Research Database
Displaying 41 - 60 of 66
Wildfire, climate, and invasive grass interactions negatively impact an indicator species by reshaping sagebrush ecosystems
Year: 2016
Iconic sagebrush ecosystems of the American West are threatened by larger and more frequent wildfires that can kill sagebrush and facilitate invasion by annual grasses, creating a cycle that alters sagebrush ecosystem recovery post disturbance. Thwarting this accelerated grass–fire cycle is at the forefront of current national conservation efforts, yet its impacts on wildlife populations inhabiting these ecosystems have not been quantified rigorously. Within a Bayesian framework, we modeled 30 y of wildfire and climatic effects on population rates of change of a sagebrush-obligate species,…
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
Restoration impacts on fuels and fire potential in a dryland tropical ecosystem dominated by the invasive grass Megathyrsus maximus
Year: 2015
Ecological restoration often attempts to promote native species while managing for disturbances such as fire and non-native invasions. The goal of this research was to investigate whether restoration of a non-native, invasive Megathyrsus maximus (guinea grass) tropical grassland could simultaneously promote native species and reduce fire potential. Megathyrsus maximus was suppressed with herbicide, and three suites of native species—each including the same groundcover and shrub, and one of three tree species—were outplanted in a randomized, complete block design that also included herbicide…
Publication Type: Journal Article
Fire and non-native grass invasion interact to suppress tree regeneration in temperate deciduous forests
Year: 2015
While many ecosystems depend on fire to maintain biodiversity, non-native plant invasions can enhance fire intensity, suppressing native species and generating a fire–invasion feedback. These dynamics have been observed in arid and semi-arid ecosystems, but fire–invasion interactions in temperate deciduous forests, where prescribed fires are often used as management tools to enhance native diversity, have rarely been investigated. Here we evaluated the effects of a widespread invasive grass on fire behaviour in eastern deciduous forests in the USA and the potential effects of fire and…
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
Fire severity and tree regeneration following bark beetle outbreaks: the role of outbreak stage and burning conditions
Year: 2014
The degree to which recent bark beetle (Dendroctonus ponderosae) outbreaks may influence fire severity and postfire tree regeneration is of heightened interest to resource managers throughout western North America, but empirical data on actual fire effects are lacking. Outcomes may depend on burning conditions (i.e., weather during fire), outbreak severity, or intervals between outbreaks and subsequent fire. We studied recent fires that burned through green-attack/red-stage (outbreaks <3 years before fire) and gray-stage (outbreaks 3–15 years before fire) subalpine forests dominated by…
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
Conditions favouring Bromus tectorum dominance of endangered sagebrush steppe ecosystems
Year: 2013
Ecosystem invasibility is determined by combinations of environmental variables, invader attributes, disturbance regimes, competitive abilities of resident species and evolutionary history between residents and disturbance regimes. Understanding the relative importance of each factor is critical to limiting future invasions and restoring ecosystems. We investigated factors potentially controlling Bromus tectorum invasions into Artemisia tridentata ssp. wyomingensis communities across 75 sites in the Great Basin. We measured soil texture, cattle grazing intensity, gaps among perennial plants…
Publication Type: Journal Article
Conifer regeneration following stand-replacing wildfires varies along an elevation gradient in a ponderosa pine forest, Oregon, USA
Year: 2013
Climate change is expected to increase disturbances such as stand-replacing wildfire in many ecosystems, which have the potential to drive rapid turnover in ecological communities. Ecosystem recovery, and therefore maintenance of critical structures and functions (resilience), is likely to vary across environmental gradients such as moisture availability, but has received little study. We examined conifer regeneration a decade following complete stand-replacing wildfire in dry coniferous forests spanning a 700 m elevation gradient where low elevation sites had relatively high moisture stress…
Publication Type: Journal Article
Sagebrush steppe recovery after fire varies by development phase of Juniperus occidentalis woodland
Year: 2013
Woodland ecosystems of the world have been changed by land use demands, altered fire regimes, invasive species and climate change. Reduced fire frequency is recognised as a main causative agent for Pinus–Juniperus L. (piñon–juniper) expansion in North American woodlands. Piñon–juniper control measures, including prescribed fire, are increasingly employed to restore sagebrush steppe communities. We compared vegetation recovery following prescribed fire on Phase 2 (mid-succession) and Phase 3 (late-succession) Juniperus occidentalis Hook. (western juniper) woodlands in Oregon. The herbaceous…
Publication Type: Journal Article
Natural tree regeneration and coarse woody debris dynamics after a forest fire in the Western Cascade range
Year: 2013
We monitored coarse woody debris dynamics and natural tree regeneration over a 14-year period after the 1991 Warner Creek Fire, a 3631-ha (8,972-ac) mixed severity fire in the western Cascade Range of Oregon. Rates for tree mortality in the fire, postfire mortality, snag fall, and snag fragmentation all showed distinct patterns by tree diameter and species, with Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) more likely to survive a fire, and to remain standing as a snag, than other common tree species. Natural seedling regeneration was abundant, rapid, and highly variable in space.…
Publication Type: Report
Management of Cheatgrass Fuel Loading in the Shrub-Steppe
Year: 2013
The Columbia Basin Natural Wildlife Refuge (CNWR) had been periodically grazed until the Refuge was established in 1944. Cheatgrass became a prominent plant in the area. In 1986 a fire occurred near the study area. The area was reseeded with Elymus wawawaiensis (Snake River Wheatgrass, Secar cultivar). This grass has established reducing cheatgrass cover to very low levels. The study area was established in 2002 to test hypotheses on the effects of herbicides on plant community structure and establishment of Elymus wawawaiensis. In 2002 study plots were established and characterized before…
Publication Type: Report
Does seeding after wildfires in rangelands reduce erosion or invasive species?
Year: 2013
Mitigation of ecological damage caused by rangeland wildfires has historically been an issue restricted to the western United States. It has focused on conservation of ecosystem function through reducing soil erosion and spread of invasive plants. Effectiveness of mitigation treatments has been debated recently. We reviewed recent literature to conduct a meta-analysis of seeding after wildfires to determine if seedings may (1) protect ecosystems against soil erosion and (2) reduce invasion or abundance of undesirable nonnative plant species. Effectiveness of postfire seedings was examined in…
Publication Type: Journal Article
Management of cheatgrass fuel loading in the shrub-steppe
Year: 2013
The fire risk experiment was in plant communities that spanned the range of B. tectorum cover. Bromus tectorum cover was grouped into five classes. Each replicate is comprised of 8 to 18 plots in the three lowest B. tectorum cover classes and 2 to 6 plots at the two highest cover classes. A replicate is a collection of plots where the risk of fire was determined as the proportion of plots that burned. Each class has four replicates. We used 176 square plots, 10 m on a side. Two hundred twenty six plots, 10 m on a side, were used to related B. tectorum cover…
Publication Type: Presentation
Latent resilience in ponderosa pine forest: effects of resumed frequent fire
Year: 2013
Ecological systems often exhibit resilient states that are maintained through negative feedbacks. In ponderosa pine forests, fire historically represented the negative feedback mechanism that maintained ecosystem resilience; fire exclusion reduced that resilience, predisposing the transition to an alternative ecosystem state upon reintroduction of fire. We evaluated the effects of reintroduced frequent wildfire in unlogged, fire-excluded, ponderosa pine forest in the Bob Marshall Wilderness, Montana, USA. Initial reintroduction of fire in 2003 reduced tree density and consumed surface fuels,…
Publication Type: Journal Article
Trajectories of change in sagebrush steppe vegetation communities in relation to multiple wildfires
Year: 2012
Repeated perturbations, both biotic and abiotic, can lead to fundamental changes in the nature of ecosystems, including changes in state. Sagebrush steppe communities provide important habitat for wildlife and grazing for livestock. Fire is an integral part of these systems, but there is concern that increased ignition frequencies and invasive species are fundamentally altering them. Despite these issues, the majority of studies of fire effects in systems dominated by Artemisia tridentata wyomingensis have focused on the effects of single burns. The Arid Lands Ecology Reserve (ALE), in south-…
Publication Type: Journal Article
Cheating Cheatgrass: New research to combat a wily invasive weed
Year: 2012
Cheatgrass and its cousin, red brome, are exotic annual grasses that have invaded and altered ecosystem dynamics in more than 41 million acres of desert shrublands between the Rockies and the Cascade-Sierra chain. A fungus naturally associated with these Bromus species has been found lethal to the plants’ soil-banked dormant seeds. Supported by the Joint Fire Science Program (JFSP), researchers Susan Meyer, Phil Allen, and Julie Beckstead cultured this fungus, Pyrenophora semeniperda, in the laboratory and developed an experimental field application that, in some trials, killed all the…
Publication Type: Report
Grassland Response to Herbicides and Seeding of Native Grasses 6 Years Posttreatment
Year: 2012
Herbicides are the primary method used to control exotic, invasive plants. This study evaluated restoration efforts applied to grasslands dominated by an invasive plant, sulfur cinquefoil, 6 yr after treatments. Of the five herbicides we evaluated, picloram continued to provide the best control of sulfur cinquefoil over 6 yr. We found the timing of picloram applications to be important to the native forb community. Plots with picloram applied in the fall had greater native forb cover. However, without the addition of native perennial grass seeds, the sites became dominated by exotic grasses.…
Publication Type: Journal Article
Ecological restoration using EBIPM
Year: 2012
When managing rangeland impacted by weeds, land managers often encounter plant communities where remnant desired vegetation is very scarce. When rangeland is this degraded, simply controlling weeds with the expectation that desired plants will be released from competition and return to dominate the site over time might not be adequate. Introducing propagules (i.e., seeds) of desired species through revegetation might be required. Ecologically Based Invasive Plant Management (EBIPM) serves as a decision-making framework for planning and implementing restoration and revegetation programs. This…
Publication Type: Journal Article
Preemergent Control of Medusahead on California Annual Rangelands with Aminopyralid
Year: 2012
Medusahead (Taeniatherum caput-medusae [L.] Nevski), the most problematic invasive grass on many California rangelands, is difficult to control selectively in grasslands. Prescribed burning, grazing, and herbicides have been tested with some success but are not practical in all situations. The selective herbicide aminopyralid, normally used for control of certain broadleaf species such as thistles, suppresses some annual grasses when applied pre- or early postemergence. In 2009–2010, we tested the efficacy of aminopyralid for medusahead control in preemergence applications at three foothill…
Publication Type: Journal Article