Ecological Importance of Ectomycorrhizal Linkages in the Ozark Mountains and the Fernow Experimental Forests

Underground stem-to-stem linkages involving ectomycorrhizal (ECM) fungi are probably important in forest ecosystems, since these linkages could assist in the survival of established trees as well as increasing the growth and development of seedlings and saplings. This study compared forest communities of the Ozark Mountains of northwest Arkansas and the Fernow Experimental Forest in West Virginia by examining species richness, diversity, relative abundance, and the potential for stems to exhibit spatial distribution and clustering patterns that reflected the existence of linkages by ECM fungi. Data on forest communities in the Ozarks were obtained from eight plot locations in Devil\u27s Den State Park, four plots in Pea Ridge National Military Park, and three plots in the Buffalo National River Park. Data also were collected from ten plots within the Fernow Experimental Forest. The two regions were chosen for their similar topography and the overall dominance of trees, including Quercus (oaks) and Fagus (beech), that had the potential to form ECM linkages. Euclidean distance calculations revealed that spatial relationships existed among ECM trees, seedlings, and saplings in which seedling and sapling displayed decreasing stem height with increasing distance from a tree. Furthermore, when the clustering algorithm MCLUST was applied to the ECM species in the two regions, stems tended to form clusters within 4 m of a tree or near each other. Although species richness and relative abundances of particular trees in the forest communities in the two regions were not similar, both were dominated by ECM trees, albeit belonging to different species. White oak dominated the forests in the Ozarks, whereas red oak and beech were the primary ECM trees in the Fernow Experimental Forest. ECM associations undoubtedly involved numerous fungal taxa but appeared to be dominated by the members of the genera Amanita and Russula, based on sequence data obtained from root tips and fruiting bodies. In summary, this study demonstrated the occurrence of patterns of spatial distribution among ECM-forming trees, seedlings, and saplings in which the presence of the trees appeared to provide a symbiotic \u27host effect\u27 that assisted in the survival and development of smaller stems