Fire History

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California Fire Return Interval Departure database: What it is and how to use it

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FRID statistics have been used for decades to help managers and scientists understand the ecological consequences of changing fire frequencies. The Forest Service Region 5 Ecology Program worked with UC-Davis to build a spatial FRID data layer that compiles information about fire return intervals for major vegetation types on the 18 National Forests in California and adjacent land jurisdictions. This data layer includes comparisons between pre-Euroamerican settlement (“pre-EAS”) and contemporary fire return intervals (FRIs). The FRID layer may be used for land and resource planning and assessment, as well as other natural resource applications such as fuels treatment planning, postfire restoration project design, management response to fire, assessing the effects of fire and fire regime change on ecosystems, and general ecological understanding of the historic and current occurrence of fire on the California National Forests and neighboring jurisdictions. This presentation focuses on the guts of the FRID data and the departure metrics, describes how to properly use the dataset, discusses some important caveats, outlines current updating and improvement work we are doing with the dataset, and describes a current national effort to develop a similar dataset and metrics for the US.

Bar graph showing increase in nonforest area burned 2000-2020

More Area Burned in Non-Forest than Forest from 2000-2020 in the West

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Wildfires burned more area on non-forested lands than forested lands over the past 20 years. This was true for all land ownerships in CONUS and the western US. Burned area increased over the 20-year time period for both non-forest and forest. Across CONUS, annual area burned was higher on non-forest than forests for 14 of the past 21 years (Fig. 1), and total area burned was almost 3,000,000 ha more in non-forest than in forest. For the western US, total burned area was almost 1,500,000 ha more in non-forest than in forest. From a federal agency perspective, approximately 74% of the burned area on Department of the Interior (DOI) lands occurred in non-forest and 78% of the burned area on US Forest Service (FS) lands occurred in the forest.

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Fire exclusion: Historical data reveal early and lasting effects of fire regime change on contemporary forest composition

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We use a unique dataset derived from contemporary (∼2016) remeasurement of 440 historical quadrats (∼4m2) in the central Sierra Nevada, California, in which overstory trees, tree regeneration, and microsite conditions were measured and mapped both before and after logging in 1928–1929. Pine relative abundance changed little with logging and declined to 5% of the contemporary regeneration layer. In contrast, the relative abundance of incense-cedar regeneration (32%) already outpaced its representation in the overstory (17% by basal area) before logging and proceeded to dominate the contemporary understory (49%). We did not find strong evidence for the positive influence of gaps on pine regeneration in any time period. However, across species, post-logging skid trails were positively associated with regeneration and woody debris was negatively associated with regeneration in at least one time period. We discovered that the occurrence of advance regeneration (regeneration that preceded and survived logging) best predicted new contemporary trees across all species. For shade-tolerant species, post-logging regeneration that established up to ten years after logging was also associated with new contemporary trees. In contrast, the few pine that transitioned into the contemporary canopy during the study period all established prior to logging. Our work provides evidence that low pine abundance in the regeneration layer as early as 1928 contributed to low rates of pine in the overstory in 2016, showcasing that the decline of pine likely began before logging and official federal fire suppression policies. We suggest that fire exclusion before logging perpetuated shifts towards shade-tolerant and fire-intolerant species in the regeneration layer that were early and lasting.

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Wildland Fire Trends Tool: A web-based data visualization tool for displaying wildlife trend and patterns in the western US

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Presenter: Douglas J. Shinneman, Research Ecologist, USGS Forest and Rangeland Ecosystem Science Center

Description: Accurately assessing recent and historical wildfire activity is critical for numerous agencies who manage fire-prone landscapes. The Wildland Fire Trends Tool (WFTT) is a data visualization and analysis tool that calculates and displays wildfire trends and patterns for the western U.S. based on user-selected regions of interest, time periods, and ecosystem types. For instance, users can determine whether the area burned by wildfire is increasing or decreasing over time for a specific ecoregion or for land ownership types of interest. The tool is available via a web application and generates a variety of maps, graphs, and tabular data that provide useful information for fire science and management objectives, as well as for the interested public.

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Fire in the western US: Big fires. Big challenges. The call for regional learning and action.

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Learn about the diverse inputs and outcomes from six large fires spanning five JFSP Regional Fire Science Exchanges. This webinar walks you through the jointly produced story map: Fire in the Western U.S.: Big fires. Big challenges. Big need for regional learning and action.

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Short-interval high-severity reburns change the playing field for forest recovery

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Reburns, sequential overlapping fires occurring in an unusually short timeframe, are expected to become more common and widespread with increases in fire-conducive weather. The context for reburns varies by ecosystem; in subalpine forests of the Northern Rockies, high-severity fires separated by less than 30 years are considered reburns. Join researchers Kristin Braziunas (Technical University of Munich, Germany) and Tyler Hoecker (Northwest Climate Adaptation Science Center) as they discuss recent studies in the Greater Yellowstone and Glacier National Park looking at post-fire recovery after short-interval reburns.

Short-interval high-severity reburns that are outside the historical range of variability of a system can erode the resilience of subalpine forests by undermining fire-adaptive traits and changing the microclimate that affects tree seedling establishment. These reburns diminish tree regeneration but could also lessen subsequent burn severity. Short-interval fire could lead to rapid, surprising changes in forest resilience during the 21st century.

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Fire history and ecology

Webinar recordings of the Forest Service’s Research and Development SCIENCEx FIRE week.

Fire History and Ecology

Introduction to SCIENCEx Fire Week​ | Jens Stevens
​Indigenous Fire Stewardship and Cultural Burning​ | Frank Lake
​Fire Exclusion and Western Forest Change​ | Eric Knapp
A History of Fire in the Eastern US: ​How Humans Modified Fire Regimes through the Holocene​ | Dan Dey

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Contemporary (1984-2020) fire history metrics for the conterminous US and ecoregional differences by land ownership

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This study calculated fire history metrics from the Landsat Burned Area Product (1984–2020) across the conterminous U.S. (CONUS) including (1) fire frequency, (2) time since last burn (TSLB), (3) year of last burn, (4) longest fire-free interval, (5) average fire interval length, and (6) contemporary fire return interval (cFRI).

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Biogeographical patterns of fire characteristics across the contiguous US

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Human-dominated pyromes (85% mean anthropogenic ignitions), with moderate fire size, area burned, and intensity, covered 59% of CONUS, primarily in the East and East Central. Physically dominated pyromes (47% mean anthropogenic ignitions) characterized by relatively large (average 439 mean annual ha per 50 km pixel) and intense (average 75 mean annual megawatts/pixel) fires occurred in 14% of CONUS, primarily in the West and West Central. The percent of anthropogenic ignitions increased over time in all pyromes (0.5–1.7% annually). Higher fire frequency was related to smaller events and lower FRP, and these relationships were moderated by vegetation, climate, and ignition type. Notably, a spatial mismatch between our derived modern pyromes and both ecoregions and historical fire regimes suggests other major drivers for modern U.S. fire patterns than vegetation-based classification systems. This effort to delineate modern U.S. pyromes based on fire observations provides a national-scale framework of contemporary fire regions and may help elucidate patterns of change in an uncertain future.

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Wildland Fire Trends Tool

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The Wildland Fire Trends Tool (WFTT) is a data visualization and analysis tool that calculates and displays wildfire trends and patterns for the western U.S. based on user-defined regions of interest, time periods, and ecosystem types. Users can use the tool to easily generate a variety of maps, graphs, and tabular data products that are informative for all levels of expertise. The WFTT provides information that can be used for a wide range of purposes, from helping to set agency fire management objectives to providing useful information to scientists, interested public, and the media.

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