长得快的树木活不长，或影响碳储量 |《自然-通讯》论文

论文标题：Forest carbon sink neutralized by pervasive growth-lifespan trade-offs

期刊：Nature communications

作者：R. J. W. Brienen, L. Caldwell et.al

发表时间：2020/09/08

数字识别码：10.1038/s41467-020-17966-z

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根据《自然-通讯》发表的一篇论文Forest carbon sink neutralized by pervasive growth-lifespan trade-offs，树木长得越快，寿命就越短。研究结果或对预测森林在气候变化条件下能储存多少碳提供借鉴。

研究人员已经发现一些树木的生长速率较快与寿命较短之间存在关系，尤其是耐寒的针叶树，但这种关系是否适用于所有物种和气候仍有争议。这种权衡关系与将树木生长速率作为碳储量替代指标的做法或存在矛盾，对全球森林碳储量的地球系统模型预测结果提出了质疑。

英国利兹大学的Roel Brienen和同事分析了一个大型数据集，里面囊括了除非洲和南极洲外所有大洲的110种树木的年轮数据。作者在不同树木物种间和物种内都发现了生长速率快与树木寿命短的联系，并证明了这不是由气候或土壤变量的协方差导致的。利用基于黑云杉（Picea mariana）的数据进行森林模拟，他们进一步证明了这种权衡关系可能会减慢甚至逆转今后的全球森林碳汇。

从树的年轮中得到最大寿命和生长率的关系

图片来源：Brienen et al.

这一研究结果挑战了对成熟林未来碳储量的大部分预测，对全球森林碳汇在今后几十年的持久性提出了质疑。作者呼吁将树木生长寿命的权衡整合到基于过程的森林碳动态模型中。

摘要：Land vegetation is currently taking up large amounts of atmospheric CO2, possibly due to tree growth stimulation. Extant models predict that this growth stimulation will continue to cause a net carbon uptake this century. However, there are indications that increased growth rates may shorten trees′ lifespan and thus recent increases in forest carbon stocks may be transient due to lagged increases in mortality. Here we show that growth-lifespan trade-offs are indeed near universal, occurring across almost all species and climates. This trade-off is directly linked to faster growth reducing tree lifespan, and not due to covariance with climate or environment. Thus, current tree growth stimulation will, inevitably, result in a lagged increase in canopy tree mortality, as is indeed widely observed, and eventually neutralise carbon gains due to growth stimulation. Results from a strongly data-based forest simulator confirm these expectations. Extant Earth system model projections of global forest carbon sink persistence are likely too optimistic, increasing the need to curb greenhouse gas emissions