不同氮肥力下菌根真菌对高寒草甸生态系统多功能性的影响

Mycorrhizal fungi can form mutualistic symbioses with the roots of most terrestrial plants (plants supply fungi with carbohydrates in exchange for fungal N and P), and play key roles in linking above- and below-ground ecosystems. It has been well accepted that mycorrhizal fungi contribute greatly in regulating biological communities above- and below-ground, and also that these fungi influence various ecosystem functions/processes directly and indirectly. In the field, however, the real functions of mycorrhizas and how mycorrhizal fungi affect ecosystem multifunctionality (EMF), are still unclear, especially under the scenario of changing soil fertility. To answer these questions, we plan to investigate the mycorrhizal functioning and the influences of mycorrhizal fungi and N enrichment on EMF in an alpine meadow ecosystem, on basis of a long-term field experiment with N addition and mycorrhizal suppression, and a newly designed microcosm experiment with inoculating different mycorrhizal communities. Five groups of biological communities above- or below-ground and ten groups of ecosystem functions, which are highly related with primary productivity, nutrient cycling and soil ecological processes, will be measured using multiple state-of-the-art techniques. We aim to elucidate the effects of experimental treatments on the measured ecosystem functions and biological communities, and to illustrate the mycorrhizal functions as well as the underlying mechanisms of mycorrhizal fungi influencing EMF under different soil N fertility. This research will facilitate our understanding of mycorrhizal functions and extend the research scope of global change ecology, and will also contribute greatly to the sustainable management and ecological restoration for alpine meadows.

菌根真菌能与多数陆生植物根系形成基于C、N、P物质交换的互惠共生体，是地上地下生态系统相互联系的重要节点。已有研究表明，菌根真菌对地上地下生物群落有重要的调控作用，直接和间接地影响着许多生态系统功能/过程。然而，在野外条件下菌根真菌的生态功能是什么？如何影响生态系统多功能性（EMF）？是否受土壤肥力的调控？这些问题迄今未得到系统的回答。针对上述问题，本项目拟在高寒草甸生态系统中，利用长期施N及菌根抑制交互处理样地和微宇宙菌根接种实验，通过测定与初级生产力、元素循环、土壤生态过程等密切相关的10类生态系统功能指标及5类地上地下生物群落，在阐明实验处理对各功能指标及生物群落的影响规律基础上，进一步揭示不同N肥力下菌根真菌的生态功能及其对EMF的影响机制。本项目预期研究结果将丰富我们对菌根生态功能的理解，拓宽全球变化生态学的研究范畴，为高寒草甸的草场管理和生态保护/恢复提供科学依据和技术支撑。

丛枝菌根（AM）真菌能与多数陆生植物的根系形成基于碳、氮（N）、磷物质交换的互惠共生体，是地上地下生态系统相互联系的重要节点，影响了诸多生态系统过程。本项目在高寒草甸系统中，通过设置长期N添加和苯菌灵抑制菌根处理样地，研究了实验处理对地上地下生物群落及生态功能的影响，进一步探究了不同氮肥力下AM真菌对生态系统多功能性（EMF）的作用及机制。结果表明，N富集会引起生态系统出现植物病原菌感染增加、花朵密度下降、温室气体排放增加、凋落物分解速率下降等一系列不利影响。抑制菌根处理虽然提高了植物的生产力，但降低了植物的物种多样性、植物群落的时间稳定性；此外，抑制菌根处理还引起了土壤养分淋失增强、植物害虫密度增加、氧化亚氮排放速率翻倍等负面效应。AM真菌对EMF的影响作用主要是通过影响植物多样性间接驱动的。本项目揭示了N富集与苯菌灵抑制菌根真菌处理对生态系统多功能性的影响，在野外条件下量化了菌根真菌的生态功能，相关研究发现为预测N富集与生物多样性丧失引起的环境变化后果提供了科学依据。

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