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• 1. [Article] Wolf, Elk, and Aspen Food Web Relationships: Context and Complexity

  This is an author's peer-reviewed final manuscript, as accepted by the publisher. The published article is copyrighted by Elsevier and can be found at: http://www.journals.elsevier.com/forest-ecology-a...

  Citation × Citation Citation Abstract Copy Title: Wolf, Elk, and Aspen Food Web Relationships: Context and Complexity Author: Seager, S. Trent, Hibbs, David E., Eisenberg, Cristina This is an author's peer-reviewed final manuscript, as accepted by the publisher. The published article is copyrighted by Elsevier and can be found at: http://www.journals.elsevier.com/forest-ecology-and-management/. Title: Wolf, Elk, and Aspen Food Web Relationships: Context and Complexity Author: Seager, S. Trent, Hibbs, David E., Eisenberg, Cristina This is an author's peer-reviewed final manuscript, as accepted by the publisher. The published article is copyrighted by Elsevier and can be found at: http://www.journals.elsevier.com/forest-ecology-and-management/. Close

• 2. [Article] A land manager's guide for creating fire-resistant forests

  Published September 2013. Please look for up-to-date information in the OSU Extension Catalog: http://extension.oregonstate.edu/catalog

  Citation × Citation Citation Abstract Copy Title: A land manager's guide for creating fire-resistant forests Author: Fitzgerald, Stephen Arthur, Bennett, Max, 1963-, Oregon State University. Extension Service Published September 2013. Please look for up-to-date information in the OSU Extension Catalog: http://extension.oregonstate.edu/catalog Title: A land manager's guide for creating fire-resistant forests Author: Fitzgerald, Stephen Arthur, Bennett, Max, 1963-, Oregon State University. Extension Service Published September 2013. Please look for up-to-date information in the OSU Extension Catalog: http://extension.oregonstate.edu/catalog Close

• 3. [Article] Potential impacts of climate change on vegetation distributions, carbon stocks, and fire regimes in the U.S. Pacific Northwest

  The U.S Pacific Northwest contains a wide variety of ecosystems, all subject to relatively dry summers and wet winters. As has been shown with paleoclimatic and paleoecological data, the region is vulnerable ...

  Citation × Citation Citation Abstract Copy Title: Potential impacts of climate change on vegetation distributions, carbon stocks, and fire regimes in the U.S. Pacific Northwest Author: Rogers, Brendan M. The U.S Pacific Northwest contains a wide variety of ecosystems, all subject to relatively dry summers and wet winters. As has been shown with paleoclimatic and paleoecological data, the region is vulnerable to changes in climate. We assessed the sensitivities of vegetation distributions, carbon stocks, and fire regimes to 21st century climate change by running MC1, a dynamic general vegetation model, over a large domain across Oregon and Washington at 800-meter resolution. During the historical period, MC1 generally overestimated carbon stocks in the Western Forests region and underestimated carbon stocks in the Eastern Forests and Columbia Plateau. MC1 displayed a strong bias in the seasonality of NPP towards decreased summer and increased winter production. This suggests the model’s productivity equations may be overly sensitive to low soil moisture and under-sensitive to low temperatures. We downscaled nine future climate projections from three General Circulation Models (CSIRO Mk3, MIROC 3.2 medres, and Hadley CM 3), each run through three CO2 emission scenarios (SRES B1, A1B, and A2). Temperatures increased ubiquitously and concurrently with increasing emission scenario, but precipitation was more varied. CSIRO climates were relatively cool and wet, MIROC climates were hot and wet, and Hadley climates were hot and dry. Precipitation generally increased in winter and decreased in summer, and temperature increases were highest in summer. Previous work showed that CSIRO performed poorly, MIROC moderately well, and Hadley very well in the Pacific Northwest for the historical period. Future climate projections amplified the seasonal trends in climatic variables, water stress, and productivity. MC1 simulated the Pacific Northwest’s western maritime forests as being vulnerable to large increases in fires, subsequent losses in carbon stocks, and encroachment from more southerly and/or easterly forest types. The arid, fire-adapted forests east of the Cascade appeared to be resilient to climate changes under MC1. With increasing precipitation, MC1 simulated vast expanses of shrublands in the Columbia Plateau and Northern Basin converting to grasslands or woodlands. Across the domain, MC1 runs under the CSIRO climate projections averaged 82% increases in biomass combusted and 1.2% (0.1 Pg C) decreases in ecosystem carbon, while those under MIROC averaged 22% increases in biomass combusted and 0.8% (0.07 Pg C) increases in ecosystem carbon. Climate projections from the Hadley model resulted in the most extreme changes, averaging 259% increases in biomass combusted and 15% (1.26 Pg C) decreases in ecosystem carbon. Our study suggests some areas within the Pacific Northwest may be vulnerable, and others resilient, to climate change, although this is highly dependent on model assumptions and uncertainties. Title: Potential impacts of climate change on vegetation distributions, carbon stocks, and fire regimes in the U.S. Pacific Northwest Author: Rogers, Brendan M. The U.S Pacific Northwest contains a wide variety of ecosystems, all subject to relatively dry summers and wet winters. As has been shown with paleoclimatic and paleoecological data, the region is vulnerable to changes in climate. We assessed the sensitivities of vegetation distributions, carbon stocks, and fire regimes to 21st century climate change by running MC1, a dynamic general vegetation model, over a large domain across Oregon and Washington at 800-meter resolution. During the historical period, MC1 generally overestimated carbon stocks in the Western Forests region and underestimated carbon stocks in the Eastern Forests and Columbia Plateau. MC1 displayed a strong bias in the seasonality of NPP towards decreased summer and increased winter production. This suggests the model’s productivity equations may be overly sensitive to low soil moisture and under-sensitive to low temperatures. We downscaled nine future climate projections from three General Circulation Models (CSIRO Mk3, MIROC 3.2 medres, and Hadley CM 3), each run through three CO2 emission scenarios (SRES B1, A1B, and A2). Temperatures increased ubiquitously and concurrently with increasing emission scenario, but precipitation was more varied. CSIRO climates were relatively cool and wet, MIROC climates were hot and wet, and Hadley climates were hot and dry. Precipitation generally increased in winter and decreased in summer, and temperature increases were highest in summer. Previous work showed that CSIRO performed poorly, MIROC moderately well, and Hadley very well in the Pacific Northwest for the historical period. Future climate projections amplified the seasonal trends in climatic variables, water stress, and productivity. MC1 simulated the Pacific Northwest’s western maritime forests as being vulnerable to large increases in fires, subsequent losses in carbon stocks, and encroachment from more southerly and/or easterly forest types. The arid, fire-adapted forests east of the Cascade appeared to be resilient to climate changes under MC1. With increasing precipitation, MC1 simulated vast expanses of shrublands in the Columbia Plateau and Northern Basin converting to grasslands or woodlands. Across the domain, MC1 runs under the CSIRO climate projections averaged 82% increases in biomass combusted and 1.2% (0.1 Pg C) decreases in ecosystem carbon, while those under MIROC averaged 22% increases in biomass combusted and 0.8% (0.07 Pg C) increases in ecosystem carbon. Climate projections from the Hadley model resulted in the most extreme changes, averaging 259% increases in biomass combusted and 15% (1.26 Pg C) decreases in ecosystem carbon. Our study suggests some areas within the Pacific Northwest may be vulnerable, and others resilient, to climate change, although this is highly dependent on model assumptions and uncertainties. Close

• 4. [Article] Carbon dynamics following landscape fire: influence of burn severity, climate, and stand history in the Metolius Watershed, Oregon

  Fire is a fundamental disturbance that drives terrestrial and atmospheric carbon dynamics. Previous studies have quantified fire effects on carbon cycling from local to global scales but have focused ...

  Citation × Citation Citation Abstract Copy Title: Carbon dynamics following landscape fire: influence of burn severity, climate, and stand history in the Metolius Watershed, Oregon Author: Meigs, Garrett W. Fire is a fundamental disturbance that drives terrestrial and atmospheric carbon dynamics. Previous studies have quantified fire effects on carbon cycling from local to global scales but have focused nearly exclusively on high-severity, stand-replacement fire. Since 2002, variable-severity wildfires have burned more than 65 000 ha across the east slope of the Oregon Cascades, including 4 large fires that burned ca. 50% of the forested area within the Metolius Watershed in 2002 and 2003. This thesis integrates data from 64 field plots, remote-sensing, and an ecosystem process model to investigate the effects of low-, moderate-, and high-severity fire. The primary research objectives were to: (a) quantify combustion and mortality effects on carbon pools, postfire net ecosystem production (NEP), and potential regeneration trajectories at the stand scale; (b) introduce novel remote-sensing datasets into a modeling framework to assess the importance of low- and moderate-severity fire across the landscape and region. At the stand-scale, the 3 levels of burn severity (overstory tree mortality) resulted in profoundly different impacts on combustion, mortality, postfire carbon balance, and potential regeneration trajectories. Simulated combustion ranged from 16.6 to 32.3 Mg C ha-1, or 13% to 35% of prefire aboveground carbon. C transfers from fire-induced tree mortality were larger in magnitude than combustion, as live aboveground C decreased by >90% from low- to high-severity stands. Despite this decline, total net primary productivity (NPP) was only 40% lower in high- vs. low-severity stands, reflecting a compensatory effect of non-tree NPP. Dead wood respiratory losses were small relative to C uptake (range: 10-35% of total NPP), suggesting important decomposition lags in this seasonally-arid system. Although soil C, soil respiration, and fine root NPP were conserved across severity classes, NEP declined with increasing severity, driven by trends in aboveground NPP. Postfire conifer seedling density was generally abundant and varied over 5 orders of magnitude (study-wide median: 812, range: 0 – 62 134 seedlings ha-1). Seedling density was negatively correlated with overstory mortality, whereas shrub biomass showed the opposite response, indicating a wide range of potential successional trajectories. Despite substantial combustion and mortality effects on carbon pools and fluxes, the rapid response of postfire vegetation, coupled with conservation of belowground processes, may offset long-term declines in carbon storage, indicating a surprising degree of postfire stability. These stand-scale results describe a broad range of fire effects—a high degree of pyrodiversity—but because burn severity was not evenly distributed across space, the landscape-level fire effects depend on the severity mosaic. At the landscape-scale, moderate- and low-severity fire contributed 25% and 11% of total estimated pyrogenic carbon emission, respectively (0.66 Tg C total, or ca. 2.2% of statewide anthropogenic CO2 emissions equivalent from the same 2-year period). Moderate- and low-severity fire accounted for 23% and 5% of landscape-level tree mortality, respectively, which resulted in the transfer of 2.00 Tg C from live to dead pools. This carbon transfer was ca. 3-fold higher than the one-time pulse from pyrogenic emission, but it will likely take decades for this dead wood to decompose via heterotrophic respiration. The inclusion of moderate-severity fire reduced postfire (2004) mean annual NEP by 39% compared to the high-severity only scenario; low-severity fire influence on NEP was small (additional reduction of 11% in mean NEP), likely because of high tree survivorship and the relatively lower areal coverage of low-severity fire. One year postfire, burned areas were a strong C source (net C exchange across 53 000 ha: -0.065 Tg C y-1; mean ± SD: -123 ± 110 g C m-2 y-1) vs. a prefire mean near C neutral (1997-2001 mean NEP ± SD: -5 ± 51 g C m-2 y-1). The model has been known to underestimate carbon uptake in mature and old semi-arid forests, so the prefire value is likely underestimated. Despite the resurgence of wildfire across western North America, including a substantial increase in the proportion of high-severity fire in the ecoregions studied here, low- and moderate-severity wildfire accounts for the majority of burned area in the Pacific Northwest region. This non-stand-replacement fire has important consequences for carbon loss and uptake at landscape- and regional-scales. The results from this thesis suggest that by accounting for the full gradient of fire effects, carbon modelers can substantially reduce uncertainties in key components of regional and global carbon budgets, particularly pyrogenic emissions, mortality, and NEP. Understanding the effects of disturbance variability on terrestrial carbon cycling will become increasingly important in the context of emerging regional and global carbon policies. Title: Carbon dynamics following landscape fire: influence of burn severity, climate, and stand history in the Metolius Watershed, Oregon Author: Meigs, Garrett W. Fire is a fundamental disturbance that drives terrestrial and atmospheric carbon dynamics. Previous studies have quantified fire effects on carbon cycling from local to global scales but have focused nearly exclusively on high-severity, stand-replacement fire. Since 2002, variable-severity wildfires have burned more than 65 000 ha across the east slope of the Oregon Cascades, including 4 large fires that burned ca. 50% of the forested area within the Metolius Watershed in 2002 and 2003. This thesis integrates data from 64 field plots, remote-sensing, and an ecosystem process model to investigate the effects of low-, moderate-, and high-severity fire. The primary research objectives were to: (a) quantify combustion and mortality effects on carbon pools, postfire net ecosystem production (NEP), and potential regeneration trajectories at the stand scale; (b) introduce novel remote-sensing datasets into a modeling framework to assess the importance of low- and moderate-severity fire across the landscape and region. At the stand-scale, the 3 levels of burn severity (overstory tree mortality) resulted in profoundly different impacts on combustion, mortality, postfire carbon balance, and potential regeneration trajectories. Simulated combustion ranged from 16.6 to 32.3 Mg C ha-1, or 13% to 35% of prefire aboveground carbon. C transfers from fire-induced tree mortality were larger in magnitude than combustion, as live aboveground C decreased by >90% from low- to high-severity stands. Despite this decline, total net primary productivity (NPP) was only 40% lower in high- vs. low-severity stands, reflecting a compensatory effect of non-tree NPP. Dead wood respiratory losses were small relative to C uptake (range: 10-35% of total NPP), suggesting important decomposition lags in this seasonally-arid system. Although soil C, soil respiration, and fine root NPP were conserved across severity classes, NEP declined with increasing severity, driven by trends in aboveground NPP. Postfire conifer seedling density was generally abundant and varied over 5 orders of magnitude (study-wide median: 812, range: 0 – 62 134 seedlings ha-1). Seedling density was negatively correlated with overstory mortality, whereas shrub biomass showed the opposite response, indicating a wide range of potential successional trajectories. Despite substantial combustion and mortality effects on carbon pools and fluxes, the rapid response of postfire vegetation, coupled with conservation of belowground processes, may offset long-term declines in carbon storage, indicating a surprising degree of postfire stability. These stand-scale results describe a broad range of fire effects—a high degree of pyrodiversity—but because burn severity was not evenly distributed across space, the landscape-level fire effects depend on the severity mosaic. At the landscape-scale, moderate- and low-severity fire contributed 25% and 11% of total estimated pyrogenic carbon emission, respectively (0.66 Tg C total, or ca. 2.2% of statewide anthropogenic CO2 emissions equivalent from the same 2-year period). Moderate- and low-severity fire accounted for 23% and 5% of landscape-level tree mortality, respectively, which resulted in the transfer of 2.00 Tg C from live to dead pools. This carbon transfer was ca. 3-fold higher than the one-time pulse from pyrogenic emission, but it will likely take decades for this dead wood to decompose via heterotrophic respiration. The inclusion of moderate-severity fire reduced postfire (2004) mean annual NEP by 39% compared to the high-severity only scenario; low-severity fire influence on NEP was small (additional reduction of 11% in mean NEP), likely because of high tree survivorship and the relatively lower areal coverage of low-severity fire. One year postfire, burned areas were a strong C source (net C exchange across 53 000 ha: -0.065 Tg C y-1; mean ± SD: -123 ± 110 g C m-2 y-1) vs. a prefire mean near C neutral (1997-2001 mean NEP ± SD: -5 ± 51 g C m-2 y-1). The model has been known to underestimate carbon uptake in mature and old semi-arid forests, so the prefire value is likely underestimated. Despite the resurgence of wildfire across western North America, including a substantial increase in the proportion of high-severity fire in the ecoregions studied here, low- and moderate-severity wildfire accounts for the majority of burned area in the Pacific Northwest region. This non-stand-replacement fire has important consequences for carbon loss and uptake at landscape- and regional-scales. The results from this thesis suggest that by accounting for the full gradient of fire effects, carbon modelers can substantially reduce uncertainties in key components of regional and global carbon budgets, particularly pyrogenic emissions, mortality, and NEP. Understanding the effects of disturbance variability on terrestrial carbon cycling will become increasingly important in the context of emerging regional and global carbon policies. Close

• 5. [Article] Does wildfire likelihood increase following insect outbreaks in conifer forests?

  This is the publisher’s final pdf. The published article is copyrighted by Ecological Society of America and can be found at: http://www.esajournals.org/loi/ecsp

  Citation × Citation Citation Abstract Copy Title: Does wildfire likelihood increase following insect outbreaks in conifer forests? Author: Shaw, David C., Campbell, John L., Bailey, John D., Kennedy, Robert E., Zald, Harold S. J., Meigs, Garrett W. This is the publisher’s final pdf. The published article is copyrighted by Ecological Society of America and can be found at: http://www.esajournals.org/loi/ecsp Title: Does wildfire likelihood increase following insect outbreaks in conifer forests? Author: Shaw, David C., Campbell, John L., Bailey, John D., Kennedy, Robert E., Zald, Harold S. J., Meigs, Garrett W. This is the publisher’s final pdf. The published article is copyrighted by Ecological Society of America and can be found at: http://www.esajournals.org/loi/ecsp Close

• 6. [Article] Does wildfire likelihood increase following insect outbreaks in conifer forests?

  This is the publisher’s final pdf. The published article is copyrighted by The Author(s) and published by the Ecological Society of America. It can be found at: http://www.esajournals.org/loi/ecsp

  Citation × Citation Citation Abstract Copy Title: Does wildfire likelihood increase following insect outbreaks in conifer forests? Author: Meigs, Garrett W., Campbell, John L., Bailey, John D., Kennedy, Robert E., Zald, Harold S. J., Shaw, David C. This is the publisher’s final pdf. The published article is copyrighted by The Author(s) and published by the Ecological Society of America. It can be found at: http://www.esajournals.org/loi/ecsp Title: Does wildfire likelihood increase following insect outbreaks in conifer forests? Author: Meigs, Garrett W., Campbell, John L., Bailey, John D., Kennedy, Robert E., Zald, Harold S. J., Shaw, David C. This is the publisher’s final pdf. The published article is copyrighted by The Author(s) and published by the Ecological Society of America. It can be found at: http://www.esajournals.org/loi/ecsp Close

• 7. [Article] Does wildfire likelihood increase following insect outbreaks in conifer forests?

  This is the publisher’s final pdf. The published article is copyrighted by The Author(s) and published by the Ecological Society of America. It can be found at: http://www.esajournals.org/loi/ecsp

  Citation × Citation Citation Abstract Copy Title: Does wildfire likelihood increase following insect outbreaks in conifer forests? Author: Shaw, David C., Campbell, John L., Bailey, John D., Kennedy, Robert E., Zald, Harold S. J., Meigs, Garrett W. This is the publisher’s final pdf. The published article is copyrighted by The Author(s) and published by the Ecological Society of America. It can be found at: http://www.esajournals.org/loi/ecsp Title: Does wildfire likelihood increase following insect outbreaks in conifer forests? Author: Shaw, David C., Campbell, John L., Bailey, John D., Kennedy, Robert E., Zald, Harold S. J., Meigs, Garrett W. This is the publisher’s final pdf. The published article is copyrighted by The Author(s) and published by the Ecological Society of America. It can be found at: http://www.esajournals.org/loi/ecsp Close

• 8. [Article] Impacts of post-fire salvage logging on soil chemistry, physical properties and bacterial community composition in a mixed-conifer forest in central Oregon

  Land managers, scientists, and the interested public are confronted with uncertainty about the impacts of salvage logging on soil productivity. In recent years, stand-replacing wildfires in the western ...

  Citation × Citation Citation Abstract Copy Title: Impacts of post-fire salvage logging on soil chemistry, physical properties and bacterial community composition in a mixed-conifer forest in central Oregon Author: Jennings, Tara Nicolle Land managers, scientists, and the interested public are confronted with uncertainty about the impacts of salvage logging on soil productivity. In recent years, stand-replacing wildfires in the western United States have increased in frequency, prompting the need to evaluate the effect of post-fire treatments on forest ecosystem recovery. This study examined whether compaction and subsoiling after post-fire salvage logging impacted the structure, metabolism, and function of soil bacterial communities, which were assessed using terminal restriction fragment length polymorphism (T-RFLP) and Biolog Ecoplates. Supporting data for these salvage logging effects included soil biological activities, soil chemistry, and physical soil properties in a mixed conifer forest in central Oregon. Post-fire salvage logging treatments had little effect on soil bacterial community richness, suggesting that soil bacteria in these post-fire landscapes are both tolerant of the occurrence of fires and resilient to disturbance. However, even though a statistically significant difference in bacterial species richness was not detected among treatments, a greater cumulative mean number of species was found across six sampling seasons in the compacted soil treatment compared to the fire-only and subsoiled treatments. This trend may be due to less predation on the soil bacteria by microbivores in the soil pores reduced in size by compaction. Additionally, there was a significant decline in the mean number of species after the spring 2007 sampling. A NMS ordination of the mean number of species suggested that the bacterial community composition changed after spring 2007. Furthermore, the lack of difference in mean number of species among treatments suggests that time since fire had a stronger effect on the structure of the soil bacterial community than did logging disturbance. Plant-available phosphorus and nitrogen concentrations were lower in the mechanically disturbed treatments than in the fire-only treatment. Soil respiration and soil phosphatase rates both were higher in the fire-only treatment. Mechanical disturbance may have long-lasting effects in an already nutrient limited system. No other differences among treatments for soil chemical properties were detected. Soil bulk density was lowest in the subsoiled treatment. Microbial community responses to burning and compaction caused by harvesting can be negative, neutral, or positive. While many factors, in addition to soil chemical and physical properties, affect the microbial community richness and functional diversity, our results support other recent studies showing that soil bacteria are resilient in disturbed environments. Title: Impacts of post-fire salvage logging on soil chemistry, physical properties and bacterial community composition in a mixed-conifer forest in central Oregon Author: Jennings, Tara Nicolle Land managers, scientists, and the interested public are confronted with uncertainty about the impacts of salvage logging on soil productivity. In recent years, stand-replacing wildfires in the western United States have increased in frequency, prompting the need to evaluate the effect of post-fire treatments on forest ecosystem recovery. This study examined whether compaction and subsoiling after post-fire salvage logging impacted the structure, metabolism, and function of soil bacterial communities, which were assessed using terminal restriction fragment length polymorphism (T-RFLP) and Biolog Ecoplates. Supporting data for these salvage logging effects included soil biological activities, soil chemistry, and physical soil properties in a mixed conifer forest in central Oregon. Post-fire salvage logging treatments had little effect on soil bacterial community richness, suggesting that soil bacteria in these post-fire landscapes are both tolerant of the occurrence of fires and resilient to disturbance. However, even though a statistically significant difference in bacterial species richness was not detected among treatments, a greater cumulative mean number of species was found across six sampling seasons in the compacted soil treatment compared to the fire-only and subsoiled treatments. This trend may be due to less predation on the soil bacteria by microbivores in the soil pores reduced in size by compaction. Additionally, there was a significant decline in the mean number of species after the spring 2007 sampling. A NMS ordination of the mean number of species suggested that the bacterial community composition changed after spring 2007. Furthermore, the lack of difference in mean number of species among treatments suggests that time since fire had a stronger effect on the structure of the soil bacterial community than did logging disturbance. Plant-available phosphorus and nitrogen concentrations were lower in the mechanically disturbed treatments than in the fire-only treatment. Soil respiration and soil phosphatase rates both were higher in the fire-only treatment. Mechanical disturbance may have long-lasting effects in an already nutrient limited system. No other differences among treatments for soil chemical properties were detected. Soil bulk density was lowest in the subsoiled treatment. Microbial community responses to burning and compaction caused by harvesting can be negative, neutral, or positive. While many factors, in addition to soil chemical and physical properties, affect the microbial community richness and functional diversity, our results support other recent studies showing that soil bacteria are resilient in disturbed environments. Close

• 9. [Article] Dead fuels and understory vegetation six years after a large mixed-severity wildfire in southwest Oregon

  Though the mixed-evergreen forests of the Klamath Siskiyous have a long history of large, mixed-severity fires, most research in this region has concentrated on the impacts of high-severity fire. Knowledge ...

  Citation × Citation Citation Abstract Copy Title: Dead fuels and understory vegetation six years after a large mixed-severity wildfire in southwest Oregon Author: Nathanson, Amy Though the mixed-evergreen forests of the Klamath Siskiyous have a long history of large, mixed-severity fires, most research in this region has concentrated on the impacts of high-severity fire. Knowledge of the ecological effects of low- and moderate-severity areas within mixed-severity fires is important because such areas may account for over half the landscape affected by a fire. The purpose of this study was to understand the relationship of fire severity with dead fuels and understory vegetation across a full range of fire severities. Study sites were located within and just outside the boundary of the 2002 Biscuit Fire, which burned 200,000 hectares in a mosaic of burn severities. Six years after the Biscuit Fire, the biomass and depth of litter and duff was lower on burned sites than unburned sites, and lowest on high-severity sites. This relationship was reversed for woody fuels >7.62 cm in diameter, where quantities were highest in high- and extreme-severity areas, though there was no evidence that quantities differed between low-severity and unburned sites. There was no evidence of a relationship between woody fuels 0.64-7.62 cm in diameter and fire severity, 6 years post-fire. There was no evidence that fuel quantities differed between sites that burned only in the Biscuit Fire with sites that also burned 15 years earlier in the 1987 Silver Fire. Fuel quantities and composition differed between burned and unburned sites, but these differences disappeared if litter and duff were not considered. Fuel classes were correlated with each other within three general size classes: small (litter, duff, and fuels <2.54 cm), medium (fuels 2.54-30 cm), and large (fuels >30 cm). There was little correlation between these size classes. Vegetation response also varied by fire severity, species, and height. Generally, density for tree seedlings <0.5 m was highest on low-severity sites and lowest on high-severity sites. For seedlings 0.5-1.37 m the relationship was reversed, with the highest seedling densities in high-severity areas. Specific seedling relationships to burn severity and other explanatory factors (e.g. shrub cover, elevation, precipitation, maxiumun August temperatures) varied by species and seedling height. Average seedling densities were above the minimum acceptable stocking levels of 333 trees per hectare (135 seedlings/acre) as identified in federal plans for the fire area. Shrub species richness and diversity did not vary with burn severity; however, shrub species and ground cover composition did differ with burn severity six years after the Biscuit Fire. The relationship of understory cover composition with burn severity aligned with species life history traits; fire-adapted, nitrogen-fixing species were more prevalent on high- and extreme-severity sites while species associated with low-severity fire or old-growth forests were more prevalent on low-severity or unburned sites. I found no evidence of difference in total graminoid or forb cover based on fire severity, but shrub quantities were lower on low-severity sites than on unburned, high-, and extreme-severity sites. This study reveals how fuel and vegetation vary across the full range of fire severities. It demonstrates that mixed-severity fires create a mix of ecological responses. It also provides a baseline for future studies, as the relationships between fire severity and fuels or vegetation may disappear or change in subsequent decades. Title: Dead fuels and understory vegetation six years after a large mixed-severity wildfire in southwest Oregon Author: Nathanson, Amy Though the mixed-evergreen forests of the Klamath Siskiyous have a long history of large, mixed-severity fires, most research in this region has concentrated on the impacts of high-severity fire. Knowledge of the ecological effects of low- and moderate-severity areas within mixed-severity fires is important because such areas may account for over half the landscape affected by a fire. The purpose of this study was to understand the relationship of fire severity with dead fuels and understory vegetation across a full range of fire severities. Study sites were located within and just outside the boundary of the 2002 Biscuit Fire, which burned 200,000 hectares in a mosaic of burn severities. Six years after the Biscuit Fire, the biomass and depth of litter and duff was lower on burned sites than unburned sites, and lowest on high-severity sites. This relationship was reversed for woody fuels >7.62 cm in diameter, where quantities were highest in high- and extreme-severity areas, though there was no evidence that quantities differed between low-severity and unburned sites. There was no evidence of a relationship between woody fuels 0.64-7.62 cm in diameter and fire severity, 6 years post-fire. There was no evidence that fuel quantities differed between sites that burned only in the Biscuit Fire with sites that also burned 15 years earlier in the 1987 Silver Fire. Fuel quantities and composition differed between burned and unburned sites, but these differences disappeared if litter and duff were not considered. Fuel classes were correlated with each other within three general size classes: small (litter, duff, and fuels <2.54 cm), medium (fuels 2.54-30 cm), and large (fuels >30 cm). There was little correlation between these size classes. Vegetation response also varied by fire severity, species, and height. Generally, density for tree seedlings <0.5 m was highest on low-severity sites and lowest on high-severity sites. For seedlings 0.5-1.37 m the relationship was reversed, with the highest seedling densities in high-severity areas. Specific seedling relationships to burn severity and other explanatory factors (e.g. shrub cover, elevation, precipitation, maxiumun August temperatures) varied by species and seedling height. Average seedling densities were above the minimum acceptable stocking levels of 333 trees per hectare (135 seedlings/acre) as identified in federal plans for the fire area. Shrub species richness and diversity did not vary with burn severity; however, shrub species and ground cover composition did differ with burn severity six years after the Biscuit Fire. The relationship of understory cover composition with burn severity aligned with species life history traits; fire-adapted, nitrogen-fixing species were more prevalent on high- and extreme-severity sites while species associated with low-severity fire or old-growth forests were more prevalent on low-severity or unburned sites. I found no evidence of difference in total graminoid or forb cover based on fire severity, but shrub quantities were lower on low-severity sites than on unburned, high-, and extreme-severity sites. This study reveals how fuel and vegetation vary across the full range of fire severities. It demonstrates that mixed-severity fires create a mix of ecological responses. It also provides a baseline for future studies, as the relationships between fire severity and fuels or vegetation may disappear or change in subsequent decades. Close

• 10. [Article] Potential effects of climate change and fire management on fire behavior and vegetation patterns on an east Cascades landscape

  Climate exerts considerable control on wildfire regimes, and climate and wildfire are both major drivers of forest growth and succession in interior Northwest forests. Estimating potential response of ...

  Citation × Citation Citation Abstract Copy Title: Potential effects of climate change and fire management on fire behavior and vegetation patterns on an east Cascades landscape Author: Greaves, Heather E. Climate exerts considerable control on wildfire regimes, and climate and wildfire are both major drivers of forest growth and succession in interior Northwest forests. Estimating potential response of these landscapes to anticipated changes in climate helps researchers and land managers understand and mitigate impacts of climate change on important ecological and economic resources. Spatially explicit, mechanistic computer simulation models are powerful tools that permit researchers to incorporate climate and disturbance events along with vegetation physiology and phenology to explore complex potential effects of climate change over wide spatial and temporal scales. In this thesis, I used the simulation model FireBGCv2 to characterize potential response of fire, vegetation, and landscape dynamics to a range of possible future climate and fire management scenarios. The simulation landscape (~43,000 hectares) is part of Deschutes National Forest, which is located at the interface of maritime and continental climates and is known for its beauty and ecological diversity. Simulation scenarios included all combinations of +0°C, +3°C, and +6°C of warming; +10%, ±0%, and -10% historical precipitation; and 10% and 90% fire suppression, and were run for 500 years. To characterize fire dynamics, I investigated how mean fire frequency, intensity, and fuel loadings changed over time in all scenarios, and how fire and tree mortality interacted over time. To explore vegetation and landscape dynamics, I described the distribution and spatial arrangement of vegetation types and forest successional stages on the landscape, and used a nonmetric multidimensional scaling (NMS) ordination to holistically evaluate overall similarity of composition, structure, and landscape pattern among all simulation scenarios over time. Changes in precipitation had little effect on fire characteristics or vegetation and landscape characteristics, indicating that simulated precipitation changes were not sufficient to significantly affect vegetation moisture stress or fire behavior on this landscape. Current heavy fuel loads controlled early fire dynamics, with high mean fire intensities occurring early in all simulations. Increases in fire frequency accompanied all temperature increases, leading to decreasing fuel loads and fire intensities over time in warming scenarios. With no increase in temperature or in fire frequency, high fire intensities and heavier fuel loads were sustained. Over time, more fire associated with warming or less fire suppression increased the percentage of the landscape occupied by non-forest and fire-sensitive early seral forest successional stages, which tended to increase the percentage of fire area burning at high severity (in terms of tree mortality). This fire-vegetation relationship may reflect a return to a more historical range of conditions on this landscape. Higher temperatures and fire frequency led to significant spatial migration of forest types across the landscape, with communities at the highest and lowest elevations particularly affected. Warming led to an upslope shift of warm mixed conifer and ponderosa pine (Pinus ponderosa) forests, severely contracting (under 3° of warming) or eliminating (under 6° of warming) area dominated by mountain hemlock (Tsuga mertensiana) and cool, wet conifer forest in the high western portion of the landscape. In lower elevations, warming and fire together contributed to significant expansion of open (<10% tree canopy cover) forest and grass- and shrubland. The compositional changes and spatial shifts simulated in the warming scenarios suggest that climate change is likely to significantly affect forests on this landscape. Warming and associated fire also tended to increase heterogeneity of forest structural stages and landscape pattern, resulting in a more diverse distribution of structural stages, especially in lower elevations, and a more divided landscape of smaller forest stands. The NMS ordination emphasized the dissimilarity between the severe +6° scenarios and the other two temperature scenarios. The +0° and +3° scenarios differed from each other in composition (mainly because cool forest was lost in the +3° scenarios), but within a given level of fire suppression they remained remarkably similar in terms of overall composition, structure, and landscape pattern, while the +6° scenarios separated noticeably from them. Such decisive differences suggest that under the simulated ranges of precipitation and fire suppression, the interval between 3 and 6 degrees of warming on this landscape may capture an ecological threshold, or tipping point. Additional simulation research that incorporates (for example) management actions, insects and pathogens, and a wider array of precipitation scenarios could help illuminate more clearly the possible range of future landscape conditions. Still, these results provide a glimpse of potential divergent outcomes on this important landscape under possible future climates, and suggest that these forests will undergo considerable changes from both historical and current conditions in response to higher temperatures expected in this area. Some changes may be inevitable with warming, such as the upslope shift of warm forest types, but careful planning for fire and fuels management might allow land managers to modulate fire behavior and steer vegetation dynamics toward the most desirable outcome possible. Title: Potential effects of climate change and fire management on fire behavior and vegetation patterns on an east Cascades landscape Author: Greaves, Heather E. Climate exerts considerable control on wildfire regimes, and climate and wildfire are both major drivers of forest growth and succession in interior Northwest forests. Estimating potential response of these landscapes to anticipated changes in climate helps researchers and land managers understand and mitigate impacts of climate change on important ecological and economic resources. Spatially explicit, mechanistic computer simulation models are powerful tools that permit researchers to incorporate climate and disturbance events along with vegetation physiology and phenology to explore complex potential effects of climate change over wide spatial and temporal scales. In this thesis, I used the simulation model FireBGCv2 to characterize potential response of fire, vegetation, and landscape dynamics to a range of possible future climate and fire management scenarios. The simulation landscape (~43,000 hectares) is part of Deschutes National Forest, which is located at the interface of maritime and continental climates and is known for its beauty and ecological diversity. Simulation scenarios included all combinations of +0°C, +3°C, and +6°C of warming; +10%, ±0%, and -10% historical precipitation; and 10% and 90% fire suppression, and were run for 500 years. To characterize fire dynamics, I investigated how mean fire frequency, intensity, and fuel loadings changed over time in all scenarios, and how fire and tree mortality interacted over time. To explore vegetation and landscape dynamics, I described the distribution and spatial arrangement of vegetation types and forest successional stages on the landscape, and used a nonmetric multidimensional scaling (NMS) ordination to holistically evaluate overall similarity of composition, structure, and landscape pattern among all simulation scenarios over time. Changes in precipitation had little effect on fire characteristics or vegetation and landscape characteristics, indicating that simulated precipitation changes were not sufficient to significantly affect vegetation moisture stress or fire behavior on this landscape. Current heavy fuel loads controlled early fire dynamics, with high mean fire intensities occurring early in all simulations. Increases in fire frequency accompanied all temperature increases, leading to decreasing fuel loads and fire intensities over time in warming scenarios. With no increase in temperature or in fire frequency, high fire intensities and heavier fuel loads were sustained. Over time, more fire associated with warming or less fire suppression increased the percentage of the landscape occupied by non-forest and fire-sensitive early seral forest successional stages, which tended to increase the percentage of fire area burning at high severity (in terms of tree mortality). This fire-vegetation relationship may reflect a return to a more historical range of conditions on this landscape. Higher temperatures and fire frequency led to significant spatial migration of forest types across the landscape, with communities at the highest and lowest elevations particularly affected. Warming led to an upslope shift of warm mixed conifer and ponderosa pine (Pinus ponderosa) forests, severely contracting (under 3° of warming) or eliminating (under 6° of warming) area dominated by mountain hemlock (Tsuga mertensiana) and cool, wet conifer forest in the high western portion of the landscape. In lower elevations, warming and fire together contributed to significant expansion of open (<10% tree canopy cover) forest and grass- and shrubland. The compositional changes and spatial shifts simulated in the warming scenarios suggest that climate change is likely to significantly affect forests on this landscape. Warming and associated fire also tended to increase heterogeneity of forest structural stages and landscape pattern, resulting in a more diverse distribution of structural stages, especially in lower elevations, and a more divided landscape of smaller forest stands. The NMS ordination emphasized the dissimilarity between the severe +6° scenarios and the other two temperature scenarios. The +0° and +3° scenarios differed from each other in composition (mainly because cool forest was lost in the +3° scenarios), but within a given level of fire suppression they remained remarkably similar in terms of overall composition, structure, and landscape pattern, while the +6° scenarios separated noticeably from them. Such decisive differences suggest that under the simulated ranges of precipitation and fire suppression, the interval between 3 and 6 degrees of warming on this landscape may capture an ecological threshold, or tipping point. Additional simulation research that incorporates (for example) management actions, insects and pathogens, and a wider array of precipitation scenarios could help illuminate more clearly the possible range of future landscape conditions. Still, these results provide a glimpse of potential divergent outcomes on this important landscape under possible future climates, and suggest that these forests will undergo considerable changes from both historical and current conditions in response to higher temperatures expected in this area. Some changes may be inevitable with warming, such as the upslope shift of warm forest types, but careful planning for fire and fuels management might allow land managers to modulate fire behavior and steer vegetation dynamics toward the most desirable outcome possible. Close