Forest restoration as a strategy to mitigate climate impacts on wildfire, vegetation, and water in semiarid forests

Abstract

Climate change and wildfire are interacting to drive vegetation change and potentially reduce water quantity and quality in the southwestern United States, Forest restoration is a management approach that could mitigate some of these negative outcomes. However, little information exists on how restoration combined with climate change might influence hydrology across large forest landscapes that incorporate multiple vegetation types and complex fire regimes. We combined spatially explicit vegetation and fire modeling with statistical water and sediment yield models for a large forested landscape (335,000 ha) on the Kaibab Plateau in northern Arizona, USA. Our objective was to assess the impacts of climate change and forest restoration on the future fire regime, forest vegetation, and watershed outputs. Our model results predict that the combination of climate change and high-severity fire will drive forest turnover, biomass declines, and compositional change in future forests. Restoration treatments may reduce the area burned in high-severity fires and reduce conversions from forested to non-forested conditions. Even though mid-elevation forests are the targets of restoration, the treatments are expected to delay the decline of high-elevation spruce-fir, aspen, and mixed conifer forests by reducing the occurrence of high-severity fires that may spread across ecoregions. We estimate that climate-induced vegetation changes will result in annual runoff declines of up to 10%, while restoration reduced or reversed this decline. The hydrologic model suggests that mid-elevation forests, which are the targets of restoration treatments, provide around 80% of runoff in this system and the conservation of mid- to high-elevation forests types provides the greatest benefit in terms of water conservation. We also predict that restoration treatments will conserve water quality by reducing patches of high-severity fire that are associated with high sediment yield. Restoration treatments are a management strategy that may reduce undesirable outcomes for multiple ecosystem services.

Wildfire severity and vegetation recovery drive post‐fire evapotranspiration in a southwestern pine‐oak forest, Arizona, USA

“…Forests in the desert Southwest comprise a critical water‐provisioning ecosystem service in an arid region (Boyanova et al., 2017; Keith et al., 2017; O'Donnell et al., 2018). Most projections indicate that western North America will continue to experience increasing aridity and larger, more severe, and more frequent wildfires (Abatzoglou & Kolden, 2013; Adams, 2013; Ault et al., 2016; Cook et al., 2015; Singleton et al., 2019), which may threaten this water resource.…”

Streamflow Response to Wildfire Differs With Season and Elevation in Adjacent Headwaters of the Lower Colorado River Basin

“…Vegetation is comprised of mixed conifer forests at the highest elevations, ponderosa pine forests and grasslands at mid elevations, and pinyon-juniper woodlands, chaparral and mesquite shrublands at lower elevations. More than 80% of mean annual streamflow originates in the forested high-elevations and mid-elevations most impacted by fire (O'Donnell et al, 2018). The average annual flow of the Salt River Basin above Roosevelt, AZ is 700 million m 3 , or 600,000 ac-ft. Precipitation is bimodal due to the influence of the summer monsoon season; however, the majority of annual streamflow (>75%) occurs following winter precipitation and spring snowmelt (Figure 2), hereafter termed winter streamflow.…”

Seismic Monitoring of Post-wildfire Debris Flows Following the 2019 Museum Fire, Arizona

“…The region has been in the Early 21st century drought since the mid-1990's (Hereford, 2007). This fire represents a common wildfire event that is becoming more likely in the western US due to climate change, a longer fire season and larger, more severe fires (Westerling, 2016;Singleton et al, 2019;Mueller et al, 2020), and increased forest density linked to the history of fire suppression (North et al, 2015;Parks et al, 2015;O'Donnell et al, 2018). While the immediate threats posed by wildfire are substantial, another concern is often the post-wildfire debris flows caused by the removal of vegetation and ground cover, and creation of water repellent soil conditions following fire (e.g., Neary et al, 2012).…”