Research Database
Displaying 21 - 40 of 57
Washington State 2020 Forest Action Plan
Year: 2020
Washington has more than 22 million acres of forestland. From the lush rainforests on our coasts, to the rugged sub-alpine forests along the Cascade Crest, to the pine-dominated hillsides surrounding the Columbia Plateau, forests are an integral part of our landscapes and communities, and they provide a wealth of benefits to Washingtonians and the planet. They provide us with sustainable timber and jobs, produce clean air and water, sequester carbon, and support world-class outdoor recreation. Our forests, however, face unprecedented threats that require bold action. Climate change is…
Publication Type: Government Report
How does tree regeneration respond to mixed‐severity fire in the western Oregon Cascades, USA?
Year: 2020
Dendroecological studies of historical tree recruitment patterns suggest mixed‐severity fire effects are common in Douglas‐fir/western hemlock forests of the Pacific Northwest (PNW), USA, but empirical studies linking observed fire severity to tree regeneration response are needed to expand our understanding into the functional role of fire in this forest type. Recent increases in mixed‐severity fires offered this opportunity, so we quantified the abundance, spatial distribution, species richness, and community composition of regenerating trees across a mixed‐severity fire gradient (unburned–…
Publication Type: Journal Article
Wildfire severity and postfire salvage harvest effects on long-term forest regeneration
Year: 2020
Following a wildfire, regeneration to forest can take decades to centuries and is no longerassured in many western U.S. environments given escalating wildfire severity and warming trends. Afterlarge fire years, managers prioritize where to allocate scarce planting resources, often with limited informationon the factors that drive successful forest establishment. Where occurring, long-term effects of postfiresalvage operations can increase uncertainty of establishment. Here, we collected field data on postfireregeneration patterns within 13- to 28-yr-old burned patches in eastern Washington…
Publication Type: Journal Article
Expansion of the invasive European mistetoe in California, USA
Year: 2020
The horticulturist Luther Burbank introduced the European mistletoe (Viscum album L.) to Sebastopol, Sonoma County, California, USA, around 1900 to grow as a Christmas ornament crop and tincture for medicinal use. The mistletoe has since spread from the point of introduction on apple to other hardwood trees, especially non-native hardwoods in yards and farms of the region. Mistletoe surveys were previously conducted in 1971,1986, and 1991. We re-surveyed the region in 2019, with emphasis on the 1991 perimeter, and documented the current farthest distribution of V. album. This represents a 120…
Publication Type: Journal Article
Post-fire management affects species composition but not Douglas-fir regeneration in the Klamath Mountains
Year: 2019
Ensuring adequate conifer regeneration after high severity wildfires is a common objective for ecologists and forest managers. In the Klamath region of Oregon and California, a global hotspot of botanical biodiversity, concerns over regeneration have led to post-fire management on many sites, which involves salvage logging followed by site preparation, conifer planting, and manual shrub release. To quantify the impacts of post-fire management, we sampled 62 field sites that burned at high severity nearly 20 years ago in the Klamath-Siskiyou Mountain bioregion, stratifying by management and…
Publication Type: Journal Article
Tamm Review: Reforestation for resilience in dry western U.S. forests
Year: 2019
The increasing frequency and severity of fire and drought events have negatively impacted the capacity and success of reforestation efforts in many dry, western U.S. forests. Challenges to reforestation include the cost and safety concerns of replanting large areas of standing dead trees, and high seedling and sapling mortality rates due to water stress, competing vegetation, and repeat fires that burn young plantations. Standard reforestation practices have emphasized establishing dense conifer cover with gridded planting, sometimes called 'pines in lines', followed by shrub control and pre-…
Publication Type: Journal Article
Short- and long-term effects of ponderosa pine fuel treatments intersected by the Egley Fire Complex, Oregon, USA
Year: 2019
Background Fuel treatments are widely used to alter fuels in forested ecosystems to mitigate wildfire behavior and effects. However, few studies have examined long-term ecological effects of interacting fuel treatments (commercial harvests, pre-commercial thinnings, pile and burning, and prescribed fire) and wildfire. Using annually fitted Landsat satellite-derived Normalized Burn Ratio (NBR) curves and paired pre-fire treated and untreated field sites, we tested changes in the differenced NBR (dNBR) and years since treatment as predictors of biophysical attributes one and nine years after…
Publication Type: Journal Article
Influence of fire refugia spatial pattern on post-fire forest recovery in Oregon’s Blue Mountains
Year: 2019
Context Fire regimes in many dry forests of western North America are substantially different from historical conditions, and there is concern about the ability of these forests to recover following severe wildfire. Fire refugia, unburned or low-severity burned patches where trees survived fire, may serve as essential propagule sources that enable forest regeneration. Objectives To quantify the influence of fire refugia spatial pattern and other biophysical factors on the process of post-fire tree regeneration; in particular examining both the proximity and density of surrounding refugia to…
Publication Type: Journal Article
What drives ponderosa pine regeneration following wildfire in the western United States?
Year: 2019
Ponderosa pine (Pinus ponderosa Lawson & C. Lawson) is a prominent tree species in forests of the western United States. Wildfire activity in ponderosa pine dominated or co-dominated forests has increased dramatically in recent decades, with these recent wildfires often burning in an uncharacteristic manner due to past land management activities and changing climate. The structure and function of vegetative communities that develop following recent wildfires are highly contingent on ponderosa pine regeneration, making it important that the factors influencing this regeneration be…
Publication Type: Journal Article
Evidence for declining forest resilience to wildfires under climate change
Year: 2018
Forest resilience to climate change is a global concern given the potential effects of increased disturbance activity, warming temperatures and increased moisture stress on plants. We used a multi-regional dataset of 1485 sites across 52 wildfires from the US Rocky Mountains to ask if and how changing climate over the last several decades impacted post-fire tree regeneration, a key indicator of forest resilience. Results highlight significant decreases in tree regeneration in the 21st century. Annual moisture deficits were significantly greater from 2000 to 2015 as compared to 1985–1999,…
Publication Type: Journal Article
Wildfires managed for restoration enhance ecological resilience
Year: 2018
Expanding the footprint of natural fire has been proposed as one potential solution to increase the pace of forest restoration programs in fire‐adapted landscapes of the western USA. However, studies that examine the long‐term socio‐ecological trade‐offs of expanding natural fire to reduce wildfire risk and create fire resilient landscapes are lacking. We used the model Envision to examine the outcomes that might result from increased area burned by what we call “restoration” wildfire in a landscape where the ecological benefits of wildfire are known, but the need to suppress high‐risk fires…
Publication Type: Journal Article
Disequilibrium of fire-prone forests sets the stage for a rapid decline in conifer dominance during the 21st century
Year: 2018
The impacts of climatic changes on forests may appear gradually on time scales of years to centuries due to the long generation times of trees. Consequently, current forest extent may not reflect current climatic patterns. In contrast with these lagged responses, abrupt transitions in forests under climate change may occur in environments where alternative vegetation states are influenced by disturbances, such as fire. The Klamath forest landscape (northern California and southwest Oregon, USA) is currently dominated by high biomass, biodiverse temperate coniferous forests, but climate change…
Publication Type: Journal Article
It takes a few to tango: changing climate and fire regimes can cause regeneration failure of two subalpine conifers
Year: 2018
Environmental change is accelerating in the 21st century, but how multiple drivers may interact to alter forest resilience remains uncertain. In forests affected by large high-severity disturbances, tree regeneration is a resilience linchpin that shapes successional trajectories for decades. We modeled stands of two widespread western U.S. conifers, Douglas-fir (Pseudotsuga menziesii var. glauca), and lodgepole pine (Pinus contorta var. latifolia), in Yellowstone National Park (Wyoming, USA) to ask (1) What combinations of distance to seed source, fire return interval, and warming-drying…
Publication Type: Journal Article
Patterns of conifer regeneration following high severity wildfire in ponderosa pine - dominated forests of the Colorado Front Range
Year: 2016
Many recent wildfires in ponderosa pine (Pinus ponderosa Lawson & C. Lawson) - dominated forests of the western United States have burned more severely than historical ones, generating concern about forest resilience. This concern stems from uncertainty about the ability of ponderosa pine and other co-occurring conifers to regenerate in areas where no surviving trees remain. We collected post-fire conifer regeneration and other data within and surrounding five 11-18 year-old Colorado Front Range wildfires to examine whether high severity burn areas (i.e., areas without surviving trees)…
Publication Type: Journal Article
Fire enhances whitebark pine seedling establishment, survival, and growth
Year: 2015
Periodic fire is thought to improve whitebark pine (Pinus albicaulis Engelm.) regeneration by reducing competition and creating openings, but the mechanisms by which fire affects seedling establishment are poorly understood. I compared seedling vegetation production in adjacent sites, one last burned in 1880 and the other in 1988, to test the hypothesis that recent fire increases whitebark pine seedling growth. I experimentally tested effects of fire on seedling recruitment and growth by planting seeds in prescribed burned and nearby unburned sites. Experimental results showed nearly three…
Publication Type: Journal Article
Temperate forest health in an era of emerging megadisturbance
Year: 2015
Although disturbances such as fire and native insects can contribute to natural dynamics of forest health, exceptional droughts, directly and in combination with other disturbance factors, are pushing some temperate forests beyond thresholds of sustainability. Interactions from increasing temperatures, drought, native insects and pathogens, and uncharacteristically severe wildfire are resulting in forest mortality beyond the levels of 20th-century experience. Additional anthropogenic stressors, such as atmospheric pollution and invasive species, further weaken trees in some regions. Although…
Publication Type: Journal Article
Pile burning creates a fifty-year legacy of openings in regenerating lodgepole pine forests in Colorado
Year: 2015
Pile burning is a common means of disposing the woody residues of logging and for post-harvest site preparation operations, in spite of the practice’s potential negative effects. To examine the long-term implications of this practice we established a 50-year sequence of pile burns within recovering clear cuts in lodgepole pine forests. We compared tree, shrub and herbaceous plant abundance and documented indicators of soil degradation in openings where logging residue was piled and burned as part of post-harvest site preparation and the adjacent forests regenerating after clear cutting. We…
Publication Type: Journal Article
Does wildfire likelihood increase following insect outbreaks in conifer forests?
Year: 2015
Although there is acute concern that insect-caused tree mortality increases the likelihood or severity of subsequent wildfire, previous studies have been mixed, with findings typically based on stand-scale simulations or individual events. This study investigates landscape- and regional-scale wildfire likelihood following outbreaks of the two most prevalent native insect pests in the US Pacific Northwest (PNW): mountain pine beetle (MPB; Dendroctonus ponderosae) and western spruce budworm (WSB; Choristoneura freemani). We leverage seamless census data across numerous insect and fire events to…
Publication Type: Journal Article
Contemporary forest restoration: A review emphasizing function
Year: 2014
The forest restoration challenge (globally 2 billion ha) and the prospect of changing climate with increasing frequency of extreme events argues for approaching restoration from a functional and landscape perspective. Because the practice of restoration utilizes many techniques common to silviculture, no clear line separates ordinary forestry practices from restoration. The distinction may be that extra-ordinary activities are required in the face of degraded, damaged, or destroyed ecosystems. Restoration is driven by the desire to increase sustainability of ecosystems and their services and…
Publication Type: Journal Article
Clearcutting and high severity wildfire have comparable effects on growth of direct-seeded interior Douglas-fir
Year: 2014
The degree to which harvesting can achieve comparable beneficial effects to wildfire on seedling establishment is a key factor in understanding regeneration dynamics in dry interior forest ecosystems. We compared the capacity of harvesting versus wildfire to support establishment of directly-seeded interior Douglas-fir over a three-year period in the interior Douglas-fir biogeoclimatic zone of British Columbia. The mixed-severity McLure Fire of August 2003 affected over 26,000 hectares in the central British Columbia, Canada. Within the fire-affected area, we assessed growth performance in…
Publication Type: Journal Article