The effects of broad and needle-leaved forest covers on soil microbial indices

Knowdays, the increasing of greenhouse gases, especially carbon dioxide, methan and nitrous oxide, and also climate change phenomena is obvious for whole of peoples (17). Findings indicated that the changes of these gases are strongly effected by variability of soil carbon and nitrogen microbial indices (16). One of important approach for reduction of these gases and their effects is achievement to way for theirs storage and sequestration. About this, afforestation in bare lands is emphasized (31). Afforestation with different species (broad-leaved and needle-leaved) has various ecological effects (41). However, the role of afforestation regarding to reduction of climate change risks was not considered collectively through regulation of factors that control the most important greenhouse gases. In this way, Yadava (2012) pointed that the plantating of Acacia catechu and Dalbergia sisso increased significantly the soil microbial biomass compared with control plot, broad-leaved natural forest, after twenty six years (45). In addition, Wen, et al. (2014) in study on soil carbon and nitrogen microbial biomass, under Pinus massoniana pure and mixed stands, claimed that the soil microbial factors are sensitive to sepcies combination and stand age. Also, they found more values of carbon and nitrogen biomass imposed by pure stands (43). Present research was carried out for studying the effect of broad-leaved (alnus, ash, maple and oak) and needle-leaved (cupressus and pine) forest covers on variability of the controller parameters of the most important greenhouse gasess.
Soil sampls were excavated in ten points from 0-10 and 10-20 cm depths, resulting 20 samples, for each forest covers located in Wood and Paper Company of Mazandaran. Soil bulk density, texture, moisture, pH, organic carbon, total nitrogen and microbial indices (microbial respiration, carbon and nitrogen microbial biomass, metabolic quotient) were measured and calculated at the laboratory.
The results are indicating significant differences of soil physico-chemical characters imposed by different land covers. Greater amounts of soil microbial respiration (1.16 mg/g), carbon (334.68 mg/kg) and nitrogen (11.19 mg/kg) microbial biomass, carbon to nitrogen microbial biomass ratio (11.99) and metabolic quotient (3.64 μg CO2-C mg-1 MBC day-1) were found in pine forest, whereas the higher values of nitrogen microbial biomass (38.33 mg/kg) was recorded in Alnus forest stand.
The findings of this study is indicating that the soil quality and health must be considered for selection of tree species in afforestation programs regarding to the reduction effect of climate changes with improving microbial indices.