气候变暖背景下西南亚高山针叶林根系分泌物对根际土壤氮素转化的影响

The importance of belowground C inputs on soil processes and functions and its feedback to climate change has increasingly been recognized. However, only limited effort has been made to link rhizosphere processes with soil processes such as N cycling and nutrient availability via root and associated microbial processes, which to some extent limits the understanding of belowground rhizosphere processes in forest ecosystems. In this study, we conducted an experiment to detremine, quantitatively and qualitatively, slouble root exudates (i.e. low molecular organic acids, dissolved monosaccharides, amino acids, total dissolved carbon (DOC) and total dissolved nitrogen (DON)) from two coniferous tree species (Picea asperata and Abies faxoniana) and their effects on soil N transformations mediated by root exudates under experimental warming. We also investigated functional microbial groups and soil enzymes associated with soil N cycling in responses to experimental warming using infrared heaters in the eastern Tibetan Plateau. The aim of this study was to determine: (1) examine how the effects of tree species on root exudation and their response differences in related to experimental warming; (2) identify the influences and potential mechanism of root exudates from differnet tree species on soil N transformation and nutrient availability under experimental warming. This project will greatly advance and deepen the development of rhizosphere ecology. Also, this information will be valuable for providing a more comprehensive view of belowground ecological processes under global climate change.

目前，有关全球气候变化条件下根系C源输入与土壤N循环的耦合机制认识十分有限，制约了全球气候变化对森林生态系统根际过程影响的深入了解。本项目以青藏高原东缘西南亚高山针叶林两种主要树种- - -粗枝云杉和岷江冷杉为研究对象，以根际过程为切入点，以根系分泌物为核心，采用红外辐射加热模拟增温的原位控制试验，结合室内控制试验，重点研究气候变暖对西南亚高山针叶林主要树种根系分泌物成分和含量变化（主要针对低分子有机酸、可溶性单糖、氨基酸以及可溶性C、N等）及其介导的根际土壤N素转化、以及与土壤N转化过程密切相关的功能微生物组群和土壤代谢酶活性的影响，试图：1）阐明气候变暖对不同树种根系分泌物成分和变化的影响差异；2）揭示气候变暖条件下根系分泌物变化对土壤N素转化及其养分有效性的影响机制。本项目的实施可加深和提升根际生态学的理论研究；同时，可为全球气候变化对典型森林生态系统地下过程的影响提供新的、全面的认识

目前，有关全球气候变化条件下植物根系C源输入与土壤N循环的耦合机制认识十分有限，制约了全球气候变化对森林根际生态过程影响的深入了解。本项目以西南亚高山针叶林为对象，通过模拟控制试验与室内试验相结合，重点研究增温背景下亚高山针叶林根系分泌物C输入通量变化及其介导的根际土壤N素转化过程及其生态反馈效应，以揭示气候变暖条件下森林根系分泌物变化对土壤N素转化影响机制及其生态反馈效应。主要研究结果如下：①构建完善了森林根系分泌物生态学效应研究的技术手段，推动了国际上根系分泌物仅关注C输入的研究现状；②发现增温导致根系C源输入增加并提高土壤N有效性以满足树木生长所需养分，揭示了气候变暖下高寒森林生产力持续增加的养分维持机制；③发现外生和丛枝菌根树种采取截然不同的“根系C投入-N养分收益”策略以适应其独特的土壤养分经济模式，诠释了根系C源输入在维持森林树种共存和群落稳定的重要调控作用；④发现不同树种由于根系形态和生理特征差异而影响根系分泌物数量和质量，并诱导特异化的土壤C-养分转化过程，为不同树种所诱导的土壤过程和功能差异提供了新的机理性解释。这些研究成果极大地丰富和推动了森林根际生态学及其对环境变化响应的认知水平。依托本项目共发表SCI论文12篇（其中一区4篇，全部为TOP10%期刊），中文2篇。