Fire Ecology & Effects
As MTBS data have been used over the course of many years and for many disparate applications, users should be aware that the MTBS burned area and severity products have been actively reviewed and revised to benefit from more robust satellite image availability and to address any observed quality issues. In a sample of 123 remapped fires, we found no significant change in the burned area boundary products when compared to the original mapped fires; however, significant changes did exist in the distribution of unburned, low, and moderate burn severity pixels within the thematic product.
Grasslands occur on all of the continents. They collectively constitute the largest ecosystem in the world, making up 40.5% of the terrestrial land area, excluding Greenland and Antarctica. Grasslands are not entirely natural because they have formed and developed under natural and anthropogenic pressures. Their importance now is to the variety of ecosystem services that they provide: livestock grazing areas, water catchments, biodiversity reserves, tourism sites, recreation areas, religious sites, wild food sources, and natural medicine sources. An important function of grasslands is their sequestration and storage of carbon (C). Mollisol soils of grasslands have deep organic matter horizons that make this vegetation type almost as important as forests for C fixation and storage. Fire has been and continues to be an important disturbance in grassland evolution and management. Natural wildfires have been a component of grasslands for over 300 million years and were important in creating and maintaining most of these ecosystems. Humans ignited fires over many millennia to improve habitat for animals and livestock. Prescribed fire practiced by humans is a component of modern grassland management. The incidence of wildfires in grasslands continues to grow as an issue as droughts persist in semi-arid regions. Knowledge of fire effects on grasslands has risen in importance to land managers because fire, as a disturbance process, is an integral part of the concept of ecosystem management and restoration ecology. Fire is an intrusive disturbance in both managed and wildland forests and grasslands. It initiates changes in ecosystems that affect the composition, structure, and patterns of vegetation on the landscape. It also affects the soil and water resources of ecosystems that are critical to overall ecosystem functions and processes.
The Northeastern California Plateaus Bioregion Science Synthesis reviews literature relevant to the ecology and management of the Great Basin ecosystems and dry pine forests of the Lassen and Modoc National Forests. Critical factors on these national forests are reduced water availability—expected to become more challenging as levels and patterns of precipitation and temperature change under climate variability—coupled with a high proportion of rangeland and open woodland whose vegetation community is influenced by grazing of livestock and wild animal populations. Conifer encroachment of rangelands and the densification of woodlands, a result of fire suppression, impact wildlife communities that rely on open woodlands and other habitats characterized by having overstories of low density. Sagebrush habitat, in particular, is threatened by fragmentation and conversion. Socioeconomic changes in the region include a transition in the economic base from extraction to that of consumption of amenity values, and the resulting fragmentation of landownership. The local human population is expected to continue its trend of decline, but increased pressure by recreationists from nearby expanding urban areas is forcing land managers to consider increasingly complex situations or actions integrating social, ecological, and economic factors. Indigenous peoples are assuming a greater role in the management of their lands. Finally, disturbance patterns, such as nonhistorical fire frequency and intensity levels, novel combinations of climate patterns, and the pervasive pressure of nonnative invasive species could result in future ecosystems different than those today, presenting additional managerial challenges. This synthesis is intended to serve as a science-based foundation that supports management of Northeastern California forests, woodlands, and rangelands.
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Description: The avifauna within the Sky Islands of southeastern Arizona includes species found nowhere else in the United States, in part due to the availability of diverse habitats created by the mixing of Madrean and Cordilleran ecosystems. Neotropical migratory bird species visit these mountains, as well as many species typical of western North American montane forests. Birdwatchers from across the globe visit the region, providing a vibrant state and local ecotourism industry. Within the last two decades, the Sky Islands have been under increased stress associated with ongoing droughts and wildfires. Nearly every mountain range in the region has been impacted by wildfires. The largest wildfire was the 2011 Horseshoe Two Fire, which burned 90,307 hectares of the Chiricahua Mountains.
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These online courses were developed by Wildland Fire Management Research, Development, and Application, Fire Regime Condition Class, LANDFIRE, National Wildfire Coordinating Group, and National Advanced Fire and Resource Institute.
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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 the 2007 Egley Fire Complex in Oregon, USA. We also assessed short- and long-term fuel treatment impacts on field-measured attributes one and nine years post fire.
Rick Miller, Professor Emeritus, OSU, discusses the intent and goals of his latest publication, The Ecology, History, Ecohydrology, and Management of Pinyon and Juniper Woodlands in the Great Basin and Northern Colorado Plateau in the Western United States. This includes 1) Describing the the woodlands and the vast variation across the GB and CP, 2) Telling the story of their history and variables influencing woodland expansion and contraction, and 3) Interpretation of the wide variation in responses and the variables influencing ecosystem response to restoration.
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This study assessed plant community succession following prescribed fire on ungrazed Wyoming big sagebrush steppe, eastern Oregon. Herbaceous yield, vegetation canopy cover and density were compared between treatments after fire (2003–18). Herbaceous yield in the Burn treatment was about double the control for most of the study period. Prior to fire, native perennials comprised 90–95% of herbaceous yield. After fire, native perennials represented 78% (range 67–93%) and exotic annuals 22% (range 7–33%) of total yield. Exotic annuals increased after fire and responded in two stages. In the first 8 years after fire, desert alyssum dominated the annual plant composition. In the last half of the study, cheatgrass co-dominated the annual component with alyssum. Sagebrush recovery was slow and we estimated sagebrush cover would return to pre-burn levels, at the earliest, in 115 years. Burning Wyoming big sagebrush steppe would be detrimental to sagebrush-obligate wildlife for an extended time period, because of lost cover and structure provided by sagebrush. The additional forage provided on burned areas may give livestock manager’s greater flexibility to rest or defer unburned habitat for wildlife species of critical concern.
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This study examined post-fire aspen stands across a regional climate gradient spanning from the north-central Great Basin to the northeastern portion of the Greater Yellowstone Ecosystem (USA). We investigated the influence of seasonal precipitation and temperature variables, snowpack, and site conditions (e.g. browsing levels, topography) on density of post-fire aspen regeneration (i.e. all small trees ha−1) and recruitment (i.e. small trees ≥2 m tall ha−1) across 15 fires that occurred between 2000 and 2009. The range of post-fire regeneration (2500–71,600 small trees ha−1) and recruitment (0–32,500 small trees ≥2 m ha−1) densities varied widely across plots. Linear mixed effects models demonstrated that both response variables increased primarily with early winter (Oct-Dec) precipitation during the ‘fire-regen period’ (i.e., fire year and five years after fire) relative to the 30-year mean. The 30-year mean of early winter precipitation and fire-regen period snowpack were also positively related to recruitment densities. Both response variables decreased with higher shrub cover, highlighting the importance of considering shrub competition in post-fire environments. Regeneration and recruitment densities were negatively related to proportion browsed aspen leaders and animal pellet densities (no./m2), respectively, indicating the influence of ungulate browsing even at the relatively low levels observed across sites. A post-hoc exploratory analysis suggests that deviation in early winter precipitation during the fire-regen period (relative to 30-year means) varied among sites along directional gradients, emphasizing the need to consider multiple spatiotemporal scales when investigating climate effects on post-fire successional dynamics.
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It is sometimes assumed the sparse and low statured vegetation in arid systems would limit the effectiveness of two remote-sensing derived indices of burn severity: the difference Normalised Burn Ratio (dNBR) and relativised difference Normalised Burn Ratio (RdNBR). We compared the relationship that dNBR, RdNBR and a ground-based index of burn severity (the Composite Burn Index, CBI) had with woody cover and woody density 1 year after burning in five fires that occurred in the Mojave Desert during 2005. Statistically, dNBR and RdNBR were both effective measures of severity in all three elevation zones; woody cover and density had steep exponential declines as the values of each remote-sensing index increased. We found though that dNBR was more ecologically interpretable than RdNBR and will likely be of most relevance in the Mojave Desert.