Implementation of different forest management methods in a natural forest: Changes in soil microbial biomass and enzyme activities

Forest management measures have changed soil characteristics, and these changes vary with respect to different management methods. The purpose of our study was to determine the effects of forest management on the soil ecological properties, especially the microbial biomass and enzyme activity. A comprehensive soil quality assessment was used to implement the Soil Quality Index (SQI) Model. Soil samples were collected from a natural oak forest (Quercus aliena var. acuteserrata) after 6 years of different management methods. Three forest management methods were implemented: selective cutting to remove the trees affecting target trees (CNFM), selective cutting to optimizing the stand's spatial structure (SBFM), selective cutting to harvest large-diameter timber and reduce the stand density (SFCS), using unmanaged plots as a reference (NT, control plots). Here, the results showed that microbial biomass C (MBC) and microbial entropy (Cmic/Corg) were both higher in the CNFM and SBFM compared to the NT. CNFM had larger the ratios for MBC and MBN than the NT, while a smaller content of microbial biomass P in the SBFM. Phosphatase and protease activities were impacted by forest management, which was manifested as decreases in protease and increases in phosphatase. Changes in soil enzyme activity may have been caused by soil organic matter and total nitrogen (TN), and the soil microbial biomass was sensitive to changes in TN, available phosphorus, urease and catalase. SQI value decreased in the order: NT > SBFM > CNFM > SFCS, which demonstrate that SFCS had strongly negative effects on comprehensive soil quality compared to CNFM and SBFM. Our finding suggest that forest management strategies that optimizing the spatial structure of forests by selective logging increased efficiency of microbial C and phosphatase activity and had less intensely negative effects on soil quality.