Environmental Change Institute, University of Oxford, Oxford OX1 3QY, UK
Lancaster Environment Centre, Lancaster University, Lancaster LA1 4YQ, UK.
Philos Trans R Soc Lond B Biol Sci. 2018 Oct 8;373(1760):20170308. doi: 10.1098/rstb.2017.0308.
Human-modified forests are an ever-increasing feature across the Amazon Basin, but little is known about how stem growth is influenced by extreme climatic events and the resulting wildfires. Here we assess for the first time the impacts of human-driven disturbance in combination with El Niño-mediated droughts and fires on tree growth and carbon accumulation. We found that after 2.5 years of continuous measurements, there was no difference in stem carbon accumulation between undisturbed and human-modified forests. Furthermore, the extreme drought caused by the El Niño did not affect carbon accumulation rates in surviving trees. In recently burned forests, trees grew significantly more than in unburned ones, regardless of their history of previous human disturbance. Wood density was the only significant factor that helped explain the difference in growth between trees in burned and unburned forests, with low wood-density trees growing significantly more in burned sites. Our results suggest stem carbon accumulation is resistant to human disturbance and one-off extreme drought events, and it is stimulated immediately after wildfires. However, these results should be seen with caution-without accounting for carbon losses, recruitment and longer-term changes in species composition, we cannot fully understand the impacts of drought and fire in the carbon balance of human-modified forests.This article is part of a discussion meeting issue 'The impact of the 2015/2016 El Nino on the terrestrial tropical carbon cycle: patterns, mechanisms and implications'.
人为干扰的森林在亚马逊盆地内不断增加，但人们对于极端气候事件及其引发的野火如何影响树干生长知之甚少。在这里，我们首次评估了人为干扰与厄尔尼诺现象引发的干旱和火灾相结合对树木生长和碳积累的影响。我们发现，经过 2.5 年的连续测量，未受干扰和人为干扰的森林之间的树干碳积累没有差异。此外，由厄尔尼诺现象引起的极端干旱并没有影响幸存树木的碳积累率。在最近发生火灾的森林中，树木的生长明显高于未燃烧的森林，而不论其先前是否有人为干扰的历史。木材密度是唯一能够帮助解释燃烧和未燃烧森林中树木生长差异的重要因素，低密度树木在燃烧的地点生长得更为显著。我们的研究结果表明，树干碳积累能够抵抗人为干扰和一次性的极端干旱事件，并且在野火之后立即得到促进。然而，这些结果应该谨慎看待——如果不考虑碳损失、补充和物种组成的长期变化，我们就无法全面了解干旱和火灾对人为干扰森林碳平衡的影响。本文是关于“2015/2016 年厄尔尼诺现象对热带陆地碳循环的影响：模式、机制和意义”讨论专题的一部分。
