To relieve water deficits and increase stem-level productivity, stand thinning using whole-tree harvesting (WTH) has been a major form of forest management for Picea crassifolia plantation in the Qilian Mountains of China. However, ecological consequences of this practice in these stands are poorly known. We investigated the effects of three thinning levels on long-term soil carbon storage, soil respiration, and soil properties.
Results/Conclusions
Our results showed that soil carbon stocks decreased significantly with increasing thinning intensity at a soil depth of 0-70 cm, while soil water storage increased, especially in the deep soil layers (30-70 cm). Mean soil respiration rates during the growing season increased significantly with increasing thinning intensity, and the dynamics of soil respiration coincided with that of soil temperature. Generally, 65 to 73% of the variation in soil respiration rates in three thinning levels was explained by the changes in soil temperature. WTH resulted in a significant increase in soil bulk density at the 0-30 cm and in soil pH at the 0-20 cm depths, and in a significant decrease in soil total nitrogen and C:N ratio in the 0-20 cm layers. As no effect of treatment intensity was detected on fine root biomass, we attributed the increase in soil respiration to accelerated decomposition of organic matter as a result of elevated soil temperature and substrate quality. The results of this study demonstrate the potential for WTH to relieve water deficits while decrease carbon sequestration in semi-arid spruce plantation.