Soil functional indicators in mixed beech forests are clearly species-specific

Beech stands are considered part of the ancient forest ecosystems in the northern hemisphere. In mixed stands in beach forest ecosystems, the type of associated tree species can significantly affect soil functions, but their influence on microbial activity, nutrient cycling and belowground properties is unknown. Here, we considered forest patches in northern Iran that are dominated by different tree species: Fagus orientalis Lipsky, Quercus castaneifolia C. A. Mey., Pterocarya fraxinifolia (Lam.), Tilia begonifolia Stev., Zelkova carpinifolia Dippe, Acer cappadocicum Gled, Acer velutinum Boiss., Fraxinus excelsior L., Carpinus betulus L., and Alnus subcordata C. A. Mey. For each forest patch-tree species, litter and soil samples (25x 25 x 10 cm, 100 of each) were analyzed for determine soil and litter properties and their relationship with tree species. The litter decomposition rate during a 1-year experiment was also determined. A PCA showed a clear difference between selected litter and soil characteristics among tree species. F. orientalis, Q. castaneifolia, P. fraxinifolia, T. begonifolia, Z. carpinifolia, A. cappadocicum, and A. velutinum enhanced soil microbial biomass of carbon, whereas patches with F. excelsior, C. betulus and A. subcordata had faster litter decomposition and enhanced biotic activities and C and N dynamics. Thus, soil function indicators were species-specific in the mixed beech forest. A. subcordata (a N-fixing species), C. betulus and F. excelsior were main drivers of microbial activities related to nutrient cycling in the old-growth beech forest.