Data from: Multiple stages of tree seedling recruitment are altered in tropical forests degraded by selective logging

Tropical forest degradation is a global environmental issue. In degraded forests, seedling recruitment of canopy trees is vital for forest regeneration and recovery. We investigated how selective logging, a pervasive driver of tropical forest degradation, impacts canopy tree seedling recruitment, focusing on an endemic dipterocarp Dryobalanops lanceolata in Sabah, Borneo. During a mast-fruiting event in intensively logged and nearby unlogged forest, we examined four stages of the seedling recruitment process: seed production, seed predation, and negative density-dependent germination and seedling survival. Our results suggest that each stage of the seedling recruitment process is altered in logged forest. The seed crop of D. lanceolata trees in logged forest was one-third smaller than that produced by trees in unlogged forest. The functional role of vertebrates in seed predation increased in logged forest while that of non-vertebrates declined. Seeds in logged forest were less likely to germinate than those in unlogged forest. Germination increased with local-scale conspecific seed density in unlogged forest, but seedling survival tended to decline. However, both germination and seedling survival increased with local-scale conspecific seed density in logged forest. Notably, seed crop size, germination and seedling survival tended to increase for larger trees in both unlogged and logged forests, suggesting that sustainable timber extraction and silvicultural practices designed to minimize damage to the residual stand are important to prevent seedling recruitment failure. Overall, these impacts sustained by several aspects of seedling recruitment in a mast-fruiting year suggest that intensive selective logging may affect long-term population dynamics of D. lanceolata. It is necessary to establish if other dipterocarp species, many of which are threatened by the timber trade, are similarly affected in tropical forests degraded by intensive selective logging.

热带森林退化是全球性环境议题。在退化森林中，冠层树木的幼苗更新（seedling recruitment）对于森林的自然更新与恢复至关重要。本研究聚焦婆罗洲（Borneo）沙巴（Sabah）地区的特有龙脑香科植物披针叶龙脑香（Dryobalanops lanceolata），探究作为热带森林退化普遍驱动因子的选择性采伐（selective logging）如何影响冠层树木的幼苗更新过程。在高强度采伐林及其邻近未采伐林的结实大年（mast-fruiting event）期间，我们针对幼苗更新过程的四个阶段展开了调查：种子生产、种子捕食，以及负密度依赖型萌发与幼苗存活。研究结果表明，采伐林内幼苗更新过程的各个阶段均发生改变。采伐林内披针叶龙脑香的种子产量较未采伐林低三分之一。采伐林中，脊椎动物在种子捕食过程中的功能作用有所提升，而无脊椎动物的相关功能作用则出现下降。采伐林内的种子萌发率低于未采伐林。未采伐林中，种子萌发率随局域尺度的同种种子密度升高而提升，但幼苗存活率则呈下降趋势。而在采伐林中，种子萌发率与幼苗存活率均随局域尺度的同种种子密度升高而提升。值得注意的是，无论未采伐林还是采伐林中，较大个体树木的种子产量、萌发率与幼苗存活率均呈上升趋势，这表明旨在最小化对保留林分损害的可持续木材采伐与营林措施，对于防止幼苗更新失败至关重要。总体而言，结实大年期间幼苗更新多个环节受到的上述影响表明，高强度选择性采伐可能会对披针叶龙脑香的长期种群动态产生影响。目前仍需明确，诸多因木材贸易而面临生存威胁的其他龙脑香科物种，是否也会在高强度选择性采伐导致退化的热带森林中受到类似影响。