This is a repository copy of Tropical tree mortality has increased with rising atmospheric water stress.

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 49 years 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.

22Background: Chemical soil factors play an important role in generating and maintaining plant diversity.

Questions: How do resource acquisition-related traits and stress tolerancerelated traits shift along Cu and Co gradients? What are the relative contributions of species turnover and intraspecific variation in driving these shifts?Location: Fungurume V hill, Katanga province, Democratic Republic of Congo.Methods: We measured five functional traits (vegetative height, leaf area, specific leaf area (SLA) and leaf Cu and leaf Co concentration) related to resource acquisition, competitive ability and metal tolerance strategy for 37 of the most abundant species from 32 plots along natural Cu and Co gradients (from 92 to 6737 mgÁkg À1 and 10 to 655 mgÁkg À1 , respectively). Linear regression was applied to analyse species-level and community-level changes in these traits along the study gradients. Using variance decomposition, we evaluated the relative contribution of intraspecific variation and species turnover to the total community variation along the Cu gradient.Results and Conclusions: At the community level, plant height and leaf area decreased while SLA and leaf metal concentrations increased with increasing soil metal concentration. At the species level, patterns were often idiosyncratic and lacked generality. As a result, species turnover was the predominant factor explaining community-level variation along the study gradients, which was particularly clear for variation in leaf Cu concentration. This reflects the constitutive ability of some species to exclude metal, while other species can tolerate high metal concentrations in their leaves. The study emphasizes the importance of evaluating the origin of phenotypic variations observed at the community level.