Global change drivers (GCDs) are expected to alter community structure and consequently, the serv... more Global change drivers (GCDs) are expected to alter community structure and consequently, the services that ecosystems provide. Yet, few experimental investigations have examined effects of GCDs on plant community structure across multiple ecosystem types, and those that do exist present conflicting patterns. In an unprecedented global synthesis of over 100 experiments that manipulated factors linked to GCDs, we show that herbaceous plant community responses depend on experimental manipulation length and number of factors manipulated. We found that plant communities are fairly resistant to experimentally manipulated GCDs in the short term (<10 y). In contrast, long-term (≥10 y) experiments show increasing community divergence of treatments from control conditions. Surprisingly, these community responses occurred with similar frequency across the GCD types manipulated in our database. However, community responses were more common when 3 or more GCDs were simultaneously manipulated,...
Conifer control in sagebrush steppe of the western United States causes various levels of site di... more Conifer control in sagebrush steppe of the western United States causes various levels of site disturbance influencing vegetation recovery and resource availability. The data set presented in this article include growing season availability of soil micronutrients and levels of total soil carbon, organic matter, and N spanning a six year period following western juniper (Juniperus occidentalis spp. occidentalis) reduction by mechanical cutting and prescribed fire of western juniper woodlands in southeast Oregon. These data can be useful to further evaluate the impacts of conifer woodland reduction to soil resources in sagebrush steppe plant communities.
Artemisia tridentata ssp. wyomingensis (Beetle & A. Young) S.L. Welsh-bunchgrass communities were... more Artemisia tridentata ssp. wyomingensis (Beetle & A. Young) S.L. Welsh-bunchgrass communities were used to analyze the influence of disturbances on invasibility after a recovery period. These communities evolved with periodic fires shifting dominance from shrubs to herbaceous species. However, fire can facilitate Bromus tectorum L. invasion of these plant communities. We evaluated the invasibility of A. tridentata ssp. wyomingensis-bunchgrass communities 4 years after prescribed fall burning at six sites by comparing burned to unburned (control) communities. These communities did not have B. tectorum present prior to introduction. B. tectorum was introduced at 1, 10, 100, 1000, and 10,000 seeds m À2 in burned and unburned communities. B. tectorum individuals established only when introduced at 10,000 seeds m À2. In the areas seeded at 10,000 seeds m À2 , B. tectorum density and cover were more than threefold higher in the control than burned treatments (P ¼ 0.04 and 0.08, respectively). Total herbaceous vegetation cover, density, and production increased with burning (Po0.01, 0.02, and o0.01, respectively). Bare ground and inorganic nitrogen were higher in the control than the burned treatment (P ¼ 0.02 and o0.01, respectively). Prescribed fall burning of late seral A. tridentata ssp. wyomingensis-bunchgrass communities stimulated the herbaceous component and increased the resistance of the communities to B. tectorum invasion 4 years post-burn. However, we do not suggest the use of prescribed burning in communities where invasive annual grasses are present or in close proximity. We acknowledge that our results would probably have been drastically different if B. tectorum or other invasive annual grasses had been a component of the plant communities prior to prescribed burning or became a component immediately after burning.
Mowing is commonly implemented to Artemisia tridentata ssp. wyomingensis (Beetle & A. Young) S.L.... more Mowing is commonly implemented to Artemisia tridentata ssp. wyomingensis (Beetle & A. Young) S.L. Welsh (Wyoming big sagebrush) plant communities to improve wildlife habitat, increase forage production for livestock, and create fuel breaks for fire suppression. However, information detailing the influence of mowing on winter habitat for wildlife is lacking. This information is crucial because many wildlife species depended on A. tridentata spp. wyomingensis plant communities for winter habitat and consume significant quantities of Artemisia during this time. Furthermore, information is generally limited describing the recovery of A. tridentata spp. wyomingensis to mowing and the impacts of mowing on stand structure. Stand characteristics and Artemisia leaf tissue crude protein (CP), acid detergent fiber (ADF), and neutral detergent fiber (NDF) concentrations were measured in midwinter on 0-, 2-, 4-, and 6-year-old fall-applied mechanical (mowed at 20 cm height) treatments and compared to adjacent untreated (control) areas. Mowing compared to the control decreased Artemisia cover, density, canopy volume, canopy elliptical area, and height (P \ 0.05), but all characteristics were recovering (P \ 0.05). Mowing A. tridentata spp. wyomingensis plant communities slightly increases the nutritional quality of Artemisia leaves (P \ 0.05), but it simultaneously results in up to 20 years of decrease in Artemisia structural characteristics. Because of the large reduction in A. tridentata spp. wyomingensis for potentially 20 years following mowing, mowing should not be applied in Artemisia facultative and obligate wildlife winter habitat. Considering the decline in A. tridentata spp. wyomingensisdominated landscapes, we caution against mowing these communities.
Restoring range sites dominated by western juniper is central to maintaining healthy functioning ... more Restoring range sites dominated by western juniper is central to maintaining healthy functioning shrub–steppe ecosystems. On sites without adequate species composition to respond favorably to juniper controlled by fire, revegetation is necessary. We tested the following two hypotheses related to restoration after juniper control: (1) higher seeding rates would translate into higher density of seeded species, and (2) a rich seeding mixture would provide higher density and biomass than monocultures. Western juniper control was done by cutting 25% of the trees in 2002, allowing cut trees to dry for one year, followed by a broadcast fire applied in October 2003 which killed the remaining live juniper trees. Seeding treatments were applied in 2003 and included seeding six native species in monocultures, seeding a mixture of all six species at four rates (16.8, 22.4, 28.0, or 33.6 kg ha−1of pure live seeds), and a nonseeded control. Treatments were applied on a Sagebrush/bunchgrass and Snowberry/fescue site. We found that bluebunch wheatgrass, Idaho fescue, big bluegrass, and western yarrow density ranged from 450 to 700 plants m−2, which was over six-fold that of the control in 2004 at both sites. Only arrowleaf balsamroot did not establish successfully. The density of big bluegrass nearly doubled from 2004 to 2005. The highest plant density resulted from the highest seeding rate. The highest biomass production was combination seeding at 22.4 kg ha−1on the Sagebrush/bunchgrass site and 33.6 kg ha−1on the Snowberry/fescue site. Seeding a combination of species resulted in a moderate to high density of plants and optimized plant diversity and richness over seeding monocultures.
Page 1. AN ABSTRACT OF THE THESIS Jonathan D. Bates for the degree of Master of Science in Agricu... more Page 1. AN ABSTRACT OF THE THESIS Jonathan D. Bates for the degree of Master of Science in Agricultural and Resource Economics presented on July 7. 1989. Title: A Comparative Assessment of Four Winter Cattle Feeding ...
Small (<40.5-ha) patch fires or mechanical manipulations to reduce big sagebrush (Artemisia tride... more Small (<40.5-ha) patch fires or mechanical manipulations to reduce big sagebrush (Artemisia tridentata) cover has been suggested as a management option to improve sage-grouse pre-nesting and brood rearing habitat and provide a diverse habitat mosaic. We evaluated the effects of prescribed fire and wildfire on sage-grouse habitat in three Wyoming big sagebrush associations (Bluebunch, Thurber s needlegrass, Thurber s needlegrass-Idaho fescue). Response variables included vegetation cover, herbaceous productivity, yield and nutritional quality of forbs preferred by greater sage-grouse, and abundance of common arthropod orders. Wildfire eliminated all sagebrush and >90 percent of the perennial grasses on the Thurber s association. On the Bluebunch association wildfire eliminated sagebrush, but most perennial grasses survived. The prescribed fire on the Thurber s needlegrass-Idaho fescue association removed 95 percent of the sagebrush with most perennial grasses surviving. Habitat cover (shrubs and tall herbaceous cover (> 18cm height)) was 33-90 percent lower after burning compared to unburned controls. The removal of big sagebrush decreased structural cover and reduced or eliminated forage provided by big sagebrush for sage-grouse. This would be potentially damaging in sage-grouse year-round and wintering habitat. Burning reduced Wyoming big sagebrush forage production by about 450 kg/ha on the Thurber s needlegrass-Idaho fescue association. Yields or cover of perennial forbs used by sage-grouse in their diets did not differ between burned sites and not burned sites in the Bluebunch and Thurber s needlegrass-Idaho fescue associations. In the Thurber s needlegrass association long leaf phlox was the only perennial forb to increase after fire. Pale alyssum, a non-native forb, was the dominant annual after fire in the Thurber s needlegrass and Thurber s needlegrass-Idaho fescue associations. Yields or cover of annual forbs used by sage-grouse in their diets increased temporarily after fire in the Bluebunch association. Although cheatgrass increased in the Thurber s association it has remained a minor component of the post-fire community. The abundance of ants (Hymenoptera) decreased after fire while the abundance of other arthropods remained unaffected in the Thurber s needlegrass-Idaho fescue association. The results indicate that prescribed fire will not improve habitat characteristics for sage-grouse in Wyoming big sagebrush steppe where the community already consists of shrubs, native grasses, and native forbs. Burning of Wyoming big sagebrush communities to enhance other species habitat requirements should minimize mortality of native perennial grasses and forb species, result in a mosaic pattern of burned and unburned patches, and avoid areas of critical habitat.
Small (<40.5-ha) patch fires or mechanical manipulations to reduce big sagebrush (Artemisia tride... more Small (<40.5-ha) patch fires or mechanical manipulations to reduce big sagebrush (Artemisia tridentata) cover has been suggested as a management option to improve sage-grouse pre-nesting and brood rearing habitat and provide a diverse habitat mosaic. We evaluated the effects of prescribed fire and wildfire on sage-grouse habitat in three Wyoming big sagebrush associations (Bluebunch, Thurber s needlegrass, Thurber s needlegrass-Idaho fescue). Response variables included vegetation cover, herbaceous productivity, yield and nutritional quality of forbs preferred by greater sage-grouse, and abundance of common arthropod orders. Wildfire eliminated all sagebrush and >90 percent of the perennial grasses on the Thurber s association. On the Bluebunch association wildfire eliminated sagebrush, but most perennial grasses survived. The prescribed fire on the Thurber s needlegrass-Idaho fescue association removed 95 percent of the sagebrush with most perennial grasses surviving. Habitat cover (shrubs and tall herbaceous cover (> 18cm height)) was 33-90 percent lower after burning compared to unburned controls. The removal of big sagebrush decreased structural cover and reduced or eliminated forage provided by big sagebrush for sage-grouse. This would be potentially damaging in sage-grouse year-round and wintering habitat. Burning reduced Wyoming big sagebrush forage production by about 450 kg/ha on the Thurber s needlegrass-Idaho fescue association. Yields or cover of perennial forbs used by sage-grouse in their diets did not differ between burned sites and not burned sites in the Bluebunch and Thurber s needlegrass-Idaho fescue associations. In the Thurber s needlegrass association long leaf phlox was the only perennial forb to increase after fire. Pale alyssum, a non-native forb, was the dominant annual after fire in the Thurber s needlegrass and Thurber s needlegrass-Idaho fescue associations. Yields or cover of annual forbs used by sage-grouse in their diets increased temporarily after fire in the Bluebunch association. Although cheatgrass increased in the Thurber s association it has remained a minor component of the post-fire community. The abundance of ants (Hymenoptera) decreased after fire while the abundance of other arthropods remained unaffected in the Thurber s needlegrass-Idaho fescue association. The results indicate that prescribed fire will not improve habitat characteristics for sage-grouse in Wyoming big sagebrush steppe where the community already consists of shrubs, native grasses, and native forbs. Burning of Wyoming big sagebrush communities to enhance other species habitat requirements should minimize mortality of native perennial grasses and forb species, result in a mosaic pattern of burned and unburned patches, and avoid areas of critical habitat.
ABSTRACT Background/Question/Methods Piñon-juniper (Pinus-Juniperus L.) woodlands have expanded i... more ABSTRACT Background/Question/Methods Piñon-juniper (Pinus-Juniperus L.) woodlands have expanded into big sagebrush (Artemisia tridentata Beetle) steppe of the western United States primarily as a result of reduced fire disturbances. Prescribed fire in post-settlement piñon-juniper woodlands has been increasingly employed to restore big sagebrush steppe plant communities. We compared vegetation recovery following cutting-prescribed fire treatments on Phase 2 (mid expansion) and Phase 3 (late expansion) western juniper (Juniperus occidentalis Hook.) woodlands on Steens Mountain, Oregon. In Phase II woodlands, trees co-dominate with shrub and herbaceous plants, and in Phase III woodlands trees are dominant and shrubs and herbaceous layers are much reduced. Twelve Phase 2 and nine Phase 3, 0.63 ha plots were established in May 2003 and all study sites were located in Mountain big sagebrush/Idaho fescue (A.t spp. vaseyana /Festuca idahoensis Elmer) associations. Pre and post-fire tree, shrub and herbaceous cover and density were collected over a seven year period. Repeated measures analysis of variance for a completely randomized design was used to test for year, woodland phase, and year by phase interaction for vegetation response variables. Results/Conclusions Herbaceous vegetation on Phase II woodland sites was comprised of native perennial and annual vegetation before and after fire. Herbaceous vegetation in Phase 3 woodlands shifted from native species to dominance by cheatgrass (Bromus tectorum L.) and other invasive weeds after fire. Shrubs on Phase 2 sites were comprised of sprouting species and snowbrush (Ceanothus velutinus Dougl.) after fire. The shrub component on Phase 3 sites was dominated by snowbrush following fire. The results indicate that woodland phase influences post-fire vegetation recovery and composition. This suggests that sagebrush steppe in Phase 1 or 2 woodland expansion stages are more likely to recover with their native vegetation components intact than Phase 3 woodland sites. The results also indicate that sites transitioning from Phase 2 to Phase 3 woodlands have crossed a recovery threshold where there is a greater potential for invasive weeds to dominate rather than native vegetation after fire. Phase 3 woodlands that are burned by wildfire or prescribed fire are likely to require additional inputs, primarily seeding and weed control, for vegetation recovery goals to be accomplished. Managers should consider applying alternative treatments in Phase 3 woodlands that would potentially improve sagebrush steppe recovery such as cutting or cutting followed by winter/spring burning.
Tradename products and services are mentioned as illustrations only. This does not mean that the ... more Tradename products and services are mentioned as illustrations only. This does not mean that the Oregon State University Agricultural Experiment Station either endorses these products and services or intends to discriminate against products and services not mentioned.
ABSTRACT Shrub steppe communities with depleted perennial herbaceous understories often need to b... more ABSTRACT Shrub steppe communities with depleted perennial herbaceous understories often need to be restored to increase resilience and resistance. Mowing has been applied to Wyoming big sagebrush (Artemisia tridentata Nutt. ssp. wyomingensis Beetle &amp; Young) steppe plant communities to reduce sagebrush dominance and restore native herbaceous vegetation, but success has been limited and hampered by increases in exotic annuals. Seeding native bunchgrasses after mowing may accelerate recovery and limit exotics. We compared mowing followed by drill-seeding native bunchgrasses to mowing and an untreated control at five sites in southeastern Oregon over a 4-year period. Mowing and seeding bunchgrasses increased bunchgrass density; however, bunchgrass cover did not differ among treatments. Exotic annuals increased with mowing whether or not post-mowing seeding occurred. Mowing, whether or not seeding occurred, also reduced biological soil crusts. Longer term evaluation is needed to determine if seeded bunchgrasses will increase enough to suppress exotic annuals. Seeded bunchgrasses may have been limited by increases in exotic annuals. Though restoration of sagebrush communities with degraded understories is needed, we do not recommend mowing and seeding native bunchgrasses because this treatment produced mixed results that may lower the resilience and resistance of these communities. Before this method is applied, research is needed to increase our understanding of how to improve establishment of seeded native bunchgrasses. Alternatively, restoration practitioners may need to apply treatments to control exotic annuals and repeatedly seed native bunchgrasses.
Biophysical Site Description Within the Pacific Northwest modeling zone, the cool sagebrush PNVG ... more Biophysical Site Description Within the Pacific Northwest modeling zone, the cool sagebrush PNVG consists of three intermingled tall shrub communities: mountain big sagebrush, threetip sagebrush, and mountain shrub. Of these, mountain big sagebrush is the principal community type. Mountain big sagebrush occurs in the cooler, moister portion of the sagebrush zone with elevation ranges from 3500 feet to 9000 feet on Steens Mountain. However, this community type is most prevalent between 5000 and 7000 feet elevation. Threetip sagebrush is intermingled with the mountain big sagebrush community at lower elevations, growing in pockets of moister soils at 3300 to 7000 feet elevation. At higher elevations, the mountain shrub community intermingles with the mountain big sagebrush community. Mean annual precipitation is typically between 14 and 22 inches, but ranges from 10 to 30 inches (Mueggler and Stewart 1980, Tart 1996). Mountain big sagebrush mostly occupies moist, productive rolling upland sites. Soils are typically moderately deep to deep, well-drained and have well developed dark organic surface horizons (Hironaka et al. 1983, Tart 1996). However, at the high ends of its precipitation and elevation ranges mountain big sagebrush occurs on shallow and/or rocky soils. Mountain big sagebrush is typically found where winter Reviewers Jon Bates
Global change drivers (GCDs) are expected to alter community structure and consequently, the serv... more Global change drivers (GCDs) are expected to alter community structure and consequently, the services that ecosystems provide. Yet, few experimental investigations have examined effects of GCDs on plant community structure across multiple ecosystem types, and those that do exist present conflicting patterns. In an unprecedented global synthesis of over 100 experiments that manipulated factors linked to GCDs, we show that herbaceous plant community responses depend on experimental manipulation length and number of factors manipulated. We found that plant communities are fairly resistant to experimentally manipulated GCDs in the short term (<10 y). In contrast, long-term (≥10 y) experiments show increasing community divergence of treatments from control conditions. Surprisingly, these community responses occurred with similar frequency across the GCD types manipulated in our database. However, community responses were more common when 3 or more GCDs were simultaneously manipulated,...
Conifer control in sagebrush steppe of the western United States causes various levels of site di... more Conifer control in sagebrush steppe of the western United States causes various levels of site disturbance influencing vegetation recovery and resource availability. The data set presented in this article include growing season availability of soil micronutrients and levels of total soil carbon, organic matter, and N spanning a six year period following western juniper (Juniperus occidentalis spp. occidentalis) reduction by mechanical cutting and prescribed fire of western juniper woodlands in southeast Oregon. These data can be useful to further evaluate the impacts of conifer woodland reduction to soil resources in sagebrush steppe plant communities.
Artemisia tridentata ssp. wyomingensis (Beetle & A. Young) S.L. Welsh-bunchgrass communities were... more Artemisia tridentata ssp. wyomingensis (Beetle & A. Young) S.L. Welsh-bunchgrass communities were used to analyze the influence of disturbances on invasibility after a recovery period. These communities evolved with periodic fires shifting dominance from shrubs to herbaceous species. However, fire can facilitate Bromus tectorum L. invasion of these plant communities. We evaluated the invasibility of A. tridentata ssp. wyomingensis-bunchgrass communities 4 years after prescribed fall burning at six sites by comparing burned to unburned (control) communities. These communities did not have B. tectorum present prior to introduction. B. tectorum was introduced at 1, 10, 100, 1000, and 10,000 seeds m À2 in burned and unburned communities. B. tectorum individuals established only when introduced at 10,000 seeds m À2. In the areas seeded at 10,000 seeds m À2 , B. tectorum density and cover were more than threefold higher in the control than burned treatments (P ¼ 0.04 and 0.08, respectively). Total herbaceous vegetation cover, density, and production increased with burning (Po0.01, 0.02, and o0.01, respectively). Bare ground and inorganic nitrogen were higher in the control than the burned treatment (P ¼ 0.02 and o0.01, respectively). Prescribed fall burning of late seral A. tridentata ssp. wyomingensis-bunchgrass communities stimulated the herbaceous component and increased the resistance of the communities to B. tectorum invasion 4 years post-burn. However, we do not suggest the use of prescribed burning in communities where invasive annual grasses are present or in close proximity. We acknowledge that our results would probably have been drastically different if B. tectorum or other invasive annual grasses had been a component of the plant communities prior to prescribed burning or became a component immediately after burning.
Mowing is commonly implemented to Artemisia tridentata ssp. wyomingensis (Beetle & A. Young) S.L.... more Mowing is commonly implemented to Artemisia tridentata ssp. wyomingensis (Beetle & A. Young) S.L. Welsh (Wyoming big sagebrush) plant communities to improve wildlife habitat, increase forage production for livestock, and create fuel breaks for fire suppression. However, information detailing the influence of mowing on winter habitat for wildlife is lacking. This information is crucial because many wildlife species depended on A. tridentata spp. wyomingensis plant communities for winter habitat and consume significant quantities of Artemisia during this time. Furthermore, information is generally limited describing the recovery of A. tridentata spp. wyomingensis to mowing and the impacts of mowing on stand structure. Stand characteristics and Artemisia leaf tissue crude protein (CP), acid detergent fiber (ADF), and neutral detergent fiber (NDF) concentrations were measured in midwinter on 0-, 2-, 4-, and 6-year-old fall-applied mechanical (mowed at 20 cm height) treatments and compared to adjacent untreated (control) areas. Mowing compared to the control decreased Artemisia cover, density, canopy volume, canopy elliptical area, and height (P \ 0.05), but all characteristics were recovering (P \ 0.05). Mowing A. tridentata spp. wyomingensis plant communities slightly increases the nutritional quality of Artemisia leaves (P \ 0.05), but it simultaneously results in up to 20 years of decrease in Artemisia structural characteristics. Because of the large reduction in A. tridentata spp. wyomingensis for potentially 20 years following mowing, mowing should not be applied in Artemisia facultative and obligate wildlife winter habitat. Considering the decline in A. tridentata spp. wyomingensisdominated landscapes, we caution against mowing these communities.
Restoring range sites dominated by western juniper is central to maintaining healthy functioning ... more Restoring range sites dominated by western juniper is central to maintaining healthy functioning shrub–steppe ecosystems. On sites without adequate species composition to respond favorably to juniper controlled by fire, revegetation is necessary. We tested the following two hypotheses related to restoration after juniper control: (1) higher seeding rates would translate into higher density of seeded species, and (2) a rich seeding mixture would provide higher density and biomass than monocultures. Western juniper control was done by cutting 25% of the trees in 2002, allowing cut trees to dry for one year, followed by a broadcast fire applied in October 2003 which killed the remaining live juniper trees. Seeding treatments were applied in 2003 and included seeding six native species in monocultures, seeding a mixture of all six species at four rates (16.8, 22.4, 28.0, or 33.6 kg ha−1of pure live seeds), and a nonseeded control. Treatments were applied on a Sagebrush/bunchgrass and Snowberry/fescue site. We found that bluebunch wheatgrass, Idaho fescue, big bluegrass, and western yarrow density ranged from 450 to 700 plants m−2, which was over six-fold that of the control in 2004 at both sites. Only arrowleaf balsamroot did not establish successfully. The density of big bluegrass nearly doubled from 2004 to 2005. The highest plant density resulted from the highest seeding rate. The highest biomass production was combination seeding at 22.4 kg ha−1on the Sagebrush/bunchgrass site and 33.6 kg ha−1on the Snowberry/fescue site. Seeding a combination of species resulted in a moderate to high density of plants and optimized plant diversity and richness over seeding monocultures.
Page 1. AN ABSTRACT OF THE THESIS Jonathan D. Bates for the degree of Master of Science in Agricu... more Page 1. AN ABSTRACT OF THE THESIS Jonathan D. Bates for the degree of Master of Science in Agricultural and Resource Economics presented on July 7. 1989. Title: A Comparative Assessment of Four Winter Cattle Feeding ...
Small (<40.5-ha) patch fires or mechanical manipulations to reduce big sagebrush (Artemisia tride... more Small (<40.5-ha) patch fires or mechanical manipulations to reduce big sagebrush (Artemisia tridentata) cover has been suggested as a management option to improve sage-grouse pre-nesting and brood rearing habitat and provide a diverse habitat mosaic. We evaluated the effects of prescribed fire and wildfire on sage-grouse habitat in three Wyoming big sagebrush associations (Bluebunch, Thurber s needlegrass, Thurber s needlegrass-Idaho fescue). Response variables included vegetation cover, herbaceous productivity, yield and nutritional quality of forbs preferred by greater sage-grouse, and abundance of common arthropod orders. Wildfire eliminated all sagebrush and >90 percent of the perennial grasses on the Thurber s association. On the Bluebunch association wildfire eliminated sagebrush, but most perennial grasses survived. The prescribed fire on the Thurber s needlegrass-Idaho fescue association removed 95 percent of the sagebrush with most perennial grasses surviving. Habitat cover (shrubs and tall herbaceous cover (> 18cm height)) was 33-90 percent lower after burning compared to unburned controls. The removal of big sagebrush decreased structural cover and reduced or eliminated forage provided by big sagebrush for sage-grouse. This would be potentially damaging in sage-grouse year-round and wintering habitat. Burning reduced Wyoming big sagebrush forage production by about 450 kg/ha on the Thurber s needlegrass-Idaho fescue association. Yields or cover of perennial forbs used by sage-grouse in their diets did not differ between burned sites and not burned sites in the Bluebunch and Thurber s needlegrass-Idaho fescue associations. In the Thurber s needlegrass association long leaf phlox was the only perennial forb to increase after fire. Pale alyssum, a non-native forb, was the dominant annual after fire in the Thurber s needlegrass and Thurber s needlegrass-Idaho fescue associations. Yields or cover of annual forbs used by sage-grouse in their diets increased temporarily after fire in the Bluebunch association. Although cheatgrass increased in the Thurber s association it has remained a minor component of the post-fire community. The abundance of ants (Hymenoptera) decreased after fire while the abundance of other arthropods remained unaffected in the Thurber s needlegrass-Idaho fescue association. The results indicate that prescribed fire will not improve habitat characteristics for sage-grouse in Wyoming big sagebrush steppe where the community already consists of shrubs, native grasses, and native forbs. Burning of Wyoming big sagebrush communities to enhance other species habitat requirements should minimize mortality of native perennial grasses and forb species, result in a mosaic pattern of burned and unburned patches, and avoid areas of critical habitat.
Small (<40.5-ha) patch fires or mechanical manipulations to reduce big sagebrush (Artemisia tride... more Small (<40.5-ha) patch fires or mechanical manipulations to reduce big sagebrush (Artemisia tridentata) cover has been suggested as a management option to improve sage-grouse pre-nesting and brood rearing habitat and provide a diverse habitat mosaic. We evaluated the effects of prescribed fire and wildfire on sage-grouse habitat in three Wyoming big sagebrush associations (Bluebunch, Thurber s needlegrass, Thurber s needlegrass-Idaho fescue). Response variables included vegetation cover, herbaceous productivity, yield and nutritional quality of forbs preferred by greater sage-grouse, and abundance of common arthropod orders. Wildfire eliminated all sagebrush and >90 percent of the perennial grasses on the Thurber s association. On the Bluebunch association wildfire eliminated sagebrush, but most perennial grasses survived. The prescribed fire on the Thurber s needlegrass-Idaho fescue association removed 95 percent of the sagebrush with most perennial grasses surviving. Habitat cover (shrubs and tall herbaceous cover (> 18cm height)) was 33-90 percent lower after burning compared to unburned controls. The removal of big sagebrush decreased structural cover and reduced or eliminated forage provided by big sagebrush for sage-grouse. This would be potentially damaging in sage-grouse year-round and wintering habitat. Burning reduced Wyoming big sagebrush forage production by about 450 kg/ha on the Thurber s needlegrass-Idaho fescue association. Yields or cover of perennial forbs used by sage-grouse in their diets did not differ between burned sites and not burned sites in the Bluebunch and Thurber s needlegrass-Idaho fescue associations. In the Thurber s needlegrass association long leaf phlox was the only perennial forb to increase after fire. Pale alyssum, a non-native forb, was the dominant annual after fire in the Thurber s needlegrass and Thurber s needlegrass-Idaho fescue associations. Yields or cover of annual forbs used by sage-grouse in their diets increased temporarily after fire in the Bluebunch association. Although cheatgrass increased in the Thurber s association it has remained a minor component of the post-fire community. The abundance of ants (Hymenoptera) decreased after fire while the abundance of other arthropods remained unaffected in the Thurber s needlegrass-Idaho fescue association. The results indicate that prescribed fire will not improve habitat characteristics for sage-grouse in Wyoming big sagebrush steppe where the community already consists of shrubs, native grasses, and native forbs. Burning of Wyoming big sagebrush communities to enhance other species habitat requirements should minimize mortality of native perennial grasses and forb species, result in a mosaic pattern of burned and unburned patches, and avoid areas of critical habitat.
ABSTRACT Background/Question/Methods Piñon-juniper (Pinus-Juniperus L.) woodlands have expanded i... more ABSTRACT Background/Question/Methods Piñon-juniper (Pinus-Juniperus L.) woodlands have expanded into big sagebrush (Artemisia tridentata Beetle) steppe of the western United States primarily as a result of reduced fire disturbances. Prescribed fire in post-settlement piñon-juniper woodlands has been increasingly employed to restore big sagebrush steppe plant communities. We compared vegetation recovery following cutting-prescribed fire treatments on Phase 2 (mid expansion) and Phase 3 (late expansion) western juniper (Juniperus occidentalis Hook.) woodlands on Steens Mountain, Oregon. In Phase II woodlands, trees co-dominate with shrub and herbaceous plants, and in Phase III woodlands trees are dominant and shrubs and herbaceous layers are much reduced. Twelve Phase 2 and nine Phase 3, 0.63 ha plots were established in May 2003 and all study sites were located in Mountain big sagebrush/Idaho fescue (A.t spp. vaseyana /Festuca idahoensis Elmer) associations. Pre and post-fire tree, shrub and herbaceous cover and density were collected over a seven year period. Repeated measures analysis of variance for a completely randomized design was used to test for year, woodland phase, and year by phase interaction for vegetation response variables. Results/Conclusions Herbaceous vegetation on Phase II woodland sites was comprised of native perennial and annual vegetation before and after fire. Herbaceous vegetation in Phase 3 woodlands shifted from native species to dominance by cheatgrass (Bromus tectorum L.) and other invasive weeds after fire. Shrubs on Phase 2 sites were comprised of sprouting species and snowbrush (Ceanothus velutinus Dougl.) after fire. The shrub component on Phase 3 sites was dominated by snowbrush following fire. The results indicate that woodland phase influences post-fire vegetation recovery and composition. This suggests that sagebrush steppe in Phase 1 or 2 woodland expansion stages are more likely to recover with their native vegetation components intact than Phase 3 woodland sites. The results also indicate that sites transitioning from Phase 2 to Phase 3 woodlands have crossed a recovery threshold where there is a greater potential for invasive weeds to dominate rather than native vegetation after fire. Phase 3 woodlands that are burned by wildfire or prescribed fire are likely to require additional inputs, primarily seeding and weed control, for vegetation recovery goals to be accomplished. Managers should consider applying alternative treatments in Phase 3 woodlands that would potentially improve sagebrush steppe recovery such as cutting or cutting followed by winter/spring burning.
Tradename products and services are mentioned as illustrations only. This does not mean that the ... more Tradename products and services are mentioned as illustrations only. This does not mean that the Oregon State University Agricultural Experiment Station either endorses these products and services or intends to discriminate against products and services not mentioned.
ABSTRACT Shrub steppe communities with depleted perennial herbaceous understories often need to b... more ABSTRACT Shrub steppe communities with depleted perennial herbaceous understories often need to be restored to increase resilience and resistance. Mowing has been applied to Wyoming big sagebrush (Artemisia tridentata Nutt. ssp. wyomingensis Beetle &amp; Young) steppe plant communities to reduce sagebrush dominance and restore native herbaceous vegetation, but success has been limited and hampered by increases in exotic annuals. Seeding native bunchgrasses after mowing may accelerate recovery and limit exotics. We compared mowing followed by drill-seeding native bunchgrasses to mowing and an untreated control at five sites in southeastern Oregon over a 4-year period. Mowing and seeding bunchgrasses increased bunchgrass density; however, bunchgrass cover did not differ among treatments. Exotic annuals increased with mowing whether or not post-mowing seeding occurred. Mowing, whether or not seeding occurred, also reduced biological soil crusts. Longer term evaluation is needed to determine if seeded bunchgrasses will increase enough to suppress exotic annuals. Seeded bunchgrasses may have been limited by increases in exotic annuals. Though restoration of sagebrush communities with degraded understories is needed, we do not recommend mowing and seeding native bunchgrasses because this treatment produced mixed results that may lower the resilience and resistance of these communities. Before this method is applied, research is needed to increase our understanding of how to improve establishment of seeded native bunchgrasses. Alternatively, restoration practitioners may need to apply treatments to control exotic annuals and repeatedly seed native bunchgrasses.
Biophysical Site Description Within the Pacific Northwest modeling zone, the cool sagebrush PNVG ... more Biophysical Site Description Within the Pacific Northwest modeling zone, the cool sagebrush PNVG consists of three intermingled tall shrub communities: mountain big sagebrush, threetip sagebrush, and mountain shrub. Of these, mountain big sagebrush is the principal community type. Mountain big sagebrush occurs in the cooler, moister portion of the sagebrush zone with elevation ranges from 3500 feet to 9000 feet on Steens Mountain. However, this community type is most prevalent between 5000 and 7000 feet elevation. Threetip sagebrush is intermingled with the mountain big sagebrush community at lower elevations, growing in pockets of moister soils at 3300 to 7000 feet elevation. At higher elevations, the mountain shrub community intermingles with the mountain big sagebrush community. Mean annual precipitation is typically between 14 and 22 inches, but ranges from 10 to 30 inches (Mueggler and Stewart 1980, Tart 1996). Mountain big sagebrush mostly occupies moist, productive rolling upland sites. Soils are typically moderately deep to deep, well-drained and have well developed dark organic surface horizons (Hironaka et al. 1983, Tart 1996). However, at the high ends of its precipitation and elevation ranges mountain big sagebrush occurs on shallow and/or rocky soils. Mountain big sagebrush is typically found where winter Reviewers Jon Bates
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