Pickles Brian J, Gorzelak Monika A, Green D Scott, Egger Keith N, Massicotte Hugues B
Ecosystem Science and Management Program, University of Northern British Columbia, 3333 University Way, Prince George, BC, V2N 4Z9, Canada.
Department of Forest and Conservation Sciences, University of British Columbia, Vancouver, BC, V6T 1Z4, Canada.
Mycorrhiza. 2015 Oct;25(7):517-31. doi: 10.1007/s00572-015-0630-y. Epub 2015 Feb 20.
Climatic and land use changes have significant consequences for the distribution of tree species, both through natural dispersal processes and following management prescriptions. Responses to these changes will be expressed most strongly in seedlings near current species range boundaries. In northern temperate forest ecosystems, where changes are already being observed, ectomycorrhizal fungi contribute significantly to successful tree establishment. We hypothesised that communities of fungal symbionts might therefore play a role in facilitating, or limiting, host seedling range expansion. To test this hypothesis, ectomycorrhizal communities of interior Douglas-fir and interior lodgepole pine seedlings were analysed in a common greenhouse environment following growth in five soils collected along an ecosystem gradient. Currently, Douglas-fir's natural distribution encompasses three of the five soils, whereas lodgepole pine's extends much further north. Host filtering was evident amongst the 29 fungal species encountered: 7 were shared, 9 exclusive to Douglas-fir and 13 exclusive to lodgepole pine. Seedlings of both host species formed symbioses with each soil fungal community, thus Douglas-fir did so even where those soils came from outside its current distribution. However, these latter communities displayed significant taxonomic and functional differences to those found within the host distribution, indicative of habitat filtering. In contrast, lodgepole pine fungal communities displayed high functional similarity across the soil gradient. Taxonomic and/or functional shifts in Douglas-fir fungal communities may prove ecologically significant during the predicted northward migration of this species; especially in combination with changes in climate and management operations, such as seed transfer across geographical regions for forestry purposes.
气候和土地利用变化对树种分布具有重大影响，这既通过自然扩散过程，也遵循管理规定。对这些变化的响应在当前物种分布范围边界附近的幼苗中表现得最为强烈。在已经观察到变化的北温带森林生态系统中，外生菌根真菌对树木的成功定植有显著贡献。我们假设，真菌共生体群落可能因此在促进或限制宿主幼苗范围扩展方面发挥作用。为了验证这一假设，在一个普通温室环境中，对内陆花旗松和内陆黑松幼苗的外生菌根群落进行了分析，这些幼苗在沿着生态系统梯度采集的五种土壤中生长。目前，花旗松的自然分布涵盖了这五种土壤中的三种，而黑松的分布则向北延伸得更远。在所遇到的29种真菌物种中，宿主筛选很明显：7种是共享的，9种是花旗松特有的，13种是黑松特有的。两种宿主物种的幼苗都与每种土壤真菌群落形成了共生关系，因此即使那些土壤来自花旗松当前分布范围之外，花旗松也能如此。然而，后一种群落与宿主分布范围内发现的群落相比，在分类学和功能上存在显著差异，这表明存在生境筛选。相比之下，黑松真菌群落在整个土壤梯度上表现出高度的功能相似性。在该物种预计向北迁移的过程中，花旗松真菌群落的分类学和/或功能变化可能在生态上具有重要意义；特别是与气候和管理操作的变化相结合，例如出于林业目的跨地理区域进行种子转移。
