title: Reduced transpiration response to precipitation pulses precedes mortality in a piñon-juniper woodland subject to prolonged drought.
abstract: Global climate change is predicted to alter the intensity and duration of droughts, but the effects of changing precipitation patterns on vegetation mortality are difficult to predict. Our objective was to determine whether prolonged drought or above-average precipitation altered the capacity to respond to the individual precipitation pulses that drive productivity and survival. We analyzed 5 yr of data from a rainfall manipulation experiment in piñon-juniper (Pinus edulis-Juniperus monosperma) woodland using mixed effects models of transpiration response to event size, antecedent soil moisture, and post-event vapor pressure deficit. Replicated treatments included irrigation, drought, ambient control and infrastructure control. Mortality was highest under drought, and the reduced post-pulse transpiration in the droughted trees that died was attributable to treatment effects beyond drier antecedent conditions and reduced event size. In particular, trees that died were nearly unresponsive to antecedent shallow soil moisture, suggesting reduced shallow absorbing root area. Irrigated trees showed an enhanced response to precipitation pulses. Prolonged drought initiates a downward spiral whereby trees are increasingly unable to utilize pulsed soil moisture. Thus, the additive effects of future, more frequent droughts may increase drought-related mortality.
authors.affiliation: Department of Biology, 1 University of New Mexico, MSC03 2020, Albuquerque, NM, 87131-0001, USA.
authors.forename: Jennifer A
authors.initials: JA
authors.lastname: Plaut
authors.affiliation: Department of Statistics, Rice University, MS 138, PO Box 1892, Houston, TX, 77251, USA.
authors.forename: W Duncan
authors.initials: WD
authors.lastname: Wadsworth
authors.affiliation: Department of Biology, 1 University of New Mexico, MSC03 2020, Albuquerque, NM, 87131-0001, USA.
authors.forename: Robert
authors.initials: R
authors.lastname: Pangle
authors.affiliation: Departamento de Ciencias del Agua y del Medio Ambiente, Instituto Tecnológico de Sonora, Ciudad Obregón Sonora, 85000, Mexico.
authors.forename: Enrico A
authors.initials: EA
authors.lastname: Yepez
authors.affiliation: Earth and Environmental Sciences Division, Los Alamos National Laboratory, Los Alamos, NM, 87545, USA.
authors.forename: Nate G
authors.initials: NG
authors.lastname: McDowell
authors.affiliation: Department of Biology, 1 University of New Mexico, MSC03 2020, Albuquerque, NM, 87131-0001, USA.
authors.forename: William T
authors.initials: WT
authors.lastname: Pockman
mesh_terms: D057914:Agricultural Irrigation; D002244:Carbon / Q000378:metabolism*; D055864:Droughts; D017753:Ecosystem; D018653:Juniperus / Q000502:physiology*; D008962:Models, Theoretical; D009516:New Mexico; D028223:Pinus / Q000502:physiology*; D018526:Plant Transpiration / Q000502:physiology*; D011891:Rain; D012987:Soil; D014197:Trees; D055548:Vapor Pressure
chemical_list: D012987:Soil; D002244:Carbon
keywords: carbon starvation; die-off; hydraulic conductance; hydraulic failure; mixed effects model; semi-arid