Research Database
Displaying 1 - 20 of 107
Active-fire landscapes demonstrate structural resistance to subsequent fire and drought
Year: 2025
A key tenet of contemporary management in dry, fire-adapted forests of western North America is the reintroduction of a frequent and low- to moderate-severity fire regime. Where this fire regime has been fully or partially restored, it is critical to evaluate the degree to which these landscapes demonstrate forest structural resistance (i.e., the capacity to retain intrinsic structures through time) under novel climates and disturbances. In this study, we used overlapping airborne lidar datasets spanning active-fire landscapes in the Sierra Nevada, California, to evaluate how tree densities,…
Publication Type: Journal Article
The western North American forestland carbon sink: will our climate commitments go up in smoke?
Year: 2025
Pathways to achieving net-zero and net-negative greenhouse-gas (GHG) emission targets rely on land-based contributions to carbon (C) sequestration. However, projections of future contributions neglect to consider ecosystems, climate change, legacy impacts of continental-scale fire exclusion, forest accretion and densification, and a century or more of management. These influences predispose western North American forests (wNAFs) to severe drought impacts, large and chronic outbreaks of insect pests, and increasingly large and severe wildfires. To realistically assess contributions of future…
Publication Type: Journal Article
Morphological and physiological response of conifer seedlings to drought conditioning
Year: 2025
Increased frequency, severity, and duration of droughts and increased wildfire severity are impacting many conifer forests globally. Reforestation in these changing disturbance regimes requires tree seedlings capable of establishing in hotter and drier climates. We evaluated the morphological and physiological effects of drought conditioning on second-year ponderosa pine (Pinus ponderosa), western white pine (Pinus monticola), and western larch (Larix occidentalis) seedlings. Treatments included a well-watered control (75% of container capacity) and a water-limited…
Publication Type: Journal Article
Spatiotemporal Synchrony of Climate and Fire Occurrence Across North American Forests (1750–1880)
Year: 2025
Aim: Increasing aridity has driven widespread synchronous fire occurrence in recent decades across North America. The lack of historical (pre-1880) fire records limits our ability to understand long-term continental fire-climate dynamics. The goal of this study is to use tree-ring reconstructions to determine the relationships between spatiotemporal patterns in historical climate and widespread fire occurrence in North American forests, and whether they are stable through time. This information will address a major knowledge gap required to inform projections of future fire.Location: North…
Publication Type: Journal Article
Carbon costs of different pathways for reducing fire hazard in the Sierra Nevada
Year: 2025
Restoring a low-intensity, frequent-fire regime in fire-prone forests offers a promising natural climate solution. Management interventions that include prescribed fire and/or mechanical treatments have effectively reduced fire hazards in the Western United States, yet concerns remain regarding their impact on forest carbon storage. This study used results from a long-term, replicated field experiment to assess the impacts of a restored disturbance regime on carbon dynamics in a Sierra Nevada, mixed conifer forest. The carbon consequences of the treatments were compared to a dynamic baseline…
Publication Type: Journal Article
Wildfires drive multi-year water quality degradation over the western United States
Year: 2025
Wildfires can dramatically alter water quality, resulting in severe implications for human and freshwater systems. However, regional-scale assessments of these impacts are often limited by data scarcity. Here, we unify observations from 1984–2021 in 245 burned watersheds across the western United States, comparing post-fire signals to baseline levels from 293 unburned basins. Organic carbon and phosphorus exhibit significantly elevated levels (p ≤ 0.05) in the first 1–5 years post-fire, while nitrogen and sediment show significant increases up to 8 years post-fire. During peak post-…
Publication Type: Journal Article
Trees in Fire-Maintained Forests Have Similar Growth Responses to Drought, but Greater Stomatal Conductance Than Trees in Fire-Excluded Forests
Year: 2025
In the western US, increased tree density in dry conifer forests from fire exclusion has caused tree growth declines, which is being compounded by hotter multi-year droughts. The reintroduction of frequent, low-severity wildfire reduces forest density by removing fire-intolerant trees, which can reduce competition for water and improve tree growth response to drought. We assessed how lower forest density following frequent, low-severity wildfire affected tree stomatal conductance and growth response to drought by coring and measuring competition surrounding ponderosa pines (Pinus…
Publication Type: Journal Article
Decreasing landscape carbon storage in western US forests with 2 °C of warming
Year: 2025
Changing climate is altering the amount of carbon that can be sustained in forest ecosystems. Increasing heat and drought is already causing increased mortality and decreased regeneration in some locations. These changes have implications for landscape carbon storage with ongoing climate change. We used a climate analogs approach to project aboveground forest carbon density under +2 °C warming above pre-industrial climate for western US forests. We calculated analogs for current climate and under +2 °C warming and associated carbon density for each time period. We found that in most…
Publication Type: Journal Article
Quantifying Western US tree carbon stocks and sequestration from fires
Year: 2025
Background: Forest ecosystems function as the largest terrestrial carbon sink globally. In the Western US, fires play a crucial role in modifying forest carbon storage, sequestration capacity, and the transfer of carbon from live to dead carbon pools. We utilized remeasurements of more than 700,000 trees from 24,000 locations from the US Department of Agriculture Forest Service’s Forest Inventory and Analysis program (FIA) and incorporated supplementary information on wildfires from the Monitoring Trends in Burn Severity dataset. These datasets allowed us to develop models that examined the…
Publication Type: Journal Article
Rapid Declines in Southern Sierra Nevada Fisher Habitat Driven by Drought and Wildfire
Year: 2025
Aim: Forest disturbances are a natural ecological process, but climate and land-use change are altering disturbance regimes at an unprecedented rate, posing significant threats to biological communities and the species of concern. Our aim was to develop an automated habitat monitoring system for the Southern Sierra Nevada Distinct Population Segment of fisher (Pekania pennanti) in California, USA, to investigate long-term habitat trends and the effects of a recent megadrought and numerous megafires on fisher habitat.Location: Southern Sierra Nevada, California, USA.Methods: We used…
Publication Type: Journal Article
Increasing wildfire frequency decreases carbon storage and leads to regeneration failure in Alaskan boreal forests
Year: 2025
BackgroundThe increasing size, severity, and frequency of wildfires is one of the most rapid ways climate warming could alter the structure and function of high-latitude ecosystems. Historically, boreal forests in western North America had fire return intervals (FRI) of 70–130 years, but shortened FRIs are becoming increasingly common under extreme weather conditions. Here, we quantified pre-fire and post-fire C pools and C losses and assessed post-fire seedling regeneration in long (> 70 years), intermediate (30–70 years), and short (< 30 years) FRIs, and triple (three fires in < 70…
Publication Type: Journal Article
Going slow to go fast: landscape designs to achieve multiple benefits
Year: 2025
Introduction: Growing concerns about fire across the western United States, and commensurate emphasis on treating expansive areas over the next 2 decades, have created a need to develop tools for managers to assess management benefits and impacts across spatial scales. We modeled outcomes associated with two common forest management objectives: fire risk reduction (fire), and enhancing multiple resource benefits (ecosystem resilience).Method: We evaluated the compatibility of these two objectives across ca. 1-million ha in the central Sierra Nevada,…
Publication Type: Journal Article
Multi-scale assessment of wildfire use on carbon stocks in the Sierra Nevada, CA
Year: 2025
BackgroundThe active use of wildfire to meet forest management objectives is an important tool to increase the scale of forest restoration in dry, historically frequent-fire forests. While there are many benefits of reintroducing fire to these forests, the impact of wildland fire use policies in frequent-fire forests on aboveground carbon stocks has not yet been studied. In this study, we begin to fill this knowledge gap by assessing how fire frequency and severity affected aboveground carbon dynamics in two basins in the Sierra Nevada with a history of wildfire use over the…
Publication Type: Journal Article
Increasing prevalence of hot drought across western North America since the 16th century
Year: 2024
Across western North America (WNA), 20th-21st century anthropogenic warming has increased the prevalence and severity of concurrent drought and heat events, also termed hot droughts. However, the lack of independent spatial reconstructions of both soil moisture and temperature limits the potential to identify these events in the past and to place them in a long-term context. We develop the Western North American Temperature Atlas (WNATA), a data-independent 0.5° gridded reconstruction of summer maximum temperatures back to the 16th century. Our evaluation of the WNATA with existing…
Publication Type: Journal Article
Managing fire-prone forests in a time of decreasing carbon carrying capacity
Year: 2024
Changing climatic conditions are increasing overstory tree mortality in forests globally. This restructuring of the distribution of biomass is making already flammable forests more combustible, posing a major challenge for managing the transition to a lower biomass state. In western US dry conifer forests, tree density resulting from over a century of fire-exclusion practices has increased the risk of high-severity wildfire and susceptibility to climate-driven mortality. Reducing dead fuel loads will require new approaches to mitigate risk to the remaining live trees by preparing forests to…
Publication Type: Journal Article
Forest Carbon Storage in the Western United States:Distribution, Drivers, and Trends
Year: 2024
Forests are a large carbon sink and could serve as natural climate solutions that help moderatefuture warming. Thus, establishing forest carbon baselines is essential for tracking climate‐mitigation targets.Western US forests are natural climate solution hotspots but are profoundly threatened by drought and altereddisturbance regimes. How these factors shape spatial patterns of carbon storage and carbon change over time ispoorly resolved. Here, we estimate live and dead forest carbon density in 19 forested western US ecoregionswith national inventory data (2005–2019) to determine: (a) current…
Publication Type: Journal Article
Prefire Drought Intensity Drives Postfire Recovery and Mortality in Pinus monticola and Pseudotsuga menziesii Saplings
Year: 2024
Increasing frequency of droughts and wildfire are sparking concerns that these compounded disturbance events are pushing forested ecosystems beyond recovery. An improved understanding of how compounded events affect tree physiology and mortality is needed given the reliance of fire management planning on accurate estimates of postfire tree mortality. In this study, we use a toxicological dose-response approach to quantify the impact of variable-intensity drought and fire on the physiology and mortality of Pinus monticola and Pseudotsuga menziesii saplings. We show that the…
Publication Type: Journal Article
A Preliminary Case Study on the Compounding Effects of Local Emissions and Upstream Wildfires on Urban Air Pollution
Year: 2024
Interactions between urban and wildfire pollution emissions are active areas of research, with numerous aircraft field campaigns and satellite analyses of wildfire pollution being conducted in recent years. Several studies have found that elevated ozone and particulate pollution levels are both generally associated with wildfire smoke in urban areas. We measured pollutant concentrations at two Utah Division of Air Quality regulatory air quality observation sites and a local hot spot (a COVID-19 testing site) within a 48 h period of increasing wildfire smoke impacts that occurred in Salt Lake…
Publication Type: Journal Article
Drought before fire increases tree mortality after fire
Year: 2024
Fire and drought are expected to increase in frequency and severity in temperate forests due to climate change. To evaluate whether drought increases the likelihood of post-fire tree mortality, we used a large database of tree survival and mortality from 32 years of wildland fires covering four dominant western North American conifers. We used Bayesian hierarchical modeling to predict the probability of individual tree mortality after fire based on species—Pinus contorta (lodgepole pine), Abies concolor (white fir), Pseudotsuga menziesii (Douglas-fir), and Pinus…
Publication Type: Journal Article
A laboratory-scale simulation framework for analysing wildfire hydrologic and water quality effects
Year: 2024
Background: Wildfires can significantly impact water quality and supply. However logistical difficulties and high variability in in situ data collection have limited previous analyses.Aims: We simulated wildfire and rainfall effects at varying terrain slopes in a controlled setting to isolate driver-response relationships.Methods: Custom-designed laboratory-scale burn and rainfall simulators were applied to 154 soil samples, measuring subsequent runoff and constituent responses. Simulated conditions included low, moderate, and high burn intensities (~100–600°C); 10…
Publication Type: Journal Article