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• 21. [Article] Seed and establishment limitation contribute to long-term native forb declines in California grasslands

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

  Citation × Citation Citation Abstract Copy Title: Seed and establishment limitation contribute to long-term native forb declines in California grasslands Author: Brandt, Angela J., Seabloom, Eric 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.esa.org/. Title: Seed and establishment limitation contribute to long-term native forb declines in California grasslands Author: Brandt, Angela J., Seabloom, Eric 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.esa.org/. Close

• 22. [Article] Germination and establishment in Willamette Valley native prairie plants

  Native plants provide many ecosystem services while also having great beauty and are a valuable component of the landscape. As use of these plants in habitat restoration, agricultural insectary plantings, ...

  Citation × Citation Citation Abstract Copy Title: Germination and establishment in Willamette Valley native prairie plants Author: Russell, Michael C. Native plants provide many ecosystem services while also having great beauty and are a valuable component of the landscape. As use of these plants in habitat restoration, agricultural insectary plantings, and home landscapes increases so does demand for information on the basic biology of a group of species that have only been sparingly studied. Germination is one of the first major events in a plant’s life cycle and can be affected by both the physiological state of the seed and the environment the seed is in. Seeds can become dormant and may require some environmental signal for germination. I conducted a series of germination trials on a set of Willamette Valley native prairie plants to test whether cold stratification or various scarification treatments can be used to break seed dormancy. I used each species’ responses to classify the dormancy type of each species. The environmental conditions that the seed experiences also affect germination. The effect of temperature on germination was studied using a temperature gradient table. Seeds were tested to characterize species based on the temperature range at which its seeds can germinate. Germination in some species was bounded within clearly defined temperature limits, while germination in others occurred over the full range of studied temperatures. The germination data were modeled with linear regression to create standard estimates for the physiological limits of each species to allow for comparisons between the species. After seeds germinate the initial stages of establishment can have great implications on the survival of the plant. A greenhouse experiment was conducted to study the competitive interactions of six of the species. Plants were grown together in pots for 90 days and biomass collected. The mean competitive effect and competitive response of each species was calculated and the results were regressed against each species' values for several physiological traits that were available from the literature. The experiment found that species with higher relative growth rates had greater competitive effects on other species. The first two experiments measured physiological traits of several Oregon native species. The third demonstrated the utility of standardized traits in predicting ecological behavior. This trait based approach has great potential as a tool for comparing ecological similarities and differences across different ecosystems and different species pools. Title: Germination and establishment in Willamette Valley native prairie plants Author: Russell, Michael C. Native plants provide many ecosystem services while also having great beauty and are a valuable component of the landscape. As use of these plants in habitat restoration, agricultural insectary plantings, and home landscapes increases so does demand for information on the basic biology of a group of species that have only been sparingly studied. Germination is one of the first major events in a plant’s life cycle and can be affected by both the physiological state of the seed and the environment the seed is in. Seeds can become dormant and may require some environmental signal for germination. I conducted a series of germination trials on a set of Willamette Valley native prairie plants to test whether cold stratification or various scarification treatments can be used to break seed dormancy. I used each species’ responses to classify the dormancy type of each species. The environmental conditions that the seed experiences also affect germination. The effect of temperature on germination was studied using a temperature gradient table. Seeds were tested to characterize species based on the temperature range at which its seeds can germinate. Germination in some species was bounded within clearly defined temperature limits, while germination in others occurred over the full range of studied temperatures. The germination data were modeled with linear regression to create standard estimates for the physiological limits of each species to allow for comparisons between the species. After seeds germinate the initial stages of establishment can have great implications on the survival of the plant. A greenhouse experiment was conducted to study the competitive interactions of six of the species. Plants were grown together in pots for 90 days and biomass collected. The mean competitive effect and competitive response of each species was calculated and the results were regressed against each species' values for several physiological traits that were available from the literature. The experiment found that species with higher relative growth rates had greater competitive effects on other species. The first two experiments measured physiological traits of several Oregon native species. The third demonstrated the utility of standardized traits in predicting ecological behavior. This trait based approach has great potential as a tool for comparing ecological similarities and differences across different ecosystems and different species pools. Close

• 23. [Article] Habitat relationships of native and non-native fishes of the Willamette River, Oregon

  The Willamette River flows north between the Cascade Mountains and Coast Range of western Oregon within a 29,728-km² basin. The fish community in the geologically young basin consists of 36 native species, ...

  Citation × Citation Citation Abstract Copy Title: Habitat relationships of native and non-native fishes of the Willamette River, Oregon Author: Williams, Joshua E. (Joshua Everett) The Willamette River flows north between the Cascade Mountains and Coast Range of western Oregon within a 29,728-km² basin. The fish community in the geologically young basin consists of 36 native species, but introductions of non-native fishes have added 33 additional species for a total of 69 fish species. During the summers of 2011-2013, fish distributions were sampled from the confluence of the McKenzie River downstream to the confluence of the Columbia River to assess: (1) fish community composition, (2) differences in community composition between mainstem river and slough habitats, and (3) relationships between native and non-native fish species and physical habitat characteristics. In addition, a 182-ha seasonally inundated floodplain habitat along the middle Willamette River was sampled during winter 2011 through spring 2012 to assess: (1) fish community composition, (2) spawning and rearing, and (3) timing of use and movement by fish species. Throughout the three years of longitudinal sampling, 36,586 fish were collected comprising 41 species, 22 native and 19 non-native. Overall, native fish represented 93% of the total fish sampled. Higher numbers of fish were collected in the upper river, and higher proportions of those fish were native species. Though non-native fish were more common in slough habitats than mainstem sties, the majority of fish collected in both habitat types were native. The strongest environmental predictors of fish community were quantitative measures of longitudinal distance, velocity, depth, percent macrophyte cover and percent embeddedness. Habitat type (slough versus mainstem) was also a significant predictor. Native fish species exhibited greater variability in habitat relationships than non-native fishes, though several native species were strongly associated with specific environmental attributes. Non-native species were more associated with slough habitats and sites with high amount of macrophyte growth and embedded substrates. Overall, 25 species had a high fidelity to mainstem or slough habitats. Equal numbers of native species showed a fidelity to either mainstem or slough sites, but non-native species were significantly related only to slough habitats. In the seasonally inundated floodplain habitat, an estimated 43,000 fish were collected comprising 23 species; 12 native and 11 non-native. Of these 98.1% were native. The most common native species were threespine stickleback Gasterosteus aculeatus and peamouth Mylocheilus caurinus while the most common non-native species were bluegill Lepomis macrochirus and western mosquitofish Gambusia affinus. Several species used the inundated floodplain for spawning and rearing, particularly threespine stickleback, peamouth and western mosquitofish. With the exception of young-of-year threespine stickleback, native species were collected mostly in the beginning and middle of the sampling period while non-native species were collected in the latter portion of the sampling. The Willamette River Basin has a long history of environmental modification. Understanding relationships of a broad range of species to their environment and to each other provides a technical foundation for ecosystem based management by state and federal agencies, local municipalities, and private landowners. The need for ecosystem based management is vital for future conservation and recovery of large river floodplain ecosystems. Title: Habitat relationships of native and non-native fishes of the Willamette River, Oregon Author: Williams, Joshua E. (Joshua Everett) The Willamette River flows north between the Cascade Mountains and Coast Range of western Oregon within a 29,728-km² basin. The fish community in the geologically young basin consists of 36 native species, but introductions of non-native fishes have added 33 additional species for a total of 69 fish species. During the summers of 2011-2013, fish distributions were sampled from the confluence of the McKenzie River downstream to the confluence of the Columbia River to assess: (1) fish community composition, (2) differences in community composition between mainstem river and slough habitats, and (3) relationships between native and non-native fish species and physical habitat characteristics. In addition, a 182-ha seasonally inundated floodplain habitat along the middle Willamette River was sampled during winter 2011 through spring 2012 to assess: (1) fish community composition, (2) spawning and rearing, and (3) timing of use and movement by fish species. Throughout the three years of longitudinal sampling, 36,586 fish were collected comprising 41 species, 22 native and 19 non-native. Overall, native fish represented 93% of the total fish sampled. Higher numbers of fish were collected in the upper river, and higher proportions of those fish were native species. Though non-native fish were more common in slough habitats than mainstem sties, the majority of fish collected in both habitat types were native. The strongest environmental predictors of fish community were quantitative measures of longitudinal distance, velocity, depth, percent macrophyte cover and percent embeddedness. Habitat type (slough versus mainstem) was also a significant predictor. Native fish species exhibited greater variability in habitat relationships than non-native fishes, though several native species were strongly associated with specific environmental attributes. Non-native species were more associated with slough habitats and sites with high amount of macrophyte growth and embedded substrates. Overall, 25 species had a high fidelity to mainstem or slough habitats. Equal numbers of native species showed a fidelity to either mainstem or slough sites, but non-native species were significantly related only to slough habitats. In the seasonally inundated floodplain habitat, an estimated 43,000 fish were collected comprising 23 species; 12 native and 11 non-native. Of these 98.1% were native. The most common native species were threespine stickleback Gasterosteus aculeatus and peamouth Mylocheilus caurinus while the most common non-native species were bluegill Lepomis macrochirus and western mosquitofish Gambusia affinus. Several species used the inundated floodplain for spawning and rearing, particularly threespine stickleback, peamouth and western mosquitofish. With the exception of young-of-year threespine stickleback, native species were collected mostly in the beginning and middle of the sampling period while non-native species were collected in the latter portion of the sampling. The Willamette River Basin has a long history of environmental modification. Understanding relationships of a broad range of species to their environment and to each other provides a technical foundation for ecosystem based management by state and federal agencies, local municipalities, and private landowners. The need for ecosystem based management is vital for future conservation and recovery of large river floodplain ecosystems. Close

• 24. [Article] The effects of native plants on non-native plant abundance in a restoration setting : differences among native species and the predictive ability of species traits

  Reducing the cover of non-native species is one of the challenges of ecosystem restoration. The goal of this study is to identify native species traits that will increase native species cover and reduce ...

  Citation × Citation Citation Abstract Copy Title: The effects of native plants on non-native plant abundance in a restoration setting : differences among native species and the predictive ability of species traits Author: Goodridge, Jennifer M. Reducing the cover of non-native species is one of the challenges of ecosystem restoration. The goal of this study is to identify native species traits that will increase native species cover and reduce non-native species cover in the first growing season at upland and wetland prairie restoration sites. Native and non-native prairie species were planted in the fall and harvested the following summer at both an upland and a wetland site. Native species traits, such as plant weight, leaf area, relative growth rate, leaf area ratio, leaf weight ratio, net assimilation rate, and specific leaf area were measured under laboratory conditions for 7- and 21-day old seedlings. Germination rate (laboratory) and phenology (field) were also measured. At the upland site, species with a large 7-day plant weight and a high germination rate also had high native cover in the field (P<0.00l, R²=0.83). At the wetland site, high 21-day leaf area, low 21-day leaf weight ratio, and high net assimilation rate predicted increased native cover in the field (P<0.00l, R²=0.87). An abundance of natives, as measured by native cover, native biomass, and number of individuals, likely results in fewer resources (light, nutrients, and water) available for the non-native species growth resulting in a reduction in the non-native cover. Intrinsic traits of native species also predicted the field performance of non-native species, although the amount of variation explained was lower than the amount of variation explained in the models that predicted native cover. In the upland site, native species with high leaf weight ratio (21-day) tended to have lower non-native cover in their field plots (P=0.087, R²=0.23). In the wetland site, the native species traits that predict non-native cover were low 21-day leaf area and high 21-day leaf weight ratio (P<0.00l, R²=0.46). These traits were similar to those that predicted native species cover at the wetland site. This study demonstrates the ability of species traits to predict field performance. Predictive models were generated using native species traits to select species for restoration that will increase native cover and decrease non-native cover in the first growing season. Traits can be measured for species not included in this study and the models generated can be used to predict the field performance of species at similar sites. Title: The effects of native plants on non-native plant abundance in a restoration setting : differences among native species and the predictive ability of species traits Author: Goodridge, Jennifer M. Reducing the cover of non-native species is one of the challenges of ecosystem restoration. The goal of this study is to identify native species traits that will increase native species cover and reduce non-native species cover in the first growing season at upland and wetland prairie restoration sites. Native and non-native prairie species were planted in the fall and harvested the following summer at both an upland and a wetland site. Native species traits, such as plant weight, leaf area, relative growth rate, leaf area ratio, leaf weight ratio, net assimilation rate, and specific leaf area were measured under laboratory conditions for 7- and 21-day old seedlings. Germination rate (laboratory) and phenology (field) were also measured. At the upland site, species with a large 7-day plant weight and a high germination rate also had high native cover in the field (P<0.00l, R²=0.83). At the wetland site, high 21-day leaf area, low 21-day leaf weight ratio, and high net assimilation rate predicted increased native cover in the field (P<0.00l, R²=0.87). An abundance of natives, as measured by native cover, native biomass, and number of individuals, likely results in fewer resources (light, nutrients, and water) available for the non-native species growth resulting in a reduction in the non-native cover. Intrinsic traits of native species also predicted the field performance of non-native species, although the amount of variation explained was lower than the amount of variation explained in the models that predicted native cover. In the upland site, native species with high leaf weight ratio (21-day) tended to have lower non-native cover in their field plots (P=0.087, R²=0.23). In the wetland site, the native species traits that predict non-native cover were low 21-day leaf area and high 21-day leaf weight ratio (P<0.00l, R²=0.46). These traits were similar to those that predicted native species cover at the wetland site. This study demonstrates the ability of species traits to predict field performance. Predictive models were generated using native species traits to select species for restoration that will increase native cover and decrease non-native cover in the first growing season. Traits can be measured for species not included in this study and the models generated can be used to predict the field performance of species at similar sites. Close

• 25. [Article] Native bee diversity and floral resource availability in two Willamette Valley Oregon ecosystems

  The importance of pollinators in native and managed landscapes is well known, and recent interest is directed towards investigating the role of native bees as providers of pollination ecosystem services. ...

  Citation × Citation Citation Abstract Copy Title: Native bee diversity and floral resource availability in two Willamette Valley Oregon ecosystems Author: Bergh, Jennifer E. The importance of pollinators in native and managed landscapes is well known, and recent interest is directed towards investigating the role of native bees as providers of pollination ecosystem services. Uncertainty about bee populations at global and local scales has prompted research and general interest in conservation of bee diversity. To sustain robust populations, bees need nesting habitat and quality forage resources. This thesis describes two studies related to the relationship between bee diversity and landscape floral resource availability in two Willamette Valley ecosystems: wet prairies and blueberry agroecosystems. The wetlands are florally diverse, heterogeneous, and temporally patchy in spring and summer, whereas blueberries are florally abundant during spring crop bloom with potentially fewer floral resources after berry set; the intention of these studies was to determine if the floral resources in each ecosystem were adequate to support robust native bee communities. For each site type, the bee fauna and associated melittophilous floral resources are described and characterized. In the studies, it was determined that bee diversity, and specifically bee abundance, was positively correlated with floral resources. This thesis presents the results of community analyses, floral resources that were identified as important forage sources, and a discussion of the relationship between landscape phenology and bee population dynamics in each ecosystem type. Implications and recommendations for landscape management to conserve and potentially enhance local native bee communities are discussed. Title: Native bee diversity and floral resource availability in two Willamette Valley Oregon ecosystems Author: Bergh, Jennifer E. The importance of pollinators in native and managed landscapes is well known, and recent interest is directed towards investigating the role of native bees as providers of pollination ecosystem services. Uncertainty about bee populations at global and local scales has prompted research and general interest in conservation of bee diversity. To sustain robust populations, bees need nesting habitat and quality forage resources. This thesis describes two studies related to the relationship between bee diversity and landscape floral resource availability in two Willamette Valley ecosystems: wet prairies and blueberry agroecosystems. The wetlands are florally diverse, heterogeneous, and temporally patchy in spring and summer, whereas blueberries are florally abundant during spring crop bloom with potentially fewer floral resources after berry set; the intention of these studies was to determine if the floral resources in each ecosystem were adequate to support robust native bee communities. For each site type, the bee fauna and associated melittophilous floral resources are described and characterized. In the studies, it was determined that bee diversity, and specifically bee abundance, was positively correlated with floral resources. This thesis presents the results of community analyses, floral resources that were identified as important forage sources, and a discussion of the relationship between landscape phenology and bee population dynamics in each ecosystem type. Implications and recommendations for landscape management to conserve and potentially enhance local native bee communities are discussed. Close

• 26. [Article] Vegetation response to prescribed fire in mountain big sagebrush ecosystems at Lava Beds National Monument, California

  Anthropogenic land use alterations such as livestock grazing and fire suppression have greatly altered sagebrush grasslands of the Great Basin, facilitating invasion of exotic annuals, increases in woody ...

  Citation × Citation Citation Abstract Copy Title: Vegetation response to prescribed fire in mountain big sagebrush ecosystems at Lava Beds National Monument, California Author: Ellsworth, Lisa M. Anthropogenic land use alterations such as livestock grazing and fire suppression have greatly altered sagebrush grasslands of the Great Basin, facilitating invasion of exotic annuals, increases in woody species, and losses of native species. Much of the current research surrounding wildland and prescribed fire in sagebrush dominated ecosystems has focused on a persistent belief that fire in sagebrush systems results in a loss of native flora and a trend toward dominance by exotic annuals. Fire was historically the dominant disturbance throughout the sagebrush steppe and the plant species that comprised these communities possess a variety of adaptations facilitating survival to the fire regime. In order to restore ecosystems, land managers will need to reintroduce natural ecosystem processes, including natural disturbance processes. To describe the response of these plant communities to fire, I examined the plant community response, seedbank response, and reproductive and density responses of three native bunchgrasses (Pseudoroegneria spicata, Achnatherum therberianum, and Elymus elymoides) as well as one native forb (Calochortus macrocarpus) following spring and fall prescribed fires at Lava Beds National Monument. Fires were applied to three Artemisia tridentata ssp. vaseyana (Mountain Big Sagebrush) plant communities with different land use and fire histories. These communities were different in composition ranging from a dominance of exotic annuals to dominance by native grasses, shrubs, and trees. Little is known about how prescribed fire affects the soil seed bank in sagebrush-dominated ecosystems. To address this, we quantified the emergence of Bromus tectorum (cheatgrass) seedlings as well as emergence of seedlings of functional groups (native forbs, bunchgrasses, and shrubs) in a seedbank germination study. At the invasive dominated site (Gillems Camp), we found 91% fewer B. tectorum seedlings germinated in spring burned sites than in controls immediately following spring prescribed burns. However, soils collected one-year following fire had 40% more B. tectorum germinants (8017 germinants/m [superscript 2]) than unburned controls (5132 germinants/m [superscript 2]). Following fall burns at this site there was a similar response, with a 56% immediate reduction in B. tectorum (as compared to unburned control) and a 59% increase in B. tectorum and 58% increase in exotic forb germinants one year following fires. There was an increase in native forb germination following spring burns (94%) and fall burns (45%) at a site dominated by native plants (Fleener Chimneys). Native bunchgrass seed germination declined following spring fire in sites dominated by sagebrush and native understory vegetation (79%), and in sites where Juniperus occidentalis (western juniper) and other woody species dominated (Merrill Caves) (71%). In invasive-dominated sites (Gillems Camp), there was a decrease in B. tectorum cover following both spring (81% decrease) and fall fires (82% decrease), and little native vegetation composition change. Shrub cover, made up predominantly of Chrysothamnus nauseosus, decreased following spring (95% decrease) and fall (93% decrease) fires. At the sagebrush, native understory site (Fleener Chimneys), there was a reduction in native bunchgrass cover (64% decrease), and an increase in native forbs (168% increase) following spring burns, with no changes following fall fires. At the juniper- woody dominated site (Merrill Caves), fire treatments resulted in a decrease in woody plant cover, with no immediate postfire differences seen in the herbaceous plant community. Density of bunchgrass species (Pseudoroegneria spicata, Achnatherum therberianum, Elymus elymoides) did not change following either spring or fall prescribed fire treatments. Fire enhanced flowering was not seen in C. macrocarpus following spring or fall burns at the native or juniper dominated sites. There was increased reproductive effort in native bunchgrass species following fires in all communities studied. Following spring fires at invasive dominated sites, there was a 245% increase in reproductive culms of P. spicata. Following fall fires in native dominated sites, we saw a 974% increase in reproductive culms of P. spicata and a 184% increase in reproductive culms of A. therberianum. Following fall fires at juniper-dominated sites, we saw in an increase in reproductive culms of P. spicata (678% increase), A. thurberianum (356% increase), and Elymus elymoides (209% increase). These results suggest that implementing prescribed fire in order to restore the natural disturbance regime in these fire-adapted ecosystems is beneficial to restoration and preservation of the native biota. Title: Vegetation response to prescribed fire in mountain big sagebrush ecosystems at Lava Beds National Monument, California Author: Ellsworth, Lisa M. Anthropogenic land use alterations such as livestock grazing and fire suppression have greatly altered sagebrush grasslands of the Great Basin, facilitating invasion of exotic annuals, increases in woody species, and losses of native species. Much of the current research surrounding wildland and prescribed fire in sagebrush dominated ecosystems has focused on a persistent belief that fire in sagebrush systems results in a loss of native flora and a trend toward dominance by exotic annuals. Fire was historically the dominant disturbance throughout the sagebrush steppe and the plant species that comprised these communities possess a variety of adaptations facilitating survival to the fire regime. In order to restore ecosystems, land managers will need to reintroduce natural ecosystem processes, including natural disturbance processes. To describe the response of these plant communities to fire, I examined the plant community response, seedbank response, and reproductive and density responses of three native bunchgrasses (Pseudoroegneria spicata, Achnatherum therberianum, and Elymus elymoides) as well as one native forb (Calochortus macrocarpus) following spring and fall prescribed fires at Lava Beds National Monument. Fires were applied to three Artemisia tridentata ssp. vaseyana (Mountain Big Sagebrush) plant communities with different land use and fire histories. These communities were different in composition ranging from a dominance of exotic annuals to dominance by native grasses, shrubs, and trees. Little is known about how prescribed fire affects the soil seed bank in sagebrush-dominated ecosystems. To address this, we quantified the emergence of Bromus tectorum (cheatgrass) seedlings as well as emergence of seedlings of functional groups (native forbs, bunchgrasses, and shrubs) in a seedbank germination study. At the invasive dominated site (Gillems Camp), we found 91% fewer B. tectorum seedlings germinated in spring burned sites than in controls immediately following spring prescribed burns. However, soils collected one-year following fire had 40% more B. tectorum germinants (8017 germinants/m [superscript 2]) than unburned controls (5132 germinants/m [superscript 2]). Following fall burns at this site there was a similar response, with a 56% immediate reduction in B. tectorum (as compared to unburned control) and a 59% increase in B. tectorum and 58% increase in exotic forb germinants one year following fires. There was an increase in native forb germination following spring burns (94%) and fall burns (45%) at a site dominated by native plants (Fleener Chimneys). Native bunchgrass seed germination declined following spring fire in sites dominated by sagebrush and native understory vegetation (79%), and in sites where Juniperus occidentalis (western juniper) and other woody species dominated (Merrill Caves) (71%). In invasive-dominated sites (Gillems Camp), there was a decrease in B. tectorum cover following both spring (81% decrease) and fall fires (82% decrease), and little native vegetation composition change. Shrub cover, made up predominantly of Chrysothamnus nauseosus, decreased following spring (95% decrease) and fall (93% decrease) fires. At the sagebrush, native understory site (Fleener Chimneys), there was a reduction in native bunchgrass cover (64% decrease), and an increase in native forbs (168% increase) following spring burns, with no changes following fall fires. At the juniper- woody dominated site (Merrill Caves), fire treatments resulted in a decrease in woody plant cover, with no immediate postfire differences seen in the herbaceous plant community. Density of bunchgrass species (Pseudoroegneria spicata, Achnatherum therberianum, Elymus elymoides) did not change following either spring or fall prescribed fire treatments. Fire enhanced flowering was not seen in C. macrocarpus following spring or fall burns at the native or juniper dominated sites. There was increased reproductive effort in native bunchgrass species following fires in all communities studied. Following spring fires at invasive dominated sites, there was a 245% increase in reproductive culms of P. spicata. Following fall fires in native dominated sites, we saw a 974% increase in reproductive culms of P. spicata and a 184% increase in reproductive culms of A. therberianum. Following fall fires at juniper-dominated sites, we saw in an increase in reproductive culms of P. spicata (678% increase), A. thurberianum (356% increase), and Elymus elymoides (209% increase). These results suggest that implementing prescribed fire in order to restore the natural disturbance regime in these fire-adapted ecosystems is beneficial to restoration and preservation of the native biota. Close

• 27. [Article] Drivers of plant community dynamics in sagebrush steppe ecosystems : cattle grazing, heat and water stress

  Sagebrush steppe ecosystems are one of the most widespread but endangered ecosystems in North America. A diverse array of human-related stressors has gradually compromised these ecosystems' resilience ...

  Citation × Citation Citation Abstract Copy Title: Drivers of plant community dynamics in sagebrush steppe ecosystems : cattle grazing, heat and water stress Author: Reisner, Michael D. Sagebrush steppe ecosystems are one of the most widespread but endangered ecosystems in North America. A diverse array of human-related stressors has gradually compromised these ecosystems' resilience to disturbance and invasion by Bromus tectorum (cheatgrass). The role of the foundational shrub Artemisia as a driver of herbaceous community structure and dynamics during this degradation process is poorly understood. Many of the individual factors driving B. tectorum invasions are well documented. However a predictive understanding of the relative importance of complex, interacting factors in the causal network of simultaneously occurring processes determining invasibility has proven elusive. I examined these issues at the landscape level across 75 sites capturing a range of soil and landscape properties and cattle grazing levels similar to those found across the Great Basin. Cumulative cattle herbivory stress levels were a predominant component of both the overlapping heat and water stress gradients driving the structure of Artemisia interactions with herbaceous species. Consistent with the stress gradient hypothesis, Artemisia facilitation of herbaceous species was most frequent and strongest at the highest stress levels, and competition was most frequent and strongest at the lowest stress levels. The two species with the highest competitive response abilities, Elymus elymoides and Poa secunda, showed the strongest facilitation at the upper limits of their stress tolerances. The structure of Artemisia interactions with the invasive B. tectorum was strikingly different than those with native bunchgrasses. Artemisia interactions with native bunchgrasses shifted from competition to facilitation with increasing heat, water, and herbivory stress, but its interactions remained competitive with B. tectorum along the entire stress gradient. Shifts in the structure of interactions between Artemisia and native bunchgrasses were associated with both an increase and decrease in community compositional and functional stability. I report the first evidence of native species facilitation decreasing community invasibility. Artemisia facilitation increased native bunchgrass composition, which reduced the magnitude of B. tectorum invasion in under-shrub compared to interspace communities. This decreased invasibility did not translate into lower invasibility at the community level because of the limited spatial scale over which such facilitation occurs. Artemisia facilitation increased community compositional and functional stability at intermediate stress levels but decreased community stability at high stress levels. Facilitation became a destabilizing force when native bunchgrass species became "obligate" beneficiaries, i.e. strongly dependent on Artemisia facilitation for their continued persistence in the community. Structural equation modeling assessed the structure of the causal network and relative importance of factors and processes predicted to drive community invasibility. The linchpin of ecosystem invasibility was the size of and connectivity between basal gaps in perennial vegetation, driven by shifts in the structure and spatial aggregation of the native bunchgrass community. Landscape orientation and soil physical properties determined inherent risk to invasion. Resident bunchgrass and biological soil crust communities provided biotic resistance to invasion by reducing the size of and connectivity between basal gaps and thereby limiting available resources and reducing safe sites for B. tectorum establishment. High levels of cattle grazing reduced ecosystem resilience by reducing native bunchgrass and biological soil crust abundance and altering bunchgrass community composition and facilitated B. tectorum invasion. Conserving and restoring resilience and resistance of these imperiled ecosystems will require reducing cumulative stress levels. As global climate change increases heat and water stress, reducing cumulative cattle grazing intensities by altering utilization rates and/or seasons of use may be the only effective means of accomplishing these goals. Title: Drivers of plant community dynamics in sagebrush steppe ecosystems : cattle grazing, heat and water stress Author: Reisner, Michael D. Sagebrush steppe ecosystems are one of the most widespread but endangered ecosystems in North America. A diverse array of human-related stressors has gradually compromised these ecosystems' resilience to disturbance and invasion by Bromus tectorum (cheatgrass). The role of the foundational shrub Artemisia as a driver of herbaceous community structure and dynamics during this degradation process is poorly understood. Many of the individual factors driving B. tectorum invasions are well documented. However a predictive understanding of the relative importance of complex, interacting factors in the causal network of simultaneously occurring processes determining invasibility has proven elusive. I examined these issues at the landscape level across 75 sites capturing a range of soil and landscape properties and cattle grazing levels similar to those found across the Great Basin. Cumulative cattle herbivory stress levels were a predominant component of both the overlapping heat and water stress gradients driving the structure of Artemisia interactions with herbaceous species. Consistent with the stress gradient hypothesis, Artemisia facilitation of herbaceous species was most frequent and strongest at the highest stress levels, and competition was most frequent and strongest at the lowest stress levels. The two species with the highest competitive response abilities, Elymus elymoides and Poa secunda, showed the strongest facilitation at the upper limits of their stress tolerances. The structure of Artemisia interactions with the invasive B. tectorum was strikingly different than those with native bunchgrasses. Artemisia interactions with native bunchgrasses shifted from competition to facilitation with increasing heat, water, and herbivory stress, but its interactions remained competitive with B. tectorum along the entire stress gradient. Shifts in the structure of interactions between Artemisia and native bunchgrasses were associated with both an increase and decrease in community compositional and functional stability. I report the first evidence of native species facilitation decreasing community invasibility. Artemisia facilitation increased native bunchgrass composition, which reduced the magnitude of B. tectorum invasion in under-shrub compared to interspace communities. This decreased invasibility did not translate into lower invasibility at the community level because of the limited spatial scale over which such facilitation occurs. Artemisia facilitation increased community compositional and functional stability at intermediate stress levels but decreased community stability at high stress levels. Facilitation became a destabilizing force when native bunchgrass species became "obligate" beneficiaries, i.e. strongly dependent on Artemisia facilitation for their continued persistence in the community. Structural equation modeling assessed the structure of the causal network and relative importance of factors and processes predicted to drive community invasibility. The linchpin of ecosystem invasibility was the size of and connectivity between basal gaps in perennial vegetation, driven by shifts in the structure and spatial aggregation of the native bunchgrass community. Landscape orientation and soil physical properties determined inherent risk to invasion. Resident bunchgrass and biological soil crust communities provided biotic resistance to invasion by reducing the size of and connectivity between basal gaps and thereby limiting available resources and reducing safe sites for B. tectorum establishment. High levels of cattle grazing reduced ecosystem resilience by reducing native bunchgrass and biological soil crust abundance and altering bunchgrass community composition and facilitated B. tectorum invasion. Conserving and restoring resilience and resistance of these imperiled ecosystems will require reducing cumulative stress levels. As global climate change increases heat and water stress, reducing cumulative cattle grazing intensities by altering utilization rates and/or seasons of use may be the only effective means of accomplishing these goals. Close

• 28. [Article] Native wildlife species (Pseudacris regilla) utilizing invasive-dominated habitat in a highly disturbed ecosystem

  The Pacific Treefrog (Pseudacris regilla) is commonly encountered throughout the Pacific Northwest and can be an indicator for ecosystem health. At each life stage P. regilla utilizes a different habitat ...

  Citation × Citation Citation Abstract Copy Title: Native wildlife species (Pseudacris regilla) utilizing invasive-dominated habitat in a highly disturbed ecosystem Author: Epperly, Haley K. The Pacific Treefrog (Pseudacris regilla) is commonly encountered throughout the Pacific Northwest and can be an indicator for ecosystem health. At each life stage P. regilla utilizes a different habitat and therefore it is important to understand habitat use at all life stages to properly manage the ecosystem, however, few studies have been conducted on the juvenile form. To determine juvenile P. regilla riparian habitat use, and thus create appropriate habitat management plans, field work must be conducted. Transect surveys were conducted at two highly disturbed ephemeral ponds with a variety of open and dense vegetative riparian habitats in the Willamette Valley, Oregon. P. regilla was found in the highest abundance in habitat shaded by a thin border of Oregon Ash around the pond perimeter, and was composed mainly of Himalayan blackberry (Rubus armeniacus). This habitat provided a moist region where P. regilla could avoid desiccation and possibly predation. Rubus armeniacus is non-native and often found in highly disturbed ecosystems. Pseudacris regilla’s use of R. armeniacus as habitat suggests that P. regilla is a generalist species capable of utilizing invasive plant species to its advantage. Future research is needed comparing P. regilla habitat use in invasive-dominated verse native-dominated ephemeral ponds. Title: Native wildlife species (Pseudacris regilla) utilizing invasive-dominated habitat in a highly disturbed ecosystem Author: Epperly, Haley K. The Pacific Treefrog (Pseudacris regilla) is commonly encountered throughout the Pacific Northwest and can be an indicator for ecosystem health. At each life stage P. regilla utilizes a different habitat and therefore it is important to understand habitat use at all life stages to properly manage the ecosystem, however, few studies have been conducted on the juvenile form. To determine juvenile P. regilla riparian habitat use, and thus create appropriate habitat management plans, field work must be conducted. Transect surveys were conducted at two highly disturbed ephemeral ponds with a variety of open and dense vegetative riparian habitats in the Willamette Valley, Oregon. P. regilla was found in the highest abundance in habitat shaded by a thin border of Oregon Ash around the pond perimeter, and was composed mainly of Himalayan blackberry (Rubus armeniacus). This habitat provided a moist region where P. regilla could avoid desiccation and possibly predation. Rubus armeniacus is non-native and often found in highly disturbed ecosystems. Pseudacris regilla’s use of R. armeniacus as habitat suggests that P. regilla is a generalist species capable of utilizing invasive plant species to its advantage. Future research is needed comparing P. regilla habitat use in invasive-dominated verse native-dominated ephemeral ponds. Close

• 29. [Article] Non-Native Plant Invasion along Elevation and Canopy Closure Gradients in a Middle Rocky Mountain Ecosystem

  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 article was published by the Public Library ...

  Citation × Citation Citation Abstract Copy Title: Non-Native Plant Invasion along Elevation and Canopy Closure Gradients in a Middle Rocky Mountain Ecosystem Author: Parks, Catherine G., DelCurto, Tim, Mata-González, Ricardo, Naylor, Bridgett J., McCune, Bruce, Averett, Joshua P. 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 article was published by the Public Library of Science and is in the public domain. The published article can be found at: http://www.plosone.org/ Title: Non-Native Plant Invasion along Elevation and Canopy Closure Gradients in a Middle Rocky Mountain Ecosystem Author: Parks, Catherine G., DelCurto, Tim, Mata-González, Ricardo, Naylor, Bridgett J., McCune, Bruce, Averett, Joshua P. 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 article was published by the Public Library of Science and is in the public domain. The published article can be found at: http://www.plosone.org/ Close

• 30. [Article] The potential of dynamic segmentation for aquatic ecosystem management : Pacific lamprey decline in the native lands of the Confederated Tribes of Siletz Indians (Oregon, USA)

  The Lamprey Eel Decline project conducted by the Confederated Tribes of Siletz Indians (CTSI) combined traditional ecological knowledge, scientific research and geographic information science. CTSI wanted ...

  Citation × Citation Citation Abstract Copy Title: The potential of dynamic segmentation for aquatic ecosystem management : Pacific lamprey decline in the native lands of the Confederated Tribes of Siletz Indians (Oregon, USA) Author: Palacios, Kelly C. The Lamprey Eel Decline project conducted by the Confederated Tribes of Siletz Indians (CTSI) combined traditional ecological knowledge, scientific research and geographic information science. CTSI wanted to learn why the Pacific lamprey (Lampetra tridentata), a culturally and ecologically important species, was declining in the streams within their native land area. The project included interviewing native elders, characterizing stream habitat, monitoring water quality, creating a geographic information system (GIS) and educating tribal members on the cultural and ecological importance of the Pacific lamprey. Dynamic segmentation, a GIS data structure, was used to link standard stream survey data on the river unit scale to a base stream coverage (1:24,000). Dynamic segmentation efficiently associates georeferenced data to a linear feature, thus allowing the data to be readily assessable on desktop computer systems. To be more useful to the tribal and local resource managers, it is recommended that these GIS coverages of aquatic habitat should be used in conjunction with additional data coverages and basic regional models for watershed analysis and better management of aquatic ecosystems. Title: The potential of dynamic segmentation for aquatic ecosystem management : Pacific lamprey decline in the native lands of the Confederated Tribes of Siletz Indians (Oregon, USA) Author: Palacios, Kelly C. The Lamprey Eel Decline project conducted by the Confederated Tribes of Siletz Indians (CTSI) combined traditional ecological knowledge, scientific research and geographic information science. CTSI wanted to learn why the Pacific lamprey (Lampetra tridentata), a culturally and ecologically important species, was declining in the streams within their native land area. The project included interviewing native elders, characterizing stream habitat, monitoring water quality, creating a geographic information system (GIS) and educating tribal members on the cultural and ecological importance of the Pacific lamprey. Dynamic segmentation, a GIS data structure, was used to link standard stream survey data on the river unit scale to a base stream coverage (1:24,000). Dynamic segmentation efficiently associates georeferenced data to a linear feature, thus allowing the data to be readily assessable on desktop computer systems. To be more useful to the tribal and local resource managers, it is recommended that these GIS coverages of aquatic habitat should be used in conjunction with additional data coverages and basic regional models for watershed analysis and better management of aquatic ecosystems. Close