Linking plant hydraulics and the fast–slow continuum to understand resilience to drought in tropical ecosystems

• Published in: The New phytologist Vol. 230; no. 3; pp. 904 - 923
• Main Authors: Oliveira, Rafael S., Eller, Cleiton B., de V. Barros, Fernanda, Hirota, Marina, Brum, Mauro, Bittencourt, Paulo
• Format: Journal Article
• Language: English
• Published: England Wiley 01.05.2021; Wiley Subscription Services, Inc
• Subjects: Amazon tropical forest; Avoidance; Avoidance behaviour; Biodiversity; Biogeochemical cycle; Biogeochemical cycles; Biogeochemistry; Capacitance; carbon; Climate system; Computational fluid dynamics; Distribution; Drought; Droughts; Ecosystem; Ecosystems; embolism resistance; Fluid flow; fluid mechanics; hydraulic conductivity; hydraulic safety margin; Hydraulics; Nutrients; plant hydraulic diversity; Plant Leaves; Rainforest; Rainforests; Rooting; Safety margins; Soil nutrients; Tansley review; terrestrial ecosystems; Trees; Tropical climate; tropical dry forest; tropical rain forests; tropical savannahs; Vegetation; Vulnerability; Water; Water availability; Water potential; drought; tropical savannahs; plant hydraulic diversity; Amazon tropical forest; rainforest; embolism resistance; hydraulic safety margin; tropical dry forest
• ISSN: 0028-646X; 1469-8137; 1469-8137
• DOI: 10.1111/nph.17266

Tropical ecosystems have the highest levels of biodiversity, cycle more water and absorb more carbon than any other terrestrial ecosystem on Earth. Consequently, these ecosystems are extremely important components of Earth’s climatic system and biogeochemical cycles. Plant hydraulics is an essential discipline to understand and predict the dynamics of tropical vegetation in scenarios of changing water availability. Using published plant hydraulic data we show that the trade-off between drought avoidance (expressed as deep-rooting, deciduousness and capacitance) and hydraulic safety (P50 – the water potential when plants lose 50% of their maximum hydraulic conductivity) is a major axis of physiological variation across tropical ecosystems. We also propose a novel and independent axis of hydraulic trait variation linking vulnerability to hydraulic failure (expressed as the hydraulic safety margin (HSM)) and growth, where inherent fast-growing plants have lower HSM compared to slow-growing plants. We surmise that soil nutrients are fundamental drivers of tropical community assembly determining the distribution and abundance of the slow-safe/fast-risky strategies. We conclude showing that including either the growth-HSM or the resistance-avoidance trade-off in models can make simulated tropical rainforest communities substantially more vulnerable to drought than similar communities without the trade-off. These results suggest that vegetation models need to represent hydraulic trade-off axes to accurately project the functioning and distribution of tropical ecosystems.