, and will use a number of innovative carbon and nitrogen isotopic tracing approaches to investigate the RPE of these two woody plants (including field-grown mature trees and greenhouse-grown 1-3-year-old seedlings) on soil carbon and nitrogen mineralization. In addition, we will measure the quantity and quality of root exudates, root traits, soil microbial community structure and enzyme activity, soil nutrient status, and use these measurements to explore the mechanism of RPE. This project is likely to make breakthrough findings in the dynamics and mechanisms of RPE of woody plants (particularly field-grown mature trees). The results of this project will provide key parameters and theoretical framework for adding RPE module to the next-generation soil organic matter models.

植物根系对土壤有机质分解的影响(根际激发效应)在陆地生态系统碳循环中发挥着重要作用，但是我们对其的认知主要是基于温室种植的草本植物或树木幼苗，而且对其影响机理也不清楚。为了更准确地预测全球变化下的土壤有机质动态，我们亟需针对木本植物的根际激发效应及其影响机制进行深入研究。本项目以我国温带和寒温带森林的两个重要物种(华北落叶松和樟子松)为研究对象，采用多种创新的碳氮同位素示踪方法研究这两种木本植物的野外成熟大树和温室1-3年生幼苗对两种土壤碳氮矿化的根际激发效应，并结合根系分泌物数量和质量、根系属性、土壤微生物群落结构和酶活性、土壤养分状况等指标来探讨根际激发效应的影响机制。本项目有望在野外大树的根际激发效应及其影响机制方面取得突破，所得结果为将根际激发效应加入新一代土壤有机质模型提供关键参数和理论依据。

植物根系对土壤有机质分解的影响(根际激发效应)在陆地生态系统碳循环中发挥着重要作用，但是我们对其的认知主要是基于温室种植的草本植物或树木幼苗，而且对其影响机制也不清楚。为了更准确地预测全球变化下的土壤有机质动态，我们亟需针对木本植物的根际激发效应及其影响机制进行深入研究。本项目结合野外根箱实验，室内盆栽实验和培养实验，文献整合分析等手段，比较全面深入地研究了木本植物激发效应的方向和强度、种间变异、以及与根系功能性状的关联。主要发现有：（1）提示了细根分泌物作为一种资源获取策略、是植物利用高吸收效率形态的细根获取土壤资源的补充；（2）发现了木本植物细根呼吸与经典的根经济型谱维度(RNC-RTD axis)表现出更强的关联性，而与协作维度(SRL-RD axis)的关联较弱；（3）阐明了根系功能性状是调控木本植物SOM分解的根际效应种间变异的关键因子。共发表SCI论文12篇，其中第一标注7篇，包括New Phytologist, Global Change Biology, Soil Biology & Biochemistry, Geoderma, Rhizosphere等期刊。总体来说，本项目较为显著地推动了木本植物根际激发效应种间变异和驱动机制的研究。