School of Agriculture and Food Sciences, the University of Queensland, St Lucia, QLD 4072, Australia.
School of Agriculture and Food Sciences, the University of Queensland, St Lucia, QLD 4072, Australia; Tropical Forests and People Research Centre, the University of Sunshine Coast, Maroochydore, QLD 4558, Australia.
Sci Total Environ. 2020 Sep 10;734:139098. doi: 10.1016/j.scitotenv.2020.139098. Epub 2020 May 4.
Managed tropical forests are a globally important carbon pool, but the effects of logging and thinning intensities on long-term biomass dynamics are poorly known. We investigated the demographic mechanisms of above-ground biomass recovery over 48 years in an Australian tropical forest following four silvicultural treatments: selective logging only as a control and selective logging followed by low-, medium- and high-intensity thinning. Initial biomass recovery rates following thinning were poor predictors of the long-term changes. Initial biomass recovery from 1969 to 1973 was slow and was largely concentrated on an increase in the biomass of residual stems. From 1973 to 1997, above ground biomass (AGB) increased almost linearly, with a similar slope for all sites. From 1997 to 2015, the rate of biomass accumulation slowed, especially for the L treatment. All thinning treatments stimulated more recruitment and regrowth of non-harvested remaining trees compared to the untreated control. Biomass at both the low and medium intensity treatments has almost fully recovered to 98% and 97% of pre-logging biomass levels respectively. The predicted times of complete above-ground biomass recovery for the logging only and high intensity treatments are 55 and 77 years respectively. The slower biomass recovery at the logging only site was largely due to increased mortality in the last measurement period. The slower recovery of the high intensity site was due to a combination of a higher initial reduction in biomass from thinning and the increased mortality in the last measurement period. The high mortality rates in the most recent measurement period are likely due to the impacts of two cyclones that impacted the study site. Our results suggest that it will take at least around 50 years for this site to recover to its pre-harvest biomass, much longer than many of the cutting cycles currently used in tropical forest management.
人工管理的热带森林是全球重要的碳汇，但采伐和间伐强度对长期生物量动态的影响还知之甚少。我们研究了澳大利亚热带森林在四种林务处理（选择性采伐作为对照，以及选择性采伐后进行低、中、高强度间伐）后 48 年期间地上生物量恢复的人口统计机制。间伐后最初的生物量恢复速率并不能很好地预测长期变化。从 1969 年到 1973 年，间伐后的初始生物量恢复缓慢，主要集中在剩余茎干生物量的增加上。从 1973 年到 1997 年，地上生物量（AGB）几乎呈线性增长，所有地点的斜率都相似。从 1997 年到 2015 年，生物量积累的速度放缓，特别是在 L 处理区。与未处理的对照相比，所有间伐处理都刺激了更多未采伐剩余树木的繁殖和再生。低强度和中强度处理的生物量分别几乎完全恢复到了采伐前生物量水平的 98%和 97%。仅采伐和高强度处理完全恢复地上生物量的预测时间分别为 55 年和 77 年。仅采伐处理的生物量恢复较慢主要是由于最后一次测量期的死亡率增加。高强度处理区恢复较慢的原因是间伐初始生物量减少和最后一次测量期死亡率增加的综合作用。最近一次测量期的高死亡率很可能是由于两次影响研究地点的气旋造成的。我们的研究结果表明，该地区需要至少 50 年才能恢复到采伐前的生物量，比热带森林管理中目前使用的许多采伐周期长得多。
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