Abstract
A better understanding of how climate affects growth in tree species is essential for improved predictions of forest dynamics under climate change. Long-term climate averages (mean climate) drive spatial variations in species' baseline growth rates, whereas deviations from these averages over time (anomalies) can create growth variation around the local baseline. However, the rarity of long-term tree census data spanning climatic gradients has so far limited our understanding of their respective role, especially in tropical systems. Furthermore, tree growth sensitivity to climate is likely to vary widely among species, and the ecological strategies underlying these differences remain poorly understood. Here, we utilize an exceptional dataset of 49years of growth data for 509 tree species across 23 tropical rainforest plots along a climatic gradient to examine how multiannual tree growth responds to both climate means and anomalies, and how species' functional traits mediate these growth responses to climate. We show that anomalous increases in atmospheric evaporative demand and solar radiation consistently reduced tree growth. Drier forests and fast-growing species were more sensitive to water stress anomalies. In addition, species traits related to water use and photosynthesis partly explained differences in growth sensitivity to both climate means and anomalies. Our study demonstrates that both climate means and anomalies shape tree growth in tropical forests and that species traits can provide insights into understanding these demographic responses to climate change, offering a promising way forward to forecast tropical forest dynamics under different climate trajectories.
Highlights
Tropical forests are key contributors to global carbon sequestration (Needham et al, 2018; Pan et al, 2011), but climate change may reduce this important ecosystem service by suppressing tree growth or increasing mortality, in tropical forests (Brodribb et al, 2020; Sullivan et al, 2020)
Our study demonstrates that both climate means and anomalies shape tree growth in tropical forests and that species traits can provide insights into understanding these demographic responses to climate change, offering a promising way forward to forecast tropical forest dynamics under different climate trajectories
We examine the effects of both mean climate and climate anomalies on interannual tree growth variation, both within and across species, and evaluate the role of functional traits in capturing species differences in growth sensitivity
Summary
Tropical forests are key contributors to global carbon sequestration (Needham et al, 2018; Pan et al, 2011), but climate change may reduce this important ecosystem service by suppressing tree growth or increasing mortality, in tropical forests (Brodribb et al, 2020; Sullivan et al, 2020). The multiannual scale of growth variation is of particular interest in the context of climate change; growth changes over long periods that include sustained periods of constraining climatic anomalies (with less opportunity for recovery) likely reflect tree performance responses that impact long-term forest dynamics with climate change (Harris et al, 2018; Jentsch et al, 2007; Sanginés de Cárcer et al, 2018; Yuan et al, 2019) Evidence of such multiannual climate anomaly effects include growth reduction in tropical dry forests following high dry season atmospheric water demand (Mendivelso et al, 2014; Uriarte et al, 2016), or the negative effect of high water deficit on stem net primary productivity (Rifai et al, 2018). Are drier and warmer forests more sensitive to positive anomalies in temperature and water stress?
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