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• 1. [Article] Final Report 1994-1997: Effects of Fire, Mowing, and Mowing with Herbicide on Native Prairie of Baskett Butte, Baskett Slough NWR

  We report results from a field experiment evaluating the effectiveness of mowing, mowing and herbicides, and burning on woody plants, key native and non-native grasses and forbs, and the Fender’s blue ...

  Citation × Citation Citation Abstract Copy Title: Final Report 1994-1997: Effects of Fire, Mowing, and Mowing with Herbicide on Native Prairie of Baskett Butte, Baskett Slough NWR Author: Wilson, Mark V., Clark, Deborah Louise, 1950- We report results from a field experiment evaluating the effectiveness of mowing, mowing and herbicides, and burning on woody plants, key native and non-native grasses and forbs, and the Fender’s blue butterfly. The goal was to find a technique that controlled woody pest plants without harming native species or promoting non-native species. Three years after the initial manipulations, all treatments significantly reduced woody plant cover. Mowing promoted the group of measured native grasses without promoting non-native species. In contrast, burning had mixed effects on herbaceous species, promoting growth for some species and decreasing growth for others. Each treatment, particularly mowing, caused local increases in numbers of Fender’s blue butterfly egg masses, probably because lupines invigorated by treatments attracted ovipositing females. Although prescribed burning seemed to kill larvae, treated areas still accumulated more eggs masses than in controls. Three years after the start of manipulations, mowing was the most effective overall treatment for controlling woody plants, increasing native species abundance without promoting non-native species, and increasing Fender’s blue butterfly numbers. We recommend mowing for restoring similar habitats. Prescribed burning would also be an effective choice for habitat restoration. Title: Final Report 1994-1997: Effects of Fire, Mowing, and Mowing with Herbicide on Native Prairie of Baskett Butte, Baskett Slough NWR Author: Wilson, Mark V., Clark, Deborah Louise, 1950- We report results from a field experiment evaluating the effectiveness of mowing, mowing and herbicides, and burning on woody plants, key native and non-native grasses and forbs, and the Fender’s blue butterfly. The goal was to find a technique that controlled woody pest plants without harming native species or promoting non-native species. Three years after the initial manipulations, all treatments significantly reduced woody plant cover. Mowing promoted the group of measured native grasses without promoting non-native species. In contrast, burning had mixed effects on herbaceous species, promoting growth for some species and decreasing growth for others. Each treatment, particularly mowing, caused local increases in numbers of Fender’s blue butterfly egg masses, probably because lupines invigorated by treatments attracted ovipositing females. Although prescribed burning seemed to kill larvae, treated areas still accumulated more eggs masses than in controls. Three years after the start of manipulations, mowing was the most effective overall treatment for controlling woody plants, increasing native species abundance without promoting non-native species, and increasing Fender’s blue butterfly numbers. We recommend mowing for restoring similar habitats. Prescribed burning would also be an effective choice for habitat restoration. Close

• 2. [Article] Final Report: Controlling Tall Oatgrass in Fender’s Blue Butterfly Habitats

  We report final results from a five-year field experiment evaluating the effects of different mowing regimes on groups of native and non-native grasses and forbs. The study site was a degraded prairie ...

  Citation × Citation Citation Abstract Copy Title: Final Report: Controlling Tall Oatgrass in Fender’s Blue Butterfly Habitats Author: Wilson, Mark V., Clark, Deborah Louise, 1950- We report final results from a five-year field experiment evaluating the effects of different mowing regimes on groups of native and non-native grasses and forbs. The study site was a degraded prairie at Baskett Slough National Wildlife Refuge dominated by the pest plant Arrhenatherum elatius (tall oatgrass). Mowing treatments differed in time of year they were applied, mowing height, and removal of cut material. Treatments started in 1994 and continued through 1998. Title: Final Report: Controlling Tall Oatgrass in Fender’s Blue Butterfly Habitats Author: Wilson, Mark V., Clark, Deborah Louise, 1950- We report final results from a five-year field experiment evaluating the effects of different mowing regimes on groups of native and non-native grasses and forbs. The study site was a degraded prairie at Baskett Slough National Wildlife Refuge dominated by the pest plant Arrhenatherum elatius (tall oatgrass). Mowing treatments differed in time of year they were applied, mowing height, and removal of cut material. Treatments started in 1994 and continued through 1998. Close

• 3. [Article] Final report: Restoration of Fender’s blue butterfly and its prairie ecosystem: Management applications of fire to Baskett Slough NWR

  We tested the recolonization ability of the Fender’s blue butterfly and monitored the vegetation response to a management-scale prescribed fire at the Baskett Slough National Wildlife Refuge, western Oregon. ...

  Citation × Citation Citation Abstract Copy Title: Final report: Restoration of Fender’s blue butterfly and its prairie ecosystem: Management applications of fire to Baskett Slough NWR Author: Wilson, Mark V., Clark, Deborah Louise, 1950- We tested the recolonization ability of the Fender’s blue butterfly and monitored the vegetation response to a management-scale prescribed fire at the Baskett Slough National Wildlife Refuge, western Oregon. The prescribed fire successfully cut shrub cover in half, but also reduced the size of Festuca roemeri, a dominant native grass. Although the fire killed all Fender’s blue butterfly larvae, as expected, adult females were able to recolonize the burned area from a nearby, unburned patch. These results support predictions that the Fender’s blue butterfly can recolonize burned areas for a distance of at least 100 m. Title: Final report: Restoration of Fender’s blue butterfly and its prairie ecosystem: Management applications of fire to Baskett Slough NWR Author: Wilson, Mark V., Clark, Deborah Louise, 1950- We tested the recolonization ability of the Fender’s blue butterfly and monitored the vegetation response to a management-scale prescribed fire at the Baskett Slough National Wildlife Refuge, western Oregon. The prescribed fire successfully cut shrub cover in half, but also reduced the size of Festuca roemeri, a dominant native grass. Although the fire killed all Fender’s blue butterfly larvae, as expected, adult females were able to recolonize the burned area from a nearby, unburned patch. These results support predictions that the Fender’s blue butterfly can recolonize burned areas for a distance of at least 100 m. Close

• 4. [Article] Effects of Soil Nutrients and Fire on Seedling Establishment of Native Prairie Species

  We sought to determine 1) the relationship between seedling establishment rates of target native prairie species and field levels of three soil nutrients (phosphate, nitrate, and ammonium) recorded in ...

  Citation × Citation Citation Abstract Copy Title: Effects of Soil Nutrients and Fire on Seedling Establishment of Native Prairie Species Author: Clark, Deborah Louise, 1950- We sought to determine 1) the relationship between seedling establishment rates of target native prairie species and field levels of three soil nutrients (phosphate, nitrate, and ammonium) recorded in fall, winter, and summer, 2) the effect of fire on these three nutrients, and 3) the overall effect of fire on seedling establishment rates of the target native prairie species. Seedling establishment rates were not significantly correlated with soil nitrate or ammonium. Phosphate was significantly correlated with seedling establishment rates but the direction and strength of the relationship depended on the species, with three species showing positive relationships and three species showing negative relationships. Soil phosphate increased significantly in the burned plots compared to the unburned plots, soil ammonium decreased significantly in the burned plots, and soil nitrate showed no significant differences. These nutrient patterns successfully predicted the overall fire effects on seedling establishment in a separate experiment. The three species with positive correlations between seedling establishment and phosphate had greater seedling establishment rates in the burned plots compared to the unburned plots (two significantly, P≤0.1), and the three species with negative correlations had fewer seeds establish in the burned plots (two significantly (P ≤ 0.1). Title: Effects of Soil Nutrients and Fire on Seedling Establishment of Native Prairie Species Author: Clark, Deborah Louise, 1950- We sought to determine 1) the relationship between seedling establishment rates of target native prairie species and field levels of three soil nutrients (phosphate, nitrate, and ammonium) recorded in fall, winter, and summer, 2) the effect of fire on these three nutrients, and 3) the overall effect of fire on seedling establishment rates of the target native prairie species. Seedling establishment rates were not significantly correlated with soil nitrate or ammonium. Phosphate was significantly correlated with seedling establishment rates but the direction and strength of the relationship depended on the species, with three species showing positive relationships and three species showing negative relationships. Soil phosphate increased significantly in the burned plots compared to the unburned plots, soil ammonium decreased significantly in the burned plots, and soil nitrate showed no significant differences. These nutrient patterns successfully predicted the overall fire effects on seedling establishment in a separate experiment. The three species with positive correlations between seedling establishment and phosphate had greater seedling establishment rates in the burned plots compared to the unburned plots (two significantly, P≤0.1), and the three species with negative correlations had fewer seeds establish in the burned plots (two significantly (P ≤ 0.1). Close

• 5. [Article] Recommendations for Control of Tall Oatgrass, Poison Oak, and Rose in Willamette Valley Upland Prairies

  Native upland prairies, which once dominated the landscape of the Willamette Valley, are considered among the rarest of Oregon's ecosystems. Even though only remnants remain today, they harbor many rare ...

  Citation × Citation Citation Abstract Copy Title: Recommendations for Control of Tall Oatgrass, Poison Oak, and Rose in Willamette Valley Upland Prairies Author: Wilson, Mark V., Clark, Deborah Louise, 1950- Native upland prairies, which once dominated the landscape of the Willamette Valley, are considered among the rarest of Oregon's ecosystems. Even though only remnants remain today, they harbor many rare and endangered species such as the Fender's blue butterfly and its host plant, Kincaid’s lupine. Invasion of remnant prairies by woody plants and weedy non-native herbaceous species is of great concern to agencies and managers responsible for conserving these native ecosystems. Available methods for the control of these pests include herbicides, biological control, prescribed burning, and mowing. This report first reviews the literature on the control of tall oatgrass and the shrubs poison oak and rose. Each of these species is an important threat to Willamette Valley upland prairies. We then presents recommendations. For control of tall oatgrass, we recommend for most situations mowing in late spring or early summer. Mowing height should be just above most of the foliage of native plants to be protected (typically 10 cm - 15 cm). In areas with Kincaid’s lupine and Fender’s blue butterfly, mowing should be delayed until July, after the flowering and flight seasons. For control of prairie shrubs, we recommend further studies to evaluate herbicide effectiveness against the target shrubs and safety for non-target native plants and animals. If herbicide use is unavailable, we recommend burning or mowing. All burning or mowing treatments should be repeated, perhaps indefinitely, to maintain pest plant control. Title: Recommendations for Control of Tall Oatgrass, Poison Oak, and Rose in Willamette Valley Upland Prairies Author: Wilson, Mark V., Clark, Deborah Louise, 1950- Native upland prairies, which once dominated the landscape of the Willamette Valley, are considered among the rarest of Oregon's ecosystems. Even though only remnants remain today, they harbor many rare and endangered species such as the Fender's blue butterfly and its host plant, Kincaid’s lupine. Invasion of remnant prairies by woody plants and weedy non-native herbaceous species is of great concern to agencies and managers responsible for conserving these native ecosystems. Available methods for the control of these pests include herbicides, biological control, prescribed burning, and mowing. This report first reviews the literature on the control of tall oatgrass and the shrubs poison oak and rose. Each of these species is an important threat to Willamette Valley upland prairies. We then presents recommendations. For control of tall oatgrass, we recommend for most situations mowing in late spring or early summer. Mowing height should be just above most of the foliage of native plants to be protected (typically 10 cm - 15 cm). In areas with Kincaid’s lupine and Fender’s blue butterfly, mowing should be delayed until July, after the flowering and flight seasons. For control of prairie shrubs, we recommend further studies to evaluate herbicide effectiveness against the target shrubs and safety for non-target native plants and animals. If herbicide use is unavailable, we recommend burning or mowing. All burning or mowing treatments should be repeated, perhaps indefinitely, to maintain pest plant control. Close

• 6. [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

• 7. [Article] Controlling woody vegetation in wetland prairies, 1994-1999

  Wetland prairies of the Willamette Valley, among the rarest of Oregon’s ecosystems, are threatened by invasion of woody species and non-native pest species. Because fire has been important in maintaining ...

  Citation × Citation Citation Abstract Copy Title: Controlling woody vegetation in wetland prairies, 1994-1999 Author: Wilson, Mark V., Clark, Deborah Louise, 1950- Wetland prairies of the Willamette Valley, among the rarest of Oregon’s ecosystems, are threatened by invasion of woody species and non-native pest species. Because fire has been important in maintaining Willamette Valley prairies for at least 1000 years, prescribed burning is a top choice of managers for preventing encroachment of woody species. However, the effects of prescribed burning on present day wetland prairie communities, with their mix of native and non-native species, are not clear. Moreover, because strict governmental requirements for smoke management hinder prescribed burning, natural-area managers are considering alternatives to fire, like mowing and hand removal of woody plants. The present study explored the ecological interactions of a wetland prairie by experimentally testing the responses of burning, hand-removal of woody species, and mowing with removal of cut material on woody plants and key native and non-native grasses and forbs. We evaluated these perturbations for their effectiveness in meeting management objectives of reducing abundance of woody species, reducing or preventing an increase in abundance of nonnative pest species, and increasing or at least maintaining native species’ abundance. After three treatments periods (1994, 1996, and 1998) the following patterns emerged: • Woody species Burning and hand-removal consistently caused the greatest reduction in cover of woody species. Mowing with removal of cut material did not reduce the abundance of woody species compared to the control. As woody plant cover decreased, plant mortality increased, indicating that treatments influenced woody plant cover at least partially through changes in survival. • Native herbaceous species All management treatments consistently failed to significantly increase the cover of Deschampsia cespitosa, while burning decreased the number of inflorescences. As a group, native graminoid flowering consistently showed no significant responses to the management treatments. Although burning and hand-removal significantly increased the cover of native forbs as group after the second treatment period in 1997, native forbs showed no significant responses to treatments in 1999. • Non-native herbaceous species Response of non-native forb cover to management treatments has been inconsistent during the five year study period with no significant differences in 1995, significant reductions by burning and hand-removal in 1997, and increases with mowing in 1997. Mowing consistently increased flowering of nonnative graminoids as a group. Overall no treatment was clearly superior in fulfilling restoration objectives. Burning was effective in reducing woody cover and did not promote non-native herbaceous, but it reduced the flowering the dominant native grass, Deschampsia cespitosa. Hand-removal woody species was also effective at reducing woody cover and sometimes promoted the abundance of some native species at different times, but it also at times promoted non-native herbaceous species. Because mowing with removal of cut material was ineffective in reducing woody cover and tended to promote non-native herbaceous species, this treatment is not a recommended management strategy. Title: Controlling woody vegetation in wetland prairies, 1994-1999 Author: Wilson, Mark V., Clark, Deborah Louise, 1950- Wetland prairies of the Willamette Valley, among the rarest of Oregon’s ecosystems, are threatened by invasion of woody species and non-native pest species. Because fire has been important in maintaining Willamette Valley prairies for at least 1000 years, prescribed burning is a top choice of managers for preventing encroachment of woody species. However, the effects of prescribed burning on present day wetland prairie communities, with their mix of native and non-native species, are not clear. Moreover, because strict governmental requirements for smoke management hinder prescribed burning, natural-area managers are considering alternatives to fire, like mowing and hand removal of woody plants. The present study explored the ecological interactions of a wetland prairie by experimentally testing the responses of burning, hand-removal of woody species, and mowing with removal of cut material on woody plants and key native and non-native grasses and forbs. We evaluated these perturbations for their effectiveness in meeting management objectives of reducing abundance of woody species, reducing or preventing an increase in abundance of nonnative pest species, and increasing or at least maintaining native species’ abundance. After three treatments periods (1994, 1996, and 1998) the following patterns emerged: • Woody species Burning and hand-removal consistently caused the greatest reduction in cover of woody species. Mowing with removal of cut material did not reduce the abundance of woody species compared to the control. As woody plant cover decreased, plant mortality increased, indicating that treatments influenced woody plant cover at least partially through changes in survival. • Native herbaceous species All management treatments consistently failed to significantly increase the cover of Deschampsia cespitosa, while burning decreased the number of inflorescences. As a group, native graminoid flowering consistently showed no significant responses to the management treatments. Although burning and hand-removal significantly increased the cover of native forbs as group after the second treatment period in 1997, native forbs showed no significant responses to treatments in 1999. • Non-native herbaceous species Response of non-native forb cover to management treatments has been inconsistent during the five year study period with no significant differences in 1995, significant reductions by burning and hand-removal in 1997, and increases with mowing in 1997. Mowing consistently increased flowering of nonnative graminoids as a group. Overall no treatment was clearly superior in fulfilling restoration objectives. Burning was effective in reducing woody cover and did not promote non-native herbaceous, but it reduced the flowering the dominant native grass, Deschampsia cespitosa. Hand-removal woody species was also effective at reducing woody cover and sometimes promoted the abundance of some native species at different times, but it also at times promoted non-native herbaceous species. Because mowing with removal of cut material was ineffective in reducing woody cover and tended to promote non-native herbaceous species, this treatment is not a recommended management strategy. Close

• 8. [Article] Controlling woody vegetation in wetland prairies, 1994-2001

  Wetland prairies of the Willamette Valley, among the rarest of Oregon’s ecosystems, are threatened by invasion of woody species and non-native pest species. Because fire has been important in maintaining ...

  Citation × Citation Citation Abstract Copy Title: Controlling woody vegetation in wetland prairies, 1994-2001 Author: Clark, Deborah Louise, 1950- Wetland prairies of the Willamette Valley, among the rarest of Oregon’s ecosystems, are threatened by invasion of woody species and non-native pest species. Because fire has been important in maintaining Willamette Valley prairies for at least 1000 years, prescribed burning is a top choice of managers for preventing encroachment of woody species. However, the effects of prescribed burning on present day wetland prairie communities, with their mix of native and non-native species, are not clear. Moreover, because strict governmental requirements for smoke management hinder prescribed burning, natural-area managers are considering alternatives to fire, like mowing and hand-removal of woody plants. The present study explored the ecological interactions of a wetland prairie by experimentally testing the responses of burning, hand-removal of woody species, and mowing with removal of cut material on woody plants and key native and non-native grasses and forbs. We evaluated these perturbations for their effectiveness in meeting management objectives of reducing abundance of woody species, reducing or preventing an increase in abundance of nonnative pest species, and increasing or at least maintaining native species’ abundance. After four treatments periods (1994, 1996, 1998, and 2000) the following patterns emerged: • Woody species Burning and hand-removal of woody plants every two years consistently decreased the cover of woody species, even with a gradual increase in the controls to over double 1994 levels. The change in woody cover after mowing with removal of cut material was not significantly different from that in the control. As woody plant cover decreased, plant mortality increased, indicating that treatments influenced woody plant cover at least partially through changes in survival. • Native herbaceous species None of the treatments had a significant effect after four treatment periods on the proportional change in cover or in number of inflorescences of Deschampsia cespitosa, although the change in number of inflorescences was consistently less than that in the control, including a significant decrease with burning in 1997. As a group, native graminoid species showed no significant differences in flowering response to treatments during any of the four treatment periods. However, burning and mowing consistently promoted flowering of Juncus tenuis. The cover of native forbs as a group was not significantly different from that of the control, with the exception of 1997, where cover increased with burning and hand-removal. Even though native forbs as a group have generally not shown significant differences, individual native forb species have shown positive responses to treatments: Sidalcea cusickii, spp. purpurea, Eriophyllum lanatum, and Sisyrinchium idahoensis. • Non-native herbaceous species Both hand-removal and mowing promoted flowering of non-native graminoids as a group. In contrast, burning maintained levels of flowering of non-native graminoids similar to that of the controls. Cover of non-native forbs as a group showed no significant treatment differences except for 1997, in which significant reductions in cover occurred after burning and hand-removal. The results to date show that prescribed burning is the best option of the three tested management treatments for achieving the restoration goals for native wetland prairies. Because mowing with removal of cut material was ineffective in reducing woody cover and tended to promote non-native herbaceous species, this treatment should be avoided. Title: Controlling woody vegetation in wetland prairies, 1994-2001 Author: Clark, Deborah Louise, 1950- Wetland prairies of the Willamette Valley, among the rarest of Oregon’s ecosystems, are threatened by invasion of woody species and non-native pest species. Because fire has been important in maintaining Willamette Valley prairies for at least 1000 years, prescribed burning is a top choice of managers for preventing encroachment of woody species. However, the effects of prescribed burning on present day wetland prairie communities, with their mix of native and non-native species, are not clear. Moreover, because strict governmental requirements for smoke management hinder prescribed burning, natural-area managers are considering alternatives to fire, like mowing and hand-removal of woody plants. The present study explored the ecological interactions of a wetland prairie by experimentally testing the responses of burning, hand-removal of woody species, and mowing with removal of cut material on woody plants and key native and non-native grasses and forbs. We evaluated these perturbations for their effectiveness in meeting management objectives of reducing abundance of woody species, reducing or preventing an increase in abundance of nonnative pest species, and increasing or at least maintaining native species’ abundance. After four treatments periods (1994, 1996, 1998, and 2000) the following patterns emerged: • Woody species Burning and hand-removal of woody plants every two years consistently decreased the cover of woody species, even with a gradual increase in the controls to over double 1994 levels. The change in woody cover after mowing with removal of cut material was not significantly different from that in the control. As woody plant cover decreased, plant mortality increased, indicating that treatments influenced woody plant cover at least partially through changes in survival. • Native herbaceous species None of the treatments had a significant effect after four treatment periods on the proportional change in cover or in number of inflorescences of Deschampsia cespitosa, although the change in number of inflorescences was consistently less than that in the control, including a significant decrease with burning in 1997. As a group, native graminoid species showed no significant differences in flowering response to treatments during any of the four treatment periods. However, burning and mowing consistently promoted flowering of Juncus tenuis. The cover of native forbs as a group was not significantly different from that of the control, with the exception of 1997, where cover increased with burning and hand-removal. Even though native forbs as a group have generally not shown significant differences, individual native forb species have shown positive responses to treatments: Sidalcea cusickii, spp. purpurea, Eriophyllum lanatum, and Sisyrinchium idahoensis. • Non-native herbaceous species Both hand-removal and mowing promoted flowering of non-native graminoids as a group. In contrast, burning maintained levels of flowering of non-native graminoids similar to that of the controls. Cover of non-native forbs as a group showed no significant treatment differences except for 1997, in which significant reductions in cover occurred after burning and hand-removal. The results to date show that prescribed burning is the best option of the three tested management treatments for achieving the restoration goals for native wetland prairies. Because mowing with removal of cut material was ineffective in reducing woody cover and tended to promote non-native herbaceous species, this treatment should be avoided. 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• 9. [Article] Promoting regeneration of native species In Willamette Valley upland prairies

  Native prairies of the Willamette Valley are considered among the rarest of Oregon’s ecosystems and are in critical need of conservation. Management strategies for increasing the abundance of native species ...

  Citation × Citation Citation Abstract Copy Title: Promoting regeneration of native species In Willamette Valley upland prairies Author: Wilson, Mark V., Clark, Deborah Louise, 1950- Native prairies of the Willamette Valley are considered among the rarest of Oregon’s ecosystems and are in critical need of conservation. Management strategies for increasing the abundance of native species are urgently needed, particularly those strategies that promote the regeneration of native species from seed. The focus of this investigation was to address this need. The general approach was to sow seeds of native species into experimental field plots, which had been burned once, burned repeatedly, mowed, or unmanaged at three sites at Baskett Slough National Wildlife Refuge. Seedling numbers were then counted one growing season after sowing. To investigate mechanisms for the regeneration responses of species to management treatments, selected abiotic and biotic factors potentially important for seed regeneration were measured in the field plots. Seedling establishment rates in unmanaged plots were relatively small, averaging 9.7% for all three sites. Only one species, Danthonia californica, showed a positive response to the mowing treatment. Of the 13 species sowed in the burn plots, six species (Bromus carinatus, Elymus glacus, Festuca roemeri/rubra, Clarkia quadrivulera, Prunella vulgaris, Sidalcea campestris) had significant more seedlings in the burn plots compared to the unmanaged plots. Seedling establishment of two species, Danthonia californica and Potentilla gracilis, was significantly lower with burn treatments. The other five species showed no significant responses to the burn treatments: Carex tumicola, Calochortus tolmiei, Zygadensus venenosus, Balsamorhiza deltoidea, and Agoseris grandilflora. The strongest fire effects were generally in plots that had been burned only once, rather than plots burned more than once. Abundance of litter and vegetation were the factors that were most often related, both positively and negatively, with seedling establishment rates. Based on the results of this investigation, prescribed burning, rather than mowing, is a more viable management option to promote regeneration of native species from seed in upland prairies. However, prescribed burning must be used with caution as it can reduce seedling establishment rates for some species. Sowing seeds in unmanaged sites is an option, but sowing rates need to be high to compensate for the small seedling establishment rates in unmanaged prairies. Title: Promoting regeneration of native species In Willamette Valley upland prairies Author: Wilson, Mark V., Clark, Deborah Louise, 1950- Native prairies of the Willamette Valley are considered among the rarest of Oregon’s ecosystems and are in critical need of conservation. Management strategies for increasing the abundance of native species are urgently needed, particularly those strategies that promote the regeneration of native species from seed. The focus of this investigation was to address this need. The general approach was to sow seeds of native species into experimental field plots, which had been burned once, burned repeatedly, mowed, or unmanaged at three sites at Baskett Slough National Wildlife Refuge. Seedling numbers were then counted one growing season after sowing. To investigate mechanisms for the regeneration responses of species to management treatments, selected abiotic and biotic factors potentially important for seed regeneration were measured in the field plots. Seedling establishment rates in unmanaged plots were relatively small, averaging 9.7% for all three sites. Only one species, Danthonia californica, showed a positive response to the mowing treatment. Of the 13 species sowed in the burn plots, six species (Bromus carinatus, Elymus glacus, Festuca roemeri/rubra, Clarkia quadrivulera, Prunella vulgaris, Sidalcea campestris) had significant more seedlings in the burn plots compared to the unmanaged plots. Seedling establishment of two species, Danthonia californica and Potentilla gracilis, was significantly lower with burn treatments. The other five species showed no significant responses to the burn treatments: Carex tumicola, Calochortus tolmiei, Zygadensus venenosus, Balsamorhiza deltoidea, and Agoseris grandilflora. The strongest fire effects were generally in plots that had been burned only once, rather than plots burned more than once. Abundance of litter and vegetation were the factors that were most often related, both positively and negatively, with seedling establishment rates. Based on the results of this investigation, prescribed burning, rather than mowing, is a more viable management option to promote regeneration of native species from seed in upland prairies. However, prescribed burning must be used with caution as it can reduce seedling establishment rates for some species. Sowing seeds in unmanaged sites is an option, but sowing rates need to be high to compensate for the small seedling establishment rates in unmanaged prairies. Close