Eastern US deciduous tree species respond dissimilarly to declining soil moisture but similarly to rising evaporative demand

  • Authors: Denham, Sander; Oishi, A Christopher; Miniat, Chelcy; Wood, Jeffrey; Yi, Koong; Benson, Michael; Novick, Kimberly A.
  • Publication Year: 2020
  • Publication Series: Scientific Journal (JRNL)
  • Source: Tree Physiology
  • DOI: 10.1093/treephys/tpaa153

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 (L) (isohydric species), and on the other hand, they allow L 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 (Gc) among widely distributed canopy-dominant species along the isohydric–anisohydric spectrum growing along a hydroclimatological gradient. Tree-level Gc 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 Gc to θ varies across sites and species, with Gc 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 Gc to D remains relatively constant across sites and species. While D limitations to Gc were similar across sites and species, ranging from 16 to 34% reductions, θ limitations to Gc 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 Gc will be experienced by all species in a future characterized by higher D.

  • Citation: Denham, Sander O; Oishi, A Christopher; Miniat, Chelcy F; Wood, Jeffrey D; Yi, Koong; Benson, Michael C; Novick, Kimberly A. 2020. Eastern US deciduous tree species respond dissimilarly to declining soil moisture but similarly to rising evaporative demand. Tree Physiology. 41(6): 944-959. https://doi.org/10.1093/treephys/tpaa153.
  • Keywords: conductance, drought, sap flux, vapor pressure deficit
  • Posted Date: July 13, 2021
  • Modified Date: July 15, 2021
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