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• 1. [Article] The Schultz Fire : an interdisciplinary perspective on its history, management, and ecological effects

  This thesis examines the Schultz Fire as a case study to explain the complex history of fire suppression management in America’s forests, and to gain further understanding of how management practices have ...

  Citation × Citation Citation Abstract Copy Title: The Schultz Fire : an interdisciplinary perspective on its history, management, and ecological effects Author: Ranseen, Susanne N. This thesis examines the Schultz Fire as a case study to explain the complex history of fire suppression management in America’s forests, and to gain further understanding of how management practices have affected the increase in fire severity levels and how forests respond to such a disturbance. The thesis objectives were: (1) to analyze the causes of the fire severity of the Schultz Fire, especially: topography, fuels, or weather; (2); to examine the possible correlation between fire severity and tree density; (3) to investigate whether post-fire species richness was related to fire severity two years after the Schultz Fire; (4) to investigate whether post-fire plant species richness, plant cover, and tree regeneration was related to fire severity two years after the Schultz Fire; and (5) to interlink and convey how these factors relate to the history of fire management and policy and public perception. The history of fire related policy and management has significantly changed the dynamics of America's national parks and forests. Understanding the larger context of this history, both of national fire management and of the effects of language and perception on policy and public reaction, is part of understanding the Schultz Fire as a whole. Based on modeling, high winds combined with the presence of high surface fuel load were the main causes of the Schultz Fire's high fire severity levels. As fire severity increased there was a statistically significant increase in species richness. Severity level had little variation on percentage of cover by plants. No statistically significant relationship between tree density and fire severity levels was found. These findings underline the need for fuel treatments in southwest Ponderosa Pine forests, and effective cooperation between communities, managers, and ecologists. The Schultz Fire serves as an example in understanding the intricacies of how history affects the present and future of fire management. How fire has been managed and portrayed in the past has left an indelible mark on how fire is presently viewed. Without a clear understanding of the history of fire management and the role of fire in the ecology, future policies towards fire will be unable to account for and manage for the diversity of ecosystems and fires effects on those ecosystems across the United States. Title: The Schultz Fire : an interdisciplinary perspective on its history, management, and ecological effects Author: Ranseen, Susanne N. This thesis examines the Schultz Fire as a case study to explain the complex history of fire suppression management in America’s forests, and to gain further understanding of how management practices have affected the increase in fire severity levels and how forests respond to such a disturbance. The thesis objectives were: (1) to analyze the causes of the fire severity of the Schultz Fire, especially: topography, fuels, or weather; (2); to examine the possible correlation between fire severity and tree density; (3) to investigate whether post-fire species richness was related to fire severity two years after the Schultz Fire; (4) to investigate whether post-fire plant species richness, plant cover, and tree regeneration was related to fire severity two years after the Schultz Fire; and (5) to interlink and convey how these factors relate to the history of fire management and policy and public perception. The history of fire related policy and management has significantly changed the dynamics of America's national parks and forests. Understanding the larger context of this history, both of national fire management and of the effects of language and perception on policy and public reaction, is part of understanding the Schultz Fire as a whole. Based on modeling, high winds combined with the presence of high surface fuel load were the main causes of the Schultz Fire's high fire severity levels. As fire severity increased there was a statistically significant increase in species richness. Severity level had little variation on percentage of cover by plants. No statistically significant relationship between tree density and fire severity levels was found. These findings underline the need for fuel treatments in southwest Ponderosa Pine forests, and effective cooperation between communities, managers, and ecologists. The Schultz Fire serves as an example in understanding the intricacies of how history affects the present and future of fire management. How fire has been managed and portrayed in the past has left an indelible mark on how fire is presently viewed. Without a clear understanding of the history of fire management and the role of fire in the ecology, future policies towards fire will be unable to account for and manage for the diversity of ecosystems and fires effects on those ecosystems across the United States. Close

• 2. [Article] Response of Soil Microbially Mediated Nutrient Cycling and Community Structure to Timber Harvest in the Pacific Northwest

  Forest harvest persists as one of the most globally important industries, and crucially provides raw wood products for both building and fuel materials. Mechanistically complex abiotic and biotic processes ...

  Citation × Citation Citation Abstract Copy Title: Response of Soil Microbially Mediated Nutrient Cycling and Community Structure to Timber Harvest in the Pacific Northwest Author: Danielson, Rachel E. Forest harvest persists as one of the most globally important industries, and crucially provides raw wood products for both building and fuel materials. Mechanistically complex abiotic and biotic processes curb ecosystem recovery following timber harvest and it is of great importance to understand the effects of this practice on biogeochemical cycling and ecosystem function to determine the potential for long-term sustainability. This thesis was motivated by a lack of comprehensive understanding as to the consistency of preexisting and post-harvest microbially mediated process rates and community composition across a large region of the same dominant vegetation type. I sought to determine how timber harvest across the Pacific Northwest impacts microbial biogeochemical cycling activity and community structure of both prokaryotic and fungal communities in response to harvest. At nine managed Douglas-fir forests, samples were collected from exact locations within sites one year prior to and twelve to fifteen months following clear-cut harvesting. The objective of the first study was to determine the degree of variability in microbially mediated process rates and pools of C and N, and generalized trends that are evident across sites one year following harvest. Samples were analyzed for various C and N pools, and the potential activities of biogeochemically important extracellular enzymes were measured. Soil incubations were performed to determine respiration rate and N production over time. Soil DNA isolates were used to quantify 16S rRNA and ITS gene copy numbers using qPCR, and all measurements were statistically compared between pre-and post-harvest samples. Total soil C and N did not change significantly following harvest, but the C: N ratio of dissolved components decreased consistently and biomass C: N ratios generally increased. Activities of β-glucosidase and cellobiohydrolase increased significantly whereas activities of phenol oxidase and peroxidase decreased significantly. Cumulative respiration over the incubation period declined substantially, and total N pools changed from primarily DON pre-harvest, to primarily NO₃⁻post-harvest. Changes in activity rates and pool sizes following harvest were generally related to C to N balances. Pre-harvest measurements suggested communities may be co-limited by C and N, while the emergence of strong C limitation was evident post-harvest. The generalized trends identified from this study can be used in future research as reference points for ecosystem status during forest succession, and for correlation with an investigation of changes in microbial community composition and structure. The objective of the second study was to determine the factors shaping soil microbial communities of Douglas-fir forests in the Pacific Northwest, and to identify generalized short-term effects of timber harvest on the richness, diversity, and structureof these communities. DNA was extracted from soils and sequenced using the Illumina® Miseq platform to determine differences in prokaryotic and fungal communities. When communities were considered separately pre-and post-harvest, pH most consistently explained community dissimilarity among sites. Although community dispersion did not vary between pre-and post-harvest samples, OTU richness was consistently and significantly higher following tree removal. Both prokaryotic and fungal community structures were significantly different in post-compared to pre-harvest soils, even when just OTUs representing the top 50% of sequences were considered. Relative abundance of the dominant three bacterial phyla (Proteobacteria, Acidobacteria, and Verrucomicrobia) did not change significantly following harvest, but some less-represented phyla decreased (Actinobacteria) or increased (Bacteroidetes) significantly in relative abundance. Basidiomycota abundance decreased significantly whereas Ascomycota and Zygomycota abundance increased. Ectomycorrhizal fungi were enriched across pre-harvest samples, whereas many known saprotrophic species were enriched post-harvest. In conclusion, general alterations in fungal communities, as well as select bacterial and archaeal taxa, may serve as appropriate indicators of disturbance and ecosystem status across this region. Title: Response of Soil Microbially Mediated Nutrient Cycling and Community Structure to Timber Harvest in the Pacific Northwest Author: Danielson, Rachel E. Forest harvest persists as one of the most globally important industries, and crucially provides raw wood products for both building and fuel materials. Mechanistically complex abiotic and biotic processes curb ecosystem recovery following timber harvest and it is of great importance to understand the effects of this practice on biogeochemical cycling and ecosystem function to determine the potential for long-term sustainability. This thesis was motivated by a lack of comprehensive understanding as to the consistency of preexisting and post-harvest microbially mediated process rates and community composition across a large region of the same dominant vegetation type. I sought to determine how timber harvest across the Pacific Northwest impacts microbial biogeochemical cycling activity and community structure of both prokaryotic and fungal communities in response to harvest. At nine managed Douglas-fir forests, samples were collected from exact locations within sites one year prior to and twelve to fifteen months following clear-cut harvesting. The objective of the first study was to determine the degree of variability in microbially mediated process rates and pools of C and N, and generalized trends that are evident across sites one year following harvest. Samples were analyzed for various C and N pools, and the potential activities of biogeochemically important extracellular enzymes were measured. Soil incubations were performed to determine respiration rate and N production over time. Soil DNA isolates were used to quantify 16S rRNA and ITS gene copy numbers using qPCR, and all measurements were statistically compared between pre-and post-harvest samples. Total soil C and N did not change significantly following harvest, but the C: N ratio of dissolved components decreased consistently and biomass C: N ratios generally increased. Activities of β-glucosidase and cellobiohydrolase increased significantly whereas activities of phenol oxidase and peroxidase decreased significantly. Cumulative respiration over the incubation period declined substantially, and total N pools changed from primarily DON pre-harvest, to primarily NO₃⁻post-harvest. Changes in activity rates and pool sizes following harvest were generally related to C to N balances. Pre-harvest measurements suggested communities may be co-limited by C and N, while the emergence of strong C limitation was evident post-harvest. The generalized trends identified from this study can be used in future research as reference points for ecosystem status during forest succession, and for correlation with an investigation of changes in microbial community composition and structure. The objective of the second study was to determine the factors shaping soil microbial communities of Douglas-fir forests in the Pacific Northwest, and to identify generalized short-term effects of timber harvest on the richness, diversity, and structureof these communities. DNA was extracted from soils and sequenced using the Illumina® Miseq platform to determine differences in prokaryotic and fungal communities. When communities were considered separately pre-and post-harvest, pH most consistently explained community dissimilarity among sites. Although community dispersion did not vary between pre-and post-harvest samples, OTU richness was consistently and significantly higher following tree removal. Both prokaryotic and fungal community structures were significantly different in post-compared to pre-harvest soils, even when just OTUs representing the top 50% of sequences were considered. Relative abundance of the dominant three bacterial phyla (Proteobacteria, Acidobacteria, and Verrucomicrobia) did not change significantly following harvest, but some less-represented phyla decreased (Actinobacteria) or increased (Bacteroidetes) significantly in relative abundance. Basidiomycota abundance decreased significantly whereas Ascomycota and Zygomycota abundance increased. Ectomycorrhizal fungi were enriched across pre-harvest samples, whereas many known saprotrophic species were enriched post-harvest. In conclusion, general alterations in fungal communities, as well as select bacterial and archaeal taxa, may serve as appropriate indicators of disturbance and ecosystem status across this region. Close

• 3. [Article] Overstory Structure and Community Characteristics of Oregon Ash (Fraxinus latifolia) Forests of the Willamette Valley, Oregon

  As species of ash trees become increasingly threatened worldwide by exotic pests and pathogens, it is important to develop descriptions of their ecologies that help guide the conservation and restoration ...

  Citation × Citation Citation Abstract Copy Title: Overstory Structure and Community Characteristics of Oregon Ash (Fraxinus latifolia) Forests of the Willamette Valley, Oregon Author: Prive, Sean As species of ash trees become increasingly threatened worldwide by exotic pests and pathogens, it is important to develop descriptions of their ecologies that help guide the conservation and restoration of forests in which they are a major component. Oregon ash (Fraxinus latifolia) is a dominant tree species in wetland forests of the Willamette Valley, Oregon. It is potentially threatened by the emerald ash borer, an exotic forest insect that is expanding in range in North America. The arrival of the emerald ash borer in the western United States is expected to cause high rates of Oregon ash mortality, which will likely highly alter structural and compositional characteristics of regional riparian and wetland forests. To investigate the structural development and plant community dynamics of Willamette Valley Oregon ash forests, I quantified species structure and composition for both overstory and understory communities along gradients of stand age and soil moisture. Community Type Wetland Index (CTWI) scores were calculated for each plot by multiplying plot-level species abundances by the national wetland indicator value for each species, and were used as an approximation of local soil moisture regimes. Ash forests and early seral savannas were sampled in 102 plots within 11 wetlands between Lane and Washington Counties, Oregon. Early seral wetland savannas were dominated by herbaceous vegetation and had highly variable ash and other tree species recruitment. Young ash forests initiated on wetland sites that were formally maintained as savannas via anthropogenic disturbance. Structural development in these forests generally followed previously described post-disturbance stages: stem exclusion, understory initiation, young multi-strata, and old growth. As stands aged, tree densities decreased and mean tree diameter increased. Mean stand densities (for trees >5 cm at 1.3 m height) ranged from 1727 trees per hectare in stem exclusion stands to 348 in old growth stands, while mean tree diameter increased from 12 to 32 cm between those same stages. Furthermore, understory vegetation shifted from herbaceous to shrub and understory tree species. Oregon ash had the greatest relative dominance of all tree species at all stages of structural development. Oregon white oak (Quercus garryana) was the only other tree species commonly found in forest canopies, though it was typically far less abundant than Oregon ash. Plots in which oak was present had a greater depth to soil mottling, indicating a lower depth to the annual high water table. Oregon ash was also the most commonly regenerating tree species in all stages of structural development, and nearly 70% of ash regeneration was vegetative. Other tree regeneration was typically restricted to understory species, especially cascara (Rhamnus purshiana) in forests and hawthorn (Crataegus spp.) in savannas. Forest structural diversity increased between each stage of development. In total, 216 plant species were identified. Of these, 147 were found in forest plots. Community composition differed significantly between forests and savannas, and between "young" (stem exclusion and understory initiation) plots and "old" (young multi-strata and old growth) plots. Nonmetric multidimensional scaling (NMS) indicated that, for all wetland plots, the environmental variables most highly correlated with community composition were CTWI scores and canopy cover. For forest plots only, NMS indicated that CTWI scores and stand density were the environmental variables most related to patterns in community composition. Species richness was not correlated with canopy cover, but was negatively correlated with CTWI scores. Exotic species cover was negatively correlated with canopy cover, but was not correlated with CTWI scores. Exotic species composition was dependent on both canopy cover and CTWI scores. On wet sites, reed canary grass (Phalaris arundinacea) was particularly abundant, and was associated with low species richness. On drier sites, common exotic species included trees and shrubs such as blackberries (Rubus spp.), exotic roses (Rosa spp.), single-seeded hawthorn (Crataegus monogyna), and common pear (Pyrus communis) as well as several grass and forb species. The results of this study suggest that, although overstory tree communities are characterized by low diversity, Oregon ash forests are important for landscape-scale structural and plant community diversity in Willamette Valley wetlands. However, overstory tree communities lack diversity; Oregon ash appears to be both an early seral, colonizing species in open wetlands and a climax species that is capable of regenerating under a closed canopy. Few other trees are present regionally that are capable of maintaining a forested state in wetlands. Furthermore, closed canopy Oregon ash forests may suppress exotic species spread, and in the absence of management, overstory ash mortality may lead to increased exotic plant cover. Regardless of future forest health threats, intact Oregon ash forests, like other regional wetland-types, are currently few and limited in extent and should be considered a conservation priority. Title: Overstory Structure and Community Characteristics of Oregon Ash (Fraxinus latifolia) Forests of the Willamette Valley, Oregon Author: Prive, Sean As species of ash trees become increasingly threatened worldwide by exotic pests and pathogens, it is important to develop descriptions of their ecologies that help guide the conservation and restoration of forests in which they are a major component. Oregon ash (Fraxinus latifolia) is a dominant tree species in wetland forests of the Willamette Valley, Oregon. It is potentially threatened by the emerald ash borer, an exotic forest insect that is expanding in range in North America. The arrival of the emerald ash borer in the western United States is expected to cause high rates of Oregon ash mortality, which will likely highly alter structural and compositional characteristics of regional riparian and wetland forests. To investigate the structural development and plant community dynamics of Willamette Valley Oregon ash forests, I quantified species structure and composition for both overstory and understory communities along gradients of stand age and soil moisture. Community Type Wetland Index (CTWI) scores were calculated for each plot by multiplying plot-level species abundances by the national wetland indicator value for each species, and were used as an approximation of local soil moisture regimes. Ash forests and early seral savannas were sampled in 102 plots within 11 wetlands between Lane and Washington Counties, Oregon. Early seral wetland savannas were dominated by herbaceous vegetation and had highly variable ash and other tree species recruitment. Young ash forests initiated on wetland sites that were formally maintained as savannas via anthropogenic disturbance. Structural development in these forests generally followed previously described post-disturbance stages: stem exclusion, understory initiation, young multi-strata, and old growth. As stands aged, tree densities decreased and mean tree diameter increased. Mean stand densities (for trees >5 cm at 1.3 m height) ranged from 1727 trees per hectare in stem exclusion stands to 348 in old growth stands, while mean tree diameter increased from 12 to 32 cm between those same stages. Furthermore, understory vegetation shifted from herbaceous to shrub and understory tree species. Oregon ash had the greatest relative dominance of all tree species at all stages of structural development. Oregon white oak (Quercus garryana) was the only other tree species commonly found in forest canopies, though it was typically far less abundant than Oregon ash. Plots in which oak was present had a greater depth to soil mottling, indicating a lower depth to the annual high water table. Oregon ash was also the most commonly regenerating tree species in all stages of structural development, and nearly 70% of ash regeneration was vegetative. Other tree regeneration was typically restricted to understory species, especially cascara (Rhamnus purshiana) in forests and hawthorn (Crataegus spp.) in savannas. Forest structural diversity increased between each stage of development. In total, 216 plant species were identified. Of these, 147 were found in forest plots. Community composition differed significantly between forests and savannas, and between "young" (stem exclusion and understory initiation) plots and "old" (young multi-strata and old growth) plots. Nonmetric multidimensional scaling (NMS) indicated that, for all wetland plots, the environmental variables most highly correlated with community composition were CTWI scores and canopy cover. For forest plots only, NMS indicated that CTWI scores and stand density were the environmental variables most related to patterns in community composition. Species richness was not correlated with canopy cover, but was negatively correlated with CTWI scores. Exotic species cover was negatively correlated with canopy cover, but was not correlated with CTWI scores. Exotic species composition was dependent on both canopy cover and CTWI scores. On wet sites, reed canary grass (Phalaris arundinacea) was particularly abundant, and was associated with low species richness. On drier sites, common exotic species included trees and shrubs such as blackberries (Rubus spp.), exotic roses (Rosa spp.), single-seeded hawthorn (Crataegus monogyna), and common pear (Pyrus communis) as well as several grass and forb species. The results of this study suggest that, although overstory tree communities are characterized by low diversity, Oregon ash forests are important for landscape-scale structural and plant community diversity in Willamette Valley wetlands. However, overstory tree communities lack diversity; Oregon ash appears to be both an early seral, colonizing species in open wetlands and a climax species that is capable of regenerating under a closed canopy. Few other trees are present regionally that are capable of maintaining a forested state in wetlands. Furthermore, closed canopy Oregon ash forests may suppress exotic species spread, and in the absence of management, overstory ash mortality may lead to increased exotic plant cover. Regardless of future forest health threats, intact Oregon ash forests, like other regional wetland-types, are currently few and limited in extent and should be considered a conservation priority. Close

• 4. [Article] Changing forest water yields in response to climate warming: results from long-term experimental watershed sites across North America

  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 the author(s) ...

  Citation × Citation Citation Abstract Copy Title: Changing forest water yields in response to climate warming: results from long-term experimental watershed sites across North America Author: Creed, Irena F., Jones, Julia A., et al., Spargo, Adam T. 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 the author(s) and published by John Wiley & Sons Ltd. The published article can be found at: http://onlinelibrary.wiley.com/journal/10.1111/%28ISSN%291365-2486. Title: Changing forest water yields in response to climate warming: results from long-term experimental watershed sites across North America Author: Creed, Irena F., Jones, Julia A., et al., Spargo, Adam T. 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 the author(s) and published by John Wiley & Sons Ltd. The published article can be found at: http://onlinelibrary.wiley.com/journal/10.1111/%28ISSN%291365-2486. Close