Hydraulic Failure Defines the Recovery and Point of Death in Water-Stressed Conifers[OA]

By Tim J. Brodribb, H. Cochard. Plant Physiology, 2008

720 citations recorded by the source corpus.

This study combines existing hydraulic principles with recently developed methods for probing leaf hydraulic function to determine whether xylem physiology can explain the dynamic response of gas exchange both during drought and in the recovery phase after rewatering. Four conifer species from wet and dry forests were exposed to a range of water stresses by withholding water and then rewatering to observe the recovery process. During both phases midday transpiration and leaf water potential (Ψleaf) were monitored. Stomatal responses to Ψleaf were established for each species and these relationships used to evaluate whether the recovery of gas exchange after drought was limited by postembolism hydraulic repair in leaves. Furthermore, the timing of gas-exchange recovery was used to determine the maximum survivable water stress for each species and this index compared with data for both leaf and stem vulnerability to water-stress-induced dysfunction measured for each species. Recovery of gas exchange after water stress took between 1 and >100 d and during this period all species showed strong 1:1 conformity to a combined hydraulic-stomatal limitation model (r2 = 0.70 across all plants). Gas-exchange recovery time showed two distinct phases, a rapid overnight recovery in plants stressed to <50% loss of leaf hydraulic conductance (Kleaf) and a highly Ψleaf-dependent phase in plants stressed to >50% loss of Kleaf. Maximum recoverable water stress (Ψmin) corresponded to a 95% loss of Kleaf. Thus, we conclude that xylem hydraulics represents a direct limit to the drought tolerance of these conifer species.

Subfields: Atmospheric Science, Global and Planetary Change, Plant Science

View Paper: https://www.semanticscholar.org/paper/1631d63ba04746b44e44b30c45f5daf2adc99d10

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Citations in the corpus

Observed and anticipated impacts of drought on forest insects and diseases in the United States (2016, background): “that have wide xylem conduits (most angiosperms) (Brodribb and Cochard, 2009).”
Plant resistance to drought depends on timely stomatal closure. (2017, methodology): “One study concerned gymnosperm species only (Brodribb & Cochard 2009) and three other studies were performed on angiosperm species only (Barigah et al. 2013; Urli et al. 2013; Li et al. 2015).”
Growth, carbon‐isotope discrimination, and drought‐associated mortality across a Pinus ponderosa elevational transect (2010, background): “…with a lack of gs sensitivity to climate r 2009 Blackwell Publishing Ltd, Global Change Biology, doi: 10.1111/j.1365-2486.2009.01994.x and has been empirically shown in seedlings (Brodribb & Cochard, 2009) and shrubs (Davis et al., 2002), but not in mature trees (Cinnirella et al., 2002).”
Will a 385 million year‐struggle for light become a struggle for water and for carbon? – How trees may cope with more frequent climate change‐type drought events (2011, background): “…for mature trees, there is very little evidence linking xylem dysfunction to mortality (Cinnirella et al., 2002, but see Sparks & Black, 1999 on small trees) other than mechanistic relationships between drought condition and theoretical ‘point of death’-xylem hydraulics (Brodribb & Cochard, 2009).”
Xylem embolism refilling and resilience against drought-induced mortality in woody plants: processes and trade-offs (2018, background): “Much research has investigated how plants avoid hydraulic failure by preventing formation and spread of catastrophic xylem embolism (Brodribb and Cochard 2009; Pittermann et al. 2013).”
Temperature sensitivity of drought-induced tree mortality portends increased regional die-off under global-change-type drought (2009, background): “Because water potential is highly correlated with the level of air embolism occluding water transport in the xylem (30, 32, 36), we saw no evidence of catastrophic loss of hydraulic transport as a primary driver of differences between treatments.”
Global convergence in the vulnerability of forests to drought (2012, positive): “Overall, gymnosperms showed greater hydraulic safety margins than angiosperms, with 42% of all angiosperms versus only 6% of all gymnosperms operatingatnegativesafetymargins, thatis, Y min below Y 50 (Figs 1,2).”
Causes and implications of the correlation between forest productivity and tree mortality rates (2011, background): “(Even the relative contribution of hydraulic failure to tree mortality during extreme drought remains unclear [e.g., McDowell et al. 2008, Brodribb and Cochard 2009, Sala et al. 2010, Hoffmann et al. 2011, McDowell 2011].)”
Hydraulic failure and repair are not routine in trees (2013, background): “Under this high-cavitation-resistance paradigm, cavitation was seen as an exceptional process occurring only after prolonged water stress with the drought tolerance of the tree depending on its capacity to avoid cavitation (Brodribb and Cochard 2009; Brodribb et al. 2010; Urli et al. 2013).”
Species-specific water use by forest tree species: from the tree to the stand (2012, background): “Stomatal performance also operates, in the specific case of forest tree species, maintaining the hydraulic system functionality within margins of security from catastrophic dysfunction (Brodribb and Cochard, 2009; Tyree and Sperry, 1989).”
Interdependence of chronic hydraulic dysfunction and canopy processes can improve integrated models of tree response to drought (2015, background): “…bypassing embolized conduits at the cost of reduced overall hydraulic conductance, K. Refilling, if it can occur, requires carbon and energy, which may be in short supply especially for isohydric plants [Dickman et al., 2014] if stomata have been closed for an extended period [Mitchell et al.,…”
A synthesis of tree functional traits related to drought-induced mortality in forests across climatic zones (2017, background): “Journal of Applied Ecology © 2017 British Ecological Society, Journal of Applied Ecology (PLC50) for conifers (Brodribb & Cochard 2009) but greater than or equal to the water potential causing 90% loss of conductivity (PLC90) in angiosperms (Urli et al. 2013).”
Life in the treetops: ecophysiological strategies of canopy epiphytes in a tropical montane cloud forest (2015, background): “…widespread effects on plant communities including changes in species distri- bution, decreases in primary productivity, and large- scale mortality due to physiological dysfunction such as hydraulic failure or poor carbon balance (McDowell et al. 2008, Brodribb and Cochard 2009, Kursar et al. 2009).”
Reconsidering plant memory: Intersections between stress recovery, RNA turnover, and epigenetics (2016, background): “The mechanism for this is not yet clear, although possibilities include both hydraulic limitations (119) and a residual ABA signal hindering stomatal opening (120).”
Meta-analysis reveals that hydraulic traits explain cross-species patterns of drought-induced tree mortality across the globe (2016, background): “Thus, the relatively narrow, “safe” tracheids of the gymnosperm conducting system are thought to be unable to recover from water potentials close to their P50 values because of their limited amount of parenchyma in wood and their monopodial growth; conifers rarely show resprouting and refilling, and”