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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 (25× 25 × 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. [ABSTRACT FROM AUTHOR]

Microbial indices and their spatial patterns are strongly affected by environmental factors. Spatial variability of soil properties is one of the most important causes of variability in soil microbial indices. This research was conducted in the Caspian forest to assess spatial variabilities and frequency distributions of microbial properties. Ninety soil samples were taken using a grid sampling design 40 × 40 m. Microbial indices, organic carbon, nitrogen and pH were determined. Soil variable distributions showed that microbial indices had abnormal distributions. Logarithmic transformation produced normal distribution. Spatial continuity using geostatistical (variogram) was studied and maps obtained by point kriging. The variograms revealed the presence of spatial autocorrelation. The results indicate that spatial dependence of soil microbial indices was affected by non-intrinsic factors and forest management procedures. The maps show that soil microbial indices and soil properties have spatial variability. The spatial pattern of microbial indices was correlated to organic carbon and nitrogen. [ABSTRACT FROM AUTHOR]