Relationship between crown thickness with soil organic matter and microbial respiration in Shastkolateh mixed beech forest, Gorgan

Soil organic matter (SOM) has form only a small fraction of most forest soils (less than 12 percent), although it has an important impact on the physical, chemical and especially biological properties of soils. Organic carbon is accessible and decomposable carbon pool that could increase microbial biomass. By different way, organic carbon increase soil aggregation and porosity and finally forest production. The aim of this study was to investigate the relationship between soil properties including texture, porosity, SOM and microbial respiration with stand properties in order to find the most important relation between stand and soil. In this research, 30 sample plots in mixed Beech forest selected with 400 square meters area. Trees allometric characteristics with DBH greater than 20 cm were measured and some physical, chemical and biological soil properties determined by standard methods. Results showed Beech was the main stand species because of abundance and became more GBH. Tree crown area and GBH were the most important factors those affecting soil properties. A direct relationship was founded between trees crown area, SOM content and microbial respiration. Therefore we should pay special attention to the porosity and soil organic matter in the management of mixed beech stand to increase the stand volume and GBH. The results confirmed that changes in microbial respiration which is affected by soil sand variation in addition to SOM, therefore soil texture and sand content were more important in forest soil studies.