Research Database
Displaying 1 - 20 of 59
Methods to assess fire-induced tree mortality: review of fire behaviour proxy and real fire experiments
Year: 2025
Background: The increased interest in why and how trees die from fire has led to several syntheses of the potential mechanisms of fire-induced tree mortality. However, these generally neglect to consider experimental methods used to simulate fire behaviour conditions.Aims: To describe, evaluate the appropriateness of and provide a historical timeline of the different approaches that have been used to simulate fire behaviour in fire-induced tree mortality studies.Methods: We conducted a historical review of the different actual and fire proxy methods that have been used to…
Publication Type: Journal Article
Long-term influence of prescribed burning on subsequent wildfire in an old-growth coast redwood forest
Year: 2025
Background: Prescribed burning is an effective tool for reducing fuels in many forest types, yet there have been few opportunities to study forest resilience to wildfire in areas previously treated. In 2020, a large-scale high-intensity wildfire burned through an old-growth coast redwood (Sequoia sempervirens) forest with a mixed land management history, providing a rare opportunity to compare early post-wildfire data between areas with and without previous application of prescribed burning. The purpose of this study was to analyze the differences between these two treatments in…
Publication Type: Journal Article
Modeling the probability of bark beetle-caused tree mortality as a function of watershed-scale host species presence and basal area
Year: 2025
In recent decades, bark beetle outbreaks have caused mass tree mortality in western US forests, which has led to altered wildfire characteristics, hydrological processes, and forest carbon dynamics. Understanding spatial variability in forest susceptibility to bark beetle outbreaks in the western US could inform strategic forest management to reduce wildfire risk, manage forest carbon, and plan for altered hydrology. The susceptibility of a forest stand to mortality by bark beetles depends on the availability and characteristics of trees of the host tree species. For multiple bark beetle…
Publication Type: Journal Article
Repeated fuel treatments fall short of fire-adapted regeneration objectives in a Sierra Nevada mixed conifer forest, USA
Year: 2024
Fire exclusion over the last two centuries has driven a significant fire deficit in the forests of western North America, leading to widespread changes in the composition and structure of these historically fire-adapted ecosystems. Fuel treatments have been increasingly applied over the last few decades to mitigate fire hazard, yet it is unclear whether these fuel-focused treatments restore the fire-adapted conditions and species that will allow forests to persist into the future. A vital prerequisite of restoring fire-adaptedness is ongoing establishment of fire-tolerant tree species, and…
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
Long-term sensitivity of ponderosa pine axial resin ducts to harvesting and prescribed burning
Year: 2024
Forest restoration treatments primarily aimed at reducing fuel load and preventing high-severity wildfires can also influence resilience to other disturbances. Many pine forests in temperate regions are subject to tree-killing bark beetle outbreaks (e.g., Dendroctonus, Ips), whose frequency and intensity are expected to increase with future climatic changes. Restoration treatments have the potential to increase resistance to bark beetle attacks, yet the underlying mechanisms of this response are still unclear. While the effect of forest restoration treatments on tree growth…
Publication Type: Journal Article
Characterizing post-fire delayed tree mortality with remote sensing: sizing up the elephant in the room
Year: 2024
BackgroundDespite recent advances in understanding the drivers of tree-level delayed mortality, we lack a method for mapping delayed mortality at landscape and regional scales. Consequently, the extent, magnitude, and effects of delayed mortality on post-fire landscape patterns of burn severity are unknown. We introduce a remote sensing approach for mapping delayed mortality based on post-fire decline in the normalized burn ratio (NBR). NBR decline is defined as the change in NBR between the first post-fire measurement and the minimum NBR value up to 5 years post-fire for each pixel…
Publication Type: Journal Article
Abiotic Factors Modify Ponderosa Pine Regeneration Outcomes After High-Severity Fire
Year: 2024
Large high-severity burn patches are increasingly common in southwestern US dry conifer forests. Seed-obligate conifers often fail to quickly regenerate large patches because their seeds rarely travel the distances required to reach core patch area. Abiotic factors may further alter the distance seeds can travel to regenerate a patch, which would change expected post-fire regeneration patterns. We used the presence and density of ponderosa pine regeneration as a proxy for seed dispersal to quantify the effect of abiotic factors on seed dispersal into high-severity patches. We established 45…
Publication Type: Journal Article
Patterns, drivers, and implications of postfire delayed tree mortality in temperate conifer forests of the western United States
Year: 2024
Conifer forest resilience may be threatened by increasing wildfire activity and compound disturbances in western North America. Fire refugia enhance forest resilience, yet may decline over time due to delayed mortality—a process that remains poorly understood at landscape and regional scales. To address this uncertainty, we used high-resolution satellite imagery (5-m pixel) to map and quantify delayed mortality of conifer tree cover between 1 and 5 years postfire, across 30 large wildfires that burned within three montane ecoregions in the western United States. We used statistical models to…
Publication Type: Journal Article
Thinning and prescribed burning increase shade-tolerant conifer regeneration in a fire excluded mixed-conifer forest
Year: 2024
Fire exclusion and past management have altered the composition, structure, and function of frequent-fire forests throughout western North America. In mixed-conifer forests of the California Sierra Nevada, fire exclusion has exacerbated the effects of drought and endemic bark beetles, resulting in extensive mortality of fire-adapted pine species. Thinning and prescribed fire are widely used in these forests to reduce fuels, moderate fire behavior, and restore ecosystems. Tree regeneration influences future forest composition and structure, and therefore future resilience to disturbances, but…
Publication Type: Journal Article
Topographic information improves simulated patterns of post-fire conifer regeneration in the southwest United States
Year: 2023
The western United States is projected to experience more frequent and severe wildfires in the future due to drier and hotter climate conditions, exacerbating destructive wildfire impacts on forest ecosystems such as tree mortality and unsuccessful post-fire regeneration. While empirical studies have revealed strong relationships between topographical information and plant regeneration, ecological processes in ecosystem models have either not fully addressed topography-mediated effects on the probability of plant regeneration, or the probability is only controlled by climate-related factors,…
Publication Type: Journal Article
Recent Douglas-fir Mortality in the Klamath Mountains Ecoregion of Oregon: Evidence for a Decline Spiral
Year: 2023
Recent increases in Douglas-fir (Psuedotsuga menziesii var. menziesii) mortality in the Klamath Mountains ecoregion raise concerns about the long-term resilience of Douglas-fir in the ecoregion and increased potential for uncharacteristic wildfire. We used data from the USDA Forest Service Aerial Detection Survey and ninety-six field plots to explore the relationships between physiographic and climate variables and Douglas-fir mortality. Our results provide strong evidence for a decline spiral in which Douglas-fir growing on hot, dry sites (predisposing factor) are further stressed by drought…
Publication Type: Journal Article
Mechanical thinning restores ecological functions in a seasonally dry ponderosa pine forest in the inland Pacific Northwest, USA
Year: 2023
An increasingly important goal of federal land managers in seasonally dry forests of the western US is restoring forest resilience. In this study, we quantified the degree to which a thinning treatment in a dry forest of eastern Oregon restored aspects of forest resilience by focusing on key functional attributes of our study system. First, we measured several physiological responses of overstory trees that are associated with resilience, including radial growth, resin production, abundance of non-structural carbohydrates (NSC), and leaf area. Second, we investigated understory vegetation…
Publication Type: Journal Article
Wildfire controls on land surface properties in mixed conifer and ponderosa pine forests of Sierra Nevada and Klamath mountains, Western US
Year: 2022
This study examines the post-fire biogeophysical and biochemical dynamics after several high-severity wildfires that occurred in mixed conifer and ponderosa pine forest types in the Sierra Nevada and Klamath Mountains regions between 1986 and 2017. We found a consistent pattern of reduced leaf area index (LAI) in the first year after fire, followed by gradual recovery over the subsequent 25 years. Recovery rate varied between forest types. For example, average summer LAI for 16-25 years post-fire was 88% of the pre-fire average for mixed conifers in the Sierra Nevada, 64% for ponderosa pine…
Publication Type: Journal Article
Tree mortality response to drought-density interactions suggests opportunities to enhance drought resistance
Year: 2022
1. The future of dry forests around the world is uncertain given predictions that rising temperatures and enhanced aridity will increase drought-induced tree mortality. Using forest management and ecological restoration to reduce density and competition for water offers one of the few pathways that forests managers can potentially minimize drought-induced tree mortality. Competition for water during drought leads to elevated tree mortality in dense stands, although the influence of density on heat-induced stress and the durations of hot or dry conditions that most impact mortality remain…
Publication Type: Journal Article
Merging prescribed fires and timber harvests in the Sierra Nevada: Burn season and pruning influences in young mixed conifer stands
Year: 2022
Highlights • Mortality of canopy trees was similar between spring and fall prescribed burns in 13-14 year old stands • Fall burns consumed more surface fuel without substantially high levels of canopy damage • Pre-fire pruning Pinus lambertiana and Calocecrus decurrens trees did not clearly reduce tree damage • Gap-based silviculture and prescribed fire can be merged to meet broad ecological goals Abstract In dry, productive forests where historically infrequent high-severity fires are now common, new silvicultural systems will be needed to better align management activity with the ecosystem'…
Publication Type: Journal Article
Repeated fall prescribed fire in previously thinned Pinus ponderosa increases growth and resistance to other disturbances
Year: 2021
In western North America beginning in the late 19th century, fire suppression and other factors resulted in denseponderosa pine (Pinus ponderosa) forests that are now prone to high severity wildfire, insect attack, and rootdiseases. Thinning and prescribed fire are commonly used to remove small trees, fire-intolerant tree species, andshrubs, and to reduce surface and aerial fuels. These treatments can be effective at lowering future fire severity,but prescribed burns must be periodically repeated to maintain favorable conditions and are feasible only outsidethe historical summer wildfire…
Publication Type: Journal Article
An ecological perspective on living with fire in ponderosa pine forests of Oregon and Washington: Resistance, gone but not forgotten
Year: 2021
Wildland fires (WLF) have become more frequent, larger, and severe with greater impacts to society and ecosys- tems and dramatic increases in firefighting costs. Forests throughout the range of ponderosa pine in Oregon and Washington are jeopardized by the interaction of anomalously dense forest structure, a warming and dry- ing climate, and an expanding human population. These forests evolved with frequent interacting disturbances including low-severity surface fires, droughts, and biological disturbance agents (BDAs). Chronic low-severity disturbances were, and still are, critical to…
Publication Type: Journal Article
High-severity wildfire reduces richness and alters composition of ectomycorrhizal fungi in low-severity adapted ponderosa pine forests
Year: 2021
Ponderosa pine (Pinus ponderosa) forests are increasingly experiencing high-severity, stand-replacing fires.Whereas alterations to aboveground ecosystems have been extensively studied, little is known about soil fungalresponses in fire-adapted ecosystems. We implement a chronosequence of four different fires that varied in timesince fire, 2 years (2015) to 11 years (2006) and contained stands of high severity burned P. ponderosa in easternWashington and compared their soil fungal communities to adjacent unburned plots. Using Illumina Miseq(ITS1), we examined changes in soil nutrients, drivers…
Publication Type: Journal Article
Repeated fall prescribed fire in previously thinned Pinus ponderosa increases growth and resistance to other disturbances
Year: 2021
In western North America beginning in the late 19th century, fire suppression and other factors resulted in dense ponderosa pine (Pinus ponderosa) forests that are now prone to high severity wildfire, insect attack, and root diseases. Thinning and prescribed fire are commonly used to remove small trees, fire-intolerant tree species, and shrubs, and to reduce surface and aerial fuels. These treatments can be effective at lowering future fire severity, but prescribed burns must be periodically repeated to maintain favorable conditions and are feasible only outside the historical summer wildfire…
Publication Type: Journal Article