Vapour pressure deficit modulates hydraulic function and structure of tropical rainforests under nonlimiting soil water supply

• Published in: The New phytologist Vol. 240; no. 4; pp. 1405 - 1420
• Main Authors: Binks, Oliver, Cernusak, Lucas A., Liddell, Michael, Bradford, Matt, Coughlin, Ingrid, Bryant, Callum, Palma, Ana C., Hoffmann, Luke, Alam, Iftakharul, Carle, Hannah J., Rowland, Lucy, Oliveira, Rafael S., Laurance, Susan G. W., Mencuccini, Maurizio, Meir, Patrick
• Format: Journal Article
• Language: English
• Published: Lancaster Wiley Subscription Services, Inc 01.11.2023
• Subjects: Allometry; Atmospheric conditions; Biomass; Canopies; Canopy; Climate change; Community composition; Conductance; Ecophysiology; evaporative demand; Forests; intraspecific variation; Mathematical analysis; Moisture availability; Moisture content; Plant cover; Rainforests; Relative abundance; Soil; Soil moisture; Soil water; Species composition; species diversity; Stomata; Stomatal conductance; Structure-function relationships; Temperature effects; Transpiration; tropical rain forests; Vapor pressure; vapor pressure deficit; Vapour pressure; Water potential; Water supply; wood density
• ISSN: 0028-646X; 1469-8137; 1469-8137
• DOI: 10.1111/nph.19257

Atmospheric conditions are expected to become warmer and drier in the future, but little is known about how evaporative demand influences forest structure and function independently from soil moisture availability, and how fast‐response variables (such as canopy water potential and stomatal conductance) may mediate longer‐term changes in forest structure and function in response to climate change. We used two tropical rainforest sites with different temperatures and vapour pressure deficits (VPD), but nonlimiting soil water supply, to assess the impact of evaporative demand on ecophysiological function and forest structure. Common species between sites allowed us to test the extent to which species composition, relative abundance and intraspecific variability contributed to site‐level differences. The highest VPD site had lower midday canopy water potentials, canopy conductance ( g c ), annual transpiration, forest stature, and biomass, while the transpiration rate was less sensitive to changes in VPD; it also had different height–diameter allometry (accounting for 51% of the difference in biomass between sites) and higher plot‐level wood density. Our findings suggest that increases in VPD, even in the absence of soil water limitation, influence fast‐response variables, such as canopy water potentials and g c , potentially leading to longer‐term changes in forest stature resulting in reductions in biomass.