More Like this

1. A changing climate is snuffing out post‐fire recovery in montane forests

   https://doi.org/10.1111/geb.13174  

   Rodman, Kyle C. ; Veblen, Thomas T. ; Battaglia, Mike A. ; Chambers, Marin E. ; Fornwalt, Paula J. ; Holden, Zachary A. ; Kolb, Thomas E. ; Ouzts, Jessica R. ; Rother, Monica T. ; McGill, ed., Brian ( August 2020 , Global Ecology and Biogeography)

   Climate warming is increasing fire activity in many of Earth’s forested ecosystems. Because fire is a catalyst for change, investigation of post‐fire vegetation response is critical to understanding the potential for future conversions from forest to non‐forest vegetation types. We characterized the influences of climate and terrain on post‐fire tree regeneration and assessed how these biophysical factors might shape future vulnerability to wildfire‐driven forest conversion.

   Montane forests, Rocky Mountains, USA.

   1981–2099.

   Pinus ponderosa;Pseudotsuga menziesii.

   We developed a database of dendrochronological samples (n = 717) and plots (n = 1,301) in post‐fire environments spanning a range of topoclimatic settings. We then used statistical models to predict annual post‐fire seedling establishment suitability and total post‐fire seedling abundance from a suite of biophysical correlates. Finally, we reconstructed recent trends in post‐fire recovery and projected future dynamics using three general circulation models (GCMs) under moderate and extreme CO₂emission scenarios.

   Though growing season (April–September) precipitation during the recent period (1981–2015) was positively associated with suitability for post‐fire tree seedling establishment, future (2021–2099) trends in precipitation were widely variable among GCMs, leading to mixed projections of future establishment suitability. In contrast, climatic water deficit (CWD), which is indicative of warm, dry conditions, was negatively associated with post‐firemore »seedling abundance during the recent period and was projected to increase throughout the southern Rocky Mountains in the future. Our findings suggest that future increases in CWD and an increased frequency of extreme drought years will substantially reduce post‐fire seedling densities.

   This study highlights the key roles of warming and drying in declining forest resilience to wildfire. Moisture stress, driven by macroclimate and topographic setting, will interact with wildfire activity to shape future vegetation patterns throughout the southern Rocky Mountains, USA.

   « less
2. Will land use land cover change drive atmospheric conditions to become more conducive to wildfires in the United States?

   https://doi.org/10.1002/joc.7036  

   Zhong, Shiyuan ; Wang, Ting ; Sciusco, Pietro ; Shen, Meicheng ; Pei, Lisi ; Nikolic, Jovanka ; McKeehan, Kevin ; Kashongwe, Herve ; Hatami‐Bahman‐Beiglou, Pouyan ; Camacho, Ken ; et al ( February 2021 , International Journal of Climatology)

   The increase in wildfire risk in the United States in recent decades has been linked to rapid growth of the wildland‐urban interface and to changing climate. While there have been numerous studies on wildfires and climate change, few have separately assessed the impact of climate response to land‐use‐land‐cover change (LULCC) on wildfires. In this study, we analyse two 10‐year regional climate simulations driven by the current (2011) and future (2100) land‐use‐land‐cover patterns to assess modifications by the projected LULCC to the frequency and severity of fire‐prone atmospheric conditions described by two fire weather indices, the Canadian Forest Fire Weather Index and the Hot‐Dry‐Windy Index. The simulation corresponding to future land‐use‐land‐cover pattern yields higher surface temperature and vapour pressure deficit and lower precipitation compared to the simulation with the current pattern in areas where urbanized landscapes replace forests and grasslands, such as along the Piedmont and outside the Chicagoland region, while in areas where croplands replace forests, such as the southeast Coastal Plains, the results are reversed. These changes to local and regional atmospheric conditions lead to longer fire seasons and more extreme fire‐weather conditions in much of the eastern United States, specifically in the Southeast and Ohio River Valleymore »where significant urban expansion is projected by the end of the century. Whereas in Southern California where some highly flammable shrublands will be replaced by urban or crop lands, fire‐prone atmospheric conditions are likely to be less frequent and less extreme in the future. However, much of California moves towards a year‐round fire season under the projected LULCC. The results suggest that by altering atmospheric conditions, LULCC may play an important role in determining fire regime, but the effects are highly heterogeneous and regionalized.

   « less
3. Co‐designed management scenarios shape the responses of seasonally dry forests to changing climate and fire regimes

   https://doi.org/10.1111/1365-2664.13630  

   Maxwell, Charles J. ; Serra‐Diaz, Josep M. ; Scheller, Robert M. ; Thompson, Jonathan R. ; Mori, ed., Akira ( May 2020 , Journal of Applied Ecology)

   Climate change is altering disturbance regimes and recovery rates of forests globally. The future of these forests will depend on how climate change interacts with management activities. Forest managers are in critical need of strategies to manage the effects of climate change.

   We co‐designed forest management scenarios with forest managers and stakeholders in the Klamath ecoregion of Oregon and California, a seasonally dry forest in the Western US subject to fire disturbances. The resultant scenarios span a broad range of forest and fire management strategies. Using a mechanistic forest landscape model, we simulated the scenarios as they interacted with forest growth, succession, wildfire disturbances and climate change. We analysed the simulations to (a) understand how scenarios affected the fire regime and (b) estimate how each scenario altered potential forest composition.

   Within the simulation timeframe (85 years), the scenarios had a large influence on fire regimes, with fire rotation periods ranging from 60 years in a minimal management scenario to 180 years with an industrial forestry style management scenario. Regardless of management strategy, mega‐fires (>100,000 ha) are expected to increase in frequency, driven by stronger climate forcing and extreme fire weather.

   High elevation conifers declined across all climate and management scenarios, reflecting an imbalance between forest types,more »climate and disturbance. At lower elevations (<1,800 m), most scenarios maintained forest cover levels; however, the minimal intervention scenario triggered 5 × 10⁵ ha of mixed conifer loss by the end of the century in favour of shrublands, whereas the maximal intervention scenario added an equivalent amount of mixed conifer.

   Policy implications. Forest management scenarios that expand beyond current policies—including privatization and aggressive climate adaptation—can strongly influence forest trajectories despite a climate‐enhanced fire regime. Forest management can alter forest trajectories by increasing the pace and scale of actions taken, such as fuel reduction treatments, or by limiting other actions, such as fire suppression.

   « less
4. Fire-regime variability impacts forest carbon dynamics for centuries to millennia

   https://doi.org/10.5194/bg-14-3873-2017  

   Hudiburg, Tara W. ; Higuera, Philip E. ; Hicke, Jeffrey A. ( January 2017 , Biogeosciences)

   Abstract. Wildfire is a dominant disturbance agent in forest ecosystems, shaping important biogeochemical processes including net carbon (C) balance. Long-term monitoring and chronosequence studies highlight a resilience of biogeochemical properties to large, stand-replacing, high-severity fire events. In contrast, the consequences of repeated fires or temporal variability in a fire regime (e.g., the characteristic timing or severity of fire) are largely unknown, yet theory suggests that such variability could strongly influence forest C trajectories (i.e., future states or directions) for millennia. Here we combine a 4500-year paleoecological record of fire activity with ecosystem modeling to investigate how fire-regime variability impacts soil C and net ecosystem carbon balance. We found that C trajectories in a paleo-informed scenario differed significantly from an equilibrium scenario (with a constant fire return interval), largely due to variability in the timing and severity of past fires. Paleo-informed scenarios contained multi-century periods of positive and negative net ecosystem C balance, with magnitudes significantly larger than observed under the equilibrium scenario. Further, this variability created legacies in soil C trajectories that lasted for millennia. Our results imply that fire-regime variability is a major driver of C trajectories in stand-replacing fire regimes. Predicting carbon balance in these systems, therefore, willmore »depend strongly on the ability of ecosystem models to represent a realistic range of fire-regime variability over the past several centuries to millennia.

   « less
5. Increasing concurrence of wildfire drivers tripled megafire critical danger days in Southern California between1982 and 2018

   https://doi.org/10.1088/1748-9326/abae9e  

   Khorshidi, Mohammad Sadegh ; Dennison, Philip E. ; Nikoo, Mohammad Reza ; AghaKouchak, Amir ; Luce, Charles H. ; Sadegh, Mojtaba ( September 2020 , Environmental Research Letters)

   Wildfire danger is often ascribed to increased temperature, decreased humidity, drier fuels, or higher wind speed. However, the concurrence of drivers—defined as climate, meteorological and biophysical factors that enable fire growth—is rarely tested for commonly used fire danger indices or climate change studies. Treating causal factors as independent additive influences can lead to inaccurate inferences about shifting hazards if the factors interact as a series of switches that collectively modulate fire growth. As evidence, we show that in Southern California very large fires and ‘megafires’ are more strongly associated withmultipledrivers exceedingmoderatethresholds concurrently, rather than direct relationships withextrememagnitudes ofindividualdrivers or additive combinations of those drivers. Days with concurrent fire drivers exceeding thresholds have increased more rapidly over the past four decades than individual drivers, leading to a tripling of annual ‘megafire critical danger days’. Assessments of changing wildfire risks should explicitly address concurrence of fire drivers to provide a more precise assessment of this hazard in the face of a changing climate.