Wildfires and climate change push low-elevation forests across a critical climate threshold for tree regeneration

Davis, Kimberley T.; Dobrowski, Solomon Z.; Higuera, Philip E.; Holden, Zachary A.; Veblen, Thomas T.; Rother, Monica T.; Parks, Sean A.; Sala, Anna; Maneta, Marco P.

doi:10.1073/pnas.1815107116

Cited by 360 publications

(306 citation statements)

References 66 publications

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“…Such fire-induced changes may have a greater impact on vegetation than the direct effects of climate change (Bond & Keeley, 2005). Such climate-mediated increases in disturbance have the potential to exceed the ecological resilience of forests, inducing broad-scale die-off (Allen et al, 2010), and shifts to non-forest ecosystems as tipping points are crossed (Batllori et al, 2018;Davis et al, 2019;Reyer et al, 2015;Stevens-Rumann et al, 2018;Tepley et al, 2018). In northern latitudes, thawing of the permafrost layer may trigger ground surface subsidence, killing trees (via waterlogging), and collapsing permafrost plateaus (Baltzer, Veness, Chasmer, Sniderhan, & Quinton, 2014).…”

Section: Study Limitationsmentioning

confidence: 99%

Climate change likely to reshape vegetation in North America's largest protected areas

Holsinger

Parks

Parisien

et al. 2019

Conservat Sci and Prac

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Climate change poses a serious threat to biodiversity and unprecedented challenges to the preservation and protection of natural landscapes. We evaluated how climate change might affect vegetation in 22 of the largest and most iconic protected area (PA) complexes across North America. We use a climate analog model to estimate how dominant vegetation types might shift under mid-(2041-2070) and latecentury (2071-2100) climate according to the RCP 8.5 scenario. Maps depicting vegetation for each PA and time period are provided. Our analysis suggests that half (11 of 22) of the PAs may have substantially different vegetation by late-21stcentury compared with reference period conditions. The overall trend is toward vegetation associated with warmer or drier climates (or both), with near complete losses of alpine communities at the highest elevations and high latitudes. At low elevation and latitudes, vegetation communities associated with novel climate conditions may assemble in PAs. These potential shifts, contractions, and expansions in vegetation portray the possible trends across landscapes that are of great concern for conservation, as such changes imply cascading ecological responses for associated flora and fauna. Overall, our findings highlight the challenges managers may face to maintain and preserve biodiversity in key PAs across North America. K E Y W O R D Sclimate analogs, climate change, ecological change, protected areas, vegetation change

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Section: Study Limitationsmentioning

confidence: 99%

Climate change likely to reshape vegetation in North America's largest protected areas

Holsinger

Parks

Parisien

et al. 2019

Conservat Sci and Prac

Self Cite

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“…, Hansen and Turner , Davis et al. ), which could cause fuels in subalpine forests to become increasingly limiting.…”

Section: Introductionmentioning

confidence: 99%

Can wildland fire management alter 21st‐century subalpine fire and forests in Grand Teton National Park, Wyoming, USA?

Hansen

Abendroth

Rammer³

et al. 2019

Ecological Applications

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In subalpine forests of the western United States that historically experienced infrequent, high‐severity fire, whether fire management can shape 21st‐century fire regimes and forest dynamics to meet natural resource objectives is not known. Managed wildfire use (i.e., allowing lightning‐ignited fires to burn when risk is low instead of suppressing them) is one approach for maintaining natural fire regimes and fostering mosaics of forest structure, stand age, and tree‐species composition, while protecting people and property. However, little guidance exists for where and when this strategy may be effective with climate change. We simulated most of the contiguous forest in Grand Teton National Park, Wyoming, USA to ask: (1) how would subalpine fires and forest structure be different if fires had not been suppressed during the last three decades? And (2) what is the relative influence of climate change vs. fire management strategy on future fire and forests? We contrasted fire and forests from 1989 to 2098 under two fire management scenarios (managed wildfire use and fire suppression), two general circulation models (CNRM‐CM5 and GFDL‐ESM2M), and two representative concentration pathways (8.5 and 4.5). We found little difference between management scenarios in the number, size, or severity of fires during the last three decades. With 21st‐century warming, fire activity increased rapidly, particularly after 2050, and followed nearly identical trajectories in both management scenarios. Area burned per year between 2018 and 2099 was 1,700% greater than in the last three decades (1989–2017). Large areas of forest were abruptly lost; only 65% of the original 40,178 ha of forest remained by 2098. However, forests stayed connected and fuels were abundant enough to support profound increases in burning through this century. Our results indicate that strategies emphasizing managed wildfire use, rather than suppression, will not alter climate‐induced changes to fire and forests in subalpine landscapes of western North America. This suggests that managers may continue to have flexibility to strategically suppress subalpine fires without concern for long‐term consequences, in distinct contrast with dry conifer forests of the Rocky Mountains and mixed conifer forest of California where maintaining low fuel loads is essential for sustaining frequent, low‐severity surface fire regimes.

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“…, Davis et al. ). Several studies highlight abundant regeneration, both following and independent of wildfire, occurring during cooler‐ and/or wetter‐than‐average growing seasons, likely due to the importance of soil moisture and low heat stress (League and Veblen , Rother et al.…”

Section: Introductionmentioning

confidence: 99%

“…, Davis et al. ). Observed and potential declines in post‐fire regeneration are of increasing management concern, requiring managers to decide if, where, and when post‐fire management interventions, such as plantings, should occur.…”

Section: Introductionmentioning

confidence: 99%

Impacts of growing‐season climate on tree growth and post‐fire regeneration in ponderosa pine and Douglas‐fir forests

et al. 2019

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We studied the impacts of climate variability on low‐elevation forests in the U.S. northern Rocky Mountains by quantifying how post‐fire tree regeneration and radial growth varied with growing‐season climate. We reconstructed post‐fire regeneration and radial growth rates of Pinus ponderosa and Pseudotsuga menziesii at 33 sites that burned between 1992 and 2007, by aging seedlings at the root–shoot boundary. We also measured radial growth in adult trees from 12 additional sites that burned between 1900 and 1990. To quantify the relationship between climate and regeneration, we characterized seasonal climate before, during, and after recruitment pulses using superposed epoch analysis. To quantify growth sensitivity to climate, we performed moving regression analysis for each species and for juvenile and adult life stages. Climatic conditions favoring regeneration and tree growth differed between species. Water deficit and temperature were significantly lower than average during recruitment pulses of ponderosa pine, suggesting that germination‐year climate limits regeneration. Growing degree days were significantly higher than average during years with Douglas‐fir recruitment pulses, but water deficit was significantly lower one year following pulses, suggesting moisture sensitivity in two‐year‐old seedlings. Growth was also sensitive to water deficit, but effects varied between life stages, species, and through time, with juvenile ponderosa pine growth more sensitive to climate than adult growth and juvenile Douglas‐fir growth. Increasing water deficit corresponded with reduced adult growth of both species. Increases in maximum temperature and water deficit corresponded with increases in juvenile growth of both species in the early 20th century but strong reductions in growth for juvenile ponderosa pine in recent decades. Changing sensitivity of growth to climate suggests that increased temperature and water deficit may be pushing these species toward the edge of their climatic tolerances. Our study demonstrates increased vulnerability of dry mixed‐conifer forests to post‐fire regeneration failures and decreased growth as temperatures and drought increase. Shifts toward unfavorable conditions for regeneration and juvenile growth may alter the composition and resilience of low‐elevation forests to future climate and fire activity.

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Wildfires and climate change push low-elevation forests across a critical climate threshold for tree regeneration

Cited by 360 publications

References 66 publications

Climate change likely to reshape vegetation in North America's largest protected areas

Climate change likely to reshape vegetation in North America's largest protected areas

Can wildland fire management alter 21st‐century subalpine fire and forests in Grand Teton National Park, Wyoming, USA?

Impacts of growing‐season climate on tree growth and post‐fire regeneration in ponderosa pine and Douglas‐fir forests

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