Seasonal variation of microbial activity in soil and forest floorunder three different fir plantations

Abstract

Microbial activity is one of the important processes for biochemical cycles in soil and forest floor of ecosystems.Because, some of the carbon dioxide and nutrients needed by plants are released during the microbial activity. In this study, the relationships between environmental factors (moisture, temperature, pH, electric conductivity, C, N, Na, Ca, Mg, K, P) and seasonal variations of microbial respiration, microbial biomass-C and metabolic quotient (qCO2) in the forest floor and soil (0-5cm) under three adjacent fir plantation plots (Abies nordmanniana ssp. bornmuelleriana Mattf. (Ab), Abies cilicica Carr. (Ac) and Abies nordmanniana ssp. nordmanniana Mattf (An))are investigated in Atatürk Arboretum, located in Istanbul-Turkey. A bimonthly sampling (from May-2012 to March-2013) was carried out by collecting 54 samples for each soil and forest floor samples within each species.According to the results, soil microbial respiration (SMR) has a significantly lower value in Ab plot. Although SMR and soil microbial biomass-C (SMBC) were correlated with moisture and temperature in An plot, they were correlated with nutrients in the other plots. In general, an increase in soil respiration rates was observed in autumn and early spring. Forest floor microbial respiration (FFMR), microbial biomass-C (FFMBC) and metabolic quotent (qCO2) did not differ among the plots. The measured FFMR, FFMBC and qCO2 parameters were lower in autumn than spring. Forest floor microbial parameters were thought to be drived by the variation of nutrients quantities. As a result, the microbial processes in both soil and forest floor were changed with the effect of different factors,although there was no clear difference among the plots.