Microbial respiration and microbial biomass C relationship with soil organic matter in different types of mixed beech forest

Soil microbial respiration (SMR) and microbial biomass C (MBC) are two important site quality indices that can be used to assess the health status and rate of carbon cycling in forest ecosystems during litter decomposition processes. The purpose of this study was to determine the relationship between SMR and MBC with soil organic matter (SOM) in mixed beech forests in a permanent plot in compartment 32 in Shastkolate Forest, Golestan province, northern Iran. Using systematic random sampling, tree characteristics were recorded and soil samples collected in 90 sample plots. SMR determined using Closed-Bottle method, MBC by fumigation-extraction method and SOM by Walkley-Black method. Linear regression analysis, ANOVA and Duncan test were conducted. In this study, four forest types including pure beech, beech-hornbeam, beech-maple and mixed beech were distinguished. ANOVA tests revealed significant differences (α=5%) between SMR and MBC in pure beech stands compared to other forest types. Linear regression showed positively significant relation between SMR and MBC with SOM. Regression R2 was about 0.89 indicating the importance of SOM in enhanced microbial richness and litter decomposition rate. Soil quality and health were shown to be highest in beech-hornbeam forest type, suggesting the importance of hornbeam intermixed with beech. Silviculturists should thus acknowledge the crucial role of hornbeam in silvicultural interventions.