Forest carbon sink neutralized by pervasive growth-lifespan trade-offs
Roel Brienen, L. Caldwell, Louis Duchesne, Steven L. Voelker, Jonathan Barichivich, Michele Baliva, Gregório Ceccantini, Alfredo Di Filippo, Samuli Helama, Giuliano Maselli Locosselli, Lidio López, Gianluca Piovesan, Jochen Schöngart, Ricardo Villalba, Emanuel Gloor
Abstract
, 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.