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• 41. [Article] Forest vegetation and fuel dynamics following stand-replacing wildfire, re-burn, and postfire management in the Siskiyou Mountains, Oregon

  Following high-severity fire, forest succession may take alternate pathways depending on the pattern of the fire and any secondary disturbances during early stand development, with lasting consequences ...

  Citation × Citation Citation Abstract Copy Title: Forest vegetation and fuel dynamics following stand-replacing wildfire, re-burn, and postfire management in the Siskiyou Mountains, Oregon Author: Donato, Daniel C. Following high-severity fire, forest succession may take alternate pathways depending on the pattern of the fire and any secondary disturbances during early stand development, with lasting consequences for ecosystem function. The objectives of this research were to quantify: (1) early postfire regeneration as influenced by the spatial pattern of a landscape-scale wildfire, and (2) the influence of secondary disturbances during early succession, specifically recurrent high-severity fire and postfire logging. Four years after the 200,000-hectare Biscuit Fire, patch-scale conifer seedling density was 80% Douglas-fir (Pseudotsuga menziesii) and ranged from 127-6494 stems/ha. Median density (1603 stems/ha) was ~12 times the prefire overstory density of 134 stems/ha. Due to the mixed-severity fire mosaic, ~58% of high-severity area was ≤ 200 m from patches of live trees, and ~81% was ≤ 400 m. Median conifer density exceeded 1000 stems/ha out to 400 m distance before declining rapidly at larger distances. Following a short-interval (15-year) repeat fire, vegetation communities contained nearly all species found in mature/old-growth stands and after a single fire, indicating high community persistence through two severe fires. The short-interval burn had the highest species richness and plant cover with additions of disturbance-adapted forbs and low shrubs, likely associated with a propagule bank that developed between fires. Sprouting capacity of hardwoods and shrubs was unaltered by recurrent fire, and conifer regeneration density (median 1495 stems/ha) was similar to single burn stands. Three to four years after fire, high-intensity postfire logging resulted in a greater proportion (28%) of felled biomass left on site as slash compared to moderate-intensity logging (14%), because tree felling was less selective. However, despite bole removal and slash generation, there was no significant difference in surface woody fuels among logged and unlogged treatments at 17-18 years after fire. Fuel profiles and fire modeling both suggested that regenerating vegetation rather than residual dead wood is the main driver of early seral fire hazard, with low fire potentials 3-4 years postfire and very high potentials at 17-18 years. Postfire logging increased fire potentials within this context due to generation of slash, with differences fading in ~15-20 years. The results from this research underscore the importance of the mixed-severity context in which stand-replacing fire often occurs, both for providing seed sources within a fire and for highly variable disturbances that interact with succession and plant adaptation. Title: Forest vegetation and fuel dynamics following stand-replacing wildfire, re-burn, and postfire management in the Siskiyou Mountains, Oregon Author: Donato, Daniel C. Following high-severity fire, forest succession may take alternate pathways depending on the pattern of the fire and any secondary disturbances during early stand development, with lasting consequences for ecosystem function. The objectives of this research were to quantify: (1) early postfire regeneration as influenced by the spatial pattern of a landscape-scale wildfire, and (2) the influence of secondary disturbances during early succession, specifically recurrent high-severity fire and postfire logging. Four years after the 200,000-hectare Biscuit Fire, patch-scale conifer seedling density was 80% Douglas-fir (Pseudotsuga menziesii) and ranged from 127-6494 stems/ha. Median density (1603 stems/ha) was ~12 times the prefire overstory density of 134 stems/ha. Due to the mixed-severity fire mosaic, ~58% of high-severity area was ≤ 200 m from patches of live trees, and ~81% was ≤ 400 m. Median conifer density exceeded 1000 stems/ha out to 400 m distance before declining rapidly at larger distances. Following a short-interval (15-year) repeat fire, vegetation communities contained nearly all species found in mature/old-growth stands and after a single fire, indicating high community persistence through two severe fires. The short-interval burn had the highest species richness and plant cover with additions of disturbance-adapted forbs and low shrubs, likely associated with a propagule bank that developed between fires. Sprouting capacity of hardwoods and shrubs was unaltered by recurrent fire, and conifer regeneration density (median 1495 stems/ha) was similar to single burn stands. Three to four years after fire, high-intensity postfire logging resulted in a greater proportion (28%) of felled biomass left on site as slash compared to moderate-intensity logging (14%), because tree felling was less selective. However, despite bole removal and slash generation, there was no significant difference in surface woody fuels among logged and unlogged treatments at 17-18 years after fire. Fuel profiles and fire modeling both suggested that regenerating vegetation rather than residual dead wood is the main driver of early seral fire hazard, with low fire potentials 3-4 years postfire and very high potentials at 17-18 years. Postfire logging increased fire potentials within this context due to generation of slash, with differences fading in ~15-20 years. The results from this research underscore the importance of the mixed-severity context in which stand-replacing fire often occurs, both for providing seed sources within a fire and for highly variable disturbances that interact with succession and plant adaptation. Close

• 42. [Article] Science basis for changing forest structure to modify wildfire behavior and severity

  Fire, other disturbances, physical setting, weather, and climate shape the structure and function of forests throughout the Western United States. More than 80 years of fire research have shown that physical ...

  Citation × Citation Citation Abstract Copy Title: Science basis for changing forest structure to modify wildfire behavior and severity Author: Graham, Russell T., McCaffrey, Sarah, Jain, Theresa B. Fire, other disturbances, physical setting, weather, and climate shape the structure and function of forests throughout the Western United States. More than 80 years of fire research have shown that physical setting, fuels, and weather combine to determine wildfire intensity (the rate at which it consumes fuel) and severity (the effect fire has on vegetation, soils, buildings, watersheds, and so forth). Millions of acres of forestlands (mainly in dry forests dominated by ponderosa pine and/or Douglas-fir) contain a high accumulation of flammable fuels compared to conditions prior to the 20th century. Forests with high stem density and fuel loading combined with extreme fire weather conditions have led to severe and large wildfires (such as those seen in the summers of 2000, 2002, and 2003) that have put a number of important values at risk. Although homes in the path of a wildfire are perhaps the most immediately recognized value, these wildfires also put numerous other human and ecological values at risk, such as power grids, drinking water supplies, firefighter safety, critical habitat, soil productivity, and air quality. For a given set of weather conditions, fire behavior is strongly influenced by stand and fuel structure. Crown fires in the dry forest types represent an increasing challenge for fire management as well as a general threat to the ecology of these forests and the closely associated human values. Crown fires are dependent on the sequence of available fuels starting from the ground surface to the canopy. Limiting crown fire in these forests can be accomplished by actions that manage in concert the surface, ladder, and crown fuels. Reducing crown fire and wildland fire growth across landscapes decreases the chances of developing large wildfires that affect human values adjacent to forested areas. However, a narrow focus on minimizing crown fire potential will not necessarily reduce the damage to homes and ecosystems when fires do occur. Homes are often ignited by embers flying far from the fire front, and by surface fires. Fire effects on ecosystems can also occur during surface fires where surface and understory fuels and deep organic layers are sufficient to generate high temperatures for long periods. Fuel treatments can help produce forest structures and fuel characteristics that then reduce the likelihood that wildfires will cause large, rapid changes in biophysical conditions. Fuel treatments can also help modify fire behavior sufficiently so that some wildfires can be suppressed more easily. Subsequent, sustained fuel treatments can maintain these conditions. Different fuel reduction methods target different components of the fuel bed. Thinning mainly affects standing vegetation, and other types of fuel treatments such as prescribed fire and pile burning woody fuels are needed to modify the combustion environment of surface fuels. In forests that have not experienced fire for many decades, multiple fuel treatments—that is, thinning and surface fuel reduction—may be required to significantly affect crown fire and surface fire hazard. Fuel treatments cannot guarantee benign fire behavior but can reduce the probability that extreme fire behavior will occur. Fuel treatments can be designed to restore forest conditions to a more resilient and resistant condition than now exists in many forests, and subsequent management could maintain these conditions, particularly in dry forests (ponderosa pine and Douglas-fir) where crown fires were historically infrequent. The degree of risk reduction will depend to some degree on the level of investment, social and economic acceptability of treatments, and concurrent consideration of other resource values (for example, wildlife). This report describes the kinds, quality, amount, and gaps of scientific knowledge for making informed decisions on fuel treatments used to modify wildfire behavior and effects in dry forests of the interior Western United States (especially forests dominated by ponderosa pine and Douglas-fir). A review of scientific principles and applications relevant to fuel treatment primarily for the dry forests is provided for the following topics: fuels, fire hazard, fire behavior, fire effects, forest structure, treatment effects and longevity, landscape fuel patterns, and scientific tools useful for management and planning. Title: Science basis for changing forest structure to modify wildfire behavior and severity Author: Graham, Russell T., McCaffrey, Sarah, Jain, Theresa B. Fire, other disturbances, physical setting, weather, and climate shape the structure and function of forests throughout the Western United States. More than 80 years of fire research have shown that physical setting, fuels, and weather combine to determine wildfire intensity (the rate at which it consumes fuel) and severity (the effect fire has on vegetation, soils, buildings, watersheds, and so forth). Millions of acres of forestlands (mainly in dry forests dominated by ponderosa pine and/or Douglas-fir) contain a high accumulation of flammable fuels compared to conditions prior to the 20th century. Forests with high stem density and fuel loading combined with extreme fire weather conditions have led to severe and large wildfires (such as those seen in the summers of 2000, 2002, and 2003) that have put a number of important values at risk. Although homes in the path of a wildfire are perhaps the most immediately recognized value, these wildfires also put numerous other human and ecological values at risk, such as power grids, drinking water supplies, firefighter safety, critical habitat, soil productivity, and air quality. For a given set of weather conditions, fire behavior is strongly influenced by stand and fuel structure. Crown fires in the dry forest types represent an increasing challenge for fire management as well as a general threat to the ecology of these forests and the closely associated human values. Crown fires are dependent on the sequence of available fuels starting from the ground surface to the canopy. Limiting crown fire in these forests can be accomplished by actions that manage in concert the surface, ladder, and crown fuels. Reducing crown fire and wildland fire growth across landscapes decreases the chances of developing large wildfires that affect human values adjacent to forested areas. However, a narrow focus on minimizing crown fire potential will not necessarily reduce the damage to homes and ecosystems when fires do occur. Homes are often ignited by embers flying far from the fire front, and by surface fires. Fire effects on ecosystems can also occur during surface fires where surface and understory fuels and deep organic layers are sufficient to generate high temperatures for long periods. Fuel treatments can help produce forest structures and fuel characteristics that then reduce the likelihood that wildfires will cause large, rapid changes in biophysical conditions. Fuel treatments can also help modify fire behavior sufficiently so that some wildfires can be suppressed more easily. Subsequent, sustained fuel treatments can maintain these conditions. Different fuel reduction methods target different components of the fuel bed. Thinning mainly affects standing vegetation, and other types of fuel treatments such as prescribed fire and pile burning woody fuels are needed to modify the combustion environment of surface fuels. In forests that have not experienced fire for many decades, multiple fuel treatments—that is, thinning and surface fuel reduction—may be required to significantly affect crown fire and surface fire hazard. Fuel treatments cannot guarantee benign fire behavior but can reduce the probability that extreme fire behavior will occur. Fuel treatments can be designed to restore forest conditions to a more resilient and resistant condition than now exists in many forests, and subsequent management could maintain these conditions, particularly in dry forests (ponderosa pine and Douglas-fir) where crown fires were historically infrequent. The degree of risk reduction will depend to some degree on the level of investment, social and economic acceptability of treatments, and concurrent consideration of other resource values (for example, wildlife). This report describes the kinds, quality, amount, and gaps of scientific knowledge for making informed decisions on fuel treatments used to modify wildfire behavior and effects in dry forests of the interior Western United States (especially forests dominated by ponderosa pine and Douglas-fir). A review of scientific principles and applications relevant to fuel treatment primarily for the dry forests is provided for the following topics: fuels, fire hazard, fire behavior, fire effects, forest structure, treatment effects and longevity, landscape fuel patterns, and scientific tools useful for management and planning. Close

• 43. [Article] Science basis for changing forest structure to modify wildfire behavior and severity

  Fire, other disturbances, physical setting, weather, and climate shape the structure and function of forests throughout the Western United States. More than 80 years of fire research have shown that physical ...

  Citation × Citation Citation Abstract Copy Title: Science basis for changing forest structure to modify wildfire behavior and severity Author: Graham, Russell T., McCaffrey, Sarah, Jain, Theresa B. Fire, other disturbances, physical setting, weather, and climate shape the structure and function of forests throughout the Western United States. More than 80 years of fire research have shown that physical setting, fuels, and weather combine to determine wildfire intensity (the rate at which it consumes fuel) and severity (the effect fire has on vegetation, soils, buildings, watersheds, and so forth). Millions of acres of forestlands (mainly in dry forests dominated by ponderosa pine and/or Douglas-fir) contain a high accumulation of flammable fuels compared to conditions prior to the 20th century. Forests with high stem density and fuel loading combined with extreme fire weather conditions have led to severe and large wildfires (such as those seen in the summers of 2000, 2002, and 2003) that have put a number of important values at risk. Although homes in the path of a wildfire are perhaps the most immediately recognized value, these wildfires also put numerous other human and ecological values at risk, such as power grids, drinking water supplies, firefighter safety, critical habitat, soil productivity, and air quality. For a given set of weather conditions, fire behavior is strongly influenced by stand and fuel structure. Crown fires in the dry forest types represent an increasing challenge for fire management as well as a general threat to the ecology of these forests and the closely associated human values. Crown fires are dependent on the sequence of available fuels starting from the ground surface to the canopy. Limiting crown fire in these forests can be accomplished by actions that manage in concert the surface, ladder, and crown fuels. Reducing crown fire and wildland fire growth across landscapes decreases the chances of developing large wildfires that affect human values adjacent to forested areas. However, a narrow focus on minimizing crown fire potential will not necessarily reduce the damage to homes and ecosystems when fires do occur. Homes are often ignited by embers flying far from the fire front, and by surface fires. Fire effects on ecosystems can also occur during surface fires where surface and understory fuels and deep organic layers are sufficient to generate high temperatures for long periods. Fuel treatments can help produce forest structures and fuel characteristics that then reduce the likelihood that wildfires will cause large, rapid changes in biophysical conditions. Fuel treatments can also help modify fire behavior sufficiently so that some wildfires can be suppressed more easily. Subsequent, sustained fuel treatments can maintain these conditions. Different fuel reduction methods target different components of the fuel bed. Thinning mainly affects standing vegetation, and other types of fuel treatments such as prescribed fire and pile burning woody fuels are needed to modify the combustion environment of surface fuels. In forests that have not experienced fire for many decades, multiple fuel treatments—that is, thinning and surface fuel reduction—may be required to significantly affect crown fire and surface fire hazard. Fuel treatments cannot guarantee benign fire behavior but can reduce the probability that extreme fire behavior will occur. Fuel treatments can be designed to restore forest conditions to a more resilient and resistant condition than now exists in many forests, and subsequent management could maintain these conditions, particularly in dry forests (ponderosa pine and Douglas-fir) where crown fires were historically infrequent. The degree of risk reduction will depend to some degree on the level of investment, social and economic acceptability of treatments, and concurrent consideration of other resource values (for example, wildlife). This report describes the kinds, quality, amount, and gaps of scientific knowledge for making informed decisions on fuel treatments used to modify wildfire behavior and effects in dry forests of the interior Western United States (especially forests dominated by ponderosa pine and Douglas-fir). A review of scientific principles and applications relevant to fuel treatment primarily for the dry forests is provided for the following topics: fuels, fire hazard, fire behavior, fire effects, forest structure, treatment effects and longevity, landscape fuel patterns, and scientific tools useful for management and planning. Title: Science basis for changing forest structure to modify wildfire behavior and severity Author: Graham, Russell T., McCaffrey, Sarah, Jain, Theresa B. Fire, other disturbances, physical setting, weather, and climate shape the structure and function of forests throughout the Western United States. More than 80 years of fire research have shown that physical setting, fuels, and weather combine to determine wildfire intensity (the rate at which it consumes fuel) and severity (the effect fire has on vegetation, soils, buildings, watersheds, and so forth). Millions of acres of forestlands (mainly in dry forests dominated by ponderosa pine and/or Douglas-fir) contain a high accumulation of flammable fuels compared to conditions prior to the 20th century. Forests with high stem density and fuel loading combined with extreme fire weather conditions have led to severe and large wildfires (such as those seen in the summers of 2000, 2002, and 2003) that have put a number of important values at risk. Although homes in the path of a wildfire are perhaps the most immediately recognized value, these wildfires also put numerous other human and ecological values at risk, such as power grids, drinking water supplies, firefighter safety, critical habitat, soil productivity, and air quality. For a given set of weather conditions, fire behavior is strongly influenced by stand and fuel structure. Crown fires in the dry forest types represent an increasing challenge for fire management as well as a general threat to the ecology of these forests and the closely associated human values. Crown fires are dependent on the sequence of available fuels starting from the ground surface to the canopy. Limiting crown fire in these forests can be accomplished by actions that manage in concert the surface, ladder, and crown fuels. Reducing crown fire and wildland fire growth across landscapes decreases the chances of developing large wildfires that affect human values adjacent to forested areas. However, a narrow focus on minimizing crown fire potential will not necessarily reduce the damage to homes and ecosystems when fires do occur. Homes are often ignited by embers flying far from the fire front, and by surface fires. Fire effects on ecosystems can also occur during surface fires where surface and understory fuels and deep organic layers are sufficient to generate high temperatures for long periods. Fuel treatments can help produce forest structures and fuel characteristics that then reduce the likelihood that wildfires will cause large, rapid changes in biophysical conditions. Fuel treatments can also help modify fire behavior sufficiently so that some wildfires can be suppressed more easily. Subsequent, sustained fuel treatments can maintain these conditions. Different fuel reduction methods target different components of the fuel bed. Thinning mainly affects standing vegetation, and other types of fuel treatments such as prescribed fire and pile burning woody fuels are needed to modify the combustion environment of surface fuels. In forests that have not experienced fire for many decades, multiple fuel treatments—that is, thinning and surface fuel reduction—may be required to significantly affect crown fire and surface fire hazard. Fuel treatments cannot guarantee benign fire behavior but can reduce the probability that extreme fire behavior will occur. Fuel treatments can be designed to restore forest conditions to a more resilient and resistant condition than now exists in many forests, and subsequent management could maintain these conditions, particularly in dry forests (ponderosa pine and Douglas-fir) where crown fires were historically infrequent. The degree of risk reduction will depend to some degree on the level of investment, social and economic acceptability of treatments, and concurrent consideration of other resource values (for example, wildlife). This report describes the kinds, quality, amount, and gaps of scientific knowledge for making informed decisions on fuel treatments used to modify wildfire behavior and effects in dry forests of the interior Western United States (especially forests dominated by ponderosa pine and Douglas-fir). A review of scientific principles and applications relevant to fuel treatment primarily for the dry forests is provided for the following topics: fuels, fire hazard, fire behavior, fire effects, forest structure, treatment effects and longevity, landscape fuel patterns, and scientific tools useful for management and planning. Close

• 44. [Article] Evaluation of the effects of silvicultural and fuels treatments on potential fire behaviour in Sierra Nevada mixed-conifer forests

  Fire suppression has increased fuel loads and fuel continuity in mixed-conifer ecosystems, resulting in forest structures that are vulnerable to catastrophic fire. This paper models fire behaviour in a ...

  Citation × Citation Citation Abstract Copy Title: Evaluation of the effects of silvicultural and fuels treatments on potential fire behaviour in Sierra Nevada mixed-conifer forests Author: Stephens, Scott Lewis Fire suppression has increased fuel loads and fuel continuity in mixed-conifer ecosystems, resulting in forest structures that are vulnerable to catastrophic fire. This paper models fire behaviour in a mixed-conifer forest and investigates how silvicultural and fuels treatments affect potential fire behaviour. The computer program FARSITE was used to spatially and temporally model fire growth and behaviour. Fire modelling was performed in the North Crane Creek watershed of Yosemite National Park. Treatments were simulated by adjusting fuel total load, load-by-size class, depth., height-to-live crown base, tree height, and crown density parameters. Treatments modeled included prescribed burn, pile and burn, cut and scatter, thinning and biomass, thinning and biomass followed by prescribed burn, and salvage or group selection harvest with and without slash and landscape-level fuel treatment. The prescribed burn, thinning and biomassing followed by prescribed burn, and salvage or group selection with slash and landscape fuel treatments resulted in the lowest average fireline intensities, heat per unit area, rate of spread, area burned, and scorch heights. Cut and scatter, salvage or group selection treatments that do not treat slash fuels resulted in fire behaviour that is more extreme than the untreated forest. Restoration of mixed-conifer ecosystems must include an examination of how proposed treatments affect fuel structures. Combinations of prescribed fire andror mechanical treatments can be used to reduce wildfire hazard. Title: Evaluation of the effects of silvicultural and fuels treatments on potential fire behaviour in Sierra Nevada mixed-conifer forests Author: Stephens, Scott Lewis Fire suppression has increased fuel loads and fuel continuity in mixed-conifer ecosystems, resulting in forest structures that are vulnerable to catastrophic fire. This paper models fire behaviour in a mixed-conifer forest and investigates how silvicultural and fuels treatments affect potential fire behaviour. The computer program FARSITE was used to spatially and temporally model fire growth and behaviour. Fire modelling was performed in the North Crane Creek watershed of Yosemite National Park. Treatments were simulated by adjusting fuel total load, load-by-size class, depth., height-to-live crown base, tree height, and crown density parameters. Treatments modeled included prescribed burn, pile and burn, cut and scatter, thinning and biomass, thinning and biomass followed by prescribed burn, and salvage or group selection harvest with and without slash and landscape-level fuel treatment. The prescribed burn, thinning and biomassing followed by prescribed burn, and salvage or group selection with slash and landscape fuel treatments resulted in the lowest average fireline intensities, heat per unit area, rate of spread, area burned, and scorch heights. Cut and scatter, salvage or group selection treatments that do not treat slash fuels resulted in fire behaviour that is more extreme than the untreated forest. Restoration of mixed-conifer ecosystems must include an examination of how proposed treatments affect fuel structures. Combinations of prescribed fire andror mechanical treatments can be used to reduce wildfire hazard. Close

• 45. [Article] Evaluation of the effects of silvicultural and fuels treatments on potential fire behaviour in Sierra Nevada mixed-conifer forests

  Fire suppression has increased fuel loads and fuel continuity in mixed-conifer ecosystems, resulting in forest structures that are vulnerable to catastrophic fire. This paper models fire behaviour in a ...

  Citation × Citation Citation Abstract Copy Title: Evaluation of the effects of silvicultural and fuels treatments on potential fire behaviour in Sierra Nevada mixed-conifer forests Author: Stephens, Scott L. Fire suppression has increased fuel loads and fuel continuity in mixed-conifer ecosystems, resulting in forest structures that are vulnerable to catastrophic fire. This paper models fire behaviour in a mixed-conifer forest and investigates how silvicultural and fuels treatments affect potential fire behaviour. The computer program FARSITE was used to spatially and temporally model fire growth and behaviour. Fire modelling was performed in the North Crane Creek watershed of Yosemite National Park. Treatments were simulated by adjusting fuel (total load, load-by-size class, depth.) height-to-live crown base, tree height, and crown density parameters. Treatments modeled included prescribed burn, pile and burn, cut and scatter, thinning and biomass, thinning and biomass followed by prescribed burn, and salvage or group selection harvest with and without slash and landscape-level fuel treatment. The prescribed burn, thinning and biomassing followed by prescribed burn, and salvage or group selection with slash and landscape fuel treatments resulted in the lowest average fireline intensities, heat per unit area, rate of spread, area burned, and scorch heights. Cut and scatter, salvage or group selection treatments that do not treat slash fuels resulted in fire behaviour that is more extreme than the untreated forest. Restoration of mixed-conifer ecosystems must include an examination of how proposed treatments affect fuel structures. Combinations of prescribed fire and/or mechanical treatments can be used to reduce wildfire hazard. Title: Evaluation of the effects of silvicultural and fuels treatments on potential fire behaviour in Sierra Nevada mixed-conifer forests Author: Stephens, Scott L. Fire suppression has increased fuel loads and fuel continuity in mixed-conifer ecosystems, resulting in forest structures that are vulnerable to catastrophic fire. This paper models fire behaviour in a mixed-conifer forest and investigates how silvicultural and fuels treatments affect potential fire behaviour. The computer program FARSITE was used to spatially and temporally model fire growth and behaviour. Fire modelling was performed in the North Crane Creek watershed of Yosemite National Park. Treatments were simulated by adjusting fuel (total load, load-by-size class, depth.) height-to-live crown base, tree height, and crown density parameters. Treatments modeled included prescribed burn, pile and burn, cut and scatter, thinning and biomass, thinning and biomass followed by prescribed burn, and salvage or group selection harvest with and without slash and landscape-level fuel treatment. The prescribed burn, thinning and biomassing followed by prescribed burn, and salvage or group selection with slash and landscape fuel treatments resulted in the lowest average fireline intensities, heat per unit area, rate of spread, area burned, and scorch heights. Cut and scatter, salvage or group selection treatments that do not treat slash fuels resulted in fire behaviour that is more extreme than the untreated forest. Restoration of mixed-conifer ecosystems must include an examination of how proposed treatments affect fuel structures. Combinations of prescribed fire and/or mechanical treatments can be used to reduce wildfire hazard. Close

• 46. [Article] Characterization of fire effects on forest ecosystems in the Tillamook Forest, Oregon

  From the 1920's through 1951 several severe fires occurred in the predominantly conifer forest ecosystems of the northern Oregon Coast Range. Of the 211,151 ha. of mapped area, 57 percent was burned. The ...

  Citation × Citation Citation Abstract Copy Title: Characterization of fire effects on forest ecosystems in the Tillamook Forest, Oregon Author: Chen, Shu-Huei From the 1920's through 1951 several severe fires occurred in the predominantly conifer forest ecosystems of the northern Oregon Coast Range. Of the 211,151 ha. of mapped area, 57 percent was burned. The effects of frequent fires with high severity on forest ecosystems over time at the landscape level is not fully understood. A reconstruction of fire history was conducted to help investigate the effects of fire severity, frequency, and area extent on distribution of postfire tree regeneration, species composition, and stand tree size, as well as on current species composition and stand tree size. I hypothesized that: 1) vegetation patterns (1950's and 1988) would vary with time, because the persistence of disturbance effects (fire, logging, reforestation) on forest vegetative responses varied, and 2) environmental controls (topography, soil, climate) would become the primary influences when disturbance events were absent. In this study historical maps, sketches and notes were used to reconstruct spatial and temporal patterns of fires from the 1920's to 1951 and to identify unburned patches on a Geographic Information System. Relationships between fire regime and postfire and current vegetative patterns were tested. Constructing precise spatial data layers from early maps, produced before the availability of aerial photography or satellite image, was difficult. Historical map accuracy and quality were variable and poor by present day standards. Geographic reference points were used to transform inappropriate map scales. The reconstruction of spatial data was used to characterize spatial patterns of historic fires: my estimates of burn areas were similar to estimates in the literature. To reduce questionable data along fire and vegetation patch boundaries for hypothesis testing, an exclusion approach was used. Data within a 100 m width of fire and vegetation type boundary lines were called a fuzzy zone and removed from raw data. The distribution of various attributes in the reduced data was similar to the distribution of the complete data set. Regression analysis examined the effects of fire, logging, reforestation, topography, climate, and soil type on vegetation patterns. Patterns of postfire (1950's) species composition, tree regeneration and tree size (DBH) were associated with the effects of fires, as well as influences of logging and soil type. Indices of fire occurrences (reflecting the time variation and severity of fires) frequently correlated to the 1950's vegetation patterns. The number of fires (frequency) did not cause great differences in vegetation patterns. Current (1988) species composition and tree size (after absence of fire for more than three decades) were correlated more with terrain variables. Plant succession also influenced the current vegetation patterns. Neither the date or number of fires caused marked differences in distribution of species and tree size, except large conifers were found in areas missed by fires. Postfire and current vegetation patterns were correlated with soil types which reflect the influence of topographic and climatic characteristics. However, historic fires occurred frequently on some soil types. Fires have a confounding influence on soil type. This confounding influence of fire on soil type cannot be avoided. Reforestation efforts appeared to have little influence on the postfire and current vegetation patterns. I inferred that the short time period of reforestation effects did not show its importance on the 1950's vegetation landscape. Although regression analysis results did not support my hypothesis, by 1988, reforested area in the northern Coast Range had increased since 1950's. Most of the large fire-open patches became mixed forest in about 3 decades may still relate to the force of reforestation. On private unburned ownerships conifer forests in 1955 were subsequently cut and replaced by mostly mixed forest by 1988. The analysis supported the hypotheses that soil type, aspect and plant succession were dominant influences on current (1988) vegetation patterns, while forest disturbances such as fire and logging were important influences on the immediate postfire (1950's) patterns. The results not only interpret the relationship between historic disturbances and vegetation distribution, but may also serve as a useful background for the management of the future forest landscape. Title: Characterization of fire effects on forest ecosystems in the Tillamook Forest, Oregon Author: Chen, Shu-Huei From the 1920's through 1951 several severe fires occurred in the predominantly conifer forest ecosystems of the northern Oregon Coast Range. Of the 211,151 ha. of mapped area, 57 percent was burned. The effects of frequent fires with high severity on forest ecosystems over time at the landscape level is not fully understood. A reconstruction of fire history was conducted to help investigate the effects of fire severity, frequency, and area extent on distribution of postfire tree regeneration, species composition, and stand tree size, as well as on current species composition and stand tree size. I hypothesized that: 1) vegetation patterns (1950's and 1988) would vary with time, because the persistence of disturbance effects (fire, logging, reforestation) on forest vegetative responses varied, and 2) environmental controls (topography, soil, climate) would become the primary influences when disturbance events were absent. In this study historical maps, sketches and notes were used to reconstruct spatial and temporal patterns of fires from the 1920's to 1951 and to identify unburned patches on a Geographic Information System. Relationships between fire regime and postfire and current vegetative patterns were tested. Constructing precise spatial data layers from early maps, produced before the availability of aerial photography or satellite image, was difficult. Historical map accuracy and quality were variable and poor by present day standards. Geographic reference points were used to transform inappropriate map scales. The reconstruction of spatial data was used to characterize spatial patterns of historic fires: my estimates of burn areas were similar to estimates in the literature. To reduce questionable data along fire and vegetation patch boundaries for hypothesis testing, an exclusion approach was used. Data within a 100 m width of fire and vegetation type boundary lines were called a fuzzy zone and removed from raw data. The distribution of various attributes in the reduced data was similar to the distribution of the complete data set. Regression analysis examined the effects of fire, logging, reforestation, topography, climate, and soil type on vegetation patterns. Patterns of postfire (1950's) species composition, tree regeneration and tree size (DBH) were associated with the effects of fires, as well as influences of logging and soil type. Indices of fire occurrences (reflecting the time variation and severity of fires) frequently correlated to the 1950's vegetation patterns. The number of fires (frequency) did not cause great differences in vegetation patterns. Current (1988) species composition and tree size (after absence of fire for more than three decades) were correlated more with terrain variables. Plant succession also influenced the current vegetation patterns. Neither the date or number of fires caused marked differences in distribution of species and tree size, except large conifers were found in areas missed by fires. Postfire and current vegetation patterns were correlated with soil types which reflect the influence of topographic and climatic characteristics. However, historic fires occurred frequently on some soil types. Fires have a confounding influence on soil type. This confounding influence of fire on soil type cannot be avoided. Reforestation efforts appeared to have little influence on the postfire and current vegetation patterns. I inferred that the short time period of reforestation effects did not show its importance on the 1950's vegetation landscape. Although regression analysis results did not support my hypothesis, by 1988, reforested area in the northern Coast Range had increased since 1950's. Most of the large fire-open patches became mixed forest in about 3 decades may still relate to the force of reforestation. On private unburned ownerships conifer forests in 1955 were subsequently cut and replaced by mostly mixed forest by 1988. The analysis supported the hypotheses that soil type, aspect and plant succession were dominant influences on current (1988) vegetation patterns, while forest disturbances such as fire and logging were important influences on the immediate postfire (1950's) patterns. The results not only interpret the relationship between historic disturbances and vegetation distribution, but may also serve as a useful background for the management of the future forest landscape. Close

• 47. [Article] Age structure, developmental pathways, and fire regime characterization of Douglas-fir/western hemlock forests in the central western Cascades of Oregon

  Descriptions of the fire regime in the Douglas-fir/western hemlock region of the Pacific Northwest traditionally have emphasized infrequent, predominantly stand-replacement fires and an associated linear ...

  Citation × Citation Citation Abstract Copy Title: Age structure, developmental pathways, and fire regime characterization of Douglas-fir/western hemlock forests in the central western Cascades of Oregon Author: Tepley, Alan J. Descriptions of the fire regime in the Douglas-fir/western hemlock region of the Pacific Northwest traditionally have emphasized infrequent, predominantly stand-replacement fires and an associated linear pathway of stand development, where all stands proceed along a common pathway until reset by the next fire. Although such a description may apply in wetter parts of the region, recent fire-history research suggests drier parts of the region support a mixed-severity regime, where most fires have substantial representation of all severity classes and most stands experience at least one non-stand-replacing fire between stand-replacement events. This study combines field and modeling approaches to better understand the complex fire regime in the central western Cascades of Oregon. Stand-structure data and ages of more than 3,000 trees were collected at 124 stands throughout two study areas with physiography representative of western and eastern portions of the western Cascade Range. Major objectives were to (1) develop a conceptual model of fire-mediated pathways of stand development, (2) determine the strengths of influences of topography on spatial variation in the fire regime, (3) provide a stronger understanding of modeling approaches commonly used to gain insight into historical landscape structure, and (4) develop methods to predict trajectories of change in landscape age structure under a non-stationary fire regime. In the study area, non-stand-replacing fire interspersed with infrequent, stand-replacement events led to a variety of even-aged and multi-cohort stands. The majority of stands (75%) had two or more age cohorts, where post-fire cohorts were dominated either by shade-intolerant species or shade-tolerant species, depending largely on fire severity. Age structure, used as a proxy for the cumulative effects of fire on stand development, showed a moderately strong relationship to topography overall, but relationships were strongest at both extremes of a continuum of the influences of fire frequency and severity on stand development and relatively weak in the middle. High topographic relief in the eastern part of the western Cascades may amplify variation in microclimate and fuel moisture, leading to a finer-scale spatial variation in fire spread and behavior, and thus a broader range of stand age structures and stronger fidelity of age structure to slope position and terrain shape in the deeply dissected terrain of the eastern part of the western Cascades than in the gentler terrain of the western part. In the modeling component of my research, I was able to use analytical procedures to reproduce much of the output provided by a stochastic, spatial simulation model previously applied to evaluate historical landscape structure of the Oregon Coast Range. The analytical approximation provides an explicit representation of the effects of input parameters and interactions among them. The increased transparency of model function given by such an analysis may facilitate communication of model output and uncertainty among ecologists and forest managers. Analytical modeling approaches were expanded to characterize trajectories of change in forest age structure in response to changes in the fire regime. Following a change in fire frequency, the proportion of the landscape covered by stands of a given age class is expected to change along a non-monotonic trajectory rather than transition directly to its equilibrium abundance under the new regime. Under some scenarios of change in fire frequency, the time for the expected age distribution of a landscape to converge to the equilibrium distribution of the new regime can be determined based only on the magnitude of change in fire frequency, regardless of the initial value or the direction of change. The theoretical modeling exercises provide insight into historical trends in the study area. Compiled across all sample sites, the age distribution of Douglas-fir trees was strongly bimodal. Peaks of establishment dates in the 16th and 19th centuries were synchronous between the two study areas, and each peak of Douglas-fir establishment coincides with one of the two periods of region-wide extensive fire identified in a previous synthesis of fire-history studies. The modeling exercises support the development of such a bimodal age distribution in response to centennial-scale changes in fire frequency, and they illustrate how the relative abundance of different stand-structure types may have varied over the last several centuries. Title: Age structure, developmental pathways, and fire regime characterization of Douglas-fir/western hemlock forests in the central western Cascades of Oregon Author: Tepley, Alan J. Descriptions of the fire regime in the Douglas-fir/western hemlock region of the Pacific Northwest traditionally have emphasized infrequent, predominantly stand-replacement fires and an associated linear pathway of stand development, where all stands proceed along a common pathway until reset by the next fire. Although such a description may apply in wetter parts of the region, recent fire-history research suggests drier parts of the region support a mixed-severity regime, where most fires have substantial representation of all severity classes and most stands experience at least one non-stand-replacing fire between stand-replacement events. This study combines field and modeling approaches to better understand the complex fire regime in the central western Cascades of Oregon. Stand-structure data and ages of more than 3,000 trees were collected at 124 stands throughout two study areas with physiography representative of western and eastern portions of the western Cascade Range. Major objectives were to (1) develop a conceptual model of fire-mediated pathways of stand development, (2) determine the strengths of influences of topography on spatial variation in the fire regime, (3) provide a stronger understanding of modeling approaches commonly used to gain insight into historical landscape structure, and (4) develop methods to predict trajectories of change in landscape age structure under a non-stationary fire regime. In the study area, non-stand-replacing fire interspersed with infrequent, stand-replacement events led to a variety of even-aged and multi-cohort stands. The majority of stands (75%) had two or more age cohorts, where post-fire cohorts were dominated either by shade-intolerant species or shade-tolerant species, depending largely on fire severity. Age structure, used as a proxy for the cumulative effects of fire on stand development, showed a moderately strong relationship to topography overall, but relationships were strongest at both extremes of a continuum of the influences of fire frequency and severity on stand development and relatively weak in the middle. High topographic relief in the eastern part of the western Cascades may amplify variation in microclimate and fuel moisture, leading to a finer-scale spatial variation in fire spread and behavior, and thus a broader range of stand age structures and stronger fidelity of age structure to slope position and terrain shape in the deeply dissected terrain of the eastern part of the western Cascades than in the gentler terrain of the western part. In the modeling component of my research, I was able to use analytical procedures to reproduce much of the output provided by a stochastic, spatial simulation model previously applied to evaluate historical landscape structure of the Oregon Coast Range. The analytical approximation provides an explicit representation of the effects of input parameters and interactions among them. The increased transparency of model function given by such an analysis may facilitate communication of model output and uncertainty among ecologists and forest managers. Analytical modeling approaches were expanded to characterize trajectories of change in forest age structure in response to changes in the fire regime. Following a change in fire frequency, the proportion of the landscape covered by stands of a given age class is expected to change along a non-monotonic trajectory rather than transition directly to its equilibrium abundance under the new regime. Under some scenarios of change in fire frequency, the time for the expected age distribution of a landscape to converge to the equilibrium distribution of the new regime can be determined based only on the magnitude of change in fire frequency, regardless of the initial value or the direction of change. The theoretical modeling exercises provide insight into historical trends in the study area. Compiled across all sample sites, the age distribution of Douglas-fir trees was strongly bimodal. Peaks of establishment dates in the 16th and 19th centuries were synchronous between the two study areas, and each peak of Douglas-fir establishment coincides with one of the two periods of region-wide extensive fire identified in a previous synthesis of fire-history studies. The modeling exercises support the development of such a bimodal age distribution in response to centennial-scale changes in fire frequency, and they illustrate how the relative abundance of different stand-structure types may have varied over the last several centuries. Close

• 48. [Article] Long and Short-Term Effects of Fire on Soil Charcoal of a Conifer Forest in Southwest Oregon

  To the best of our knowledge, one or more authors of this paper were federal employees when contributing to this work. This is the publisher’s final pdf. The published article is copyrighted by Multidisciplinary ...

  Citation × Citation Citation Abstract Copy Title: Long and Short-Term Effects of Fire on Soil Charcoal of a Conifer Forest in Southwest Oregon Author: Darbyshire, Robyn, Morrissette, Brett, Pingree, Melissa R. A., Homann, Peter S. To the best of our knowledge, one or more authors of this paper were federal employees when contributing to this work. This is the publisher’s final pdf. The published article is copyrighted by Multidisciplinary Digital Publishing Institute and can be found at: [link to http://www.mdpi.com/. Title: Long and Short-Term Effects of Fire on Soil Charcoal of a Conifer Forest in Southwest Oregon Author: Darbyshire, Robyn, Morrissette, Brett, Pingree, Melissa R. A., Homann, Peter S. To the best of our knowledge, one or more authors of this paper were federal employees when contributing to this work. This is the publisher’s final pdf. The published article is copyrighted by Multidisciplinary Digital Publishing Institute and can be found at: [link to http://www.mdpi.com/. Close

• 49. [Article] Report of the forest fuels and hazard mitigation committee to the Oregon Department of Forestry and Oregon Fire Program Review

  Many Oregon communities face serious and growing risks from wildfires. These fires are increasingly large and severe after many decades of fire suppression and land use changes, flammable fuel buildups ...

  Citation × Citation Citation Abstract Copy Title: Report of the forest fuels and hazard mitigation committee to the Oregon Department of Forestry and Oregon Fire Program Review Author: Institute for Natural Resources, Behan, Jeff, Lynn, Kathy Many Oregon communities face serious and growing risks from wildfires. These fires are increasingly large and severe after many decades of fire suppression and land use changes, flammable fuel buildups and interactions with climate. The wildland-urban interface (WUI) continues to expand as people relocate to rural areas where they often expect structural fire protection similar to what they experienced in cities. But conditions are different in rural communities located in fire-prone forests. The risk of severe wildfire is greater and limited resources are available to deal with severe fires when they break out. Fire prevention and suppression without vegetation management to reduce accumulated fuels has and will result in a continuation of uncharacteristically severe, stand-replacing wildfires, particularly in eastern and southwestern Oregon. These fires are difficult and expensive to control. They also place firefighters at high risk. Federal, state and rural fire protection agencies are struggling to cope as wildfire threats, costs, and the scope of protection responsibilities continue to increase. Federal agencies have initiated efforts to reduce hazardous fuels and increase community wildfire readiness as directed by the 2000 National Fire Plan (NFP) and 2003 Healthy Forests Restoration Act (HFRA). These mandates are now being implemented at multiple levels with every effort to coordinate for greater efficiency. As part of the 2004 Oregon Fire Program Review, the Oregon Department of Forestry (ODF) formed the Forest Fuels and Hazard Mitigation (FFHM) Committee to assess hazardous fuel loading issues, and recommend ways to reduce risk, and improve and strengthen the multiple hazard mitigation strategies in Oregon. Title: Report of the forest fuels and hazard mitigation committee to the Oregon Department of Forestry and Oregon Fire Program Review Author: Institute for Natural Resources, Behan, Jeff, Lynn, Kathy Many Oregon communities face serious and growing risks from wildfires. These fires are increasingly large and severe after many decades of fire suppression and land use changes, flammable fuel buildups and interactions with climate. The wildland-urban interface (WUI) continues to expand as people relocate to rural areas where they often expect structural fire protection similar to what they experienced in cities. But conditions are different in rural communities located in fire-prone forests. The risk of severe wildfire is greater and limited resources are available to deal with severe fires when they break out. Fire prevention and suppression without vegetation management to reduce accumulated fuels has and will result in a continuation of uncharacteristically severe, stand-replacing wildfires, particularly in eastern and southwestern Oregon. These fires are difficult and expensive to control. They also place firefighters at high risk. Federal, state and rural fire protection agencies are struggling to cope as wildfire threats, costs, and the scope of protection responsibilities continue to increase. Federal agencies have initiated efforts to reduce hazardous fuels and increase community wildfire readiness as directed by the 2000 National Fire Plan (NFP) and 2003 Healthy Forests Restoration Act (HFRA). These mandates are now being implemented at multiple levels with every effort to coordinate for greater efficiency. As part of the 2004 Oregon Fire Program Review, the Oregon Department of Forestry (ODF) formed the Forest Fuels and Hazard Mitigation (FFHM) Committee to assess hazardous fuel loading issues, and recommend ways to reduce risk, and improve and strengthen the multiple hazard mitigation strategies in Oregon. Close

• 50. [Article] Chaparral history, dynamics, and response to disturbance in southwest Oregon : insights from age structure

  Fuels management on Bureau of Land Management lands in SW Oregon, USA, is motivated by the needs to reduce fire hazard and restore ecosystems thought to be impacted by fire suppression. Chaparral is one ...

  Citation × Citation Citation Abstract Copy Title: Chaparral history, dynamics, and response to disturbance in southwest Oregon : insights from age structure Author: Duren, Olivia Fuels management on Bureau of Land Management lands in SW Oregon, USA, is motivated by the needs to reduce fire hazard and restore ecosystems thought to be impacted by fire suppression. Chaparral is one of the most characteristic vegetation communities of SW Oregon's interior valleys, and extensive acreages within this system are targeted annually for fuels treatment. However, this community is also poorly understood. Little is known about its response to fire suppression, and the assumptions justifying the need for fuels reduction and on which treatment prescriptions are based are extrapolations from other ecosystems. I studied patterns in chaparral age structure of two obligate-seeding shrubs, Arctostaphylos viscida C. Parry and Ceanothus cuneatus (Hook.) Nutt., for insights into the influences of environment and the two dominant disturbances in SW Oregon, fire and grazing, on population structure and dynamics. My 31 low to mid-elevation study sites represent four chaparral 'types' and a range in times since fire (22 yr to > 114 yr). My study area is near the northernmost extension of the California chaparral vegetation type, and results indicate that SW Oregon chaparral populations diverge from studied California chaparral populations in several fundamental ways. All stands unburned for > 30 yr were uneven-aged due to prolific recruitment in the absence of fire and appreciable fire survivorship. Relatively high shrub densities were associated with even-aged sites, but these sites were all young (< 30 yr) and density declined the longer stands were unburned. No relationships were detected between site environment or disturbance history and age structure in general, or the relative amount of fire-free recruitment or fire survivorship in particular. Results suggest that most, if not all, chaparral stands would over time develop uneven-aged structure across the range of environments represented in the study area. Current fuels treatment prescriptions in SW Oregon chaparral are predicated on the assumption that fire suppression has replaced naturally high-frequency, low-severity fires with less frequent and higher-severity fires due to an unnatural accumulation of fuels. However, it appears that this model is not appropriate for chaparral vegetation. Chaparral has apparently experienced a fire regime that is distinct from that of adjacent vegetation communities, and fire suppression does not appear to have altered overall chaparral structure or fire severity. Current fuels treatments are unlikely to reproduce stand structures observed in mature chaparral or in post-wildfire stands. Rather, fuels treatments are likely to alter the trajectory of chaparral development that appears to have been in place for the last century. Results clearly illuminate that chaparral encompasses a wide range of structures and responses to environment and disturbance, and imply that precepts of chaparral ecology and management should be tailored on a geographic basis. Results also underscore the need for management objectives to recognize differences among vegetation communities in complex environments. Title: Chaparral history, dynamics, and response to disturbance in southwest Oregon : insights from age structure Author: Duren, Olivia Fuels management on Bureau of Land Management lands in SW Oregon, USA, is motivated by the needs to reduce fire hazard and restore ecosystems thought to be impacted by fire suppression. Chaparral is one of the most characteristic vegetation communities of SW Oregon's interior valleys, and extensive acreages within this system are targeted annually for fuels treatment. However, this community is also poorly understood. Little is known about its response to fire suppression, and the assumptions justifying the need for fuels reduction and on which treatment prescriptions are based are extrapolations from other ecosystems. I studied patterns in chaparral age structure of two obligate-seeding shrubs, Arctostaphylos viscida C. Parry and Ceanothus cuneatus (Hook.) Nutt., for insights into the influences of environment and the two dominant disturbances in SW Oregon, fire and grazing, on population structure and dynamics. My 31 low to mid-elevation study sites represent four chaparral 'types' and a range in times since fire (22 yr to > 114 yr). My study area is near the northernmost extension of the California chaparral vegetation type, and results indicate that SW Oregon chaparral populations diverge from studied California chaparral populations in several fundamental ways. All stands unburned for > 30 yr were uneven-aged due to prolific recruitment in the absence of fire and appreciable fire survivorship. Relatively high shrub densities were associated with even-aged sites, but these sites were all young (< 30 yr) and density declined the longer stands were unburned. No relationships were detected between site environment or disturbance history and age structure in general, or the relative amount of fire-free recruitment or fire survivorship in particular. Results suggest that most, if not all, chaparral stands would over time develop uneven-aged structure across the range of environments represented in the study area. Current fuels treatment prescriptions in SW Oregon chaparral are predicated on the assumption that fire suppression has replaced naturally high-frequency, low-severity fires with less frequent and higher-severity fires due to an unnatural accumulation of fuels. However, it appears that this model is not appropriate for chaparral vegetation. Chaparral has apparently experienced a fire regime that is distinct from that of adjacent vegetation communities, and fire suppression does not appear to have altered overall chaparral structure or fire severity. Current fuels treatments are unlikely to reproduce stand structures observed in mature chaparral or in post-wildfire stands. Rather, fuels treatments are likely to alter the trajectory of chaparral development that appears to have been in place for the last century. Results clearly illuminate that chaparral encompasses a wide range of structures and responses to environment and disturbance, and imply that precepts of chaparral ecology and management should be tailored on a geographic basis. Results also underscore the need for management objectives to recognize differences among vegetation communities in complex environments. Close