Effect of Thinning on Belowground Biomass in Chestnut Coppices

Abstract

Thinning maintenance is frequently applied in forest management, and it regulates the stand structure by reducing stand density and encouraging faster growth of trees left in the stand. Tree roots have sensitivity to environmental factors that change due to interventions such as thinning. The aim of this study is to investigate the effects of thinning applied at different intensities on the belowground biomass in Anatolian chestnut (Castanea sativa Mill.) coppices in Gölcük region (Kocaeli). In thinning experiments set up in chestnut coppices in Gölcük region, thinning varying at rates of 0% (control), 20% (light), 35% (heavy) and 50% (very heavy) of the basal area were applied. Seven years after thinning, four different intensities of random trial plots were determined within the trial field and root sampling was performed from six different points of each plot according to the soil core technique. The roots cleaned from the soil were classified as fine root (0-2 mm), small root (2-5 mm) and dead root. The variance analysis revealed significant variability in the biomass belowground of chestnut coppices that were thinned at different intensities. Belowground biomass in chestnut coppices varied between 530.4 g m^-2 and 994.2 g m^-2. Total root biomass, live root biomass, fine root biomass, and dead root biomass in very heavily thinned sites were 60%, 44%, 43%, and 300% higher than in other sites, respectively. Small root biomass did not vary among sites. The increase in rhododendron density under the forest caused by intense thinning led to the high belowground biomass in very heavy thinned sites. As a result, while the belowground biomass does not change significantly at thinning intensities of up to 35% in chestnut coppice, the underground biomass increases due to the increase in the density of the forest understory at very heavy thinning of up to 50%.