Abstract
There is a heated debate about the effect of global change on tropical forests. Many scientists predict large-scale tree mortality while others point to mitigating roles of CO2 fertilization and – the notoriously unknown – physiological trait acclimation of trees. In this opinion article we provided a first quantification of the potential of trait acclimation to mitigate the negative effects of warming on tropical canopy tree growth and survival. We applied a physiological tree growth model that incorporates trait acclimation through an optimization approach. Our model estimated the maximum effect of acclimation when trees optimize traits that are strongly plastic on a week to annual time scale (leaf photosynthetic capacity, total leaf area, stem sapwood area) to maximize carbon gain. We simulated tree carbon gain for temperatures (25–35°C) and ambient CO2 concentrations (390–800 ppm) predicted for the 21st century. Full trait acclimation increased simulated carbon gain by up to 10–20% and the maximum tolerated temperature by up to 2°C, thus reducing risks of tree death under predicted warming. Functional trait acclimation may thus increase the resilience of tropical trees to warming, but cannot prevent tree death during extremely hot and dry years at current CO2 levels. We call for incorporating trait acclimation in field and experimental studies of plant functional traits, and in models that predict responses of tropical forests to climate change.
Highlights
The effect of climate change on tropical forests is highly uncertain and subject to a heated debate (Körner, 2009; Lewis et al, 2009; Clark et al, 2010; Rammig et al, 2010; Corlett, 2011)
We developed and used a mechanistic, mathematical, plant model that calculates the daily carbon gain of trees based on the hydraulic tree structure accounting for the acquisition, transport and transpiration of water, leaf stomatal coordination, and chemistry and temperature dependency of photosynthesis and respiration of C3-plants (Figure 1, Supporting Information Text S1; Sterck et al, 2011)
When considering tree carbon gain, our results suggest that the negative impacts of temperature and water stress on tree carbon gain will likely be more than offset by the positive impacts of trait acclimation and increase in ambient CO2 under the 2–4◦C warming scenarios predicted for the end of this century
Summary
The effect of climate change on tropical forests is highly uncertain and subject to a heated debate (Körner, 2009; Lewis et al, 2009; Clark et al, 2010; Rammig et al, 2010; Corlett, 2011). In spite of its potential importance in mitigating the negative impacts of warming on tropical forest trees, trait acclimation has so far remained notoriously understudied (Wright et al, 2009; Corlett, 2011). The potential effect of trait acclimation on tree carbon gain under climate change has not been quantified so far (Corlett, 2011) and is not incorporated in current dynamic global vegetation models, DGVMs (Galbraith et al, 2010; Huntingford et al, 2013). If trait acclimation mitigates negative effects of warming for trees and forests, it may increase maximum temperatures at which tropical trees survive with potential implications for the risks of tropical forest dieback
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