Climate will increasingly determine post‐fire tree regeneration success in low‐elevation forests, Northern Rockies,<scp>USA</scp>

Kemp, Kerry B.; Higuera, Philip E.; Morgan, Penelope; Abatzoglou, John T.

doi:10.1002/ecs2.2568

Cited by 91 publications

(104 citation statements)

References 65 publications

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“…, Kemp et al. ). Consequently, disturbance often catalyzes abrupt vegetation change under disequilibrium conditions caused by a changing climate (Turner , Crausbay et al.…”

Section: Discussionmentioning

confidence: 99%

Living on the edge: trailing edge forests at risk of fire‐facilitated conversion to non‐forest

et al. 2019

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Forests are an incredibly important resource across the globe, yet they are threatened by climate change through stressors such as drought, insect outbreaks, and wildfire. Trailing edge forests—those areas expected to experience range contractions under a changing climate—are of particular concern because of the potential for abrupt conversion to non‐forest. However, due to plant‐climate disequilibrium, broad‐scale forest die‐off and range contraction in trailing edge forests are unlikely to occur over short timeframes (<~25–50 yr) without a disturbance catalyst (e.g., wildfire). This underscores that explicit attention to both climate and disturbance is necessary to understand how the distribution of forests will respond to climate change. As such, we first identify the expected location of trailing edge forests in the intermountain western United States by mid‐21st century. We then identify those trailing edge forests that have a high probability of stand‐replacing fire and consider such sites to have an elevated risk of fire‐facilitated transition to non‐forest. Results show that 18% of trailing edge forest and 6.6% of all forest are at elevated risk of fire‐facilitated conversion to non‐forest in the intermountain western United States by mid‐21st century. This estimate, however, assumes that fire burns under average weather conditions. For a subset of the study area (the southwestern United States), we were able to incorporate expected fire severity under extreme weather conditions. For this spatial subset, we found that 61% of trailing edge forest and 30% of all forest are at elevated risk of fire‐facilitated conversion to non‐forest under extreme burning conditions. However, due to compounding error in our process that results in unknowable uncertainty, we urge caution in a strict interpretation of these estimates. Nevertheless, our findings suggest the potential for transformed landscapes in the intermountain western United States that will affect ecosystem services such as watershed integrity, wildlife habitat, wood production, and recreation.

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“…, Kemp et al. ). Consequently, disturbance often catalyzes abrupt vegetation change under disequilibrium conditions caused by a changing climate (Turner , Crausbay et al.…”

Section: Discussionmentioning

confidence: 99%

Living on the edge: trailing edge forests at risk of fire‐facilitated conversion to non‐forest

et al. 2019

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“…, Kemp et al. , Davis et al. ), as harsh (micro‐) climate conditions decrease seedling survival (Rother et al.…”

Section: Discussionmentioning

confidence: 99%

“…, Kemp et al. ), given projected increases in fire activity and prolonged periods of warm, dry conditions (Flannigan et al. , Littell et al.…”

Section: Discussionmentioning

confidence: 99%

“…Several studies highlight abundant regeneration, both following and independent of wildfire, occurring during cooler-and/or wetter-thanaverage growing seasons, likely due to the importance of soil moisture and low heat stress (League and Veblen 2006, Rother et al 2015, Rother and Veblen 2017. The combined effects of changing climate and fire activity could therefore lead to declines in postfire regeneration in lower-treeline forests throughout western North America, due to changes in seed availability and warm and dry conditions (Welch et al 2016, Stevens-Rumann et al 2018, Kemp et al 2019, Davis et al 2019a). 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%

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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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“…For example, conversion to nonforest can occur following unusually large or shortinterval burns that reduce seed supply and constrain postfire tree regeneration (Brown and Johnstone 2012, Kemp et al 2016. Even if sufficient seed is available, drought in the first few growing seasons following fire can kill tree seedlings (Walck et al 2011, Clark et al 2016, Harvey et al 2016b, Kemp et al 2019.…”

Section: St-century Fire and Forest Trajectoriesmentioning

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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Climate will increasingly determine post‐fire tree regeneration success in low‐elevation forests, Northern Rockies,USA

Cited by 91 publications

References 65 publications

Living on the edge: trailing edge forests at risk of fire‐facilitated conversion to non‐forest

Living on the edge: trailing edge forests at risk of fire‐facilitated conversion to non‐forest

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

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

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