Thinning effects on stand growth, carbon stocks, and soil properties in Brutia pine plantations.

BACKGROUND: The purpose of this study was to investigate the effects of thinning on stand growth, carbon (C) sequestration, and soil properties in Brutia pine (Pinus brutia Ten.) plantations. The study was conducted at two experimental sites -the Antalya-Kaş and Isparta-Eğirdir plantation areas- in Turkey between 1985 and 2015. Different thinning intensities -unthinned (control), moderate, and heavy- were replicated in four blocks. We determined the C in the living biomass, litter, soil, and some soil features for each experimental parcel.

RESULTS: We found no statistically significant difference in total stand volume between thinning-intensity treatments 30 years after thinning. This may be due to more light availability and less competition between trees and faster tree-diameter growth rate after thinning, thus explaining the volume in the treated parcels compared to the control over time. The C stocks in the biomass, litter, and soil were not significantly influenced by the thinning intensity. The nutrients in the litter and soil, and other soil properties, were not significantly different among thinning parcels. This implies that the C and other nutrients in the litter and soil are related to the stand volume and biomass, which were not changed by thinning in time.

CONCLUSION: This finding is important in terms of showing that there was no change in total stand volume by thinning, which has been debated in the literature. This information is useful for forest managers when determining thinning strategy.