FIRED (Fire Events Delineation): An Open, Flexible Algorithm and Database of US Fire Events Derived from the MODIS Burned Area Product (2001-2019)

Harnessing the fire data revolution, i.e., the abundance of information from satellites, government records, social media, and human health sources, now requires complex and challenging data integration approaches. Defining fire events is key to that effort. In order to understand the spatial and temporal characteristics of fire, or the classic fire regime concept, we need to critically define fire events from remote sensing data. Events, fundamentally a geographic concept with delineated spatial and temporal boundaries around a specific phenomenon that is homogenous in some property, are key to understanding fire regimes and more importantly how they are changing. Here, we describe Fire Events Delineation (FIRED), an event-delineation algorithm, that has been used to derive fire events (N = 51,871) from the MODIS MCD64 burned area product for the coterminous US (CONUS) from January 2001 to May 2019. The optimized spatial and temporal parameters to cluster burned area pixels into events were an 11-day window and a 5-pixel (2315 m) distance, when optimized against 13,741 wildfire perimeters in the CONUS from the Monitoring Trends in Burn Severity record. The linear relationship between the size of individual FIRED and Monitoring Trends in Burn Severity (MTBS) events for the CONUS was strong (R2 = 0.92 for all events). Importantly, this algorithm is open-source and flexible, allowing the end user to modify the spatio-temporal threshold or even the underlying algorithm approach as they see fit. We expect the optimized criteria to vary across regions, based on regional distributions of fire event size and rate of spread. We describe the derived metrics provided in a new national database and how they can be used to better understand US fire regimes. The open, flexible FIRED algorithm could be utilized to derive events in any satellite product. We hope that this open science effort will help catalyze a community-driven, data-integration effort (termed OneFire) to build a more complete picture of fire.</p

Harnessing the NEON data revolution to advance open environmental science with a diverse and data-capable community

It is a critical time to reflect on the National Ecological Observatory Network (NEON) science to date as well as envision what research can be done right now with NEON (and other) data and what training is needed to enable a diverse user community. NEON became fully operational in May 2019 and has pivoted from planning and construction to operation and maintenance. In this overview, the history of and foundational thinking around NEON are discussed. A framework of open science is described with a discussion of how NEON can be situated as part of a larger data constellation—across existing networks and different suites of ecological measurements and sensors. Next, a synthesis of early NEON science, based on >100 existing publications, funded proposal efforts, and emergent science at the very first NEON Science Summit (hosted by Earth Lab at the University of Colorado Boulder in October 2019) is provided. Key questions that the ecology community will address with NEON data in the next 10 yr are outlined, from understanding drivers of biodiversity across spatial and temporal scales to defining complex feedback mechanisms in human–environmental systems. Last, the essential elements needed to engage and support a diverse and inclusive NEON user community are highlighted: training resources and tools that are openly available, funding for broad community engagement initiatives, and a mechanism to share and advertise those opportunities. NEON users require both the skills to work with NEON data and the ecological or environmental science domain knowledge to understand and interpret them. This paper synthesizes early directions in the community’s use of NEON data, and opportunities for the next 10 yr of NEON operations in emergent science themes, open science best practices, education and training, and community building

Interactions between bark beetle outbreak and wildland fire in intermountain subalpine forests of the western United States: legacies and future projections under a changing climate

Over the past 30 years, wildland fire and native bark beetle outbreaks have increased in intensity, severity, and extent across the fire-prone forests of the western United States, raising concerns about whether bark beetle outbreaks increase wildfire severity and/or wildfire occurrence. Furthermore, current estimates predict a two-fold increase in area burned by wildland fires over the next 25 years and bark beetles are forecasted to expand in the coming century, shifting toward higher latitudes and elevations. Thus, it is important to better understand how insect-driven tree mortality may affect fire risk and how these disturbance interactions may affect ecosystem structure and dynamics across biophysical settings under current and future climate scenarios. In this dissertation, I investigated the relationships between bark beetle outbreaks, wildfire, and climate across the western United States and within subalpine forests of the Southern Rocky Mountains, CO, USA. The main research questions of this dissertation were: (Chapter II) what is the relative importance of mountain pine beetle (Dendroctonus ponderosae (Hopkins)) outbreaks versus antecedent climatic variability on the occurrence of large wildfires in the western U.S.? (Chapter III) how do pre-outbreak forest conditions mediate the effects of spruce beetle (Dendroctonus rufipennis (Kirby)) outbreaks on fuels complexes in subalpine forests of Colorado? and (Chapter IV) how do changes in fuels following spruce beetle outbreaks affect expected fire potential under current and future climate conditions? Chapter II employed a variety of remotely sensed data and GIS products of fire occurrence, mountain pine beetle outbreaks, physiographic gradients, and climatic condition to test whether prior-disturbance or antecedent climate conditions influenced subsequent wildfire events. Extensive field surveys of stand attributes and fuel arrangements across a chronosequence of spruce beetle outbreaks in the 20th and 21st century were employed to address research questions of Chapter III. Results from Chapter III were used as base inputs for custom fire behavior models in Chapter IV, to test the sensitivity of potential fire behavior across a variety of wind speeds, weather, and climate scenarios. Despite widespread concern that mountain pine beetle outbreaks lead to unprecedented increases in wildfire activity, results from Chapter II demonstrated minimal effects of these pre-fire disturbances on subsequent fire occurrence. Instead, occurrence of large wildfires across the western US has been driven by extreme weather (e.g., hot, dry conditions). Chapter III revealed that the changes to fuels following spruce beetle outbreaks are strongly contingent on pre-outbreak stand structure and disturbance history. For instance, we found that spruce beetle outbreaks reduce canopy fuels in all stands, yet this effect is relatively minor in old spruce-fir stands as compared to young spruce-fir stands. Spruce beetle outbreaks during the 20th and 21st century decreased canopy fuels and increased their heterogeneity, regardless of pre-outbreak conditions. Surface fuel loads were more variable with increased time since spruce beetle outbreak and did not return to pre-outbreak conditions over the 75-year period considered in this study in both young and old stands. Chapter IV concluded that under all weather and climate scenarios, stands affected by spruce beetle had the lowest potential for increased surface fireline intensities, rates of spread, and active crowning among both young and old stands as compared to endemic stands (i.e., non-outbreak). Chapter IV used future climate projections (2016-2100) of RCP 4.5 and RCP 8.5 as proxies for moderate and severe climate change and concluded that moderate climate change will not substantially increase the most important types of fire behavior among young or old stands, nor stands affected by spruce beetle outbreak as compared to current climate (1985-2015). However, under severe climate change projections (RCP 8.5) all characteristics of fire behavior will increase, regardless of stand age, spruce beetle outbreak, and wind and weather scenarios. This research provides much needed insight into the disturbance dynamics in fire-prone forests and informs forest management and policy concerns under a changing climate. Overall, this research highlights the 1) dominant effect of climate, rather than outbreaks, has on fire regimes across the western United States and 2) the importance of accounting for pre-disturbance stand structure and disturbance histories on subsequent disturbance patterns and severities

NateMietk/spruce-beetle-fuels: First release of data associated with Mietkiewicz et al. 2017.

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Relative importance of climate and mountain pine beetle outbreaks on the occurrence of large wildfires in the western USA

Extensive outbreaks of bark beetles have killed trees across millions of hectares of forests and woodlands in western North America. These outbreaks have led to spirited scientific, public, and policy debates about consequential increases in fire risk, especially in the wildland-urban interface (WUI), where homes and communities are at particular risk from wildfires. At the same time, large wildfires have become more frequent across this region. Widespread expectations that outbreaks increase extent, severity, and/or frequency of wildfires are based partly on visible and dramatic changes in foliar moisture content and other fuel properties following outbreaks, as well as associated modeling projections. A competing explanation is that increasing wildfires are driven primarily by climatic extremes, which are becoming more common with climate change. However, the relative importance of bark beetle outbreaks vs. climate on fire occurrence has not been empirically examined across very large areas and remains poorly understood. The most extensive outbreaks of tree-killing insects across the western United States have been of mountain pine beetle (MPB; Dendroctonus ponderosae), which have killed trees over \u3e650,000 km2, mostly in forests dominated by lodgepole pine (Pinus contorta). We show that outbreaks of MPB in lodgepole pine forests of the western United States have been less important than climatic variability for the occurrence of large fires over the past 29 years. In lodgepole pine forests in general, as well as those in the WUI, occurrence of large fires was determined primarily by current and antecedent high temperatures and low precipitation but was unaffected by preceding outbreaks. Trends of increasing co-occurrence of wildfires and outbreaks are due to a common climatic driver rather than interactions between these disturbances. Reducing wildfire risk hinges on addressing the underlying climatic drivers rather than treating beetle-affected forests

Land cover change detection

The purpose of this chapter is to explore the current trends in land cover change detection and to identify those trends that are potentially transformative to our understanding of land change, as well as identify knowledge/information gaps that should require attention in the future. The current level of understanding of the scale and pace of land cover change is inadequate (Frey and Smith 2007; Turner et al. 2007; Hansen et al. 2013). However, it is understood that land cover change is an undisputed component of global environmental change (Kennedy et al. 2014). Land cover changes and their impacts range widely from regional temperature warming to land degradation and biodiversity loss and from diminished food production to the spread of infectious diseases (Vitousek et al. 1997; Farrow and Winograd 2001). Land cover change, manifested as either land cover modification or conversion, can occur at all spatial scales, and changes at local scales can have cumulative impacts at broader scales (Stow 1995)

Relative Importance of Climate and Mountain Pine Beetle Outbreaks on the Occurrence of Large Wildfires in the Western USA

Extensive outbreaks of bark beetles have killed trees across millions of hectares of forests and woodlands in western North America. These outbreaks have led to spirited scientific, public, and policy debates about consequential increases in fire risk, especially in the wildland–urban interface (WUI), where homes and communities are at particular risk from wildfires. At the same time, large wildfires have become more frequent across this region. Widespread expectations that outbreaks increase extent, severity, and/or frequency of wildfires are based partly on visible and dramatic changes in foliar moisture content and other fuel properties following outbreaks, as well as associated modeling projections. A competing explanation is that increasing wildfires are driven primarily by climatic extremes, which are becoming more common with climate change. However, the relative importance of bark beetle outbreaks vs. climate on fire occurrence has not been empirically examined across very large areas and remains poorly understood. The most extensive outbreaks of tree‐killing insects across the western United States have been of mountain pine beetle (MPB; Dendroctonus ponderosae), which have killed trees over \u3e650,000 km2, mostly in forests dominated by lodgepole pine (Pinus contorta). We show that outbreaks of MPB in lodgepole pine forests of the western United States have been less important than climatic variability for the occurrence of large fires over the past 29 years. In lodgepole pine forests in general, as well as those in the WUI, occurrence of large fires was determined primarily by current and antecedent high temperatures and low precipitation but was unaffected by preceding outbreaks. Trends of increasing co‐occurrence of wildfires and outbreaks are due to a common climatic driver rather than interactions between these disturbances. Reducing wildfire risk hinges on addressing the underlying climatic drivers rather than treating beetle‐affected forests

Pre-outbreak forest conditions mediate the effects of spruce beetle outbreaks on fuels in subalpine forests of Colorado

Over the past 30 years, forest disturbances have increased in size, intensity, and frequency globally, and are predicted to continue increasing due to climate change, potentially relaxing the constraints of vegetation properties on disturbance regimes. However, the consequences of the potentially declining importance of vegetation in determining future disturbance regimes are not well understood. Historically, bark beetles preferentially attack older trees and stands in later stages of development. However, as climate warming intensifies outbreaks by promoting growth of beetle populations and compromising tree defenses, smaller diameter trees and stands in early stages of development now are being affected by outbreaks. To date, no study has considered how stand age and other pre-outbreak forest conditions mediate the effects of outbreaks on surface and aerial fuel arrangements. We collected fuels data across a chronosequence of post-outbreak sites affected by spruce beetle (SB) between the 1940s and the 2010s, stratified by young (\u3c130 \u3eyr) and old (\u3e130 yr) post-fire stands. Canopy and surface fuel loads were calculated for each tree and stand, and available crown fuel load, crown bulk density, and canopy bulk densities were estimated. Canopy bulk density and density of live canopy individuals were reduced in all stands affected by SB, though foliage loss was proportionally greater in old stands as compared to young stands. Fine surface fuel loads in young stands were three times greater shortly (\u3c30 \u3eyr) following outbreak as compared to young stands not affected by outbreak, after which the abundance of fine surface fuels decreased to below endemic (i.e., non-outbreak) levels. In both young and old stands, the net effect of SB outbreaks during the 20th and 21st centuries reduced total canopy fuels and increased stand-scale spatial heterogeneity of canopy fuels following outbreak. Importantly, the decrease in canopy fuels following outbreaks was greater in young post-fire stands than in older stands, suggesting that SB outbreaks may more substantially reduce risk of active crown fire when they affect stands in earlier stages of development. The current study shows that the effects of SB outbreaks on forest structure and on fuel profiles are strongly contingent on pre-outbreak conditions as determined by pre-outbreak disturbance history

The relative importance of tree and stand properties in susceptibility to spruce beetle outbreak in the mid-20th century

Tree susceptibility to potentially lethal agents is determined not only by attributes of individual trees, but also by neighborhood effects at a range of scales. For example, effects of disturbances on individual trees are often contingent on the size, configuration, and other properties of neighboring trees. Wildfires can modify postfire properties of individual trees as well as of entire forest stands, both of which can affect subsequent ecological processes, including subsequent disturbances. In recent years, much has been learned about how disturbances interact, but numerous questions concerning underlying mechanisms remain unresolved. For example, the relative importance of forest properties at different spatial scales in determining how fires affect forest susceptibility to subsequent disturbances is not well understood. This study explicitly compares the relative importance of tree vs. fine-scale neighborhood effects (e.g., stand properties at radii), on susceptibility to a 1940s\u27 spruce beetle outbreak. Attributes of individual trees and of stand structure were spatially reconstructed at five 250-m2 sites that were partly burned in the late 19th century and then affected by spruce beetle outbreak in the 1940s. Random Forest models and classification trees were used to compare the relative importance of variables for susceptibility to spruce beetle attack. Individual tree properties (diameter at breast height and age) were the most important predictors of susceptibility to the outbreak across all sites combined and at each of the sites individually. In contrast, neighborhood effects were poor predictors of susceptibility. This study suggests wildfires reduce susceptibility to outbreaks primarily by reducing the size of postfire live trees and only secondarily by modifying stand structure. One implication of this is that management strategies that aim to modify stand structure over large areas in order to reduce susceptibility to spruce beetle outbreaks may be unnecessarily intensive. Copyright

Long-term change in sub-alpine forest cover, tree line and species composition in the Swiss Alps

Aims: The 20th century has been marked by dramatic changes in land use, disturbance regimes and climate, which have interacted to affect global ecological patterns and dynamics, including changes in the extent, composition and structure of forest cover. Although much research has highlighted dramatic, short-term ecological change, on-going trends of land-use change and climate change began more than a century ago. Consequently, quantifying and understanding long-term (e.g. centennial) ecological change is critical to contextualizing recent patterns and processes. Here we document changes in the extent, position and composition of sub-alpine forests over the past century in eastern Switzerland. Location: Davos region of the Swiss Alps, eastern Switzerland. Methods: Position of tree line, forest cover and forest composition were evaluated using a unique combination of Object-Based Image Classification of an historical (1909) map, recent (2009) aerial photography and repeat terrestrial photography to minimize the inherent bias of each data source, while providing the most robust representation of long-term ecological change. Results: Over the past century total forest cover expanded by 64.6% and the position of sub-alpine tree line increased on all aspects. Total forest cover also increased at the highest and lowest elevations on all aspects. Dominance of European larch increased at the highest elevations, but decreased at the lowest elevations, where it was replaced by Norway spruce. These patterns suggest land use has been the most important driver of forest change over the past century. Conclusions: Major changes in the extent, structure and dynamics of sub-alpine forests in the Alps initiated earlier than previously documented and most change occurred prior to the middle of the 20th century. Furthermore, these changes were likely driven primarily by changes in land use, rather than by changes in climate. A combination of data sources and methodological approaches, such as those of the current study, provides a clearer view of long-term changes and minimize the biases associated with any single data source or methodology