title: Reconciling seasonal hydraulic risk and plant water use through probabilistic soil-plant dynamics.
abstract: Current models used for predicting vegetation responses to climate change are often guided by the dichotomous needs to resolve either (i) internal plant water status as a proxy for physiological vulnerability or (ii) external water and carbon fluxes and atmospheric feedbacks. Yet, accurate representation of fluxes does not always equate to accurate predictions of vulnerability. We resolve this discrepancy using a hydrodynamic framework that simultaneously tracks plant water status and water uptake. We couple a minimalist plant hydraulics model with a soil moisture model and, for the first time, translate rainfall variability at multiple timescales - with explicit descriptions at daily, seasonal, and interannual timescales - into a physiologically meaningful metric for the risk of hydraulic failure. The model, parameterized with measured traits from chaparral species native to Southern California, shows that apparently similar transpiration patterns throughout the dry season can emerge from disparate plant water potential trajectories, and vice versa. The parsimonious set of parameters that captures the role of many traits across the soil-plant-atmosphere continuum is then used to establish differences in species sensitivities to shifts in seasonal rainfall statistics, showing that co-occurring species may diverge in their risk of hydraulic failure despite minimal changes to their seasonal water use. The results suggest potential shifts in species composition in this region due to species-specific changes in hydraulic risk. Our process-based approach offers a quantitative framework for understanding species sensitivity across multiple timescales of rainfall variability and provides a promising avenue toward incorporating interactions of temporal variability and physiological mechanisms into drought response models.
authors.affiliation: Department of Civil and Environmental Engineering, University of California, Berkeley, CA, 94720, USA.|Department of Civil, Environmental, and Geo-Engineering, University of Minnesota, Twin Cities, MN, 55455, USA.
authors.forename: Xue
authors.identifier: 0000-0003-1381-3118
authors.initials: X
authors.lastname: Feng
authors.affiliation: Department of Integrative Biology, University of California, Berkeley, CA, 94720, USA.|Department of Environmental Sciences, Policy, and Management, University of California, Berkeley, CA, 94720, USA.
authors.forename: Todd E
authors.initials: TE
authors.lastname: Dawson
authors.affiliation: Department of Integrative Biology, University of California, Berkeley, CA, 94720, USA.
authors.forename: David D
authors.initials: DD
authors.lastname: Ackerly
authors.affiliation: Department of Botany & Plant Sciences, University of California, Riverside, CA, 92521, USA.
authors.forename: Louis S
authors.initials: LS
authors.lastname: Santiago
authors.affiliation: Department of Civil and Environmental Engineering, University of California, Berkeley, CA, 94720, USA.
authors.forename: Sally E
authors.identifier: 0000-0003-4618-5066
authors.initials: SE
authors.lastname: Thompson
mesh_terms: D002140:California; D057231:Climate Change; D018526:Plant Transpiration; D012621:Seasons; D012987:Soil; D014867:Water
chemical_list: D012987:Soil; D014867:Water
keywords: drought response; plant hydraulic risk; rainfall variability; soil-plant feedback; stochastic soil moisture dynamics