Increased vapor pressure deficit due to higher temperature leads to greater transpiration and faster mortality during drought for tree seedlings common to the forest–grassland ecotone

Will, Rodney E.; Wilson, Stuart M.; Zou, Chris B.; Hennessey, Thomas

doi:10.1111/nph.12321

Cited by 250 publications

(143 citation statements)

References 33 publications

(53 reference statements)

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“…There are more trees still alive at higher elevations with concomitant lower temperatures and greater rainfall. It has been demonstrated that a small increase in temperature can increase vapour pressure deficit (VPD) which increases tree water use resulting in an increase in mortality during severe drought due to xylem cavitation [33]. This increased mortality with increased temperature is also demonstrated by our model showing a significant increase in mortality on warmer north facing slopes.…”

Section: Discussionsupporting

confidence: 72%

Collapse of an iconic conifer: long-term changes in the demography of Widdringtonia cedarbergensis using repeat photography

et al. 2016

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BackgroundConifer populations appear disproportionately threatened by global change. Most examples are, however, drawn from the northern hemisphere and long-term rates of population decline are not well documented as historical data are often lacking. We use a large and long-term (1931–2013) repeat photography dataset together with environmental data and fire records to account for the decline of the critically endangered Widdringtonia cedarbergensis. Eighty-seven historical and repeat photo-pairs were analysed to establish 20th century changes in W. cedarbergensis demography. A generalized linear mixed-effects model was fitted to determine the relative importance of environmental factors and fire-return interval on mortality for the species.ResultsFrom an initial total of 1313 live trees in historical photographs, 74% had died and only 44 (3.4%) had recruited in the repeat photographs, leaving 387 live individuals. Juveniles (mature adults) had decreased (increased) from 27% (73%) to 8% (92%) over the intervening period. Our model demonstrates that mortality is related to greater fire frequency, higher temperatures, lower elevations, less rocky habitats and aspect (i.e. east-facing slopes had the least mortality).ConclusionsOur results show that W. cedarbergensis populations have declined significantly over the recorded period, with a pronounced decline in the last 30 years. Individuals that established in open habitats at lower, hotter elevations and experienced a greater fire frequency appear to be more vulnerable to mortality than individuals growing within protected, rocky environments at higher, cooler locations with less frequent fires. Climate models predict increasing temperatures for our study area (and likely increases in wildfires). If these predictions are realised, further declines in the species can be expected. Urgent management interventions, including seedling out-planting in fire-protected high elevation sites, reducing fire frequency in higher elevation populations, and assisted migration, should be considered.Electronic supplementary materialThe online version of this article (doi:10.1186/s12898-016-0108-6) contains supplementary material, which is available to authorized users.

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Section: Discussionsupporting

confidence: 72%

Collapse of an iconic conifer: long-term changes in the demography of Widdringtonia cedarbergensis using repeat photography

et al. 2016

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“…For anisohydric A. auriculiformis and E. citriodora, their water use strategy was conservative, imparted minimal effects on regional hydrological budget under current meteorological and soil conditions. The temperature or D would inevitably be enhanced under land use and global climate warming scenarios (Kalnay and Cai, 2003;Will et al, 2013), which probably increases the water use of timber trees, but has little effects on water flux of mature trees (Kagawa et al, 2009). In conclusion, the specific tree hydraulic architectures such as the resistance to embolism, the sensitivity to D, and the regulator (wood density in this research) of G sref should be considered when quantifying the influences of land use changes on water flux.…”

Section: Resultsmentioning

confidence: 95%

Biophysical limits to responses of water flux to vapor pressure deficit in seven tree species with contrasting land use regimes

Gao

Zhao

Shen

et al. 2015

Agricultural and Forest Meteorology

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“…stomatal conductance; g s ). Plants protect themselves from excessive water losses (diffusion out of the leaf) under water-limited environments through a reduction of stomatal conductance, which in turn leads to less carbon uptake (diffusion of CO 2 into the leaf) and possibly subsequent physiological stress (McDowell et al, 2008;Will et al, 2013).…”

Section: Introductionmentioning

confidence: 99%

Response of water use efficiency to summer drought in a boreal Scots pine forest in Finland

et al. 2017

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Abstract. The influence of drought on plant functioning has received considerable attention in recent years, however our understanding of the response of carbon and water coupling to drought in terrestrial ecosystems still needs to be improved. A severe soil moisture drought occurred in southern Finland in the late summer of 2006. In this study, we investigated the response of water use efficiency to summer drought in a boreal Scots pine forest (Pinus sylvestris) on the daily time scale mainly using eddy covariance flux data from the Hyytiälä (southern Finland) flux site. In addition, simulation results from the JSBACH land surface model were evaluated against the observed results. Based on observed data, the ecosystem level water use efficiency (EWUE; the ratio of gross primary production, GPP, to evapotranspiration, ET) showed a decrease during the severe soil moisture drought, while the inherent water use efficiency (IWUE; a quantity defined as EWUE multiplied with mean daytime vapour pressure deficit, VPD) increased and the underlying water use efficiency (uWUE, a metric based on IWUE and a simple stomatal model, is the ratio of GPP multiplied with a square root of VPD to ET) was unchanged during the drought. The decrease in EWUE was due to the stronger decline in GPP than in ET. The increase in IWUE was because of the decreased stomatal conductance under increased VPD. The unchanged uWUE indicates that the trade-off between carbon assimilation and transpiration of the boreal Scots pine forest was not disturbed by this drought event at the site. The JS-BACH simulation showed declines of both GPP and ET under the severe soil moisture drought, but to a smaller extent compared to the observed GPP and ET. Simulated GPP and ET led to a smaller decrease in EWUE but a larger increase in IWUE because of the severe soil moisture drought in comparison to observations. As in the observations, the simulated uWUE showed no changes in the drought event. The model deficiencies exist mainly due to the lack of the limiting effect of increased VPD on stomatal conductance during the low soil moisture condition. Our study provides a deeper understanding of the coupling of carbon and water cycles in the boreal Scots pine forest ecosystem and suggests possible improvements to land surface models, which play an important role in the prediction of biosphere-atmosphere feedbacks in the climate system.

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Increased vapor pressure deficit due to higher temperature leads to greater transpiration and faster mortality during drought for tree seedlings common to the forest–grassland ecotone

Cited by 250 publications

References 33 publications

Collapse of an iconic conifer: long-term changes in the demography of Widdringtonia cedarbergensis using repeat photography

Collapse of an iconic conifer: long-term changes in the demography of Widdringtonia cedarbergensis using repeat photography

Biophysical limits to responses of water flux to vapor pressure deficit in seven tree species with contrasting land use regimes

Response of water use efficiency to summer drought in a boreal Scots pine forest in Finland

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