An Ecophysiological Approach to Understanding Mycorrhizal Community Functioning

最近关于生物多样性和生态功能之间关系的研究表明，生态系统的过程受到物种多样性的影响。然而，物种多样性控制生态过程的机制仍然不清楚，也没有经过检验。这项研究将测试一个将外生菌根(EM)真菌的物种多样性与寄主树木表现联系起来的机制模型。外生菌根是真菌与许多林木根系之间的共生协会。这些真菌极大地提高了树木对养分和水分的吸收。尽管EM真菌多样性具有生态重要性，但关于其在森林生态系统功能中的作用的信息很少。大多数生理学研究都是关于单一真菌物种与单一树种的相互作用。研究人员建议调查多种真菌对单一树种寄主的影响。由于大多数被管理用于商业用材生产的森林都是外生菌根，因此了解EM真菌多样性的作用对于可持续地管理这些森林可能是重要的。因此，显然有必要进行实验测试，以评估EM真菌多样性在森林生态系统中的作用。拟议的研究将测试一个概念模型，该模型将EM真菌多样性的变化与宿主的养分吸收和生长联系起来。在单株寄主上构建具有不同养分获取能力的EM真菌组合。该模型将通过：1)比较一系列EM真菌在培养和寄主联合中获取无机和有机养分的生理能力；2)操纵单个树木根系上的EM多样性，并量化树木的表现；3)测量寄主对选定的两种和四种EM群落的反应，这些群落的养分吸收能力有很大差异。这项研究之所以重要，有几个原因。首先，需要了解多样性生态社区的作用，以便制定适当的保护战略和有效管理世界自然资源。其次，这项拟议的研究将为生物多样性和生态系统功能之间的关系提供第一个合理的生理机制的实验测试。第三，人类活动造成的菌根物种多样性的丧失或转移可能会对生态功能产生广泛的影响。

Recent studies of the relationship between biodiversity and ecological functioning suggest that ecosystem processes are influenced by species diversity. However, the mechanisms by which species diversity controls ecological processes remain unclear and untested. This research will test a mechanistic model relating the species diversity of ectomycorrhizal (EM) fungi to host tree performance based on the physiology of the associations.Ectomycorrhizae are symbiotic associations between fungi and the roots of many forest trees. These fungi greatly enhance nutrient and water uptake by trees. Despite their ecological importance, there is little information on the role of EM fungal diversity in the functioning of forest ecosystems. Most physiological studies have been conducted on interactions of single fungal species with single tree species. The PIs propose to investigate the effect of multiple fungal species on a single tree host. Because most forests managed for commercial timber production are ectomycorrhizal, understanding the role of EM fungal diversity may be important for sustainably managing these forests. Thus, there is a clear need for experimental tests that assess the role of EM fungal diversity in forest ecosystems.The proposed research will test a conceptual model relating changes in EM fungal diversity to host nutrient uptake and growth. Assemblages of EM fungi with differing nutrient acquisition capacities will be constructed on single tree hosts. The model will be tested by: 1) comparing the physiological capacity of a range of EM fungi to acquire inorganic and organic nutrients in culture and in host association; 2) manipulating EM diversity on individual tree root systems and quantifying tree performance; and 3) measuring host responses to selected two- and four-species EM communities that differ substantially in their nutrient uptake capacities.This research is important for several reasons. First, understanding the role of a diverse ecological community is needed for developing appropriate conservation strategies and effective management of the world's natural resources. Second, the proposed research will provide the first experimental test of a plausible physiological mechanism for the relationship between biodiversity and ecosystem function. Third, loss of, or shifts in, mycorrhizal species diversity due to human activities may have broad implications for ecological functioning.