Eastern US deciduous tree species respond dissimilarly to declining soil moisture but similarly to rising evaporative demand. (13th November 2020)

• Record Type: Journal Article
• Authors: Denham, Sander O; Oishi, A Christopher; Miniat, Chelcy F; Wood, Jeffrey D; Yi, Koong; Benson, Michael C; Novick, Kimberly A
• Editors: Whitehead, David
• Is Part Of: Tree physiology. Volume 41:Number 6(2021)
• Page Start: 944
• Page End: 959
• Publication Date: 2020-11-13
• Subjects: conductance -- drought -- sap flux -- vapor pressure deficit; Trees -- Physiology -- Periodicals; 582.16
• DOI: 10.1093/treephys/tpaa153
• Languages: English
• ISSNs: 0829-318X

Abstract

Abstract: Hydraulic stress in plants occurs under conditions of low water availability (soil moisture; θ) and/or high atmospheric demand for water (vapor pressure deficit; D ). Different species are adapted to respond to hydraulic stress by functioning along a continuum where, on one hand, they close stomata to maintain a constant leaf water potential (ΨL ) (isohydric species), and on the other hand, they allow ΨL to decline (anisohydric species). Differences in water-use along this continuum are most notable during hydrologic stress, often characterized by low θ and high D ; however, θ and D are often, but not necessarily, coupled at time scales of weeks or longer, and uncertainty remains about the sensitivity of different water-use strategies to these variables. We quantified the effects of both θ and D on canopy conductance ( G c ) among widely distributed canopy-dominant species along the isohydric–anisohydric spectrum growing along a hydroclimatological gradient. Tree-level G c was estimated using hourly sap flow observations from three sites in the eastern United States: a mesic forest in western North Carolina and two xeric forests in southern Indiana and Missouri. Each site experienced at least 1 year of substantial drought conditions. Our results suggest that sensitivity of G c to θ varies across sites and species, with G c sensitivity being greater in dry than in wet sites, and greater for isohydric compared with anisohydric species. However, once θ limitations are accounted for, sensitivity of G c to D remains relatively constant across sites and species. While D limitations to G c were similar across sites and species, ranging from 16 to 34% reductions, θ limitations to G c ranged from 0 to 40%. The similarity in species sensitivity to D is encouraging from a modeling perspective, though it implies that substantial reduction to G c will be experienced by all species in a future characterized by higher D .