Seasonal changes of soil organic carbon pool in the managed and unmanaged beech-hornbeam stands

Soil organic carbon (SOC) is a major component of global carbon cycle, hence forest soil as one of the major carbon sinks has a key role in the control of atmospheric Co2 concentrations. Consequently, changes of carbon release or uptake by forest ecosystems due to disturbance or management in an unsuitable period can have a considerable impact on atmospheric Co2 concentrations and global warming. In this study, the effect of selection systems were investigated on seasonal changes of soil organic carbon pool (SOCP) in the mixed beech-hornbeam stand in district one of Shastkolate forest, Golestan province. For this purpose, SOCP was determined in depth of 0-20 cm from February of 2014 to February of 2015 in four stands with one hectare area (one in compartment 32 of virgin forest) and three in compartments 30, 33 and 31 in managed forest, in which the last interventions date back to 10, 7 and 1 years ago). Soil temperature and moisture changes were measured through one year as effective factors on SOCP. One-way ANOVA were used to determine soil moisture and temperature variability in each treatment through one year, and seasonal dynamics of SOCP were comprised using repeated measures design (General linear model). The SOCP relationship with soil moisture and temperature were analyzed using Pearson correlation coefficient. Results showed that the monthly changes of soil moisture and temperature had a significant difference in each treatment. SOCP was also significantly correlated with soil moisture and temperature. SOCP difference in different seasons was also significant, which was more obvious in the managed treatments. SOCP showed severe decrease in the managed stands compared to the unmanaged stand in the summer.