小柯机器人

英国牛津大学David Bauman团队近期取得重要工作进展。他们研究发现热带树木的死亡率随着大气水分压力的增加而增加。该项研究成果2022年5月18日在线发表于《自然》杂志上

在这里，研究人员分析了澳大利亚湿润热带地区24个古老森林样地49年的树木动态记录，发现在过去35年里，所有样地和物种的年度树木死亡风险平均增加了一倍，表明预期寿命和碳停留时间可能减少一半。生物量的相关损失没有被增长和补充的收益所抵消。在不太潮湿的局部气候条件下，样地的平均死亡风险较高，但局部平均气候不能预测死亡风险的时间增长速度。物种的死亡风险轨迹各不相同，最高的平均风险发现接近物种的大气蒸汽压不足生态位的上限。整个地区的蒸汽压赤字长期增加很明显，这表明由全球变暖驱动的涉及大气水分压力的阈值可能是潮湿热带森林树木死亡率增加的主要原因。

据介绍，有证据表明热带地区中某些地区的树木死亡率正在加速，这对热带碳汇的未来和全球人为碳预算产生了深远的影响，从而将全球变暖峰值限制在2°C以下。然而，可能导致这种死亡率变化的机制以及特定物种是否特别脆弱仍不清楚。

附：英文原文

Title: Tropical tree mortality has increased with rising atmospheric water stress

Author: Bauman, David, Fortunel, Claire, Delhaye, Guillaume, Malhi, Yadvinder, Cernusak, Lucas A., Bentley, Lisa Patrick, Rifai, Sami W., Aguirre-Gutirrez, Jess, Menor, Imma Oliveras, Phillips, Oliver L., McNellis, Brandon E., Bradford, Matt, Laurance, Susan G. W., Hutchinson, Michael F., Dempsey, Raymond, Santos-Andrade, Paul E., Ninantay-Rivera, Hugo R., Chambi Paucar, Jimmy R., McMahon, Sean M.

Issue&Volume: 2022-05-18

Abstract: Evidence exists that tree mortality is accelerating in some regions of the tropics1,2, with profound consequences for the future of the tropical carbon sink and the global anthropogenic carbon budget left to limit peak global warming below 2°C. However, the mechanisms that may be driving such mortality changes and whether particular species are especially vulnerable remain unclear3,4,5,6,7,8. Here we analyse a 49-year record of tree dynamics from 24 old-growth forest plots encompassing a broad climatic gradient across the Australian moist tropics and find that annual tree mortality risk has, on average, doubled across all plots and species over the last 35 years, indicating a potential halving in life expectancy and carbon residence time. Associated losses in biomass were not offset by gains from growth and recruitment. Plots in less moist local climates presented higher average mortality risk, but local mean climate did not predict the pace of temporal increase in mortality risk. Species varied in the trajectories of their mortality risk, with the highest average risk found nearer to the upper end of the atmospheric vapour pressure deficit niches of species. A long-term increase in vapour pressure deficit was evident across the region, suggesting that thresholds involving atmospheric water stress, driven by global warming, may be a primary cause of increasing tree mortality in moist tropical forests.

DOI: 10.1038/s41586-022-04737-7

Source: https://www.nature.com/articles/s41586-022-04737-7

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