Effects of shelterwood and single-tree cutting systems on topsoil quality and functions in northern Iranian forests

Abstract

Foresters always emphasize the understanding of soil properties in evaluating site capacity to support productive forests. In order to conserve and improve soil quality and functions, sophisticated forest management systems are of particular importance. Hyrcanian forests of Iran have been harvested under different silvicultural operations such as shelterwood and selective cutting systems. So far, no studies have been conducted to explore the effects of forest management systems on soil properties in this ecosystem. Consequently, the present study aimed to investigate the impact of shelterwood and single-tree cutting systems on soil quality and functions (i.e. organic matter fractions, biota and microbial/enzyme activities), 10 and 20 years after employing these systems in Hyrcanian beech stands, compared to intact forests (control areas). A total of 60 soil samples (30 × 30 × 10 cm) including 30 samples in August 2008 and 30 samples in August 2018 from each site (i.e. control areas, shelterwood and single-tree systems) were transferred to the laboratory. In addition, topsoil water content, temperature and biological dynamics (August 2008, November 2008, August 2013, November 2013, August 2018 and November 2018) were monitored across the different forest management systems. Based on our data, the studied forest sites and soil properties could be separated by PCA output. The first and second axes, respectively, accounted for 38.59 and 10.95% of the explained variance. The control areas enhanced soil organic matter fractions, biota and microbial/enzyme activities. Between different silvicultural operations, the single-tree system, which is considered as a close-to-nature system, has provided better conditions for soil quality and functions as compared to the shelterwood management system. The understanding of ecological changes within widespread forest management systems can be helpful in forest management and plays a significant role in evaluating silvicultural systems.