Smithsonian Tropical Research Institute, Ancon, Panama.
Morton Arboretum, Lisle, IL, USA.
Glob Chang Biol. 2020 Mar;26(3):1485-1498. doi: 10.1111/gcb.14833. Epub 2019 Oct 15.
Tropical forest responses to climate and atmospheric change are critical to the future of the global carbon budget. Recent studies have reported increases in estimated above-ground biomass (EAGB) stocks, productivity, and mortality in old-growth tropical forests. These increases could reflect a shift in forest functioning due to global change and/or long-lasting recovery from past disturbance. We introduce a novel approach to disentangle the relative contributions of these mechanisms by decomposing changes in whole-plot biomass fluxes into contributions from changes in the distribution of gap-successional stages and changes in fluxes for a given stage. Using 30 years of forest dynamic data at Barro Colorado Island, Panama, we investigated temporal variation in EAGB fluxes as a function of initial EAGB (EAGB ) in 10 × 10 m quadrats. Productivity and mortality fluxes both increased strongly with initial quadrat EAGB. The distribution of EAGB (and thus EAGB ) across quadrats hardly varied over 30 years (and seven censuses). EAGB fluxes as a function of EAGB varied largely and significantly among census intervals, with notably higher productivity in 1985-1990 associated with recovery from the 1982-1983 El Niño event. Variation in whole-plot fluxes among census intervals was explained overwhelmingly by variation in fluxes as a function of EAGB , with essentially no contribution from changes in EAGB distributions. The high observed temporal variation in productivity and mortality suggests that this forest is very sensitive to climate variability. There was no consistent long-term trend in productivity, mortality, or biomass in this forest over 30 years, although the temporal variability in productivity and mortality was so strong that it could well mask a substantial trend. Accurate prediction of future tropical forest carbon budgets will require accounting for disturbance-recovery dynamics and understanding temporal variability in productivity and mortality.
热带森林对气候和大气变化的响应对全球碳预算的未来至关重要。最近的研究报告称，原始热带森林的地上生物量（EAGB）储量、生产力和死亡率增加。这些增加可能反映了由于全球变化和/或过去干扰的长期恢复而导致的森林功能的转变。我们引入了一种新的方法，通过将整个斑块生物量通量的变化分解为间隙演替阶段分布变化和给定阶段通量变化的贡献，来区分这些机制的相对贡献。利用巴拿马巴罗科罗拉多岛 30 年的森林动态数据，我们研究了 EAGB 通量随初始 EAGB（EAGB ）在 10×10m 样方中的时间变化。生产力和死亡率通量都随初始样方 EAGB 强烈增加。30 年来（和七次清查），EAGB 在样方中的分布（因此 EAGB ）几乎没有变化。EAGB 通量随 EAGB 的变化在清查间隔之间差异很大且显著，特别是 1985-1990 年的生产力较高，与 1982-1983 年厄尔尼诺事件后的恢复有关。清查间隔之间的整个斑块通量的变化主要由通量随 EAGB 的变化解释，EAGB 分布的变化几乎没有贡献。生产力和死亡率的高观察到的时间变化表明该森林对气候变率非常敏感。在 30 年内，该森林的生产力、死亡率或生物量没有一致的长期趋势，尽管生产力和死亡率的时间变异性如此强烈，以至于很可能掩盖了实质性的趋势。准确预测未来热带森林碳预算需要考虑干扰-恢复动态，并了解生产力和死亡率的时间变异性。
