Multi-scale predictions of massive conifer mortality due to chronic temperature rise

McDowell, N. G.; Williams, A. Park; Xu, Chonggang; Pockman, William T.; Dickman, L. Turin; Sevanto, Sanna; Pangle, Robert E.; Limousin, Jean Marc; Plaut, J.; Mackay, D. S.; Ogée, Jérôme; Domec, Jean‐Christophe; Allen, Craig D.; Fisher, Rosie A.; Jiang, Xiaoyan; Muss, J. D.; Breshears, David D.; Rauscher, Sara A.; Koven, C.

doi:10.1038/nclimate2873

Cited by 329 publications

(273 citation statements)

References 28 publications

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“…However, to our knowledge, few modeling studies have considered the impacts of climate change coupled with changes in vegetation (Buma and Livneh, 2015;Carroll et al, 2017;Pribulick et al, 2016). In this study, we incorporated changes from the CMIP5 dynamic vegetation models and from an estimate of forest mortality (McDowell et al, 2016) to consider the impacts of both climate and vegetation changes on the water balance in a headwater system of the CRB, the San Juan River basin. We found that failing to consider climate change coupled with vegetation disturbances could result in a ∼ 10 % over-estimation of the annual water availability for this basin.…”

Section: Discussionmentioning

confidence: 99%

“…For both the dynamic and disturbed scenarios, historical forest cover fractions were reduced and concordantly replaced by shrubs in increments of ∼ 10 years (2006)(2007)(2008)(2009)(2010)(2010)(2011)(2012)(2013)(2014)(2015)(2016)(2017)(2018)(2019)(2020), and so forth); we then ran the projections in 10 year segments, with each segment having a new (constant) forest fraction and starting with the state from the previous time period. Forest cover was reduced by approximately 90 % by 2100 for the disturbed scenario McDowell et al, 2016;Fig. 2c, d).…”

Section: Climate and Vegetation Change Scenariosmentioning

confidence: 99%

“…Both IPSL-CM5B-LR and MPI-ESM-LR show only a small amount of change in terms of land cover shifts by the 2080s. The disturbed scenario reflects regional changes expected in the southwestern USA (McDowell et al, 2016) and therefore projects a more severe, and likely realistic, scenario in terms of projected forest cover change in the San Juan River basin (Fig. 2d).…”

Section: Changing Climate and Land Covermentioning

confidence: 99%

“…2c); and (3) disturbed, which uses disturbance projections based on empirical statistical estimates of forest mortality in the southwest USA ( Fig. 2d; McDowell et al, 2016). Vegetation classes were aggregated to six dominant cover types from 16 classes in the IGBP vegetation classification and from 9-13 classes in the ESMs (Table 2).…”

Section: Climate and Vegetation Change Scenariosmentioning

confidence: 99%

“…Widespread forest disturbances are projected to increase with climate change (McDowell et al, 2016;Allen et al, 2010;Van Mantgem et al, 2009) and this will have major implications for ecosystem services (Anderegg et al, 2013). These ecosystem services impact the provision of food, water, and energy and therefore necessitate a more robust understanding of (a) how the landscape will respond to the associated shifts in timing and frequency of streamflow and (b) the dominant processes driving these changes.…”

Section: Introductionmentioning

confidence: 99%

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Climate-driven disturbances in the San Juan River sub-basin of the Colorado River

Bennett

Bohn

Solander

et al. 2018

Hydrol. Earth Syst. Sci.

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Abstract. Accelerated climate change and associated forest disturbances in the southwestern USA are anticipated to have substantial impacts on regional water resources. Few studies have quantified the impact of both climate change and land cover disturbances on water balances on the basin scale, and none on the regional scale. In this work, we evaluate the impacts of forest disturbances and climate change on a headwater basin to the Colorado River, the San Juan River watershed, using a robustly calibrated (Nash-Sutcliffe efficiency 0.76) hydrologic model run with updated formulations that improve estimates of evapotranspiration for semiarid regions. Our results show that future disturbances will have a substantial impact on streamflow with implications for water resource management. Our findings are in contradiction with conventional thinking that forest disturbances reduce evapotranspiration and increase streamflow. In this study, annual average regional streamflow under the coupled climate-disturbance scenarios is at least 6-11 % lower than those scenarios accounting for climate change alone; for forested zones of the San Juan River basin, streamflow is 15-21 % lower. The monthly signals of altered streamflow point to an emergent streamflow pattern related to changes in forests of the disturbed systems. Exacerbated reductions of mean and low flows under disturbance scenarios indicate a high risk of low water availability for forested headwater systems of the Colorado River basin. These findings also indicate that explicit representation of land cover disturbances is required in modeling efforts that consider the impact of climate change on water resources.

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Section: Discussionmentioning

confidence: 99%

Section: Climate and Vegetation Change Scenariosmentioning

confidence: 99%

Section: Changing Climate and Land Covermentioning

confidence: 99%

Section: Climate and Vegetation Change Scenariosmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Climate-driven disturbances in the San Juan River sub-basin of the Colorado River

Bennett

Bohn

Solander

et al. 2018

Hydrol. Earth Syst. Sci.

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Latitudinal gradients in tree ring stable carbon and oxygen isotopes reveal differential climate influences of the North American Monsoon System

et al. 2016

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The arrival of the North American Monsoon System (NAMS) terminates a presummer hyperarid period in the southwestern United States (U.S.), providing summer moisture that is favorable for forest growth. Montane forests in this region rely on winter snowpack to drive much of their growth; the extent to which they use NAMS moisture is uncertain. We addressed this by studying stable carbon and oxygen isotopes in earlywood and latewood from 11 sites along a latitudinal gradient extending from Arizona and New Mexico to Utah. This study provides the first regional perspective on the relative roles of winter versus summer precipitation as an ecophysiological resource. Here we present evidence that Ponderosa pine uses NAMS moisture differentially across this gradient. 13C/12C ratios suggest that photosynthetic water use efficiency during latewood formation is more sensitive to summer precipitation at the northern than at the southern sites. This is likely due to the fact that NAMS moisture provides sufficiently favorable conditions for tree photosynthesis and growth during most years in the southern sites, whereas the northern sites experience larger summer moisture variability, which in some years is limiting growth. Cellulose δ18O and δ13C values revealed that photoassimilates in the southern sites were produced under higher vapor pressure deficit conditions during spring compared to summer, demonstrating a previously underappreciated effect of seasonal differences in atmospheric humidity on tree ring isotope ratios. Our findings suggest that future changes in NAMS will potentially alter productivity and photosynthetic water use dynamics differentially along latitudinal gradients in southwestern U.S. montane forests.

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Tree Mortality Decreases Water Availability and Ecosystem Resilience to Drought in Piñon‐Juniper Woodlands in the Southwestern U.S.

et al. 2017

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Climate‐driven tree mortality has increased globally in response to warmer temperature and more severe drought. To examine how tree mortality in semiarid biomes impacts surface water balance, we experimentally manipulated a piñon‐juniper (PJ) woodland by girdling all adult piñon trees in a 4 ha area, decreasing piñon basal area by ~65%. Over 3.5 years (2009–2013), we compared water flux measurements from this girdled site with those from a nearby intact PJ woodland. Before and after girdling, the ratio of evapotranspiration (ET) to incoming precipitation was similar between the two sites. Girdling altered the partitioning of ET such that the contribution of canopy transpiration to ET decreased 9–14% over the study period, relative to the intact control, while noncanopy ET increased. We attributed the elevated noncanopy ET in the girdled site each year to winter increases in sublimation and summer increases in both soil evaporation and below‐canopy transpiration. Although we expected that mortality of a canopy dominant would increase the availability of water and other resources to surviving vegetation, we observed a decrease in both soil volumetric water content and sap flow rates in the remaining trees at the girdled site, relative to the control. This postgirdling decrease in the performance of the remaining trees occurred during the severe 2011–2012 drought, suggesting that piñon mortality may trigger feedback mechanisms that leave PJ woodlands drier relative to undisturbed sites and potentially more vulnerable to drought.

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Multi-scale predictions of massive conifer mortality due to chronic temperature rise

Cited by 329 publications

References 28 publications

Climate-driven disturbances in the San Juan River sub-basin of the Colorado River

Climate-driven disturbances in the San Juan River sub-basin of the Colorado River

Latitudinal gradients in tree ring stable carbon and oxygen isotopes reveal differential climate influences of the North American Monsoon System

Tree Mortality Decreases Water Availability and Ecosystem Resilience to Drought in Piñon‐Juniper Woodlands in the Southwestern U.S.

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