Reduced transpiration response to precipitation pulses precedes mortality in a piñon–juniper woodland subject to prolonged drought

• Published in: The New phytologist Vol. 200; no. 2; pp. 375 - 387
• Main Authors: Plaut, Jennifer A., Wadsworth, W. Duncan, Pangle, Robert, Yepez, Enrico A., McDowell, Nate G., Pockman, William T.
• Format: Journal Article
• Language: English
• Published: England New Phytologist Trust 01.10.2013; Wiley Subscription Services, Inc
• Subjects: Additives; Agricultural Irrigation; Atmospheric precipitations; Carbon - metabolism; carbon starvation; Climate change; Climate prediction; die‐off; Drought; Droughts; Ecosystem; hydraulic conductance; hydraulic failure; Hydraulics; Irrigation; Juniperus - physiology; mixed effects model; Modeling; Models, Theoretical; Mortality; New Mexico; Pinus; Pinus - physiology; Plant Transpiration - physiology; Precipitation; Pulse irrigation; Rain; Rainfall; semi‐arid; Soil; Soil moisture; Soil water; Survival; Transpiration; Trees; Vapor Pressure; Vapour pressure; Woodlands; hydraulic conductance; die-off; carbon starvation; hydraulic failure; semi-arid; mixed effects model
• ISSN: 0028-646X; 1469-8137
• DOI: 10.1111/nph.12392

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.