摘要:多次刀耕火种弃耕后自然恢复的热带次生林恢复速度通常较为缓慢。抚育是提高森林恢复和木材生产速度的重要营林措施，因此利用抚育间伐的方式加快热带次生林的恢复速度是当前森林经营和保护的重要议题。基于海南岛60个0.25 hm²热带次生林样地开展了抚育间伐对比试验。研究表明，经过5年的自然恢复，30个抚育样地和30个对照样地的地上生物量分别提高了24.5%和13.4%，而且抚育样地中减少的地上生物量迅速接近对照样地。抚育主要减少了清除种的地上生物量，而提高了保留种的地上生物量。次生林经过抚育处理后，其地上生物量的绝对增长量显著提高了58.74%，相对增长率显著提高了67.93%。在抚育样地中，地上生物量的绝对增长量和相对增长量均随着抚育强度呈现单峰曲线变化的趋势，抚育强度在（10±2.5）%时地上生物量的相对和绝对增长量最高。抚育强度是影响地上生物量增长量的重要因素，而物种多样性和功能离散度的作用较小。决定地上生物量的相对增长量最重要的因素（负作用）是初始生物量。本研究为我国热带次生林的未来管理提供了重要的理论基础和实践证据。



Abstract:Many studies have proved that human-impacted forests could still provide potential habitats for conserving biodiversity and ecosystem functioning. Protecting and actively restoring degraded tropical forests has become more important than ever under global change. The recovery rate of tropical secondary forests on abandoned lands of multiple cycles of shifting cultivation is usually slow. In improving the recovery rate and timber production in tropical forests, there is a long history in applying silvicultural treatment. Thinning is one of important forest management approach to improve forest restoration and timber production. Thus, using thinning to accelerate the recovery of tropical secondary forests is an important issue for forest management and protection. There is little empirical or experimental evidence of species-focused thinning with the goal of altering forest recovery in the tropical regions. Based on five years census data of 60 0.25 hm² permanent plots of tropical secondary forests of on Hainan Island, a thinning experiment was conducted. All species in sixty plots were classified into three groups:eliminated species, assistant species, and reserved species. Thirty plots were thinned in 2013. During the thinning treatment, all stems ≥ 5 cm DBH (diameter at breast height) of eliminated species were cut (DBH<8 cm) or girdled (8 cm ≤ DBH<15 cm). The result showed that the aboveground biomass (AGB) of 30 thinning plot and 30 control plots (no thinning treatment) increased by 24.5% and 13.4%, respectively. Moreover, the lost AGB in the thinning plots recovered rapidly and had no significant difference to the control plots. The AGB of the reserved species was increased at the expense of reducing AGB of eliminated species after thinning treatment. The absolute increment of AGB in secondary forests after thinning increased significantly by 58.74% and the relative increment by 67.93%. In the 30 thinning plots, the absolute and relative increment of AGB showed unimodal pattern with the increase of thinning intensity. The relative and absolute increment of AGB reached the highest with the thinning intensity of (10±2.5)%. Thinning intensity was important factor affecting the increment of AGB, while species diversity and functional dispersion played less roles. The most important factor of determining the relative increment of AGB (negative effect) is the initial biomass of the secondary forests. This study confirmed that recovery rates of aboveground biomass could be accelerated. This active restoration activity would be likely successful under low thinning intensity. Our study provides important theoretical foundation and practical evidence for the future management of tropical secondary forests of China.





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