International journal of geographical information systems, 1995
Waquoit Bay, a shallow bay on Cape Cod, Massachusetts, is exhibiting symptoms of eutrophication, ... more Waquoit Bay, a shallow bay on Cape Cod, Massachusetts, is exhibiting symptoms of eutrophication, largely attributed to septic nitrogen inputs. This study assessed septic nitrogen inputs by linking a three-dimensional ground-water model, a geographic information system (GIS), and a customized spatio-temporal nitrogen loading program. Owing to the slow speed of ground-water movement, the bulk of septic nitrogen entering the bay lags behind development by nearly a decade. Even if residential development is held at 1989 levels, nitrogen input from septic systems will increase by 36% over the current levels. At full residential build-out (i.e., development), septic nitrogen loading will eventually increase to more than twice the current levels.
... Keeley et al. (1999) examined age classes burned in large fires in the Santa Monica Mountains... more ... Keeley et al. (1999) examined age classes burned in large fires in the Santa Monica Mountains, California and found no relationship to older fuels. These results were based on a subset of fires (ie, size >5000 ha, since 1967, n = 8), so it is difficult to assess their generality. ...
... affecting the dynamics of many ecosystems, and quantitative measures of fire regimes and thei... more ... affecting the dynamics of many ecosystems, and quantitative measures of fire regimes and their statistical distributions (eg, time-since-fire) have been investigated in forest ecosystem research (Heinselman 1973, Johnson and Van Wagner 1985, Johnson and Gutsell 1994). ...
Effects associated with the directional reflectance properties of land surfaces, solar and sensor... more Effects associated with the directional reflectance properties of land surfaces, solar and sensor geometries, atmospheric turbidity, sub-pixel heterogeneity, and sensor response and calibration interact in a complex manner to produce significant uncertainty in satellite-based estimates of land surface parameters such as leaf area index (LAI). Because all of these effects are present in varying degrees within any remotely sensed image,
The Klamath-Siskiyou region of northwestern California and southwestern Oregon supports globally ... more The Klamath-Siskiyou region of northwestern California and southwestern Oregon supports globally outstanding temperate biodiversity. Fire has been important in the evolutionary history that shaped this diversity, but recent human influences have altered the fire environment. We tested for modern human impacts on the fire regime by analyzing temporal patterns in fire extent and spatial patterns of fire severity in relation to vegetation structure, past fire occurrence, roads, and timber management in a 98,814-ha area burned in 1987. Fire severity was mapped by the U.S. Department of Agriculture Forest Service as low, moderate, and high based on levels of canopy scorch and consumption. We found (1) a trend of increasing fire size in recent decades; (2) that overall fire-severity proportions were 59% low, 29% moderate, and 12% high, which is comparable to both contemporary and historic fires in the region; (3) that multiaged, closed forests, the predominant vegetation, burned with much lower severity than did open forest and shrubby nonforest vegetation; (4) that considerably less high-severity fire occurred where fire had previously be absent since 1920 in closed forests compared to where the forests had burned since 1920 (7% vs. 16%); (5) that nonforest vegetation burned with greater severity where there was a history of fire since 1920 and in roaded areas; and (6) that tree plantations experienced twice as much severe fire as multi-aged forests. We concluded that fuel buildup in the absence of fire did not cause increased fire severity as hypothesized. Instead, fuel that is receptive to combustion may decrease in the long absence of fire in the closed forests of our study area, which will favor the fire regime that has maintained these forests. However, plantations are now found in one-third of the roaded landscape. Together with warming climate, this may increase the size and severity of future fires, favoring further establishment of structurally and biologically simple plantations. Patrones de Severidad de Fuego y Condiciones del Bosque en las Montañas Klamath Occidentales, California Resumen: La region Klamath-Siskiyou (Noroeste de California y Suroeste de Oregon) sostiene una biodiversidad templada globalmente sobresaliente. El fuego ha sido importante en la historia evolutiva que moldeó a esta diversidad, sin embargo, influencias humanas recientes han alterado el ambiente del fuego. Probamos los impactos humanos modernos sobre el régimen de fuego analizando los patrones temporales de la extensión del fuego y los patrones de severidad del fuego en relación con la estructura de la vegetación, incidencia de fuego en el pasado, caminos y manejo de madera en unárea de 98,814 ha quemada en 1987. La severidad del fuego fue clasificada en el mapa por el Servicio Forestal de EE. UU. como baja, moderada o alta tomando en cuenta el grado de chamuscado y consumo del dosel. Encontramos (1) que hubo una tendencia hacia un aumento del tamaño del fuego en décadas recientes; (2) que las proporciones totales de severidad de fuego fueron: 59% bajo, Fire Severity in the Western Klamath-Siskiyou Odion et al. 29% moderado y 12% alto (lo cual es comparable tanto para incendios contemporáneos como históricos en la región); (3) que los bosques cerrados, de edades múltiples, la vegetación predominante, se quemó mucho menos severamente que los bosques abiertos y la vegetación arbustiva no boscosa.; (4) que hubo considerablemente menos fuego de alta intensidad donde no habían ocurrido incendios en bosques cerrados desde 1920 en comparación con bosques que se han quemado desde 1920 (7% vs. 16%); (5) que la vegetación no boscosa se quemó con mayor severidad donde había una historia de fuego desde 1920 y enáreas con caminos; y (6) que las plantaciones deárboles tenían dos veces la cantidad de fuego severo que los bosques de edades múltiples. Concluimos que la acumulación de combustible en ausencia de fuego no causó incremento en la severidad del fuego, como se planteó. En cambio, el combustible que es receptivo a la combustión puede disminuir en la larga ausencia de fuego en los bosques cerrados de nuestraárea de estudio. Esto favorecerá al régimen con fuego que ha mantenido a estos bosques. Sin embargo, las plantaciones se encuentran en un tercio del paisaje con caminos. En combinación con el calentamiento del clima, esto puede incrementar el tamaño y severidad de futuros incendios, lo que favorecerá el establecimiento de plantaciones estructural y biológicamente simples. Palabras Clave:áreas sin caminos, intensidad de fuego, maderas duras, Pino de Douglas, regímenes de fuego, región Klamath-Siskiyou, silvicultura
Fire is often integral to forest ecology and can affect forest disease dynamics. Sudden oak death... more Fire is often integral to forest ecology and can affect forest disease dynamics. Sudden oak death has spread across a large, fire-prone portion of California, killing large numbers of oaks and tanoaks and infecting most associated woody plants. Building on our earlier study of fire-disease dynamics, we examined spatial patterns of confirmed infections in relation to past fire history for a single county using a geographic information system (GIS). The region analyzed here is Sonoma County, where infections have been documented in past burn areas and exposure to the disease is thought to be extensive. We found that the disease is extremely rare inside recently burned areas (since 1950), although the relationship in this region is somewhat weaker than previous findings across a much larger area. This highlights how factors, such as variation in vegetation, climate, and patterns of severity, within burn areas are important to consider in the landscape pathology of sudden oak death. Despite confirmation of earlier findings at a different scale of analysis, it remains to be seen whether the observed negative relationship between current infection locations and past fires is due to a fire-related mechanism, a surrogate of fire, and/or an artifact of the datasets used. Regardless, it is likely that interactions between the disease and fire will vary with local differences in host species composition, the stage of disease progression, and the scales of space and time used in analyses.
Background/Question/Methods Nearly a century of fire management in the Sierra Nevada of Californi... more Background/Question/Methods Nearly a century of fire management in the Sierra Nevada of California has had the unintended consequence of placing millions of hectares of forest at risk of catastrophic fire. Several management actions have been proposed to modify fire behavior on the forest landscape. One approach is based on the theory that disconnected fuel treatment patches that overlap in the direction of the head fire spread reduce the overall rate and intensity of the fire. Simulations have shown that with as little as 30% of the area in these strategically placed area treatments (SPLATs), fire risk can be decreased for the entire landscape. Another is a Defensible Fuel Profile Zone (DFPZ) that is composed of interlocked landscape fuels breaks designed to provide safe access for fire fighters, limit fire behavior to prescribed levels, and create conditions in which canopy fires are less likely to spread. Despite sound conceptual underpinnings for both approaches, there is uncert...
ABSTRACT Altered disturbance regimes in the context of global change are likely to have profound ... more ABSTRACT Altered disturbance regimes in the context of global change are likely to have profound consequences for ecosystems. Interactions between fire and vegetation are of particular interest, as fire is a major driver of vegetation change, and vegetation properties (e.g., amount, flammability) alter fire regimes. Mediterranean-type ecosystems (MTEs) constitute a paradigmatic example of temperate fire-prone vegetation. Although these ecosystems may be heavily impacted by global change, disturbance regime shifts and the implications of fire-vegetation feedbacks in the dynamics of such biomes are still poorly characterized. We developed a minimal modeling framework incorporating key aspects of fire ecology and successional processes to evaluate the relative influence of extrinsic and intrinsic factors on disturbance and vegetation dynamics in systems composed of grassland, shrubland, and woodland mosaics, which characterize many MTEs. In this theoretical investigation, we performed extensive simulations representing different background rates of vegetation succession and disturbance regime (fire frequency and severity) processes that reflect a broad range of MTE environmental conditions. Varying fire-vegetation feedbacks can lead to different critical points in underlying processes of disturbance and sudden shifts in the vegetation state of grassland–shrubland–woodland systems, despite gradual changes in ecosystem drivers as defined by the environment. Vegetation flammability and disturbance stochasticity effectively modify system behavior, determining its heterogeneity and the existence of alternative stable states in MTEs. Small variations in system flammability and fire recurrence induced by climate or vegetation changes may trigger sudden shifts in the state of such ecosystems. The existence of threshold dynamics, alternative stable states, and contrasting system responses to environmental change has broad implications for MTE management.
ABSTRACT Background/Question/Methods We used the Maxent spatial distribution modeling tool in com... more ABSTRACT Background/Question/Methods We used the Maxent spatial distribution modeling tool in combination with BIOCLIM long-term climate normals and derived water-balance metrics (generated for this project) to produce spatially explicit maps of relative wildfire probabilities with 1-km resolution. In this project, we investigate spatial transferability of a suite of California-based fire models to similar climatic regions in Oregon, which has only incomplete, spatially biased data. One point per fire instance was used for training and testing data, and non-fuels areas were masked out during model generation. We present a multi-model average of 4 bootstrapped models, as well as Fire Return Interval (FRI) predictions for one example common vegetation community. Final Maxent models are based on an average of a suite of 4 models for each region: the product of 2 different variable sets (32 variable ensemble and 15 variable ensemble), and 2 different fire size thresholds in each region (1,000 acre and 5,000 acre), intentionally giving more weight to the 15 variables and the larger 5,000-acre fires, which are involved in all 4 models. Results/Conclusions Fire instances are used to generate baseline relative fire probability maps for California and Oregon, which we present here. One data set comprised of Oregon fire points is geographically restricted, in that it completely lacks fires in such places as the southeastern and north-central portion of state. A second data set of fire instances in Oregon consists of polygons spanning eight years, and these appear geographically consistent, although the number of years of data is limited. By incorporating rich California fire history data, we attempted to overcome some of the limitations of the fire data available for Oregon. As new Oregon fire instance data becomes available, we will be able to better evaluate the spatial transferability of California data. We compared predicted FRI’s within test regions for various common ecosystem types in northern California and Oregon based on 20- and 50-year average burn rates in California, and found that FRI is sensitive to choice of both spatial and temporal extent used to calculate the conversion factor. These sensitivites may be comparable to or larger than model uncertainty. Sensitivity of FRI to choice of temporal extent is demonstrated in the Sierra Mixed Conifer community, where expected median FRI’s differ by 120 years based on choice of burn rate.
The recently established Center for Fire Research and Outreach at the University of California, B... more The recently established Center for Fire Research and Outreach at the University of California, Berkeley has developed a web-based toolkit, the Fire Information Engine Toolkit (FIET), for wild- fire-related needs. The FIET is intended to meet the needs of diverse user groups (homeowners, decision-makers, including fire operations, and researchers) at a variety of scales (local, community, and regional levels) before,
ABSTRACT Establishing protection networks to ensure that biodiversity and associated ecosystem se... more ABSTRACT Establishing protection networks to ensure that biodiversity and associated ecosystem services persist under changing environments is a major challenge for conservation planning. The potential consequences of altered climates for the structure and function of ecosystems necessitates new and complementary approaches be incorporated into traditional conservation plans. The conterminous United States of America (CONUS) has an extensive system of protected areas managed by federal agencies, but a comprehensive assessment of how this network represents the CONUS climate is lacking. We present a quantitative classification of the climate space that is independent from the geographic locations of climatic observations to evaluate the climatic representation of the existing protected area network. We use this classification to evaluate the coverage of each agency's jurisdiction and to identify current conservation deficits. Our findings reveal that the existing network poorly represents the CONUS climatic diversity. Although rare climates are generally well represented within the network, the most common climates are particularly underrepresented. Overall, 83% of the area of the CONUS corresponds to climates underrepresented by the network. The addition of some currently unprotected federal lands to the network would enhance the coverage of the CONUS climates. However, to fully palliate current conservation deficits, large-scale private-land conservation initiatives will be critical.
where these trees are abundant, and other densitydependent effects (e.g. shading) can reduce reso... more where these trees are abundant, and other densitydependent effects (e.g. shading) can reduce resource allocation to defenses. Despite these findings about a fire-disease relationship, a much deeper understanding is necessary before fire can be actively used as a tool in slowing the epidemic.
ABSTRACT As temperatures soar, forests blaze and houses burn, the media and public may be forced ... more ABSTRACT As temperatures soar, forests blaze and houses burn, the media and public may be forced to face up to the reality of a changing climate, says Max A. Moritz.
The recently established Center for Fire Research and Outreach at the University of California, B... more The recently established Center for Fire Research and Outreach at the University of California, Berkeley has developed a web-based toolkit, the Fire Information Engine Toolkit (FIET), for wildfire-related needs. The FIET is intended to meet the needs of diverse user groups (homeowners, decision-makers, including fire operations, and researchers) at a variety of scales (local, community, and regional levels) before, during, and after wildfires. During the initial phase of the FIET, we have focused on developing pre-fire tools for homeowners and decision-makers at the local and community levels. For example, we have developed a science-based, parcel-level structure vulnerability assess-
The earliest examples of alternative community states in the literature appear to be descriptions... more The earliest examples of alternative community states in the literature appear to be descriptions of natural vegetation said to both depend on and promote fire. Nonetheless, alternative community states determined by fire have rarely been documented at landscape scales and in natural vegetation. This is because spatial autocorrelation may confound analyses, experimental manipulations are difficult and a long-term perspective is needed to demonstrate that alternative community states can persist for multiple generations. 2. We hypothesized that alternative community states occur in a largely forested landscape in the Klamath Mountains, north-western California, USA, where shrub-dominated sclerophyllous vegetation establishes after fire that is lethal to forests. Forests redevelop if succession is not arrested by fire. Our hypothesis would require that sclerophyll and forest vegetation states each be maintained by different self-reinforcing relationships with fire. 3. To test this hypothesis, we examined pyrogenicity of forest and sclerophyll vegetation as a function of time since the previous fire, accounting for spatial autocorrelation. Fire exclusion served as a de facto experimental treatment. Areas where fire had proceeded to occur served as controls. 4. Our findings are consistent with the occurrence of alternative community states established and maintained by different self-reinforcing feedbacks with fire. Sclerophyll vegetation was more pyrogenic, especially where time-since-fire (TSF) was relatively short, a favourable relationship for this fire-dependent vegetation. Forests were much less pyrogenic, especially where TSF was long, favouring their maintenance. Fire exclusion therefore has led to afforestation and rapid retreat of fire-dependent vegetation. 5. Synthesis: We have documented how different self-reinforcing combustion properties of forest and sclerophyll vegetation can naturally produce alternative states coexisting side-by-side in the same environment. Such fire-mediated alternative states may be underappreciated, in part, because they are difficult to demonstrate definitively. In addition, the dynamics they exhibit contrast with common perceptions that fire hazard increases deterministically with TSF in forests and shrublands. Addressing the impacts of fire exclusion will probably require a management shift to better allow fire to perform its ecological role in shaping landscape diversity and maintaining firedependent biota.
International journal of geographical information systems, 1995
Waquoit Bay, a shallow bay on Cape Cod, Massachusetts, is exhibiting symptoms of eutrophication, ... more Waquoit Bay, a shallow bay on Cape Cod, Massachusetts, is exhibiting symptoms of eutrophication, largely attributed to septic nitrogen inputs. This study assessed septic nitrogen inputs by linking a three-dimensional ground-water model, a geographic information system (GIS), and a customized spatio-temporal nitrogen loading program. Owing to the slow speed of ground-water movement, the bulk of septic nitrogen entering the bay lags behind development by nearly a decade. Even if residential development is held at 1989 levels, nitrogen input from septic systems will increase by 36% over the current levels. At full residential build-out (i.e., development), septic nitrogen loading will eventually increase to more than twice the current levels.
... Keeley et al. (1999) examined age classes burned in large fires in the Santa Monica Mountains... more ... Keeley et al. (1999) examined age classes burned in large fires in the Santa Monica Mountains, California and found no relationship to older fuels. These results were based on a subset of fires (ie, size >5000 ha, since 1967, n = 8), so it is difficult to assess their generality. ...
... affecting the dynamics of many ecosystems, and quantitative measures of fire regimes and thei... more ... affecting the dynamics of many ecosystems, and quantitative measures of fire regimes and their statistical distributions (eg, time-since-fire) have been investigated in forest ecosystem research (Heinselman 1973, Johnson and Van Wagner 1985, Johnson and Gutsell 1994). ...
Effects associated with the directional reflectance properties of land surfaces, solar and sensor... more Effects associated with the directional reflectance properties of land surfaces, solar and sensor geometries, atmospheric turbidity, sub-pixel heterogeneity, and sensor response and calibration interact in a complex manner to produce significant uncertainty in satellite-based estimates of land surface parameters such as leaf area index (LAI). Because all of these effects are present in varying degrees within any remotely sensed image,
The Klamath-Siskiyou region of northwestern California and southwestern Oregon supports globally ... more The Klamath-Siskiyou region of northwestern California and southwestern Oregon supports globally outstanding temperate biodiversity. Fire has been important in the evolutionary history that shaped this diversity, but recent human influences have altered the fire environment. We tested for modern human impacts on the fire regime by analyzing temporal patterns in fire extent and spatial patterns of fire severity in relation to vegetation structure, past fire occurrence, roads, and timber management in a 98,814-ha area burned in 1987. Fire severity was mapped by the U.S. Department of Agriculture Forest Service as low, moderate, and high based on levels of canopy scorch and consumption. We found (1) a trend of increasing fire size in recent decades; (2) that overall fire-severity proportions were 59% low, 29% moderate, and 12% high, which is comparable to both contemporary and historic fires in the region; (3) that multiaged, closed forests, the predominant vegetation, burned with much lower severity than did open forest and shrubby nonforest vegetation; (4) that considerably less high-severity fire occurred where fire had previously be absent since 1920 in closed forests compared to where the forests had burned since 1920 (7% vs. 16%); (5) that nonforest vegetation burned with greater severity where there was a history of fire since 1920 and in roaded areas; and (6) that tree plantations experienced twice as much severe fire as multi-aged forests. We concluded that fuel buildup in the absence of fire did not cause increased fire severity as hypothesized. Instead, fuel that is receptive to combustion may decrease in the long absence of fire in the closed forests of our study area, which will favor the fire regime that has maintained these forests. However, plantations are now found in one-third of the roaded landscape. Together with warming climate, this may increase the size and severity of future fires, favoring further establishment of structurally and biologically simple plantations. Patrones de Severidad de Fuego y Condiciones del Bosque en las Montañas Klamath Occidentales, California Resumen: La region Klamath-Siskiyou (Noroeste de California y Suroeste de Oregon) sostiene una biodiversidad templada globalmente sobresaliente. El fuego ha sido importante en la historia evolutiva que moldeó a esta diversidad, sin embargo, influencias humanas recientes han alterado el ambiente del fuego. Probamos los impactos humanos modernos sobre el régimen de fuego analizando los patrones temporales de la extensión del fuego y los patrones de severidad del fuego en relación con la estructura de la vegetación, incidencia de fuego en el pasado, caminos y manejo de madera en unárea de 98,814 ha quemada en 1987. La severidad del fuego fue clasificada en el mapa por el Servicio Forestal de EE. UU. como baja, moderada o alta tomando en cuenta el grado de chamuscado y consumo del dosel. Encontramos (1) que hubo una tendencia hacia un aumento del tamaño del fuego en décadas recientes; (2) que las proporciones totales de severidad de fuego fueron: 59% bajo, Fire Severity in the Western Klamath-Siskiyou Odion et al. 29% moderado y 12% alto (lo cual es comparable tanto para incendios contemporáneos como históricos en la región); (3) que los bosques cerrados, de edades múltiples, la vegetación predominante, se quemó mucho menos severamente que los bosques abiertos y la vegetación arbustiva no boscosa.; (4) que hubo considerablemente menos fuego de alta intensidad donde no habían ocurrido incendios en bosques cerrados desde 1920 en comparación con bosques que se han quemado desde 1920 (7% vs. 16%); (5) que la vegetación no boscosa se quemó con mayor severidad donde había una historia de fuego desde 1920 y enáreas con caminos; y (6) que las plantaciones deárboles tenían dos veces la cantidad de fuego severo que los bosques de edades múltiples. Concluimos que la acumulación de combustible en ausencia de fuego no causó incremento en la severidad del fuego, como se planteó. En cambio, el combustible que es receptivo a la combustión puede disminuir en la larga ausencia de fuego en los bosques cerrados de nuestraárea de estudio. Esto favorecerá al régimen con fuego que ha mantenido a estos bosques. Sin embargo, las plantaciones se encuentran en un tercio del paisaje con caminos. En combinación con el calentamiento del clima, esto puede incrementar el tamaño y severidad de futuros incendios, lo que favorecerá el establecimiento de plantaciones estructural y biológicamente simples. Palabras Clave:áreas sin caminos, intensidad de fuego, maderas duras, Pino de Douglas, regímenes de fuego, región Klamath-Siskiyou, silvicultura
Fire is often integral to forest ecology and can affect forest disease dynamics. Sudden oak death... more Fire is often integral to forest ecology and can affect forest disease dynamics. Sudden oak death has spread across a large, fire-prone portion of California, killing large numbers of oaks and tanoaks and infecting most associated woody plants. Building on our earlier study of fire-disease dynamics, we examined spatial patterns of confirmed infections in relation to past fire history for a single county using a geographic information system (GIS). The region analyzed here is Sonoma County, where infections have been documented in past burn areas and exposure to the disease is thought to be extensive. We found that the disease is extremely rare inside recently burned areas (since 1950), although the relationship in this region is somewhat weaker than previous findings across a much larger area. This highlights how factors, such as variation in vegetation, climate, and patterns of severity, within burn areas are important to consider in the landscape pathology of sudden oak death. Despite confirmation of earlier findings at a different scale of analysis, it remains to be seen whether the observed negative relationship between current infection locations and past fires is due to a fire-related mechanism, a surrogate of fire, and/or an artifact of the datasets used. Regardless, it is likely that interactions between the disease and fire will vary with local differences in host species composition, the stage of disease progression, and the scales of space and time used in analyses.
Background/Question/Methods Nearly a century of fire management in the Sierra Nevada of Californi... more Background/Question/Methods Nearly a century of fire management in the Sierra Nevada of California has had the unintended consequence of placing millions of hectares of forest at risk of catastrophic fire. Several management actions have been proposed to modify fire behavior on the forest landscape. One approach is based on the theory that disconnected fuel treatment patches that overlap in the direction of the head fire spread reduce the overall rate and intensity of the fire. Simulations have shown that with as little as 30% of the area in these strategically placed area treatments (SPLATs), fire risk can be decreased for the entire landscape. Another is a Defensible Fuel Profile Zone (DFPZ) that is composed of interlocked landscape fuels breaks designed to provide safe access for fire fighters, limit fire behavior to prescribed levels, and create conditions in which canopy fires are less likely to spread. Despite sound conceptual underpinnings for both approaches, there is uncert...
ABSTRACT Altered disturbance regimes in the context of global change are likely to have profound ... more ABSTRACT Altered disturbance regimes in the context of global change are likely to have profound consequences for ecosystems. Interactions between fire and vegetation are of particular interest, as fire is a major driver of vegetation change, and vegetation properties (e.g., amount, flammability) alter fire regimes. Mediterranean-type ecosystems (MTEs) constitute a paradigmatic example of temperate fire-prone vegetation. Although these ecosystems may be heavily impacted by global change, disturbance regime shifts and the implications of fire-vegetation feedbacks in the dynamics of such biomes are still poorly characterized. We developed a minimal modeling framework incorporating key aspects of fire ecology and successional processes to evaluate the relative influence of extrinsic and intrinsic factors on disturbance and vegetation dynamics in systems composed of grassland, shrubland, and woodland mosaics, which characterize many MTEs. In this theoretical investigation, we performed extensive simulations representing different background rates of vegetation succession and disturbance regime (fire frequency and severity) processes that reflect a broad range of MTE environmental conditions. Varying fire-vegetation feedbacks can lead to different critical points in underlying processes of disturbance and sudden shifts in the vegetation state of grassland–shrubland–woodland systems, despite gradual changes in ecosystem drivers as defined by the environment. Vegetation flammability and disturbance stochasticity effectively modify system behavior, determining its heterogeneity and the existence of alternative stable states in MTEs. Small variations in system flammability and fire recurrence induced by climate or vegetation changes may trigger sudden shifts in the state of such ecosystems. The existence of threshold dynamics, alternative stable states, and contrasting system responses to environmental change has broad implications for MTE management.
ABSTRACT Background/Question/Methods We used the Maxent spatial distribution modeling tool in com... more ABSTRACT Background/Question/Methods We used the Maxent spatial distribution modeling tool in combination with BIOCLIM long-term climate normals and derived water-balance metrics (generated for this project) to produce spatially explicit maps of relative wildfire probabilities with 1-km resolution. In this project, we investigate spatial transferability of a suite of California-based fire models to similar climatic regions in Oregon, which has only incomplete, spatially biased data. One point per fire instance was used for training and testing data, and non-fuels areas were masked out during model generation. We present a multi-model average of 4 bootstrapped models, as well as Fire Return Interval (FRI) predictions for one example common vegetation community. Final Maxent models are based on an average of a suite of 4 models for each region: the product of 2 different variable sets (32 variable ensemble and 15 variable ensemble), and 2 different fire size thresholds in each region (1,000 acre and 5,000 acre), intentionally giving more weight to the 15 variables and the larger 5,000-acre fires, which are involved in all 4 models. Results/Conclusions Fire instances are used to generate baseline relative fire probability maps for California and Oregon, which we present here. One data set comprised of Oregon fire points is geographically restricted, in that it completely lacks fires in such places as the southeastern and north-central portion of state. A second data set of fire instances in Oregon consists of polygons spanning eight years, and these appear geographically consistent, although the number of years of data is limited. By incorporating rich California fire history data, we attempted to overcome some of the limitations of the fire data available for Oregon. As new Oregon fire instance data becomes available, we will be able to better evaluate the spatial transferability of California data. We compared predicted FRI’s within test regions for various common ecosystem types in northern California and Oregon based on 20- and 50-year average burn rates in California, and found that FRI is sensitive to choice of both spatial and temporal extent used to calculate the conversion factor. These sensitivites may be comparable to or larger than model uncertainty. Sensitivity of FRI to choice of temporal extent is demonstrated in the Sierra Mixed Conifer community, where expected median FRI’s differ by 120 years based on choice of burn rate.
The recently established Center for Fire Research and Outreach at the University of California, B... more The recently established Center for Fire Research and Outreach at the University of California, Berkeley has developed a web-based toolkit, the Fire Information Engine Toolkit (FIET), for wild- fire-related needs. The FIET is intended to meet the needs of diverse user groups (homeowners, decision-makers, including fire operations, and researchers) at a variety of scales (local, community, and regional levels) before,
ABSTRACT Establishing protection networks to ensure that biodiversity and associated ecosystem se... more ABSTRACT Establishing protection networks to ensure that biodiversity and associated ecosystem services persist under changing environments is a major challenge for conservation planning. The potential consequences of altered climates for the structure and function of ecosystems necessitates new and complementary approaches be incorporated into traditional conservation plans. The conterminous United States of America (CONUS) has an extensive system of protected areas managed by federal agencies, but a comprehensive assessment of how this network represents the CONUS climate is lacking. We present a quantitative classification of the climate space that is independent from the geographic locations of climatic observations to evaluate the climatic representation of the existing protected area network. We use this classification to evaluate the coverage of each agency's jurisdiction and to identify current conservation deficits. Our findings reveal that the existing network poorly represents the CONUS climatic diversity. Although rare climates are generally well represented within the network, the most common climates are particularly underrepresented. Overall, 83% of the area of the CONUS corresponds to climates underrepresented by the network. The addition of some currently unprotected federal lands to the network would enhance the coverage of the CONUS climates. However, to fully palliate current conservation deficits, large-scale private-land conservation initiatives will be critical.
where these trees are abundant, and other densitydependent effects (e.g. shading) can reduce reso... more where these trees are abundant, and other densitydependent effects (e.g. shading) can reduce resource allocation to defenses. Despite these findings about a fire-disease relationship, a much deeper understanding is necessary before fire can be actively used as a tool in slowing the epidemic.
ABSTRACT As temperatures soar, forests blaze and houses burn, the media and public may be forced ... more ABSTRACT As temperatures soar, forests blaze and houses burn, the media and public may be forced to face up to the reality of a changing climate, says Max A. Moritz.
The recently established Center for Fire Research and Outreach at the University of California, B... more The recently established Center for Fire Research and Outreach at the University of California, Berkeley has developed a web-based toolkit, the Fire Information Engine Toolkit (FIET), for wildfire-related needs. The FIET is intended to meet the needs of diverse user groups (homeowners, decision-makers, including fire operations, and researchers) at a variety of scales (local, community, and regional levels) before, during, and after wildfires. During the initial phase of the FIET, we have focused on developing pre-fire tools for homeowners and decision-makers at the local and community levels. For example, we have developed a science-based, parcel-level structure vulnerability assess-
The earliest examples of alternative community states in the literature appear to be descriptions... more The earliest examples of alternative community states in the literature appear to be descriptions of natural vegetation said to both depend on and promote fire. Nonetheless, alternative community states determined by fire have rarely been documented at landscape scales and in natural vegetation. This is because spatial autocorrelation may confound analyses, experimental manipulations are difficult and a long-term perspective is needed to demonstrate that alternative community states can persist for multiple generations. 2. We hypothesized that alternative community states occur in a largely forested landscape in the Klamath Mountains, north-western California, USA, where shrub-dominated sclerophyllous vegetation establishes after fire that is lethal to forests. Forests redevelop if succession is not arrested by fire. Our hypothesis would require that sclerophyll and forest vegetation states each be maintained by different self-reinforcing relationships with fire. 3. To test this hypothesis, we examined pyrogenicity of forest and sclerophyll vegetation as a function of time since the previous fire, accounting for spatial autocorrelation. Fire exclusion served as a de facto experimental treatment. Areas where fire had proceeded to occur served as controls. 4. Our findings are consistent with the occurrence of alternative community states established and maintained by different self-reinforcing feedbacks with fire. Sclerophyll vegetation was more pyrogenic, especially where time-since-fire (TSF) was relatively short, a favourable relationship for this fire-dependent vegetation. Forests were much less pyrogenic, especially where TSF was long, favouring their maintenance. Fire exclusion therefore has led to afforestation and rapid retreat of fire-dependent vegetation. 5. Synthesis: We have documented how different self-reinforcing combustion properties of forest and sclerophyll vegetation can naturally produce alternative states coexisting side-by-side in the same environment. Such fire-mediated alternative states may be underappreciated, in part, because they are difficult to demonstrate definitively. In addition, the dynamics they exhibit contrast with common perceptions that fire hazard increases deterministically with TSF in forests and shrublands. Addressing the impacts of fire exclusion will probably require a management shift to better allow fire to perform its ecological role in shaping landscape diversity and maintaining firedependent biota.
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