Fungi provide essential ecosystem services and engage in a variety of symbiotic relationships with trees. In this study, we investigate the spatial relationship of trees and fungi at a community level. We characterized the spatial dynamics for above- and belowground fungi using a series of forest monitoring plots, at nested spatial scales, located in the tropical South Pacific, in Vanuatu. Fungal communities from different habitats were sampled using metagenomic analysis of the nuclear ribosomal ITS1 region. Fungal communities exhibited strong distance–decay of similarity across our entire sampling range (3–110,000 m) and also at small spatial scales (< 50 m). Unexpectedly, this pattern was inverted at an intermediate scale (3.7–26 km). At large scales (80–110 km), belowground and aboveground fungal communities responded inversely to increasing geographic distance. Aboveground fungal community turnover (beta diversity) was best explained, at all scales, by geographic distance. In contrast, belowground fungal community turnover was best explained by geographic distance at small scales and tree community composition at large scales. Fungal communities from various habitats respond differently to the influences of habitat and geographic distance. At large geographic distances (80–110 km), community turnover for aboveground fungi is better explained by spatial distance, whereas community turnover for belowground fungi is better explained by plant community turnover. Future syntheses of spatial dynamics among fungal communities must explicitly consider geographic scale to appropriately contextualize community turnover.

真菌提供必要的生态系统服务，并与树木建立各种共生关系。在这项研究中，我们在社区层面调查了树木和真菌的空间关系。我们使用一系列位于瓦努阿图热带南太平洋的嵌套空间尺度的森林监测图来表征地上和地下真菌的空间动态。使用核糖体 ITS1 区域的宏基因组分析对来自不同栖息地的真菌群落进行采样。真菌群落在我们的整个采样范围（3-110,000 m）以及小空间尺度（< 50 m）中表现出强烈的距离衰减相似性。出乎意料的是，这种模式在中等规模（3.7-26 公里）时发生了逆转。在大范围内（80-110 公里），地下和地上真菌群落对地理距离的增加有相反的反应。地上真菌群落周转率（β 多样性）在所有尺度上都可以通过地理距离得到最好的解释。相比之下，地下真菌群落更替最好用小尺度的地理距离和大尺度的树木群落组成来解释。来自不同栖息地的真菌群落对栖息地和地理距离的影响有不同的反应。在较大的地理距离（80-110 公里）上，空间距离可以更好地解释地上真菌的群落周转，而植物群落周转可以更好地解释地下真菌的群落周转。