[Effects of thinning intensity on Pinus tabulaeformis plantation in Huanglong Mountain, Northwest China: a...

A sampling plot investigation was conducted on the seedling regeneration, stand growth, species diversity, and soil characteristics in a Pinus tabulaeformis plantation in Huanglong Mountain on the Loess Plateau of Northwest China after 7 years of close-to-natural management thinning 15% (light thinning), 30% (medium thinning), and 45% (heavy thinning), with the effect of different thinning intensities evaluated. With the increase of thinning intensity, the amount and growth indices of 1-7 years old P. tabulaeformis seedlings increased, but the mean annual increments of the growth indices decreased after an initial increase, with the maximum under medium thinning. As compared with the control (un-thinned plantation), the individual volume under light, medium, and heavy thinning was increased by 20.9%, 32.1% and 52.6%, the volume per hm2 decreased by 4.4%, 15.1%, and 25.3%, and the mean annual growth rate of volume increased by 28.6%, 46.2% and 82.0%, respectively. The species diversity and soil characteristics were improved under thinning, with the order of heavy thinning > medium thinning > light thinning > un-thinning. In this study, 45% thinning was most suitable to the management of P. tabulaeformis plantation in Huanglong Mountain.