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• 1. [Article] Fire effects on wetland prairie species: final report

  Project No. 14-48-0001-96749

  Citation × Citation Citation Abstract Copy Title: Fire effects on wetland prairie species: final report Author: Wilson, Mark V., Clark, Deborah Louise, 1950- Project No. 14-48-0001-96749 Title: Fire effects on wetland prairie species: final report Author: Wilson, Mark V., Clark, Deborah Louise, 1950- Project No. 14-48-0001-96749 Close

• 2. [Article] Interactive effects of silvicultural herbicides and cervid herbivory on early seral plant communities of the northern Oregon Coast Range

  Intensive forest management (IFM, dense conifer plantings and herbicide applications) may alter the characteristics of early seral plant communities that function as major habitat resources for a host ...

  Citation × Citation Citation Abstract Copy Title: Interactive effects of silvicultural herbicides and cervid herbivory on early seral plant communities of the northern Oregon Coast Range Author: Stokely, Thomas Intensive forest management (IFM, dense conifer plantings and herbicide applications) may alter the characteristics of early seral plant communities that function as major habitat resources for a host of wildlife species, including cervid herbivores such as Cervus elaphus and Odocoileus hemionus. Such large herbivores can also substantially affect plant community characteristics and succession, especially in disturbed early seral habitats. I hypothesized that the effect of cervid herbivory on early seral plant communities is mediated by the effect of silvicultural herbicide treatments. If that is the case, intensively treated stands with low plant cover and diversity should be most susceptible to herbivory, as cervids are less selective and herbivory impacts are highly concentrated where forage has been diminished. To test this hypothesis, I experimentally established paired 225 m² cervid Exclusion and Open-Herbivory treatment plots in 28, 12-15 ha early seral plantation stands throughout the northern Oregon Coast Range, USA, representing a gradient in IFM. The gradient included three herbicide treatments and a no-spray Control applied at the stand scale and replicated using a randomized complete block design. I compared estimates of cover, height and diversity for entire plant communities and specific functional groups among herbivory and herbicide treatments using mixed-effects models with a blocked split-plot design. I found convincing evidence that the effect of herbivory was mediated by herbicide treatment. No-spray Control stands were too vigorous, diverse and rich with native perennial herb and deciduous shrub forage to be substantially impacted by cervid herbivory. The herbaceous specific, Light herbicide treatment reduced Shannon diversity and the cover and richness of native-perennial herbs, releasing deciduous shrub height growth where cervids where excluded. Highly selective herbivory suppressed the shrub height response by 20.5 cm, increasing the abundance and richness of introduced herb species. The broad spectrum, Moderate herbicide treatment reduced diversity, forage cover and diminished the cover and richness of deciduous shrubs and native-perennial herbs, favoring the dominance of introduced-ruderal herbs. Herbivory in the Moderate treatment reduced total cover by 17.7 percent cover, moderate-quality forage cover by 13.2 percent cover and native perennial herb richness by 1.5 species, while suppressing the cover of introduced-ruderal herbs by 4.58 percent cover and reducing the height of ferns and introduced-perennial herbs by 19.9 and 17.3 cm, respectively. Plant communities subject to the Heavy treatment were the most depauperate of all and herbivory exacerbated the effect of this treatment on native-perennial herbs only. Average height of dominant vegetation was consistently lower with cervid access across all stands, especially with Moderate herbicide treatment. My results provide evidence that by reducing diversity and the abundance of native forage species, herbicide treatments altered herbivory selectivity and pressure. The alteration of herbivory pressure in turn influenced the outcome of herbicide treatments, resulting in an exacerbated effect with Moderate and Heavy treatments. The effect of herbivory in controlling vegetation in managed stands may have positive implications for conifer seedling growth, constituting a possible 'ecosystem service' by cervids in the Pacific Northwest. This 'service' may be to the detriment of biodiversity and other early seral associates when coupled with common intensive forest management practices. Title: Interactive effects of silvicultural herbicides and cervid herbivory on early seral plant communities of the northern Oregon Coast Range Author: Stokely, Thomas Intensive forest management (IFM, dense conifer plantings and herbicide applications) may alter the characteristics of early seral plant communities that function as major habitat resources for a host of wildlife species, including cervid herbivores such as Cervus elaphus and Odocoileus hemionus. Such large herbivores can also substantially affect plant community characteristics and succession, especially in disturbed early seral habitats. I hypothesized that the effect of cervid herbivory on early seral plant communities is mediated by the effect of silvicultural herbicide treatments. If that is the case, intensively treated stands with low plant cover and diversity should be most susceptible to herbivory, as cervids are less selective and herbivory impacts are highly concentrated where forage has been diminished. To test this hypothesis, I experimentally established paired 225 m² cervid Exclusion and Open-Herbivory treatment plots in 28, 12-15 ha early seral plantation stands throughout the northern Oregon Coast Range, USA, representing a gradient in IFM. The gradient included three herbicide treatments and a no-spray Control applied at the stand scale and replicated using a randomized complete block design. I compared estimates of cover, height and diversity for entire plant communities and specific functional groups among herbivory and herbicide treatments using mixed-effects models with a blocked split-plot design. I found convincing evidence that the effect of herbivory was mediated by herbicide treatment. No-spray Control stands were too vigorous, diverse and rich with native perennial herb and deciduous shrub forage to be substantially impacted by cervid herbivory. The herbaceous specific, Light herbicide treatment reduced Shannon diversity and the cover and richness of native-perennial herbs, releasing deciduous shrub height growth where cervids where excluded. Highly selective herbivory suppressed the shrub height response by 20.5 cm, increasing the abundance and richness of introduced herb species. The broad spectrum, Moderate herbicide treatment reduced diversity, forage cover and diminished the cover and richness of deciduous shrubs and native-perennial herbs, favoring the dominance of introduced-ruderal herbs. Herbivory in the Moderate treatment reduced total cover by 17.7 percent cover, moderate-quality forage cover by 13.2 percent cover and native perennial herb richness by 1.5 species, while suppressing the cover of introduced-ruderal herbs by 4.58 percent cover and reducing the height of ferns and introduced-perennial herbs by 19.9 and 17.3 cm, respectively. Plant communities subject to the Heavy treatment were the most depauperate of all and herbivory exacerbated the effect of this treatment on native-perennial herbs only. Average height of dominant vegetation was consistently lower with cervid access across all stands, especially with Moderate herbicide treatment. My results provide evidence that by reducing diversity and the abundance of native forage species, herbicide treatments altered herbivory selectivity and pressure. The alteration of herbivory pressure in turn influenced the outcome of herbicide treatments, resulting in an exacerbated effect with Moderate and Heavy treatments. The effect of herbivory in controlling vegetation in managed stands may have positive implications for conifer seedling growth, constituting a possible 'ecosystem service' by cervids in the Pacific Northwest. This 'service' may be to the detriment of biodiversity and other early seral associates when coupled with common intensive forest management practices. Close

• 3. [Article] Modeling the Economic Potential of Silvopasture in Eastern North Carolina and Northeastern Oregon and Exploring Eligibility of Silvopasture to Enroll in Carbon Markets in the United States

  Silvopasture is the planned and managed agroforestry system in which forage, livestock, and trees or shrubs are integrated in order to enhance individual components. Silvopasture has been identified as ...

  Citation × Citation Citation Abstract Copy Title: Modeling the Economic Potential of Silvopasture in Eastern North Carolina and Northeastern Oregon and Exploring Eligibility of Silvopasture to Enroll in Carbon Markets in the United States Author: Bruck, Sonia Rose Silvopasture is the planned and managed agroforestry system in which forage, livestock, and trees or shrubs are integrated in order to enhance individual components. Silvopasture has been identified as the most promising agroforestry system for the Pacific Northwest and Southeast United States. However, there have been few studies describing the economic viability of silvopasture in these regions. There are two objectives explored in this study: first, to determine the potential for silvopasture as an economically viable income source to farmers in eastern North Carolina and northeastern Oregon by calculating the Land Expectation Value (LEV), Net Present Value (NPV), Internal Rate of Return (IRR), and Annual Expectation Value (AEV), of realistic silvopastoral management regimes, compared to traditionally managed timber or livestock farms; second, to explore whether silvopasture can store as much or more carbon than a traditionally stocked timber plantation, and whether profits from sequestered carbon are possible at this time in the United States. The most profitable silvopasture regimes for eastern North Carolina were cool season grasses combined with loblolly pine at a four percent real discount rate (LEV = $1,025 per acre) and cool season grasses combined with longleaf pine at a four percent real discount rate (LEV = $285 per acre). Traditionally stocked loblolly pine at a four percent real discount rate accrued an LEV of $1,777 per acre, while longleaf pine had negative returns (LEV = -$143 per acre). The cattle standard model for eastern North Carolina accrued an LEV of $2,069 per acre at a four percent real discount rate. The most profitable silvopasture regime for northeast Oregon was native forage establishment with ponderosa pine at a four percent real discount rate (LEV = $274 per acre). Planted ponderosa pine had negative returns for all economic indicators (LEV at four percent real discount rate = -$411). The cattle standard model accrued an LEV of $954 per acre at a four percent real discount rate. Models suggest loblolly pine timber management and cattle management is more profitable than silvopasture management in eastern North Carolina. Additionally, cattle management is more profitable than silvopasture in northeastern Oregon. Longleaf pine and ponderosa pine are not profitable when solely managed for timber, and benefit economically when combined with livestock. There is a growing appreciation for ecosystem services from Silvopasture in the scientific and public community. Tree canopy provides shade and a barrier from adverse weather for livestock herds. Silvopasture can also aid in increased biological diversity, reduced erosion, increased nutrient uptake, and enhanced carbon sequestration. In addition, silvopasture has the potential to store significant amounts of carbon, which benefits society as a whole. Therefore, it is amenable to include the social externalities of profitability in cash flow analyses. Currently there are only voluntary cap and trade markets. The most well-known is arguably the California Air Resources Board (ARB), regulated by the California Environmental Protection Agency. Unfortunately, silvopasture does not qualify at this time for carbon markets in the United States. Title: Modeling the Economic Potential of Silvopasture in Eastern North Carolina and Northeastern Oregon and Exploring Eligibility of Silvopasture to Enroll in Carbon Markets in the United States Author: Bruck, Sonia Rose Silvopasture is the planned and managed agroforestry system in which forage, livestock, and trees or shrubs are integrated in order to enhance individual components. Silvopasture has been identified as the most promising agroforestry system for the Pacific Northwest and Southeast United States. However, there have been few studies describing the economic viability of silvopasture in these regions. There are two objectives explored in this study: first, to determine the potential for silvopasture as an economically viable income source to farmers in eastern North Carolina and northeastern Oregon by calculating the Land Expectation Value (LEV), Net Present Value (NPV), Internal Rate of Return (IRR), and Annual Expectation Value (AEV), of realistic silvopastoral management regimes, compared to traditionally managed timber or livestock farms; second, to explore whether silvopasture can store as much or more carbon than a traditionally stocked timber plantation, and whether profits from sequestered carbon are possible at this time in the United States. The most profitable silvopasture regimes for eastern North Carolina were cool season grasses combined with loblolly pine at a four percent real discount rate (LEV = $1,025 per acre) and cool season grasses combined with longleaf pine at a four percent real discount rate (LEV = $285 per acre). Traditionally stocked loblolly pine at a four percent real discount rate accrued an LEV of $1,777 per acre, while longleaf pine had negative returns (LEV = -$143 per acre). The cattle standard model for eastern North Carolina accrued an LEV of $2,069 per acre at a four percent real discount rate. The most profitable silvopasture regime for northeast Oregon was native forage establishment with ponderosa pine at a four percent real discount rate (LEV = $274 per acre). Planted ponderosa pine had negative returns for all economic indicators (LEV at four percent real discount rate = -$411). The cattle standard model accrued an LEV of $954 per acre at a four percent real discount rate. Models suggest loblolly pine timber management and cattle management is more profitable than silvopasture management in eastern North Carolina. Additionally, cattle management is more profitable than silvopasture in northeastern Oregon. Longleaf pine and ponderosa pine are not profitable when solely managed for timber, and benefit economically when combined with livestock. There is a growing appreciation for ecosystem services from Silvopasture in the scientific and public community. Tree canopy provides shade and a barrier from adverse weather for livestock herds. Silvopasture can also aid in increased biological diversity, reduced erosion, increased nutrient uptake, and enhanced carbon sequestration. In addition, silvopasture has the potential to store significant amounts of carbon, which benefits society as a whole. Therefore, it is amenable to include the social externalities of profitability in cash flow analyses. Currently there are only voluntary cap and trade markets. The most well-known is arguably the California Air Resources Board (ARB), regulated by the California Environmental Protection Agency. Unfortunately, silvopasture does not qualify at this time for carbon markets in the United States. Close

• 4. [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

• 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 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

• 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: 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

• 7. [Article] Comparison of Contemporary and Heritage Fish Consumption Rates in the Columbia River Basin

  This is an author's peer-reviewed final manuscript, as accepted by the publisher. The published article is copyrighted by Springer and can be found at: http://link.springer.com/journal/10745

  Citation × Citation Citation Abstract Copy Title: Comparison of Contemporary and Heritage Fish Consumption Rates in the Columbia River Basin Author: Harper, Barbara L., Walker, Deward E., Jr. This is an author's peer-reviewed final manuscript, as accepted by the publisher. The published article is copyrighted by Springer and can be found at: http://link.springer.com/journal/10745 Title: Comparison of Contemporary and Heritage Fish Consumption Rates in the Columbia River Basin Author: Harper, Barbara L., Walker, Deward E., Jr. This is an author's peer-reviewed final manuscript, as accepted by the publisher. The published article is copyrighted by Springer and can be found at: http://link.springer.com/journal/10745 Close

• 8. [Article] Mapping disturbance interactions from earth and space : insect effects on tree mortality, fuels, and wildfires across forests of the Pacific Northwest

  Given the vital role of forest ecosystems in landscape pattern and process, it is important to quantify the effects, feedbacks, and uncertainties associated with forest disturbance dynamics. In western ...

  Citation × Citation Citation Abstract Copy Title: Mapping disturbance interactions from earth and space : insect effects on tree mortality, fuels, and wildfires across forests of the Pacific Northwest Author: Meigs, Garrett W. Given the vital role of forest ecosystems in landscape pattern and process, it is important to quantify the effects, feedbacks, and uncertainties associated with forest disturbance dynamics. In western North America, insects and wildfires are both native disturbances that have influenced forests for millennia, and both are projected to increase with anthropogenic climate change. Although there is acute concern that insect-caused tree mortality increases the likelihood or severity of subsequent wildfire, previous research has been mixed, with results often based on individual fire or insect events. Much of the ambivalence in the literature can be attributed to differences in the particular insect of interest, forest type, and fire event, but it is also related to the spatiotemporal scale of analysis and a general lack of geospatial datasets spanning enough time and space to capture multiple forest disturbances consistently and accurately. This dissertation presents a regional-scale framework to map, quantify, and understand insect-wildfire interactions across numerous insect and fire events across the Pacific Northwest region (PNW). Through three related studies, I worked with many collaborators to develop regionally extensive but fine-grained maps to assess the spatiotemporal patterns of wildfires and the two most pervasive, damaging forest insects in the PNW – mountain pine beetle (MPB; Dendroctonus ponderosae Hopkins [Coleoptera: Scolytidae]; a bark beetle) and western spruce budworm (WSB; Choristoneura freemani Razowksi [Lepidoptera: Tortricidae]; a defoliator). The proximate objectives of developing new maps and summarizing where and when insects have occurred before wildfires enable us to address the ultimate question: How does forest insect activity influence the likelihood of subsequent wildfire? In a pilot study focused on the forest stand scale (Chapter Two), we leveraged a Landsat time series change detection algorithm (LandTrendr), annual forest health aerial detection surveys (ADS), and field measurements to investigate MPB and WSB effects on spectral trajectories, tree mortality, and fuel profiles at 38 plots in the Cascade Range of Oregon. Insect effects were evident in the Landsat time series as combinations of both short- and long-duration changes. WSB trajectories appeared to show a consistent temporal evolution of long-duration spectral decline followed by recovery, whereas MPB trajectories exhibited both short- and long-duration spectral declines and variable recovery rates. When comparing remote sensing data with field measurements of insect impacts, we found that spectral changes were related to cover-based estimates (e.g., tree basal area mortality and down coarse woody detritus). In contrast, ADS changes were related to count-based estimates (e.g., dead tree density). Fine woody detritus and forest floor depth were not well correlated with Landsat- or aerial survey-based change metrics. This study demonstrated the utility of insect mapping methods that capture a wide range of spectral trajectories, setting the stage for regional-scale mapping and analysis. In a regional assessment of MPB and WSB effects on tree mortality (Chapter Three), we developed Landsat-based insect maps and presented comparisons across space, time, and insect agents that have not been possible to date, complementing existing ADS maps by: (1) quantifying change in terms of field-measured tree mortality; (2) providing consistent estimates of change for multiple agents, particularly long-duration changes; (3) capturing variation of insect impacts at a finer spatial scale within ADS polygons, substantially reducing estimated insect extent. Despite high variation across the study region, spatiotemporal patterns were evident in both the ADS- and Landsat-based maps of insect activity. MPB outbreaks occurred in two phases -- first during the 1970s and 1980s in eastern and central Oregon and then more synchronously during the 2000s throughout the dry interior conifer forests of the PNW. Reflecting differences in habitat susceptibility and epidemiology, WSB outbreaks exhibited early activity in northern Washington and an apparent spread from the eastern to central PNW during the 1980s, returning to northern Washington during the 1990s and 2000s. Across the region, WSB exceeded MPB in extent and tree mortality impacts in all ecoregions except for one, suggesting that ongoing studies should account for both bark beetles and defoliators, particularly given recent and projected increases in wildfire extent. By combining these insect maps with an independent wildfire database (Chapter Four), we investigated wildfire likelihood following recent MPB and WSB outbreaks at ecoregional and regional scales. We computed wildfire likelihood with two-way binary matrices between fire and insects, testing for paired differences between percent burned with and without prior insect activity. All three disturbance agents occurred primarily in the drier, interior conifer forests east of the Cascade Range, with recent wildfires extending through the southern West Cascades and Klamath Mountains. In general, insect extent exceeded wildfire extent, and each disturbance typically affected less than 2% annually of a given ecoregion. In recent decades across the PNW, wildfire likelihood is not consistently higher in forests with prior insect outbreaks, but there is evidence of linked interactions that vary across insect agent (MPB and WSB), space (ecoregions), and time (interval since insect onset). For example, fire likelihood is higher following MPB activity in the North Cascades and West Cascades, particularly within the past 10 years, whereas fire likelihood is lower at various time lags following MPB in the Northern Rockies, East Cascades, and Blue Mountains. In contrast, fire likelihood is lower following WSB outbreaks at multiple time lags across all ecoregions. In addition, there are no consistent relationships between insect-fire likelihood and interannual fire extent, suggesting that other factors (such as climate) control the disproportionately large fire years accounting for the majority of regional fire extent. Although insects and wildfires do not appear to overlap enough to facilitate consistently positive linked disturbance interactions, specific fire events and years – such as 2003 and 2006 in the North Cascades – demonstrate high insect-fire co-occurrence and potential compound disturbance effects at the landscape scale. The results from this dissertation highlight the key ecological roles that native disturbances play in PNW forests. WSB, MPB, and wildfire have been relatively rare at the regional scale, but all three have had and will continue to have profound effects on particular forest stands and landscapes. Because scale is such an important aspect of both the disturbance phenomena themselves as well as our ability to detect the ecological changes they render, our results also underscore the importance of geospatial datasets that span multiple scales in space and time. Given concerns about forest health in a rapidly changing climate, long-term monitoring will enable forest managers to quantify and anticipate the independent and interactive effects of insects, wildfires, and other disturbances. Title: Mapping disturbance interactions from earth and space : insect effects on tree mortality, fuels, and wildfires across forests of the Pacific Northwest Author: Meigs, Garrett W. Given the vital role of forest ecosystems in landscape pattern and process, it is important to quantify the effects, feedbacks, and uncertainties associated with forest disturbance dynamics. In western North America, insects and wildfires are both native disturbances that have influenced forests for millennia, and both are projected to increase with anthropogenic climate change. Although there is acute concern that insect-caused tree mortality increases the likelihood or severity of subsequent wildfire, previous research has been mixed, with results often based on individual fire or insect events. Much of the ambivalence in the literature can be attributed to differences in the particular insect of interest, forest type, and fire event, but it is also related to the spatiotemporal scale of analysis and a general lack of geospatial datasets spanning enough time and space to capture multiple forest disturbances consistently and accurately. This dissertation presents a regional-scale framework to map, quantify, and understand insect-wildfire interactions across numerous insect and fire events across the Pacific Northwest region (PNW). Through three related studies, I worked with many collaborators to develop regionally extensive but fine-grained maps to assess the spatiotemporal patterns of wildfires and the two most pervasive, damaging forest insects in the PNW – mountain pine beetle (MPB; Dendroctonus ponderosae Hopkins [Coleoptera: Scolytidae]; a bark beetle) and western spruce budworm (WSB; Choristoneura freemani Razowksi [Lepidoptera: Tortricidae]; a defoliator). The proximate objectives of developing new maps and summarizing where and when insects have occurred before wildfires enable us to address the ultimate question: How does forest insect activity influence the likelihood of subsequent wildfire? In a pilot study focused on the forest stand scale (Chapter Two), we leveraged a Landsat time series change detection algorithm (LandTrendr), annual forest health aerial detection surveys (ADS), and field measurements to investigate MPB and WSB effects on spectral trajectories, tree mortality, and fuel profiles at 38 plots in the Cascade Range of Oregon. Insect effects were evident in the Landsat time series as combinations of both short- and long-duration changes. WSB trajectories appeared to show a consistent temporal evolution of long-duration spectral decline followed by recovery, whereas MPB trajectories exhibited both short- and long-duration spectral declines and variable recovery rates. When comparing remote sensing data with field measurements of insect impacts, we found that spectral changes were related to cover-based estimates (e.g., tree basal area mortality and down coarse woody detritus). In contrast, ADS changes were related to count-based estimates (e.g., dead tree density). Fine woody detritus and forest floor depth were not well correlated with Landsat- or aerial survey-based change metrics. This study demonstrated the utility of insect mapping methods that capture a wide range of spectral trajectories, setting the stage for regional-scale mapping and analysis. In a regional assessment of MPB and WSB effects on tree mortality (Chapter Three), we developed Landsat-based insect maps and presented comparisons across space, time, and insect agents that have not been possible to date, complementing existing ADS maps by: (1) quantifying change in terms of field-measured tree mortality; (2) providing consistent estimates of change for multiple agents, particularly long-duration changes; (3) capturing variation of insect impacts at a finer spatial scale within ADS polygons, substantially reducing estimated insect extent. Despite high variation across the study region, spatiotemporal patterns were evident in both the ADS- and Landsat-based maps of insect activity. MPB outbreaks occurred in two phases -- first during the 1970s and 1980s in eastern and central Oregon and then more synchronously during the 2000s throughout the dry interior conifer forests of the PNW. Reflecting differences in habitat susceptibility and epidemiology, WSB outbreaks exhibited early activity in northern Washington and an apparent spread from the eastern to central PNW during the 1980s, returning to northern Washington during the 1990s and 2000s. Across the region, WSB exceeded MPB in extent and tree mortality impacts in all ecoregions except for one, suggesting that ongoing studies should account for both bark beetles and defoliators, particularly given recent and projected increases in wildfire extent. By combining these insect maps with an independent wildfire database (Chapter Four), we investigated wildfire likelihood following recent MPB and WSB outbreaks at ecoregional and regional scales. We computed wildfire likelihood with two-way binary matrices between fire and insects, testing for paired differences between percent burned with and without prior insect activity. All three disturbance agents occurred primarily in the drier, interior conifer forests east of the Cascade Range, with recent wildfires extending through the southern West Cascades and Klamath Mountains. In general, insect extent exceeded wildfire extent, and each disturbance typically affected less than 2% annually of a given ecoregion. In recent decades across the PNW, wildfire likelihood is not consistently higher in forests with prior insect outbreaks, but there is evidence of linked interactions that vary across insect agent (MPB and WSB), space (ecoregions), and time (interval since insect onset). For example, fire likelihood is higher following MPB activity in the North Cascades and West Cascades, particularly within the past 10 years, whereas fire likelihood is lower at various time lags following MPB in the Northern Rockies, East Cascades, and Blue Mountains. In contrast, fire likelihood is lower following WSB outbreaks at multiple time lags across all ecoregions. In addition, there are no consistent relationships between insect-fire likelihood and interannual fire extent, suggesting that other factors (such as climate) control the disproportionately large fire years accounting for the majority of regional fire extent. Although insects and wildfires do not appear to overlap enough to facilitate consistently positive linked disturbance interactions, specific fire events and years – such as 2003 and 2006 in the North Cascades – demonstrate high insect-fire co-occurrence and potential compound disturbance effects at the landscape scale. The results from this dissertation highlight the key ecological roles that native disturbances play in PNW forests. WSB, MPB, and wildfire have been relatively rare at the regional scale, but all three have had and will continue to have profound effects on particular forest stands and landscapes. Because scale is such an important aspect of both the disturbance phenomena themselves as well as our ability to detect the ecological changes they render, our results also underscore the importance of geospatial datasets that span multiple scales in space and time. Given concerns about forest health in a rapidly changing climate, long-term monitoring will enable forest managers to quantify and anticipate the independent and interactive effects of insects, wildfires, and other disturbances. Close