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Contributed Talk

Session: : Climate Change: Plants 6

COS 122-6 - CANCELLED - Tree growth sensitivity to climate and its mediation by species functional traits across the Tropics

Tuesday, August 8, 2023
4:45 PM – 5:00 PM PDT
Location: B118
Abstract:

Introduction: Tropical forests represent key terrestrial ecosystems for carbon stocks and biodiversity. The dynamics of carbon sequestration in forests is primarily driven by tree growth, but climate change is altering tree performances, with important consequences for the carbon cycle, climate regulation and biodiversity. Yet, we are still lacking a mechanistic understanding of the variability observed in the responses of tropical forest to altered climate. While demographic approaches have traditionally focused on how individual performance vary with ontogeny, trait-based approaches have focused on how properties of individuals (traits) change with abiotic and biotic factors and relate to performance. In spite of traits mediating individual fitness and therefore populations and communities, we still understand little of how species traits may control interspecific differences in growth sensitivities to spatial and temporal climatic variations.

Methods: Here, we use Bayesian multilevel models embedded into a causal framework to investigate how tropical tree species growth respond to different average climates as well as to climate anomalies (effects of climate change). To do so, we gathered decades of multi-annual tree growth data encompassing Africa, South America, South-East Asia and Oceania, as well as multiple environmental gradients distributed across the tropical continents. We use morphological, chemical and physiological traits of >700 tropical tree species to test whether species’ traits and strategies can shed a mechanistic light on the interspecific and regional differences in demographic responses to climate.

Results: We show that tree growth responds negatively to increasing anomalies in temperature, atmospheric evaporative demand and maximum water deficit, but growth sensitivity to climate anomalies also vary widely across species and biogeographic regions. Interspecific differences are partly accounted for by traits related to acquisition resource strategies. We also highlight a range of trade-offs in species positive and negative responses to climate, suggesting eco-evolutionary constraints related to local climatic variations and biogeography.

Implications: Our work shows that both average climate conditions and climate anomalies shape tree growth in tropical forests across continents, and that species traits can help to understand the mechanisms underlying the variability of demographic responses to climate change, providing promising ways to improve the representativity of the diversity of functional strategies of tropical tree species and how they affect demographic responses in Dynamic Global Vegetation Models. We also show that considering region-specific variations and long-term climates variations in growth responses to climate enhances the accuracy of tropical forest responses to environmental changes.