The effect of simulation of rainfall reduction on soil organic carbon and microbial biomass carbon in managed and unmanaged forest

One of the most important consequences of climate change is the anticipated reduction of rainfall in the future. This study aimed to investigate the dynamics of organic carbon and microbial biomass carbon in the simulated condition of the rainfall reduction in the beech-hornbeam managed stands, followed by its comparison with unmanaged stand. Following site selection of district one of Dr. Bahramnia Forest Management Plan (Shastkalate experimental Forest), 24 sub-samples in each stand were considered as the control treatments as well as treatments of 25, 50 and 75 percent decrease in precipitation. A comparison of the temporal variation of these two important soil characteristics indicated that the soil microbial carbon was more variable to changing environmental conditions. In addition to the significant temporal variations of soil microbial biomass carbon, annual changes in the gaps and below-canopy were also different. The results showed that the effects of 50 and 75 percent of precipitation reduction on soil organic and microbial carbon were significantly different from both 25% and control treatments that showed similar conditions. Changes in these markers in the current condition and the decrease shown by simulated rainfall revealed no significant difference and were similar in the control and managed stands with the selection system. Therefore, and provided the decrease of precipitation in future climatic conditions, forestry plans and harvesting operations with selection systems in mixed beech stands would not lead to significant changes in the amount and temporal pattern of soil organic carbon and microbial biomass carbon. Therefore, it is recommended to apply the selection system for the management of the eastern beech forests of Iran.