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• 1. [Article] Forest associations and secondary plant succession in the southern Oregon coastal range

  Forest associations, secondary succession, and relationships of plant communities to Roosevelt elk were investigated. Stratification of vegetation into ecological units and an understanding of secondary succession ...

  Citation × Citation Citation Abstract Copy Title: Forest associations and secondary plant succession in the southern Oregon coastal range Author: Bailey, Arthur Wesley, 1938- Forest associations, secondary succession, and relationships of plant communities to Roosevelt elk were investigated. Stratification of vegetation into ecological units and an understanding of secondary succession by habitat-type were a necessary first step in investigations into browsing of conifers by elk. The study was jointly conducted by the Oregon State Game Commission and the Weyerhaeuser Company. Vegetation, soils, and physiography were studied together. Vegetation cover data, recorded in thirty-two, 275 to 500-year-old forest stands, formed the basis of a synecological classification. Lightspots are a natural component of these forests. The dense forest and a lightspot were separately sampled in each stand. Light-spot cover data were analyzed separately in an association table. Lightspot data were compared with dense forest data to check validity of the phytosociological classification. This approach increased phytosociological understanding of these forests. The climax dominant tree and shrub and herb layer species with highest cover are used in naming the following associations (in order of increasing xerism): Thuja/Adiantum-Athyrium Tsuga/Polystichum/Oxalis Tsuga/Acer/Berberis Tsuga-Pseudotsuga/Rhododendron/Berberis Pseudotsuga/Holodiscus/Gaultheria. The exceptions are Adiantum pedatum and Athyrium filix-femina, high constancy, low cover, indicator species, used in naming the Thuja/Adiantum-Athyrium association. Polystichum munitum and Oxalis oregana dominate the herb layer of this association. Associations will be referred to in the abstract by a two-part name. The Adiantum-Athyrium association has the following additional indicator species: Blechnum spicant and Marah oreganus. Stands usually occur near the bottoms of lower elevation canyons. The moist, stony, Slickrock soil series underlies most stands. The Polystichum/Oxalis association is the most widespread and variable community studied. Tiarella trifoliata has high indicator value for this association. The presence of any one of Stellaria crispa, Montia sibirica, Dicentra formosa or Athyrium filix-femina in lightspots effectively differentiates stands of this association from related ones of the Acer/Berberis association. Stands frequently occur on lower and middle slopes and are usually underlain by the Matson or Apt soil series. In the Acer/Berberis association, Acer circinatum has high cover only in lightspots. Most stands are found on the Millicoma or Matson soil series. Stands occur on lower and middle slopes. Stands of the Rhododendron/Berberis association usually occur on south-facing, upper slopes and ridgetops where high winds frequently cause blowdown. The resultant large openings allow regeneration of Pseudotsuga menziesii. Rhododendron macrophyllum has low cover in the dense forest but high cover in lightspots. Allotropa virgata, a low constancy (saprophyte), has high fidelity to the association. The Millicoma, Matson or Ivers soil series underlie most stands. The Holodiscus/Gaultheria association has the following high fidelity species: Philadelphus lewisii, Symphoricarpos mollis, Madia gracilis, Hierochloe occidentalis, Ligusticum apiifolium, and Lonicera hispidula. This is the only association studied in which the lightspot phenomenon was not important. With the exception of Pseudotsuga menziesii regeneration, understory vegetation did not increase in cover when the tree canopy was removed. Stands usually occur on south-facing, upper slopes and ridgetops. The Digger or Agony soil series are associated with most stands. The successional influence of soil-surface disturbance caused by logging was studied in 1 to 15-year-old stands of the Polystichum/Oxalis and Rhododendron/Berberis habitat-types. In the Polystichum/Oxalis habitat-type, the vegetative dominants by years since logging are: Senecio sylvaticus--first year; Deschampsia elongata--years 2 to 4; Aira caryophyllea, Rubus ursinus, Hypochaeris radicata and Crepis capillaris share dominance--years 5 to 9; Hypochaeris radicata and Pteridium aquilinum share dominance--years 10 to 15. Pseudotsuga menziesii increased to 16 percent cover in the 10 to 15-year period. Disturbed areas of the Rhododendron/Berberis habitat-type have more than 65 percent bare ground for two years after logging. The vegetation dominants by years are: Deschampsia elongata--years 3 to 4; Hypochaeris radicata and Rubus ursinus--years 5 to 7; and Pseudotsuga menziesii--years 8 to 15. Other high cover species in the 8 to 15-year period are Thermopsis montana, Rubus ursinus, and Pteridium aquilinum. Selected stages in secondary succession were studied from one year after logging to climax in the two most important habitat-types. In the Polystichum/Oxalis habitat-type, Pseudotsuga menziesii is the seral tree dominant but is replaced by Tsuga heterophylla in climax. The tall shrub Acer circinatum has high cover in those serai stages with a comparatively open tree canopy. The herb layer is dominated throughout secondary succession by Polystichum munitum and Oxalis oregana. The tree layer of serai stands of the Rhododendron/Berberis habitat-type is dominated by Pseudotsuga menziesii. Either Tsuga heterophylla or Pseudotsuga menziesii dominate near-climax stands. The shrub layer dominant is Rhododendron macrophyllum throughout secondary succession. It has low cover in the dense forest but high cover in lightspots of near-climax stands. Berberis nervosa has nearly constant coverage throughout secondary succession in the Rhododendron/Berberis habitat-type and is the herb layer dominant in near-climax stands. Herb layer dominants in early serai stages are: Senecio sylvaticus--year 1; Erechtites prenanthoides--year 2; Rubus ursinus and Gaultheria shallon--years 4-15. Classification and recognition of habitat-types are possible throughout secondary succession from logging to climax on the basis of the same indicator species. The dominance level of some species changes with seral stage, but the change is predictable. Preferred elk food is about twice as abundant in the Polystichum/Oxalis as the Rhododendron/Berberis habitat-type. Nutritious, preferred elk food is most available in the 4 to 9-year period of secondary succession. Present logging methods which leave a mosaic of intermingled disturbed and undisturbed areas create a habitat beneficial to elk. The animals forage on disturbed areas for preferred invader species and on adjacent undisturbed areas for forest remnant species. Title: Forest associations and secondary plant succession in the southern Oregon coastal range Author: Bailey, Arthur Wesley, 1938- Forest associations, secondary succession, and relationships of plant communities to Roosevelt elk were investigated. Stratification of vegetation into ecological units and an understanding of secondary succession by habitat-type were a necessary first step in investigations into browsing of conifers by elk. The study was jointly conducted by the Oregon State Game Commission and the Weyerhaeuser Company. Vegetation, soils, and physiography were studied together. Vegetation cover data, recorded in thirty-two, 275 to 500-year-old forest stands, formed the basis of a synecological classification. Lightspots are a natural component of these forests. The dense forest and a lightspot were separately sampled in each stand. Light-spot cover data were analyzed separately in an association table. Lightspot data were compared with dense forest data to check validity of the phytosociological classification. This approach increased phytosociological understanding of these forests. The climax dominant tree and shrub and herb layer species with highest cover are used in naming the following associations (in order of increasing xerism): Thuja/Adiantum-Athyrium Tsuga/Polystichum/Oxalis Tsuga/Acer/Berberis Tsuga-Pseudotsuga/Rhododendron/Berberis Pseudotsuga/Holodiscus/Gaultheria. The exceptions are Adiantum pedatum and Athyrium filix-femina, high constancy, low cover, indicator species, used in naming the Thuja/Adiantum-Athyrium association. Polystichum munitum and Oxalis oregana dominate the herb layer of this association. Associations will be referred to in the abstract by a two-part name. The Adiantum-Athyrium association has the following additional indicator species: Blechnum spicant and Marah oreganus. Stands usually occur near the bottoms of lower elevation canyons. The moist, stony, Slickrock soil series underlies most stands. The Polystichum/Oxalis association is the most widespread and variable community studied. Tiarella trifoliata has high indicator value for this association. The presence of any one of Stellaria crispa, Montia sibirica, Dicentra formosa or Athyrium filix-femina in lightspots effectively differentiates stands of this association from related ones of the Acer/Berberis association. Stands frequently occur on lower and middle slopes and are usually underlain by the Matson or Apt soil series. In the Acer/Berberis association, Acer circinatum has high cover only in lightspots. Most stands are found on the Millicoma or Matson soil series. Stands occur on lower and middle slopes. Stands of the Rhododendron/Berberis association usually occur on south-facing, upper slopes and ridgetops where high winds frequently cause blowdown. The resultant large openings allow regeneration of Pseudotsuga menziesii. Rhododendron macrophyllum has low cover in the dense forest but high cover in lightspots. Allotropa virgata, a low constancy (saprophyte), has high fidelity to the association. The Millicoma, Matson or Ivers soil series underlie most stands. The Holodiscus/Gaultheria association has the following high fidelity species: Philadelphus lewisii, Symphoricarpos mollis, Madia gracilis, Hierochloe occidentalis, Ligusticum apiifolium, and Lonicera hispidula. This is the only association studied in which the lightspot phenomenon was not important. With the exception of Pseudotsuga menziesii regeneration, understory vegetation did not increase in cover when the tree canopy was removed. Stands usually occur on south-facing, upper slopes and ridgetops. The Digger or Agony soil series are associated with most stands. The successional influence of soil-surface disturbance caused by logging was studied in 1 to 15-year-old stands of the Polystichum/Oxalis and Rhododendron/Berberis habitat-types. In the Polystichum/Oxalis habitat-type, the vegetative dominants by years since logging are: Senecio sylvaticus--first year; Deschampsia elongata--years 2 to 4; Aira caryophyllea, Rubus ursinus, Hypochaeris radicata and Crepis capillaris share dominance--years 5 to 9; Hypochaeris radicata and Pteridium aquilinum share dominance--years 10 to 15. Pseudotsuga menziesii increased to 16 percent cover in the 10 to 15-year period. Disturbed areas of the Rhododendron/Berberis habitat-type have more than 65 percent bare ground for two years after logging. The vegetation dominants by years are: Deschampsia elongata--years 3 to 4; Hypochaeris radicata and Rubus ursinus--years 5 to 7; and Pseudotsuga menziesii--years 8 to 15. Other high cover species in the 8 to 15-year period are Thermopsis montana, Rubus ursinus, and Pteridium aquilinum. Selected stages in secondary succession were studied from one year after logging to climax in the two most important habitat-types. In the Polystichum/Oxalis habitat-type, Pseudotsuga menziesii is the seral tree dominant but is replaced by Tsuga heterophylla in climax. The tall shrub Acer circinatum has high cover in those serai stages with a comparatively open tree canopy. The herb layer is dominated throughout secondary succession by Polystichum munitum and Oxalis oregana. The tree layer of serai stands of the Rhododendron/Berberis habitat-type is dominated by Pseudotsuga menziesii. Either Tsuga heterophylla or Pseudotsuga menziesii dominate near-climax stands. The shrub layer dominant is Rhododendron macrophyllum throughout secondary succession. It has low cover in the dense forest but high cover in lightspots of near-climax stands. Berberis nervosa has nearly constant coverage throughout secondary succession in the Rhododendron/Berberis habitat-type and is the herb layer dominant in near-climax stands. Herb layer dominants in early serai stages are: Senecio sylvaticus--year 1; Erechtites prenanthoides--year 2; Rubus ursinus and Gaultheria shallon--years 4-15. Classification and recognition of habitat-types are possible throughout secondary succession from logging to climax on the basis of the same indicator species. The dominance level of some species changes with seral stage, but the change is predictable. Preferred elk food is about twice as abundant in the Polystichum/Oxalis as the Rhododendron/Berberis habitat-type. Nutritious, preferred elk food is most available in the 4 to 9-year period of secondary succession. Present logging methods which leave a mosaic of intermingled disturbed and undisturbed areas create a habitat beneficial to elk. The animals forage on disturbed areas for preferred invader species and on adjacent undisturbed areas for forest remnant species. Close

• 2. [Article] Realized and potential climate responses of lichen and bryophyte communities in a national forest inventory

  Climate and terrestrial vegetation have had mutual feedbacks for nearly five hundred million years, yet both are now departing from recent historical norms, with uncertain implications for forest ecosystems. ...

  Citation × Citation Citation Abstract Copy Title: Realized and potential climate responses of lichen and bryophyte communities in a national forest inventory Author: Smith, Robert J. Climate and terrestrial vegetation have had mutual feedbacks for nearly five hundred million years, yet both are now departing from recent historical norms, with uncertain implications for forest ecosystems. This dissertation outlines the current and potential future climate responses of lichen and bryophyte communities in the United States as part of a national forest inventory. The first task was to identify influences on carbon and nitrogen storage of moss and lichen “ground layers” in subarctic interior Alaska. Nutrient stores were more sensitive to local vegetation and topography than regional macroclimate. Nutrients and biomass were greatest among apparently less disturbed stands. This suggests that climatic changes could diminish ground layer nutrient storage indirectly if they promote intensifying wildfire regimes or expansions of competitive vascular vegetation. Turning to focus on species diversity, the next task was to quantify the strength of relationship between epiphytic lichen community composition and macroclimate across the 4,000 km-long swath of the U.S. Pacific coastal states. The strongest fitting lichen response gradients involved precipitation, temperature, and a heat-moisture index. Lichen indicator species (diagnostic of ten defined climate zones) emerged as useful monitoring tools because their abundance changes could signal shifting climate zone boundaries. After establishing key present-day climatic relationships, the next task was to pinpoint nationwide locations where epiphytic lichen communities will be most vulnerable to species losses under current and future warming scenarios. Novel niche-based metrics revealed greatest vulnerability among supposedly “warm-adapted” communities in southern/lowland locations, contrary to usual assumptions centering on cooler northern/montane habitats. Vulnerability analyses can steer conservation and monitoring attention to specific locations where warming is most expected to affect ecological communities. The final task, to anticipate how warming will impact individual lichen performance, was addressed by quantifying how experimental climate treatments (whole-ecosystem warming and CO2 additions) affected growth of the boreal epiphytic lichen species Evernia mesomorpha. Over just one year, incremental warming and concurrent drying caused progressive growth declines and biomass losses among individual transplants. Such warming-induced biomass losses of epiphytic lichens could precede local population extinctions and regional range contractions. Overall, this dissertation weaves together multiple lines of evidence from nutrient, diversity and growth responses to indicate the ecological effects of climate and climatic changes on vegetation in a national forest inventory context. This work suggests a pathway for integrating lichen and bryophyte responses into nationwide climate monitoring to address emergent interactions between humans, vegetation, and the global climate commons. Title: Realized and potential climate responses of lichen and bryophyte communities in a national forest inventory Author: Smith, Robert J. Climate and terrestrial vegetation have had mutual feedbacks for nearly five hundred million years, yet both are now departing from recent historical norms, with uncertain implications for forest ecosystems. This dissertation outlines the current and potential future climate responses of lichen and bryophyte communities in the United States as part of a national forest inventory. The first task was to identify influences on carbon and nitrogen storage of moss and lichen “ground layers” in subarctic interior Alaska. Nutrient stores were more sensitive to local vegetation and topography than regional macroclimate. Nutrients and biomass were greatest among apparently less disturbed stands. This suggests that climatic changes could diminish ground layer nutrient storage indirectly if they promote intensifying wildfire regimes or expansions of competitive vascular vegetation. Turning to focus on species diversity, the next task was to quantify the strength of relationship between epiphytic lichen community composition and macroclimate across the 4,000 km-long swath of the U.S. Pacific coastal states. The strongest fitting lichen response gradients involved precipitation, temperature, and a heat-moisture index. Lichen indicator species (diagnostic of ten defined climate zones) emerged as useful monitoring tools because their abundance changes could signal shifting climate zone boundaries. After establishing key present-day climatic relationships, the next task was to pinpoint nationwide locations where epiphytic lichen communities will be most vulnerable to species losses under current and future warming scenarios. Novel niche-based metrics revealed greatest vulnerability among supposedly “warm-adapted” communities in southern/lowland locations, contrary to usual assumptions centering on cooler northern/montane habitats. Vulnerability analyses can steer conservation and monitoring attention to specific locations where warming is most expected to affect ecological communities. The final task, to anticipate how warming will impact individual lichen performance, was addressed by quantifying how experimental climate treatments (whole-ecosystem warming and CO2 additions) affected growth of the boreal epiphytic lichen species Evernia mesomorpha. Over just one year, incremental warming and concurrent drying caused progressive growth declines and biomass losses among individual transplants. Such warming-induced biomass losses of epiphytic lichens could precede local population extinctions and regional range contractions. Overall, this dissertation weaves together multiple lines of evidence from nutrient, diversity and growth responses to indicate the ecological effects of climate and climatic changes on vegetation in a national forest inventory context. This work suggests a pathway for integrating lichen and bryophyte responses into nationwide climate monitoring to address emergent interactions between humans, vegetation, and the global climate commons. Close

• 3. [Article] Early stages in plant succession on Douglas fir clearcuts on the Mary's Peak watershed near Corvallis, Oregon

  This study has been concerned with the patterns of vegetative changes which occur during the first five years following logging and burning on Douglas-fir clear cuts. Knowledge of the successional sequence in ...

  Citation × Citation Citation Abstract Copy Title: Early stages in plant succession on Douglas fir clearcuts on the Mary's Peak watershed near Corvallis, Oregon Author: Brown, Eugene Allen This study has been concerned with the patterns of vegetative changes which occur during the first five years following logging and burning on Douglas-fir clear cuts. Knowledge of the successional sequence in the coastal forests of western Oregon is of primary importance to those concerned with the management of this resource. From the more theoretical point of view, there are many unique features associated with this type of vegetation of special interest to the ecologist. Published accounts of studies in Oregon and Washington have been of a generalized nature. None have approached a localized area with the degree of intensity attempted in this study. Due to its close proximity to Oregon State University and the cutting and burning history of the area, the Mary's Peak Watershed has been especially suitable for this study. Mary's Peak is the highest point of the Oregon Coast range having an elevation of 4,097 feet. The Corvallis watershed is located on the eastern slope of the peak and includes both the Rock Creek and Griffith Creek drainages. The area is about five miles long east and west by four miles north and south. The area is managed as a unit by the United States Forest Service. Due to the marine influence, the area has a humid climate averaging approximately 65 inches of precipitation annually with an annual mean temperature of approximately 52°F. Soils are basaltic in origin and are primarily clay loam in texture. In 1950, an epidemic of Douglas fir bark beetles made necessary a program of development which included cutting of dead and infected trees and establishing a road system. Cutting was restricted to small clear cuts. The vegetation in the study area is a Douglas fir-vine maple association. Gaultheria shallon and Berberis nervosa dominate the forest floor with traces of Castanopsis, Corylus, and Cornus. Study plots were located on nine clear cut and burned areas ranging in elevation from 1,300 to 2,800 feet and including north, south, and east exposures. Nineteen study plots, which were 100 x 100 feet, were established in uniform vegetative areas. Plots were also established in the undisturbed areas adjacent to the clear cuts for comparative purposes. Vegetative sampling was done using a device called an ocular point frame which provided a reliable indication of vegetative cover. Sampling was done in both the spring and fall on the second, third, fourth, and fifth years following burning. The stable undisturbed vegetation was sampled only once. Results of the five-year study showed a general increase in total number of plant species. The average total vegetative cover rose abruptly the third, fourth, and fifth years. An analysis indicated that south exposed plots had the greatest vegetative cover the first five years after burning. East plots ranked second and north plots third. By the fourth year, average cover values on clear cut areas exceeded the cover values of understory vegetation on the adjacent uncut forest. Analysis of data regarding seasonal variation indicated sharp decreases in total cover from spring to fall during the first three years. Increasing amounts of perennial vegetation during the fourth and fifth years reduced this seasonal variation markedly. In terms of mean cover trends, the annual herb, Senecio sylvaticus, dominated the second year; Lotus stipularis and Circium vulgare, the third; Lotus and Holcus lanatus , the fourth and fifth. All plant species indicated a wide range of cover values on the plots sampled. Some consistent trends in the sequence of cover dominance are noted. Title: Early stages in plant succession on Douglas fir clearcuts on the Mary's Peak watershed near Corvallis, Oregon Author: Brown, Eugene Allen This study has been concerned with the patterns of vegetative changes which occur during the first five years following logging and burning on Douglas-fir clear cuts. Knowledge of the successional sequence in the coastal forests of western Oregon is of primary importance to those concerned with the management of this resource. From the more theoretical point of view, there are many unique features associated with this type of vegetation of special interest to the ecologist. Published accounts of studies in Oregon and Washington have been of a generalized nature. None have approached a localized area with the degree of intensity attempted in this study. Due to its close proximity to Oregon State University and the cutting and burning history of the area, the Mary's Peak Watershed has been especially suitable for this study. Mary's Peak is the highest point of the Oregon Coast range having an elevation of 4,097 feet. The Corvallis watershed is located on the eastern slope of the peak and includes both the Rock Creek and Griffith Creek drainages. The area is about five miles long east and west by four miles north and south. The area is managed as a unit by the United States Forest Service. Due to the marine influence, the area has a humid climate averaging approximately 65 inches of precipitation annually with an annual mean temperature of approximately 52°F. Soils are basaltic in origin and are primarily clay loam in texture. In 1950, an epidemic of Douglas fir bark beetles made necessary a program of development which included cutting of dead and infected trees and establishing a road system. Cutting was restricted to small clear cuts. The vegetation in the study area is a Douglas fir-vine maple association. Gaultheria shallon and Berberis nervosa dominate the forest floor with traces of Castanopsis, Corylus, and Cornus. Study plots were located on nine clear cut and burned areas ranging in elevation from 1,300 to 2,800 feet and including north, south, and east exposures. Nineteen study plots, which were 100 x 100 feet, were established in uniform vegetative areas. Plots were also established in the undisturbed areas adjacent to the clear cuts for comparative purposes. Vegetative sampling was done using a device called an ocular point frame which provided a reliable indication of vegetative cover. Sampling was done in both the spring and fall on the second, third, fourth, and fifth years following burning. The stable undisturbed vegetation was sampled only once. Results of the five-year study showed a general increase in total number of plant species. The average total vegetative cover rose abruptly the third, fourth, and fifth years. An analysis indicated that south exposed plots had the greatest vegetative cover the first five years after burning. East plots ranked second and north plots third. By the fourth year, average cover values on clear cut areas exceeded the cover values of understory vegetation on the adjacent uncut forest. Analysis of data regarding seasonal variation indicated sharp decreases in total cover from spring to fall during the first three years. Increasing amounts of perennial vegetation during the fourth and fifth years reduced this seasonal variation markedly. In terms of mean cover trends, the annual herb, Senecio sylvaticus, dominated the second year; Lotus stipularis and Circium vulgare, the third; Lotus and Holcus lanatus , the fourth and fifth. All plant species indicated a wide range of cover values on the plots sampled. Some consistent trends in the sequence of cover dominance are noted. Close

• 4. [Article] The influence of tree cover and shade pattern upon the distribution of understory plants in ponderosa pine stands of central Oregon

  Seven sites of uniform topography and soil were selected within a self perpetuating ponderosa pine forest found on the eastern flank of the central Oregon Cascades. These plots were located along a vegetational ...

  Citation × Citation Citation Abstract Copy Title: The influence of tree cover and shade pattern upon the distribution of understory plants in ponderosa pine stands of central Oregon Author: Robinson, Andrew Frederick, Jr. Seven sites of uniform topography and soil were selected within a self perpetuating ponderosa pine forest found on the eastern flank of the central Oregon Cascades. These plots were located along a vegetational gradient caused mainly by an orographic rain shadow. Data gathered included density, frequency, and cover for all understory species, amount of direct overhead tree cover, and amount of shade cast by the tree canopy. An attempt was made to relate the distributional pattern of understory species to influences caused by shade, overhead tree cover, and shrub cover within each pIot. The Dfd index and Cole's index were statistical methods used to correlate the herbaceous species pattern to overhead tree cover, shrub cover, and shade. Of the two, Cole's index appeared to be a more sensitive tool for this study. All the shrub species with the exception of Purshia tridentata showed a consistent distributional pattern to insolation. The position along the vegetational gradient appeared to be related with the shrub's affinity for an insolation class. Those shrubs restricted to the mesic end of the gradient showed an affinity for Iow insolation or deep shade. Conversely, those shrubs occurring on the xeric end showed an affinity for higher insolation. Those shrubs found in the center of the gradient showed an affinity for moderate insolation. Ten herbaceous species out of a total of 16 observed showed apparent affinities for a certain microhabitat within the stand. Plot location, shade, overhead vertical crown cover, and shrub cover influenced the distribution of herbaceous species within the plot. Species found within mesic plots showed a weak affinity for cover, but those on xeric plots showed a strong affinity for cover. A weak indication of the spatial ecological niche was gained for 15 herbaceous species, but a strong indication was observed for Trientalis latifolia. Similarly, some insight into the ecological performance of the species was gained in regard to insolation. Usually the plot location coincided with the species' affinity for an insolation class. If the species occurred mainly on the mesic end of the gradient, it showed an affinity, for deep shade (Lupinus caudatus, Fragaria virginiana, Trientalis latifolia, and Pteridium aquilinum). If the species occurred mainly on the xeric end of the gradient, it showed an affinity for high insolation (Viola purpurea, Carex inops, and Madia minirna). Five species showed some affinity for moderate insolation (Clarkia rhornboidea, Eriogonurn urnbellaturn, Kelloggia galioides , Mimulus nanus, and Stipa occidentalis), but the correlation with plot location was less clear. Four species (Festuca idahoensis, Sitanion hvstrix, Achillea rnillefoliurn, and Lathvrus lanswertii) were not restricted to any part of the gradient. These species showed preference to insolation with the plot, but this preference was not usually the same throughout the gradient. Indications of the limits of ecological potential were found for some of these species, in particular Achillea millefolium which did not occur on any plot where insolation was less than 10%. Title: The influence of tree cover and shade pattern upon the distribution of understory plants in ponderosa pine stands of central Oregon Author: Robinson, Andrew Frederick, Jr. Seven sites of uniform topography and soil were selected within a self perpetuating ponderosa pine forest found on the eastern flank of the central Oregon Cascades. These plots were located along a vegetational gradient caused mainly by an orographic rain shadow. Data gathered included density, frequency, and cover for all understory species, amount of direct overhead tree cover, and amount of shade cast by the tree canopy. An attempt was made to relate the distributional pattern of understory species to influences caused by shade, overhead tree cover, and shrub cover within each pIot. The Dfd index and Cole's index were statistical methods used to correlate the herbaceous species pattern to overhead tree cover, shrub cover, and shade. Of the two, Cole's index appeared to be a more sensitive tool for this study. All the shrub species with the exception of Purshia tridentata showed a consistent distributional pattern to insolation. The position along the vegetational gradient appeared to be related with the shrub's affinity for an insolation class. Those shrubs restricted to the mesic end of the gradient showed an affinity for Iow insolation or deep shade. Conversely, those shrubs occurring on the xeric end showed an affinity for higher insolation. Those shrubs found in the center of the gradient showed an affinity for moderate insolation. Ten herbaceous species out of a total of 16 observed showed apparent affinities for a certain microhabitat within the stand. Plot location, shade, overhead vertical crown cover, and shrub cover influenced the distribution of herbaceous species within the plot. Species found within mesic plots showed a weak affinity for cover, but those on xeric plots showed a strong affinity for cover. A weak indication of the spatial ecological niche was gained for 15 herbaceous species, but a strong indication was observed for Trientalis latifolia. Similarly, some insight into the ecological performance of the species was gained in regard to insolation. Usually the plot location coincided with the species' affinity for an insolation class. If the species occurred mainly on the mesic end of the gradient, it showed an affinity, for deep shade (Lupinus caudatus, Fragaria virginiana, Trientalis latifolia, and Pteridium aquilinum). If the species occurred mainly on the xeric end of the gradient, it showed an affinity for high insolation (Viola purpurea, Carex inops, and Madia minirna). Five species showed some affinity for moderate insolation (Clarkia rhornboidea, Eriogonurn urnbellaturn, Kelloggia galioides , Mimulus nanus, and Stipa occidentalis), but the correlation with plot location was less clear. Four species (Festuca idahoensis, Sitanion hvstrix, Achillea rnillefoliurn, and Lathvrus lanswertii) were not restricted to any part of the gradient. These species showed preference to insolation with the plot, but this preference was not usually the same throughout the gradient. Indications of the limits of ecological potential were found for some of these species, in particular Achillea millefolium which did not occur on any plot where insolation was less than 10%. Close

• 5. [Article] Ectomycorrhizal populations on a chronosequence of disturbed areas in the central Cascades

  A greenhouse bioassay was used to investigate effects of natural and manmade disturbances on native ectomycorrhizal populations of Douglas-fir and western hemlock on a steep southeast slope in the west ...

  Citation × Citation Citation Abstract Copy Title: Ectomycorrhizal populations on a chronosequence of disturbed areas in the central Cascades Author: Meyer, Michele Marie A greenhouse bioassay was used to investigate effects of natural and manmade disturbances on native ectomycorrhizal populations of Douglas-fir and western hemlock on a steep southeast slope in the west central Cascade Mountains. Total and mycorrhizal root tips were counted on seedlings grown in soils collected from (a) two 100+ year old forests, (b) a 36-40 year old forest established after wildfire, (c) a recent clearcut in which residue had not been burned, (d) a recent clearcut which had been broadcast burned, and (e) a 20 year old Douglas-fir plantation. With Douglas-fir, the greatest number of total and ectomycorrhizal root tips were produced on seedlings grown in soils from the unburned clearcut. The least number of tips were produced in soils from the plantation and one of the old forests. The natural burn, the other old forest, and clearcut and burn plots were intermediate in total and mycorrhizal root production. The pattern of root tip formation on western hemlock was quite different. Plots with no recent burn history (the clearcut with no burn, the natural burn, and the two old growth forests) produced equivalent numbers of total and mycorrhizal root tips. Total root and mycorrhizal tip formation was depressed in soils from the clearcut and burn and from the young plantation. Soil variables measured, particularly nitrogen, carbon, and moisture, were highly correlated with both root dry weight and total mycorrhizal tips of Douglas-fir and western hemlock and occurrence of Cenococcuni geophilum Fr., a mycorrhizal fungus common to both seedling species. Differences among soils of the disturbance units obscured the relationship between root size, root tip numbers, and mycorrhizae. Data from the greenhouse bioassay, however, particularly regarding occurrence of Cenococcum, and the litter experiment indicated that differences in these parameters were at least in part due to differences in mycorrhizal response. Differential responses of Douglas-fir and western hemlock species also suggested that the mycorrhizal fungi, save for Cenococcum, were different for each seedling species. Title: Ectomycorrhizal populations on a chronosequence of disturbed areas in the central Cascades Author: Meyer, Michele Marie A greenhouse bioassay was used to investigate effects of natural and manmade disturbances on native ectomycorrhizal populations of Douglas-fir and western hemlock on a steep southeast slope in the west central Cascade Mountains. Total and mycorrhizal root tips were counted on seedlings grown in soils collected from (a) two 100+ year old forests, (b) a 36-40 year old forest established after wildfire, (c) a recent clearcut in which residue had not been burned, (d) a recent clearcut which had been broadcast burned, and (e) a 20 year old Douglas-fir plantation. With Douglas-fir, the greatest number of total and ectomycorrhizal root tips were produced on seedlings grown in soils from the unburned clearcut. The least number of tips were produced in soils from the plantation and one of the old forests. The natural burn, the other old forest, and clearcut and burn plots were intermediate in total and mycorrhizal root production. The pattern of root tip formation on western hemlock was quite different. Plots with no recent burn history (the clearcut with no burn, the natural burn, and the two old growth forests) produced equivalent numbers of total and mycorrhizal root tips. Total root and mycorrhizal tip formation was depressed in soils from the clearcut and burn and from the young plantation. Soil variables measured, particularly nitrogen, carbon, and moisture, were highly correlated with both root dry weight and total mycorrhizal tips of Douglas-fir and western hemlock and occurrence of Cenococcuni geophilum Fr., a mycorrhizal fungus common to both seedling species. Differences among soils of the disturbance units obscured the relationship between root size, root tip numbers, and mycorrhizae. Data from the greenhouse bioassay, however, particularly regarding occurrence of Cenococcum, and the litter experiment indicated that differences in these parameters were at least in part due to differences in mycorrhizal response. Differential responses of Douglas-fir and western hemlock species also suggested that the mycorrhizal fungi, save for Cenococcum, were different for each seedling species. Close

• 6. [Article] Interactions Among Fuel Management, Species Composition, Bark Beetles, and Climate Change and the Potential Effects on Forests of the Lake Tahoe Basin

  Climate-driven increases in wildfires, drought conditions, and insect outbreaks are critical threats to forest carbon stores. In particular, bark beetles are important disturbance agents although their ...

  Citation × Citation Citation Abstract Copy Title: Interactions Among Fuel Management, Species Composition, Bark Beetles, and Climate Change and the Potential Effects on Forests of the Lake Tahoe Basin Author: Scheller, Robert M., Kretchun, Alec M., Loudermilk, E. Louise, Hurteau, Matthew D., Weisberg, Peter J., Skinner, Carl Year: 2017 Climate-driven increases in wildfires, drought conditions, and insect outbreaks are critical threats to forest carbon stores. In particular, bark beetles are important disturbance agents although their long-term interactions with future climate change are poorly understood. Droughts and the associated moisture deficit contribute to the onset of bark beetle outbreaks although outbreak extent and severity is dependent upon the density of host trees, wildfire, and forest management. Our objective was to estimate the effects of climate change and bark beetle outbreaks on ecosystem carbon dynamics over the next century in a western US forest. Specifically, we hypothesized that (a) bark beetle outbreaks under climate change would reduce net ecosystem carbon balance (NECB) and increase uncertainty and (b) these effects could be ameliorated by fuels management. We also examined the specific tree species dynamics—competition and release—that determined NECB response to bark beetle outbreaks. Our study area was the Lake Tahoe Basin (LTB), CA and NV, USA, an area of diverse forest types encompassing steep elevation and climatic gradients and representative of mixed-conifer forests throughout the western United States. We simulated climate change, bark beetles, wildfire, and fuels management using a landscape-scale stochastic model of disturbance and succession. We simulated the period 2010–2100 using downscaled climate projections. Recurring droughts generated conditions conducive to large-scale outbreaks; the resulting large and sustained outbreaks significantly increased the probability of LTB forests becoming C sources over decadal time scales, with slower-than-anticipated landscape-scale recovery. Tree species composition was substantially altered with a reduction in functional redundancy and productivity. Results indicate heightened uncertainty due to the synergistic influences of climate change and interacting disturbances. Our results further indicate that current fuel management practices will not be effective at reducing landscape-scale outbreak mortality. Our results provide critical insights into the interaction of drivers (bark beetles, wildfire, fuel management) that increase the risk of C loss and shifting community composition if bark beetle outbreaks become more frequent. Title: Interactions Among Fuel Management, Species Composition, Bark Beetles, and Climate Change and the Potential Effects on Forests of the Lake Tahoe Basin Author: Scheller, Robert M., Kretchun, Alec M., Loudermilk, E. Louise, Hurteau, Matthew D., Weisberg, Peter J., Skinner, Carl Year: 2017 Climate-driven increases in wildfires, drought conditions, and insect outbreaks are critical threats to forest carbon stores. In particular, bark beetles are important disturbance agents although their long-term interactions with future climate change are poorly understood. Droughts and the associated moisture deficit contribute to the onset of bark beetle outbreaks although outbreak extent and severity is dependent upon the density of host trees, wildfire, and forest management. Our objective was to estimate the effects of climate change and bark beetle outbreaks on ecosystem carbon dynamics over the next century in a western US forest. Specifically, we hypothesized that (a) bark beetle outbreaks under climate change would reduce net ecosystem carbon balance (NECB) and increase uncertainty and (b) these effects could be ameliorated by fuels management. We also examined the specific tree species dynamics—competition and release—that determined NECB response to bark beetle outbreaks. Our study area was the Lake Tahoe Basin (LTB), CA and NV, USA, an area of diverse forest types encompassing steep elevation and climatic gradients and representative of mixed-conifer forests throughout the western United States. We simulated climate change, bark beetles, wildfire, and fuels management using a landscape-scale stochastic model of disturbance and succession. We simulated the period 2010–2100 using downscaled climate projections. Recurring droughts generated conditions conducive to large-scale outbreaks; the resulting large and sustained outbreaks significantly increased the probability of LTB forests becoming C sources over decadal time scales, with slower-than-anticipated landscape-scale recovery. Tree species composition was substantially altered with a reduction in functional redundancy and productivity. Results indicate heightened uncertainty due to the synergistic influences of climate change and interacting disturbances. Our results further indicate that current fuel management practices will not be effective at reducing landscape-scale outbreak mortality. Our results provide critical insights into the interaction of drivers (bark beetles, wildfire, fuel management) that increase the risk of C loss and shifting community composition if bark beetle outbreaks become more frequent. Close

• 7. [Article] Carbon Dynamics in the Future Forest: the Importance of Long-Term Successional Legacy and Climate–Fire Interactions

  Understanding how climate change may influence forest carbon (C) budgets requires knowledge of forest growth relationships with regional climate, long-term forest succession, and past and future disturbances, ...

  Citation × Citation Citation Abstract Copy Title: Carbon Dynamics in the Future Forest: the Importance of Long-Term Successional Legacy and Climate–Fire Interactions Author: Loudermilk, E. Louise, Scheller, Robert M., Weisberg, Peter J., Yang, Jian, Dilts, Thomas E., Karam, Sarah L., Skinner, Carl Year: 2013 Understanding how climate change may influence forest carbon (C) budgets requires knowledge of forest growth relationships with regional climate, long-term forest succession, and past and future disturbances, such as wildfires and timber harvesting events. We used a landscape-scale model of forest succession, wildfire, and C dynamics (LANDIS-II) to evaluate the effects of a changing climate (A2 and B1 IPCC emissions; Geophysical Fluid Dynamics Laboratory General Circulation Models) on total forest C, tree species composition, and wildfire dynamics in the Lake Tahoe Basin, California, and Nevada. The independent effects of temperature and precipitation were assessed within and among climate models. Results highlight the importance of modeling forest succession and stand development processes at the landscape scale for understanding the C cycle. Due primarily to landscape legacy effects of historic logging of the Comstock Era in the late 1880s, C sequestration may continue throughout the current century, and the forest will remain a C sink (Net Ecosystem Carbon Balance > 0), regardless of climate regime. Climate change caused increases in temperatures limited simulated C sequestration potential because of augmented fire activity and reduced establishment ability of subalpine and upper montane trees. Higher temperatures influenced forest response more than reduced precipitation. As the forest reached its potential steady state, the forest could become C neutral or a C source, and climate change could accelerate this transition. The future of forest ecosystem C cycling in many forested systems worldwide may depend more on major disturbances and landscape legacies related to land use than on projected climate change alone. Title: Carbon Dynamics in the Future Forest: the Importance of Long-Term Successional Legacy and Climate–Fire Interactions Author: Loudermilk, E. Louise, Scheller, Robert M., Weisberg, Peter J., Yang, Jian, Dilts, Thomas E., Karam, Sarah L., Skinner, Carl Year: 2013 Understanding how climate change may influence forest carbon (C) budgets requires knowledge of forest growth relationships with regional climate, long-term forest succession, and past and future disturbances, such as wildfires and timber harvesting events. We used a landscape-scale model of forest succession, wildfire, and C dynamics (LANDIS-II) to evaluate the effects of a changing climate (A2 and B1 IPCC emissions; Geophysical Fluid Dynamics Laboratory General Circulation Models) on total forest C, tree species composition, and wildfire dynamics in the Lake Tahoe Basin, California, and Nevada. The independent effects of temperature and precipitation were assessed within and among climate models. Results highlight the importance of modeling forest succession and stand development processes at the landscape scale for understanding the C cycle. Due primarily to landscape legacy effects of historic logging of the Comstock Era in the late 1880s, C sequestration may continue throughout the current century, and the forest will remain a C sink (Net Ecosystem Carbon Balance > 0), regardless of climate regime. Climate change caused increases in temperatures limited simulated C sequestration potential because of augmented fire activity and reduced establishment ability of subalpine and upper montane trees. Higher temperatures influenced forest response more than reduced precipitation. As the forest reached its potential steady state, the forest could become C neutral or a C source, and climate change could accelerate this transition. The future of forest ecosystem C cycling in many forested systems worldwide may depend more on major disturbances and landscape legacies related to land use than on projected climate change alone. Close

• 8. [Article] Temporal Variation in Nutrient Uptake Capacity by Intact Roots of Mature Loblolly Pine

  Nutrient uptake is generally thought to exhibit a simple seasonal pattern, but few studies have measured temporal variation of nutrient uptake capacity in mature trees. We measured net uptake capacity ...

  Citation × Citation Citation Abstract Copy Title: Temporal Variation in Nutrient Uptake Capacity by Intact Roots of Mature Loblolly Pine Author: Lucash, Melissa S., Joslin, J. Devereux, Yanai, Ruth D. Year: 2005 Nutrient uptake is generally thought to exhibit a simple seasonal pattern, but few studies have measured temporal variation of nutrient uptake capacity in mature trees. We measured net uptake capacity of K, NH+ 4, NO 3 −, Mg and Ca across a range of solution concentrations by roots of mature loblolly pine at Calhoun Experimental Forest in October 2001, July 2001, and April 2002. Uptake capacity was generally lowest in July; rates in October were similar to those in April. Across a range of concentrations, antecedent nutrient solution concentrations affected the temporal patterns in uptake in July but not in October or April. In July, uptake of NH+ 4, Mg and Ca was positively correlated with concentration when roots were exposed to successively lower concentrations, but negatively correlated with concentration when exposed to successively higher concentrations. In contrast, uptake in October was constant across the range of concentrations, while uptake increased with concentration in April. As in studies of other species, we found greater uptake of NH+ 4 than NO 3 −. Temporal patterns of uptake capacity are difficult to predict, and our results indicate that experimental conditions, such as experiment duration, antecedent root conditions and nutrient solution concentration, affect measured rates of nutrient uptake. Title: Temporal Variation in Nutrient Uptake Capacity by Intact Roots of Mature Loblolly Pine Author: Lucash, Melissa S., Joslin, J. Devereux, Yanai, Ruth D. Year: 2005 Nutrient uptake is generally thought to exhibit a simple seasonal pattern, but few studies have measured temporal variation of nutrient uptake capacity in mature trees. We measured net uptake capacity of K, NH+ 4, NO 3 −, Mg and Ca across a range of solution concentrations by roots of mature loblolly pine at Calhoun Experimental Forest in October 2001, July 2001, and April 2002. Uptake capacity was generally lowest in July; rates in October were similar to those in April. Across a range of concentrations, antecedent nutrient solution concentrations affected the temporal patterns in uptake in July but not in October or April. In July, uptake of NH+ 4, Mg and Ca was positively correlated with concentration when roots were exposed to successively lower concentrations, but negatively correlated with concentration when exposed to successively higher concentrations. In contrast, uptake in October was constant across the range of concentrations, while uptake increased with concentration in April. As in studies of other species, we found greater uptake of NH+ 4 than NO 3 −. Temporal patterns of uptake capacity are difficult to predict, and our results indicate that experimental conditions, such as experiment duration, antecedent root conditions and nutrient solution concentration, affect measured rates of nutrient uptake. Close

• 9. [Article] A new index for describing the structural complexity of forests

  Despite the critical ecological roles of structural features in forests, ecologically relevant quantitative measures of structure that allow comparisons among forest stands are still limited. A new index, ...

  Citation × Citation Citation Abstract Copy Title: A new index for describing the structural complexity of forests Author: Zenner, Eric K. Despite the critical ecological roles of structural features in forests, ecologically relevant quantitative measures of structure that allow comparisons among forest stands are still limited. A new index, the structural complexity index (SCI), was developed to characterize and compare the structural complexity of different forests. Point patterns of stem-mapped trees were converted into nearest neighbor triangles (with x, y, and z coordinates) by spatial tessellation, where x and y represent horizontal spatial location of points, and z represents a character of the point like height or diameter. The SCI was defined as the sum of the surface areas of a network of non-overlapping triangles, which form a continuous faceted surface in 3-D. Structural gradients were defined as the maximum size difference among the trees forming a triangle, with greater differences indicating higher structure. To compare structure at different vertical scales, size differences among neighbors that are below a certain magnitude (grain) are considered similar, trees sizes are set equal, giving a lower SCI limit of 1. The SCI was found to be strongly related to tree size variation, tree density, density of emergent canopy trees (> 100 cm dbh), and species mixture in multiple-aged stands. Different structural conditions were simulated by randomly assigning values of the tree size distribution to each tree position while holding the tree positions fixed, allowing an assessment of the maximum possible structural complexity (potential structure) given the observed tree size distribution. Based on the observed or effective structure and the potential structure, the 'maximum structure hypothesis for natural mixed conifer forests" was proposed, stating that in the absence of large-scale, stand replacement disturbances and in the presence of small-scale disturbances associated with mortality and replacement of individual trees, the effective structure is near the potential structure. There was strong evidence in young and mature stands in favor of the maximum structure hypothesis, but stands resembling old-growth structures had effective structures less that their potential. Although rejected in its simplistic form, the maximum structure hypothesis may prove to be a powerful concept in the analysis of forest ecosystems. Title: A new index for describing the structural complexity of forests Author: Zenner, Eric K. Despite the critical ecological roles of structural features in forests, ecologically relevant quantitative measures of structure that allow comparisons among forest stands are still limited. A new index, the structural complexity index (SCI), was developed to characterize and compare the structural complexity of different forests. Point patterns of stem-mapped trees were converted into nearest neighbor triangles (with x, y, and z coordinates) by spatial tessellation, where x and y represent horizontal spatial location of points, and z represents a character of the point like height or diameter. The SCI was defined as the sum of the surface areas of a network of non-overlapping triangles, which form a continuous faceted surface in 3-D. Structural gradients were defined as the maximum size difference among the trees forming a triangle, with greater differences indicating higher structure. To compare structure at different vertical scales, size differences among neighbors that are below a certain magnitude (grain) are considered similar, trees sizes are set equal, giving a lower SCI limit of 1. The SCI was found to be strongly related to tree size variation, tree density, density of emergent canopy trees (> 100 cm dbh), and species mixture in multiple-aged stands. Different structural conditions were simulated by randomly assigning values of the tree size distribution to each tree position while holding the tree positions fixed, allowing an assessment of the maximum possible structural complexity (potential structure) given the observed tree size distribution. Based on the observed or effective structure and the potential structure, the 'maximum structure hypothesis for natural mixed conifer forests" was proposed, stating that in the absence of large-scale, stand replacement disturbances and in the presence of small-scale disturbances associated with mortality and replacement of individual trees, the effective structure is near the potential structure. There was strong evidence in young and mature stands in favor of the maximum structure hypothesis, but stands resembling old-growth structures had effective structures less that their potential. Although rejected in its simplistic form, the maximum structure hypothesis may prove to be a powerful concept in the analysis of forest ecosystems. Close

• 10. [Article] Spatial and chronological patterns of Purshia tridentata as influenced by Pinus ponderosa overstory

  Twelve sites of uniform topography and soils were selected in the Pinus ponderosa/Purshia tridentata/Festuca idahoensis Association. These sites were located in the rain shadow on the east flank of the ...

  Citation × Citation Citation Abstract Copy Title: Spatial and chronological patterns of Purshia tridentata as influenced by Pinus ponderosa overstory Author: Sherman, Robert James Twelve sites of uniform topography and soils were selected in the Pinus ponderosa/Purshia tridentata/Festuca idahoensis Association. These sites were located in the rain shadow on the east flank of the Oregon Cascades. A fire history in the form of fire scars on ponderosa pine was available for nine of these sites. The bitter-brush populations on these sites were sampled at distances of 0-34.5 feet from a large ponderosa pine which clearly dominated the area for at least 50 feet. Density, cover, age, and clumping data for the bitterbrush were obtained. Density was found to be greatest on plots with the most recent occurrence of fire (22 years past). Cover was extremely variable within any one plot. Only slight variation was found in percent of live crown among the various plots regardless of their density or fire history. Age determinations using growth ring analysis or direct ring counts provided information indicating that although most bitterbrush do not survive a fire, sites are rapidly repopulated and generally show a peak repopulation year within 20 years after burning. Plants on sites with most recent fire tended to show more rapid height growth than did plants on "old" sites. Most "old" sites presently have a rather uniform age class profile with only slight indications of peak germination years. Most age class profiles do not fit a concave survivorship curve. Rodent caching as evidenced by plants growing in clumps was found to occur extensively on all sites. Most of the one year old clumps were large with as many as 21 living plants encountered. Progressive reduction in clump size probably occurs both through rodent browsing of young plants and later through moisture stress. By the time a clump has attained an average age of 30 it is likely that only two or three individuals remain alive. Clump distribution and litter distribution appear to be closely correlated. Most recently planted clumps were found to be outside of major litter deposit areas around ponderosa pine. Apparently rodents prefer to cache seeds in areas of essentially bare soil. The question of the perpetuation of bitterbrush in the absence of fire may be raised. Present fire control practices which allow extensive litter accumulation, especially on mesic sites, are resulting in an elimination of suitable planting sites for bitterbrush and may favor other species from more mesic associations less dependent upon fire and litter removal for their continued existence. Title: Spatial and chronological patterns of Purshia tridentata as influenced by Pinus ponderosa overstory Author: Sherman, Robert James Twelve sites of uniform topography and soils were selected in the Pinus ponderosa/Purshia tridentata/Festuca idahoensis Association. These sites were located in the rain shadow on the east flank of the Oregon Cascades. A fire history in the form of fire scars on ponderosa pine was available for nine of these sites. The bitter-brush populations on these sites were sampled at distances of 0-34.5 feet from a large ponderosa pine which clearly dominated the area for at least 50 feet. Density, cover, age, and clumping data for the bitterbrush were obtained. Density was found to be greatest on plots with the most recent occurrence of fire (22 years past). Cover was extremely variable within any one plot. Only slight variation was found in percent of live crown among the various plots regardless of their density or fire history. Age determinations using growth ring analysis or direct ring counts provided information indicating that although most bitterbrush do not survive a fire, sites are rapidly repopulated and generally show a peak repopulation year within 20 years after burning. Plants on sites with most recent fire tended to show more rapid height growth than did plants on "old" sites. Most "old" sites presently have a rather uniform age class profile with only slight indications of peak germination years. Most age class profiles do not fit a concave survivorship curve. Rodent caching as evidenced by plants growing in clumps was found to occur extensively on all sites. Most of the one year old clumps were large with as many as 21 living plants encountered. Progressive reduction in clump size probably occurs both through rodent browsing of young plants and later through moisture stress. By the time a clump has attained an average age of 30 it is likely that only two or three individuals remain alive. Clump distribution and litter distribution appear to be closely correlated. Most recently planted clumps were found to be outside of major litter deposit areas around ponderosa pine. Apparently rodents prefer to cache seeds in areas of essentially bare soil. The question of the perpetuation of bitterbrush in the absence of fire may be raised. Present fire control practices which allow extensive litter accumulation, especially on mesic sites, are resulting in an elimination of suitable planting sites for bitterbrush and may favor other species from more mesic associations less dependent upon fire and litter removal for their continued existence. Close