An Ecophysiological Approach to Understanding Mycorrhizal Community Functioning

生物多样性与生态功能关系的最新研究表明，生态系统过程受物种多样性的影响。然而，物种多样性控制生态过程的机制仍然不清楚，也未经检验。本研究将基于外生菌根（EM）真菌物种多样性与寄主树性能的生理联系，测试一个机制模型。外生菌根是真菌和许多森林树木的根之间的共生关系。这些真菌极大地提高了树木对养分和水分的吸收。尽管EM真菌具有重要的生态意义，但关于EM真菌多样性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针对单一真菌种与单一树种的相互作用进行的。研究人员建议研究多种真菌对单一树宿主的影响。由于大多数用于商业木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很重要。因此，显然需要进行实验测试，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EM真菌多样性变化与宿主营养吸收和生长的概念模型。具有不同营养获取能力的EM真菌组合将在单个树宿主上构建。该模型将通过以下方式进行测试：1)比较EM真菌在培养和寄主关联中获取无机和有机营养物质的生理能力；2)利用EM多样性对单个树木根系的影响，量化树木的表现；3)测量宿主对选择的两种和四种EM群落的反应，这些群落在营养吸收能力上存在很大差异。这项研究之所以重要，有几个原因。首先，了解多样化生态群落的作用是制定适当的保护战略和有效管理世界自然资源所必需的。其次，本研究将首次为生物多样性与生态系统功能之间的关系提供一个合理的生理机制的实验检验。第三，人类活动导致的菌根物种多样性的丧失或变化可能对生态功能产生广泛影响。

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.