Mangan Scott A, Eom Ahn-Heum, Adler Gregory H, Yavitt Joseph B, Herre Edward A
Department of Biology, Indiana University, Bloomington, IN 47405, USA.
Oecologia. 2004 Dec;141(4):687-700. doi: 10.1007/s00442-004-1684-2. Epub 2004 Aug 19.
It is now understood that alterations in the species composition of soil organisms can lead to changes in aboveground communities. In this study, we assessed the importance of spatial scale and forest size on changes in arbuscular mycorrhizal fungal (AMF) spore communities by sampling AMF spores in soils of forested mainland and island sites in the vicinity of Gatun Lake, Republic of Panama. We encountered a total of 27 AMF species or morphospecies, with 17, 8, 1 and 1 from the genera Glomus, Acaulospora, Sclerosystis, and Scutellospora, respectively. At small scales (<100 m2), we found little evidence for spatial structuring of AMF communities (decay of Morisita-Horn community similarity with distance). However, at large spatial scales, we found that the AMF spore community of a mainland plot was more similar to other mainland plots several kilometers (>5) away than to nearby island plots (within 0.7 km). Likewise, most island plots were more similar to other island plots regardless of geographic separation. There was no decay in AMF species richness (number of species), or Shannon diversity (number of species and their spore numbers) either with decreasing forest-fragment size, or with decreasing plant species richness. Of the six most common species that composed almost 70% of the total spore volume, spores of Glomus "tsh" and G. clavisporum were more common in soils of mainland plots, while spores of Glomus "small brown" and Acaulospora mellea were more abundant in soils of island plots. None of these common AMF species showed significant associations with soil chemistry or plant diversity. We suggest that the convergence of common species found in AMF spore communities in soils of similar forest sizes was a result of forest fragmentation. Habitat-dependent convergence of AMF spore communities may result in differential survival of tree seedlings regenerating on islands versus mainland.
现在人们已经认识到，土壤生物物种组成的改变会导致地上群落的变化。在本研究中，我们通过对巴拿马共和国加通湖附近大陆和岛屿森林土壤中的丛枝菌根真菌（AMF）孢子进行采样，评估了空间尺度和森林面积对AMF孢子群落变化的重要性。我们总共发现了27种AMF物种或形态种，其中分别有17种、8种、1种和1种来自球囊霉属、无梗囊霉属、硬囊霉属和盾巨孢囊霉属。在小尺度（<100平方米）下，我们几乎没有发现AMF群落存在空间结构的证据（莫利西塔 - 霍恩群落相似性随距离衰减）。然而，在大空间尺度下，我们发现一个大陆样地的AMF孢子群落与几公里（>5公里）外的其他大陆样地比与附近（0.7公里内）的岛屿样地更相似。同样，大多数岛屿样地彼此之间更相似，无论地理距离远近。AMF物种丰富度（物种数量）或香农多样性（物种数量及其孢子数量）既没有随着森林片段面积的减小而衰减，也没有随着植物物种丰富度的降低而衰减。在构成孢子总体积近70%的六种最常见物种中，“tsh”球囊霉和棒孢球囊霉的孢子在大陆样地土壤中更常见，而“小棕色”球囊霉和蜜色无梗囊霉的孢子在岛屿样地土壤中更为丰富。这些常见的AMF物种均未显示出与土壤化学或植物多样性有显著关联。我们认为，在相似森林面积土壤中AMF孢子群落中常见物种的趋同是森林碎片化的结果。AMF孢子群落的栖息地依赖性趋同可能导致岛屿和大陆上再生的树苗有不同的存活率。
