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• 351. [Article] Improving estimates of forest disturbance by combining observations from Landsat time series with U.S. Forest Service Forest Inventory and Analysis data

  To the best of our knowledge, one or more authors of this paper were federal employees when contributing to this work. This is the publisher’s final pdf. The published article is copyrighted by Elsevier ...

  Citation × Citation Citation Abstract Copy Title: Improving estimates of forest disturbance by combining observations from Landsat time series with U.S. Forest Service Forest Inventory and Analysis data Author: Yang, Zhiqiang, Schroeder, Todd A., Healey, Sean P., et al., Moisen, Gretchen G. To the best of our knowledge, one or more authors of this paper were federal employees when contributing to this work. This is the publisher’s final pdf. The published article is copyrighted by Elsevier and can be found at: http://www.journals.elsevier.com/remote-sensing-of-environment/. Title: Improving estimates of forest disturbance by combining observations from Landsat time series with U.S. Forest Service Forest Inventory and Analysis data Author: Yang, Zhiqiang, Schroeder, Todd A., Healey, Sean P., et al., Moisen, Gretchen G. To the best of our knowledge, one or more authors of this paper were federal employees when contributing to this work. This is the publisher’s final pdf. The published article is copyrighted by Elsevier and can be found at: http://www.journals.elsevier.com/remote-sensing-of-environment/. Close

• 352. [Article] Establishment tolerance of six native sagebrush steppe species to imazapic (PLATEAU®) herbicide implications for restoration and recovery

  Scientists and land managers realize that integrated weed management (IWM) strategies are needed to attain successful and lasting improvements of weed infested landscapes. At this time no broadly reliable ...

  Citation × Citation Citation Abstract Copy Title: Establishment tolerance of six native sagebrush steppe species to imazapic (PLATEAU®) herbicide implications for restoration and recovery Author: Bekedam, Steven Scientists and land managers realize that integrated weed management (IWM) strategies are needed to attain successful and lasting improvements of weed infested landscapes. At this time no broadly reliable and environmentally safe IWM strategy has been developed to control exotic annual grasses that dominate many ecosystems of the northern Great Basin. This study determined the efficacy of several nascent control strategies at a site near Mountain Home, ID, USA with particular emphasis on the tolerance of native species to chemical control techniques applied before their emergence. In autumn 2002, prescribed burning and a single preemergent application of imazapic (PLATEAU®) herbicide were used separately and combined to control medusahead wildrye (Taeniatherum caput-medusae (L.) Nevski) and cheatgrass (Bromus tectorum L.). Seeds of six native perennial species, selected for their range of life histories and ability to provide effective competition, were planted as monocultures two-weeks after fire and herbicide applications. A monthly census determined native seedling emergence and survival from late winter through autumn 2003. In addition, end-of-season population size and reproduction were determined for both exotic annual grasses in each treatment. We hypothesized that application of imazapic would reduce and delay emergence, cause earlier mortality rates, and lower overall persistence of seeded natives because of adverse impacts to early seedling development throughout the growing season. Burning and imazapic applications combined would amplify these effects with reduced plant residue cover and increased surface evaporation. Prescribed treatments reduced densities of mature exotic annual grasses by 31.1% for burning alone, 79.1% for imazapic alone, and 92.1% for areas with burning and imazapic combined when compared to untreated controls. Few seedlings of globemallow (Sphaeralcea grossularifolia (Hook & Arn.) Rydb.) emerged from any treatment due to extreme dormancy and/or poor site adaptation. Significant responses of the five remaining native species fell into three general patterns associated with three functional/structural plant groups. Deeper-rooted perennials, big squirreltail (Elymus multisetus M.E. Jones) and Snake River wheatgrass (Elymus wawawaiensis J. Carlson & Barkworth), showed positive responses to imazapic applications. For E. multisetus, more seedlings emerged in areas treated with imazapic alone than in any other treatment (P<0.01). Rather than impacts from imazapic application, E. multisetus seedlings emerged earlier in unburned versus burned areas (P<0.01) likely due to greater moisture retention and moderated temperature extremes from the presence of surface litter. For native dicots, Wyoming big sagebrush (Artemisia tridentata Nutt. ssp. wyomingensis Beetle and Young) and western yarrow (Achillea millefolium L. var. occidentalis DC.), overall emergence was reduced by an average of 20% in burned relative to unburned plots likely because of variable surface temperatures, frost heaving of the upper soil profile, and more rapid evaporation of available moisture early in the growing season. Emergence was 3.2 and 2.2 times sooner for A. tridentata (P=0.02) and A. millefolium (P=0.02) on unburned relative to burned treatments for reasons similar to those of deeper-rooted perennials. A. millefolium seedlings experienced particularly slow emergence in plots burned and treated with imazapic. Prescribed burn plots had seedlings emerge 2.1 times (P=0.04) sooner than burning with imazapic. This implies that imazapic, as well as burning, may be slowing seedling development of this species. Burned plots also exhibited seedling mortality in nine-tenths the time than unburned plots for A. tridentata and A. millefolium (P=0.03 and P=0.05). The shallow-rooted perennial, Sandberg bluegrass (Poa secunda J. Presl.), was the only seeded species to carry on a population into the fall of 2003. Untreated controls had 3.3 times more plants per m² than plots applied with imazapic alone (P=0.03) implying a degree of imazapic intolerance for this species. Although this research indicates that some native arid species are tolerant to imazapic, experiments should continue to incorporate fall preemergent applications of this herbicide to improve our understanding of native species responses and foster the development of an effective IWM strategy for arid rangelands of the Great Basin. Title: Establishment tolerance of six native sagebrush steppe species to imazapic (PLATEAU®) herbicide implications for restoration and recovery Author: Bekedam, Steven Scientists and land managers realize that integrated weed management (IWM) strategies are needed to attain successful and lasting improvements of weed infested landscapes. At this time no broadly reliable and environmentally safe IWM strategy has been developed to control exotic annual grasses that dominate many ecosystems of the northern Great Basin. This study determined the efficacy of several nascent control strategies at a site near Mountain Home, ID, USA with particular emphasis on the tolerance of native species to chemical control techniques applied before their emergence. In autumn 2002, prescribed burning and a single preemergent application of imazapic (PLATEAU®) herbicide were used separately and combined to control medusahead wildrye (Taeniatherum caput-medusae (L.) Nevski) and cheatgrass (Bromus tectorum L.). Seeds of six native perennial species, selected for their range of life histories and ability to provide effective competition, were planted as monocultures two-weeks after fire and herbicide applications. A monthly census determined native seedling emergence and survival from late winter through autumn 2003. In addition, end-of-season population size and reproduction were determined for both exotic annual grasses in each treatment. We hypothesized that application of imazapic would reduce and delay emergence, cause earlier mortality rates, and lower overall persistence of seeded natives because of adverse impacts to early seedling development throughout the growing season. Burning and imazapic applications combined would amplify these effects with reduced plant residue cover and increased surface evaporation. Prescribed treatments reduced densities of mature exotic annual grasses by 31.1% for burning alone, 79.1% for imazapic alone, and 92.1% for areas with burning and imazapic combined when compared to untreated controls. Few seedlings of globemallow (Sphaeralcea grossularifolia (Hook & Arn.) Rydb.) emerged from any treatment due to extreme dormancy and/or poor site adaptation. Significant responses of the five remaining native species fell into three general patterns associated with three functional/structural plant groups. Deeper-rooted perennials, big squirreltail (Elymus multisetus M.E. Jones) and Snake River wheatgrass (Elymus wawawaiensis J. Carlson & Barkworth), showed positive responses to imazapic applications. For E. multisetus, more seedlings emerged in areas treated with imazapic alone than in any other treatment (P<0.01). Rather than impacts from imazapic application, E. multisetus seedlings emerged earlier in unburned versus burned areas (P<0.01) likely due to greater moisture retention and moderated temperature extremes from the presence of surface litter. For native dicots, Wyoming big sagebrush (Artemisia tridentata Nutt. ssp. wyomingensis Beetle and Young) and western yarrow (Achillea millefolium L. var. occidentalis DC.), overall emergence was reduced by an average of 20% in burned relative to unburned plots likely because of variable surface temperatures, frost heaving of the upper soil profile, and more rapid evaporation of available moisture early in the growing season. Emergence was 3.2 and 2.2 times sooner for A. tridentata (P=0.02) and A. millefolium (P=0.02) on unburned relative to burned treatments for reasons similar to those of deeper-rooted perennials. A. millefolium seedlings experienced particularly slow emergence in plots burned and treated with imazapic. Prescribed burn plots had seedlings emerge 2.1 times (P=0.04) sooner than burning with imazapic. This implies that imazapic, as well as burning, may be slowing seedling development of this species. Burned plots also exhibited seedling mortality in nine-tenths the time than unburned plots for A. tridentata and A. millefolium (P=0.03 and P=0.05). The shallow-rooted perennial, Sandberg bluegrass (Poa secunda J. Presl.), was the only seeded species to carry on a population into the fall of 2003. Untreated controls had 3.3 times more plants per m² than plots applied with imazapic alone (P=0.03) implying a degree of imazapic intolerance for this species. Although this research indicates that some native arid species are tolerant to imazapic, experiments should continue to incorporate fall preemergent applications of this herbicide to improve our understanding of native species responses and foster the development of an effective IWM strategy for arid rangelands of the Great Basin. Close

• 353. [Article] Comparing vegetation and soils of remnant and restored prairie wetlands in the northern Willamette Valley

  Native prairies of the Willamette Valley are considered among the rarest of Oregon's ecosystems (Clark and Wilson, 2001). As a result of agriculture conversion, urban development and cessation of native ...

  Citation × Citation Citation Abstract Copy Title: Comparing vegetation and soils of remnant and restored prairie wetlands in the northern Willamette Valley Author: Taylor, Sara M. Native prairies of the Willamette Valley are considered among the rarest of Oregon's ecosystems (Clark and Wilson, 2001). As a result of agriculture conversion, urban development and cessation of native burning, Willamette Valley prairies have become highly fragmented and invaded by non-native species, leaving little room for native plant diversity. Even though wetland prairie conservation and restoration has been a priority for many government agencies there is a need for research on what restoration techniques and management are necessary for increasing native species richness and abundance in remnant and restored wet prairie sites. In this research project, two studies were conducted. In the first study, data were collected on species presence and abundance from three 100m² randomized plots within three remnant wet prairies (Green Mountain, Gotter Prairie South, Knez) and three restored wet prairies (Hutchinson, Gotter Prairie North, Lovejoy) to answer the following research question, 'Are there differences between remnant and restored prairie plant communities with respect to the diversity and abundance of native species?' Analysis of variance and multivariate ordination techniques were used to assess the ecological differences between uncultivated, minimally-managed remnant wet prairies and newly-restored, highly managed wet prairies. Data on soils collected from agricultural sites (Westbrook, Zurcher, Gotter Prairie Ag), as well as the remnant and restored wet prairies mentioned above, were also used to compare soil quality and processes with the remnant and restored wetlands. Restored wet prairie had 23% higher native species cover than remnant prairie (p-value=0.089, N=6). Remnant and restored sites did not differ in native species richness (p-value=0.949, N=6). The relatively high per cent cover of native species at restored sites, (significant at the 10% level), suggests that land managers have successfully restored agricultural properties with an abundance of native species. The lack of significant difference in native species richness between remnant and restored sites also suggests that land managers have also been able to restore native plant diversity into former agricultural properties equivalent to some of the best intact remnant prairies within the Northern Willamette Valley in a short period of time (8 years or less). However, a non-metric scaling (NMS) ordination of the species matrix separated the remnant sites from the restored sites, suggesting that community composition distinguishes restored sites from remnants. The NMS results, which include environmental data in the analysis, also suggest that there is a positive correlation of percent soil moisture and percent soil organic matter associated with the remnant prairies and a positive correlation of management practices such as yearly chemical use, mowing, and clean crops, associated with the restored prairies. The location of Gotter Prairie North restoration within the ordination, between the remnant and restored sites, suggests an intermediate plant composition and soil quality. This could be attributed to intensive weed suppression and soil organic matter build up over time (8 years) in comparison to younger restored sites (3 and 4 years). Indicator species analysis identified many species with high indicator values (IVs) in the remnant prairies; Holcus lanatus, Deschampsia cespitosa, Carex densa and Phalaris arundinacea being the highest. The use of fire as a management tool produced only one species with a high IV (Camassia quamash). In the second study, three seeding treatments (Grass first, Grass and Forb together, Forb first) were compared within a 4 hectare experimental wet prairie unit to answer the research question „Which of the three seeding treatments used leads to the highest native species abundance and species richness?‟ Results from an analysis of variance indicated significant differences between treatments in native species richness for 2009 and 2010 (p-values=0.002 & 0.004 respectively) at the 5% level and native species abundance in 2010 only (p-value=0.099) at the 10% level. The Grass and Forb and Forb first treatments were highest in native species richness for 2009 and 2010, whereas the Grass and Forb and Grass first treatments were highest in native species abundance in 2010. A NMS ordination suggests that Juncus tenuis is one of the dominant species, in all seeding treatments, after one year of growth. Title: Comparing vegetation and soils of remnant and restored prairie wetlands in the northern Willamette Valley Author: Taylor, Sara M. Native prairies of the Willamette Valley are considered among the rarest of Oregon's ecosystems (Clark and Wilson, 2001). As a result of agriculture conversion, urban development and cessation of native burning, Willamette Valley prairies have become highly fragmented and invaded by non-native species, leaving little room for native plant diversity. Even though wetland prairie conservation and restoration has been a priority for many government agencies there is a need for research on what restoration techniques and management are necessary for increasing native species richness and abundance in remnant and restored wet prairie sites. In this research project, two studies were conducted. In the first study, data were collected on species presence and abundance from three 100m² randomized plots within three remnant wet prairies (Green Mountain, Gotter Prairie South, Knez) and three restored wet prairies (Hutchinson, Gotter Prairie North, Lovejoy) to answer the following research question, 'Are there differences between remnant and restored prairie plant communities with respect to the diversity and abundance of native species?' Analysis of variance and multivariate ordination techniques were used to assess the ecological differences between uncultivated, minimally-managed remnant wet prairies and newly-restored, highly managed wet prairies. Data on soils collected from agricultural sites (Westbrook, Zurcher, Gotter Prairie Ag), as well as the remnant and restored wet prairies mentioned above, were also used to compare soil quality and processes with the remnant and restored wetlands. Restored wet prairie had 23% higher native species cover than remnant prairie (p-value=0.089, N=6). Remnant and restored sites did not differ in native species richness (p-value=0.949, N=6). The relatively high per cent cover of native species at restored sites, (significant at the 10% level), suggests that land managers have successfully restored agricultural properties with an abundance of native species. The lack of significant difference in native species richness between remnant and restored sites also suggests that land managers have also been able to restore native plant diversity into former agricultural properties equivalent to some of the best intact remnant prairies within the Northern Willamette Valley in a short period of time (8 years or less). However, a non-metric scaling (NMS) ordination of the species matrix separated the remnant sites from the restored sites, suggesting that community composition distinguishes restored sites from remnants. The NMS results, which include environmental data in the analysis, also suggest that there is a positive correlation of percent soil moisture and percent soil organic matter associated with the remnant prairies and a positive correlation of management practices such as yearly chemical use, mowing, and clean crops, associated with the restored prairies. The location of Gotter Prairie North restoration within the ordination, between the remnant and restored sites, suggests an intermediate plant composition and soil quality. This could be attributed to intensive weed suppression and soil organic matter build up over time (8 years) in comparison to younger restored sites (3 and 4 years). Indicator species analysis identified many species with high indicator values (IVs) in the remnant prairies; Holcus lanatus, Deschampsia cespitosa, Carex densa and Phalaris arundinacea being the highest. The use of fire as a management tool produced only one species with a high IV (Camassia quamash). In the second study, three seeding treatments (Grass first, Grass and Forb together, Forb first) were compared within a 4 hectare experimental wet prairie unit to answer the research question „Which of the three seeding treatments used leads to the highest native species abundance and species richness?‟ Results from an analysis of variance indicated significant differences between treatments in native species richness for 2009 and 2010 (p-values=0.002 & 0.004 respectively) at the 5% level and native species abundance in 2010 only (p-value=0.099) at the 10% level. The Grass and Forb and Forb first treatments were highest in native species richness for 2009 and 2010, whereas the Grass and Forb and Grass first treatments were highest in native species abundance in 2010. A NMS ordination suggests that Juncus tenuis is one of the dominant species, in all seeding treatments, after one year of growth. Close

• 354. [Article] Influence of silvicultural treatments, overstory, and understory vegetation on quaking aspen (Populus tremuloides) regeneration in southeastern Idaho

  Quaking aspen (Populus tremuloides Michx.) is known to be a widely distributed, shade-intolerant and short-lived hardwood found in both seral, even-aged and stable, uneven aged stands. There have been ...

  Citation × Citation Citation Abstract Copy Title: Influence of silvicultural treatments, overstory, and understory vegetation on quaking aspen (Populus tremuloides) regeneration in southeastern Idaho Author: Muñoz, Bethany L. Quaking aspen (Populus tremuloides Michx.) is known to be a widely distributed, shade-intolerant and short-lived hardwood found in both seral, even-aged and stable, uneven aged stands. There have been reports of extensive aspen mortality, crown thinning, and branch dieback across North America that have been linked to the occurrence of severe droughts since 2001-2002. Because of reports of low aspen regeneration across the Intermountain West, as well as predictions of increases in aspen regeneration in the Northeastern US, researchers and land managers have now focused on managing aspen stands under the assumption that there are multiple aspen types. They have focused on improving resilience within quaking aspen stands with changing ecological conditions. For this thesis I focused on a project the Bureau of Land Management (BLM), Pocatello Field Office initiated in part to improve aspen restoration and resilience of stands in Soda Springs, ID. The BLM conducted two mechanical removal treatments: cut and pile, and slash/lop and scatter. In addition several sites were broadcast burned to reduce fuel loads and conifer density, to enhance aspen regeneration and improve aspen stand resilience. According to the Soda Springs Hills Fuels Reduction and Ecosystem Restoration Environmental Assessment (EA), the BLM aimed to meet the objective of 2500 quaking aspen suckers per ha (1000 suckers per ac) within the two years following treatment, an index of treatment adequacy. My primary objective for this thesis was to assess the influence of each silvicultural treatment, including the change in overstory and understory vegetation, on regeneration of aspen. Mean aspen regeneration two growing seasons after treatment was 11,532 suckers/ha on sites that received slash/lop and scatter treatment, followed by broadcast burning. With these high levels of suckering, there were also low densities of residual overstory conifers (≤ 4 trees/ha with a basal area ≤ 2 m²/ha). In comparison, sites that received the cut and pile treatment followed by a broadcast burn had a mean aspen regeneration of 44 suckers/ha, with higher densities of overstory conifers (≥ 32 trees/ha with a basal area ≥ 26 m²/ha). In slash/lop and scatter treatments without burning, sucker densities were as high as 1117 suckers/ha with low densities of conifers (0 trees/ha). In comparison, the site that received the cut and pile treatment without burning had an aspen regeneration of 0 suckers/ha, with a high density of conifers (36 trees/ha with a basal area of 47 m²/ha). Overall, sites with low residual overstory cover of large conifer trees (< 4 trees/ha), regardless of the treatment, had higher sucker densities two growing seasons after treatment (6244 suckers/ha, on average) than those seen in sites with a remnant overstory of >16 trees/ha (29 suckers/ha, on average). Also, sites that were burned, regardless of the mechanical treatment used, had higher sucker densities (11,244 suckers/ha) than those seen in sites that were not burned (576 suckers/ha). When comparing aspen sucker densities to competing understory woody cover following mechanical treatment, aspen sucker density was lowest (411 suckers/ha) on the site where both tree and shrub percent cover were highest (10 and 16%, respectively). Suckering appeared to be positively correlated with grass cover, however, with as high as 1117 suckers/ha growing with a high percentage of grass cover (≥ 26 %), on sites measured for change in understory following mechanical treatment. Results were collected on a small number of sites and thus have limited statistical significance. However, we are confident that observed trends have values for managers. We suggest that transects should continue to be monitored to observe the long-term effects of silvicultural treatments on overstory and understory vegetation, which are likely to be influenced by climate variability and other disturbances into the future. Title: Influence of silvicultural treatments, overstory, and understory vegetation on quaking aspen (Populus tremuloides) regeneration in southeastern Idaho Author: Muñoz, Bethany L. Quaking aspen (Populus tremuloides Michx.) is known to be a widely distributed, shade-intolerant and short-lived hardwood found in both seral, even-aged and stable, uneven aged stands. There have been reports of extensive aspen mortality, crown thinning, and branch dieback across North America that have been linked to the occurrence of severe droughts since 2001-2002. Because of reports of low aspen regeneration across the Intermountain West, as well as predictions of increases in aspen regeneration in the Northeastern US, researchers and land managers have now focused on managing aspen stands under the assumption that there are multiple aspen types. They have focused on improving resilience within quaking aspen stands with changing ecological conditions. For this thesis I focused on a project the Bureau of Land Management (BLM), Pocatello Field Office initiated in part to improve aspen restoration and resilience of stands in Soda Springs, ID. The BLM conducted two mechanical removal treatments: cut and pile, and slash/lop and scatter. In addition several sites were broadcast burned to reduce fuel loads and conifer density, to enhance aspen regeneration and improve aspen stand resilience. According to the Soda Springs Hills Fuels Reduction and Ecosystem Restoration Environmental Assessment (EA), the BLM aimed to meet the objective of 2500 quaking aspen suckers per ha (1000 suckers per ac) within the two years following treatment, an index of treatment adequacy. My primary objective for this thesis was to assess the influence of each silvicultural treatment, including the change in overstory and understory vegetation, on regeneration of aspen. Mean aspen regeneration two growing seasons after treatment was 11,532 suckers/ha on sites that received slash/lop and scatter treatment, followed by broadcast burning. With these high levels of suckering, there were also low densities of residual overstory conifers (≤ 4 trees/ha with a basal area ≤ 2 m²/ha). In comparison, sites that received the cut and pile treatment followed by a broadcast burn had a mean aspen regeneration of 44 suckers/ha, with higher densities of overstory conifers (≥ 32 trees/ha with a basal area ≥ 26 m²/ha). In slash/lop and scatter treatments without burning, sucker densities were as high as 1117 suckers/ha with low densities of conifers (0 trees/ha). In comparison, the site that received the cut and pile treatment without burning had an aspen regeneration of 0 suckers/ha, with a high density of conifers (36 trees/ha with a basal area of 47 m²/ha). Overall, sites with low residual overstory cover of large conifer trees (< 4 trees/ha), regardless of the treatment, had higher sucker densities two growing seasons after treatment (6244 suckers/ha, on average) than those seen in sites with a remnant overstory of >16 trees/ha (29 suckers/ha, on average). Also, sites that were burned, regardless of the mechanical treatment used, had higher sucker densities (11,244 suckers/ha) than those seen in sites that were not burned (576 suckers/ha). When comparing aspen sucker densities to competing understory woody cover following mechanical treatment, aspen sucker density was lowest (411 suckers/ha) on the site where both tree and shrub percent cover were highest (10 and 16%, respectively). Suckering appeared to be positively correlated with grass cover, however, with as high as 1117 suckers/ha growing with a high percentage of grass cover (≥ 26 %), on sites measured for change in understory following mechanical treatment. Results were collected on a small number of sites and thus have limited statistical significance. However, we are confident that observed trends have values for managers. We suggest that transects should continue to be monitored to observe the long-term effects of silvicultural treatments on overstory and understory vegetation, which are likely to be influenced by climate variability and other disturbances into the future. Close

• 355. [Article] Sediment accumulation and human impacts in Tillamook Bay, Oregon

  Tillamook Bay is the second largest estuary on the Oregon coast, and concerns have been raised whether human induced impacts have been responsible for the perceived increase in sedimentation rates during ...

  Citation × Citation Citation Abstract Copy Title: Sediment accumulation and human impacts in Tillamook Bay, Oregon Author: Styllas, Michael N. Tillamook Bay is the second largest estuary on the Oregon coast, and concerns have been raised whether human induced impacts have been responsible for the perceived increase in sedimentation rates during the past century. Major land-use practices within the five watersheds of the Bay include logging, forest fires, the construction of forest roads, the placement of dikes along the channels of the main rivers and in the estuary, the removal of riparian vegetation, and the construction of jetties at the tidal inlet. Each of these practices has led to impacts on the entire ecosystem of the watersheds and the Bay, but this study focuses on the effects of human disturbances on the Bay's sediment accumulation. This study examines in detail the land-use practices that have occurred in the watersheds, on the beaches, and in the estuary, focusing on those that have had a direct impact on the sedimentation regime of the Bay. One goal of the study is to assess the relative roles of natural processes versus human impacts on the sedimentation. A general description of the physical characteristics of Tillamook Bay and its surroundings is included, and a brief discussion is provided about the tectonic setting of the Northwest Coast, including its history of subduction earthquakes and the associate sea-level changes. Also provided is a summary of the existing information concerning the arrival of Indians and their environmental impacts, followed by a more detailed account of the major impacts that have resulted from the settlement of the Euro-Americans in the Tillamook area, in the 1850's. The study then focuses on the description of the watersheds from a geomorphologic point of view, and the important land-use practices that may have affected sediment yields during the past century. Analyses of the hydrology of the Tillamook Bay watersheds are included, and the relations between annual water yields and total precipitation are examined in distinct time intervals, each corresponding to a different period with different amounts of land uses. The results of these hydrology analyses suggest that the Tillamook watershed gradually recovered from a period of major disturbances (from 1933 to 1955) to more normal conditions (from 1977 to 1998). In addition, this part of the study attempts to quantify the sediment transport regime of the rivers draining the watershed by using a hydraulic model that is based on the principle of stream power, and on considerations of availability of transported material. Application of this model during the 1933-1955 period for the major rivers suggests an average sediment yield on the order of 410,540 tons/year, but most important are the relative changes of the delivered sediment through time. The results of the model suggest a 1.6-factor decrease of the amount of river sediments from the Heavily Impacted Period (1933-1955) of major disturbances to the Normal Period (1977- 1998). The spatial variations of beach and river derived sediments throughout the Bay are determined from textural and mineralogical analyses of surface sediment samples, with the beach sands dominating the area close to the inlet and the river derived sands being mainly deposited at the southeast and northeast parts of the Bay. The relative contributions of these two major sources of sediment were found to be 60% for the marine beach and 40% for the river sands. Further attempt is made to distinguish between the sand transported into the Bay from the individual rivers, and to determine the main processes that are responsible for the dispersion of sediments within the Bay. The attempts to distinguish sands contributed by the individual rivers involved modal analyses of the frequency curves of the surface sediment samples, and the results mainly suggest a grain-size increase away from the mouth of the rivers as a result of sediment reworking by estuarine processes following its initial deposition during episodic river flooding. The main processes that control the dispersion of sediments and their deposition within the Bay were identified by using factor analysis, the results of which suggest that various estuarine processes are responsible for the observed dispersal patterns. A brief review is provided of the study undertaken by Dr. James McManus for the collection and analyses of core samples from Tillamook Bay. Down-core geochemical analyses of major and minor elements indicate that there have been times of episodic input of marine sediment in the central and western portions of the Bay, which is a result of either periodic breaching or washover of Bayocean Spit, so that the beach sand source was more important in the past. This episodic input of marine sand as inferred from the down-core geochemical variations was related to the most recent subduction earthquake, which occurred on January 26th, 1700. Finally, a summary of the results and conclusions of different aspects of this study is presented, so that sedimentation in Tillamook Bay can be viewed as an integrated process involving the watersheds, the estuary, and the ocean beaches. Title: Sediment accumulation and human impacts in Tillamook Bay, Oregon Author: Styllas, Michael N. Tillamook Bay is the second largest estuary on the Oregon coast, and concerns have been raised whether human induced impacts have been responsible for the perceived increase in sedimentation rates during the past century. Major land-use practices within the five watersheds of the Bay include logging, forest fires, the construction of forest roads, the placement of dikes along the channels of the main rivers and in the estuary, the removal of riparian vegetation, and the construction of jetties at the tidal inlet. Each of these practices has led to impacts on the entire ecosystem of the watersheds and the Bay, but this study focuses on the effects of human disturbances on the Bay's sediment accumulation. This study examines in detail the land-use practices that have occurred in the watersheds, on the beaches, and in the estuary, focusing on those that have had a direct impact on the sedimentation regime of the Bay. One goal of the study is to assess the relative roles of natural processes versus human impacts on the sedimentation. A general description of the physical characteristics of Tillamook Bay and its surroundings is included, and a brief discussion is provided about the tectonic setting of the Northwest Coast, including its history of subduction earthquakes and the associate sea-level changes. Also provided is a summary of the existing information concerning the arrival of Indians and their environmental impacts, followed by a more detailed account of the major impacts that have resulted from the settlement of the Euro-Americans in the Tillamook area, in the 1850's. The study then focuses on the description of the watersheds from a geomorphologic point of view, and the important land-use practices that may have affected sediment yields during the past century. Analyses of the hydrology of the Tillamook Bay watersheds are included, and the relations between annual water yields and total precipitation are examined in distinct time intervals, each corresponding to a different period with different amounts of land uses. The results of these hydrology analyses suggest that the Tillamook watershed gradually recovered from a period of major disturbances (from 1933 to 1955) to more normal conditions (from 1977 to 1998). In addition, this part of the study attempts to quantify the sediment transport regime of the rivers draining the watershed by using a hydraulic model that is based on the principle of stream power, and on considerations of availability of transported material. Application of this model during the 1933-1955 period for the major rivers suggests an average sediment yield on the order of 410,540 tons/year, but most important are the relative changes of the delivered sediment through time. The results of the model suggest a 1.6-factor decrease of the amount of river sediments from the Heavily Impacted Period (1933-1955) of major disturbances to the Normal Period (1977- 1998). The spatial variations of beach and river derived sediments throughout the Bay are determined from textural and mineralogical analyses of surface sediment samples, with the beach sands dominating the area close to the inlet and the river derived sands being mainly deposited at the southeast and northeast parts of the Bay. The relative contributions of these two major sources of sediment were found to be 60% for the marine beach and 40% for the river sands. Further attempt is made to distinguish between the sand transported into the Bay from the individual rivers, and to determine the main processes that are responsible for the dispersion of sediments within the Bay. The attempts to distinguish sands contributed by the individual rivers involved modal analyses of the frequency curves of the surface sediment samples, and the results mainly suggest a grain-size increase away from the mouth of the rivers as a result of sediment reworking by estuarine processes following its initial deposition during episodic river flooding. The main processes that control the dispersion of sediments and their deposition within the Bay were identified by using factor analysis, the results of which suggest that various estuarine processes are responsible for the observed dispersal patterns. A brief review is provided of the study undertaken by Dr. James McManus for the collection and analyses of core samples from Tillamook Bay. Down-core geochemical analyses of major and minor elements indicate that there have been times of episodic input of marine sediment in the central and western portions of the Bay, which is a result of either periodic breaching or washover of Bayocean Spit, so that the beach sand source was more important in the past. This episodic input of marine sand as inferred from the down-core geochemical variations was related to the most recent subduction earthquake, which occurred on January 26th, 1700. Finally, a summary of the results and conclusions of different aspects of this study is presented, so that sedimentation in Tillamook Bay can be viewed as an integrated process involving the watersheds, the estuary, and the ocean beaches. Close

• 356. [Article] Canyon Grasslands of the Hells Canyon National Recreation Area : How have they changed over time and what is their future trajectory?

  The canyon grasslands of the Hells Canyon National Recreation Area (HCNRA) are a unique ecosystem within the Pacific Northwest Bunchgrass Region (PNWBR) with a long history of natural and anthropogenic ...

  Citation × Citation Citation Abstract Copy Title: Canyon Grasslands of the Hells Canyon National Recreation Area : How have they changed over time and what is their future trajectory? Author: Pack, Samantha J. The canyon grasslands of the Hells Canyon National Recreation Area (HCNRA) are a unique ecosystem within the Pacific Northwest Bunchgrass Region (PNWBR) with a long history of natural and anthropogenic disturbances including fire, invasive species introduction, historical livestock grazing, and cultivation. Even with this history, these canyon grasslands contain some of the last remnants of the Pacific Northwest Bunchgrass Region. For thousands of years, these grasslands were occupied by the Nez Perce Tribe and have been grazed since the 1700s. In addition to grazing, settlers cultivated many parts of the HCNRA and some of these homesteads can still be seen today. Both historical and current land uses are strongly influenced by the natural topography of these canyon grasslands, with the highest concentration of land use centered on benchlands while steep canyon slopes avoided cultivation and were used less by livestock. The different plant associations of these grasslands are also influenced by the unique topography of the HCNRA due to the relationships between soil moisture and depth and abrupt alterations in aspect, slope, and elevation. Very few studies have examined the plant associations of the canyon grasslands of the HCNRA, even fewer have asked how they have changed over time, and there are no studies looking into their future trajectory by assessing the seed bank. The first study in my thesis (Chapter 2) focused on how canyon grasslands have changed over time using a repeated survey of vegetation from four different plant associations within the Lower Imnaha Subbasin. From the original study conducted in 1981, a total of 19 different plots in four plant associations were chosen to be resampled in 2014. Since the original study was used to classify seral stages within the plant associations, these successional stages were used to determine if the plant communities had transitioned between the seral classes over the 33 year-time-period. In addition, given the importance of topography to these grasslands, elevation, slope, and aspect were evaluated for their relationship to successional changes. Both Nonmetric Multidimensional Scaling (NMS) and Indicator Species Analysis were used to verify the seral stage classifications for each plot in 1981 and 2014. To evaluate how each association had changed between sampling years, Multi-response Permutation Procedures (MRPP) and NMS were used. Most of these plant associations were relatively stable and had, for the most part, remained at the same seral stage or transitioned to a later seral stage. Among the plant associations, slope was the topographical variable that appeared most related to the transitions in seral stages. Steeper slopes either remained at the same seral stage or transitioned to a later one, while gentler slopes (< 20%) tended to shift from later to earlier seral stages. A relatively new introduced annual grass to the region, Ventenata dubia (not present in the 1981 sampling), was found in three of the four plant associations and was most abundant on the benchlands. The results of this resurvey suggest that topography is related to both the distribution of plant associations and which sites will shift in seral stage over time across the canyon grasslands of the Lower Imnaha Subbasin. The second study of my thesis (Chapter 3) focused on using a seed bank study as one of the many ways to examine the future trajectory of the plant communities in the canyon grasslands of the Lower Imnaha Subbasin, with a particular focus on the benchlands. The seed bank contains the regenerative pool for plant communities and represents the potential for a community to respond to disturbances. The seed bank from benchland sites in one plant association was evaluated in relation to the standing vegetation, successional stage, and historical cultivation. To my knowledge, this was the first seed bank study for the grasslands of this region. Vegetation cover and soil samples were collected from 8 sites, including two previously cultivated and two reference noncultivated sites. NMS was used to extract the strongest community gradients, which naturally separated out the seral stage classifications of the vegetation. To evaluate differences between the vegetation and the seed bank, between successional stages, and between cultivation histories, MRPP was used. Results from the seed bank study are consistent with many other studies around the world in perennial grasslands showing that the vegetation and seed bank are often dissimilar. Similarities between the vegetation and seed bank were highest in the annual grass dominated stage compared to the early seral stage. The effects of cultivation appear to still be evident in the seed bank, where cultivated sites have significantly more introduced grasses compared to noncultivated sites (p < 0.05). There was an overall greater abundance of introduced annual forb and grass species in the seed bank on these benchland sites, suggesting that they may be native seed limited and could easily shift to invasive species dominance after further disturbance, especially on previously cultivated areas. The results of both of these studies suggest that benchlands and lower sloped sites surrounding them in the canyon grasslands of the Lower Imnaha Subbasin may less resistant and resilient to disturbance. Priorities for future research and management may also need to focus on the plant communities of benchlands in these unique grasslands. Title: Canyon Grasslands of the Hells Canyon National Recreation Area : How have they changed over time and what is their future trajectory? Author: Pack, Samantha J. The canyon grasslands of the Hells Canyon National Recreation Area (HCNRA) are a unique ecosystem within the Pacific Northwest Bunchgrass Region (PNWBR) with a long history of natural and anthropogenic disturbances including fire, invasive species introduction, historical livestock grazing, and cultivation. Even with this history, these canyon grasslands contain some of the last remnants of the Pacific Northwest Bunchgrass Region. For thousands of years, these grasslands were occupied by the Nez Perce Tribe and have been grazed since the 1700s. In addition to grazing, settlers cultivated many parts of the HCNRA and some of these homesteads can still be seen today. Both historical and current land uses are strongly influenced by the natural topography of these canyon grasslands, with the highest concentration of land use centered on benchlands while steep canyon slopes avoided cultivation and were used less by livestock. The different plant associations of these grasslands are also influenced by the unique topography of the HCNRA due to the relationships between soil moisture and depth and abrupt alterations in aspect, slope, and elevation. Very few studies have examined the plant associations of the canyon grasslands of the HCNRA, even fewer have asked how they have changed over time, and there are no studies looking into their future trajectory by assessing the seed bank. The first study in my thesis (Chapter 2) focused on how canyon grasslands have changed over time using a repeated survey of vegetation from four different plant associations within the Lower Imnaha Subbasin. From the original study conducted in 1981, a total of 19 different plots in four plant associations were chosen to be resampled in 2014. Since the original study was used to classify seral stages within the plant associations, these successional stages were used to determine if the plant communities had transitioned between the seral classes over the 33 year-time-period. In addition, given the importance of topography to these grasslands, elevation, slope, and aspect were evaluated for their relationship to successional changes. Both Nonmetric Multidimensional Scaling (NMS) and Indicator Species Analysis were used to verify the seral stage classifications for each plot in 1981 and 2014. To evaluate how each association had changed between sampling years, Multi-response Permutation Procedures (MRPP) and NMS were used. Most of these plant associations were relatively stable and had, for the most part, remained at the same seral stage or transitioned to a later seral stage. Among the plant associations, slope was the topographical variable that appeared most related to the transitions in seral stages. Steeper slopes either remained at the same seral stage or transitioned to a later one, while gentler slopes (< 20%) tended to shift from later to earlier seral stages. A relatively new introduced annual grass to the region, Ventenata dubia (not present in the 1981 sampling), was found in three of the four plant associations and was most abundant on the benchlands. The results of this resurvey suggest that topography is related to both the distribution of plant associations and which sites will shift in seral stage over time across the canyon grasslands of the Lower Imnaha Subbasin. The second study of my thesis (Chapter 3) focused on using a seed bank study as one of the many ways to examine the future trajectory of the plant communities in the canyon grasslands of the Lower Imnaha Subbasin, with a particular focus on the benchlands. The seed bank contains the regenerative pool for plant communities and represents the potential for a community to respond to disturbances. The seed bank from benchland sites in one plant association was evaluated in relation to the standing vegetation, successional stage, and historical cultivation. To my knowledge, this was the first seed bank study for the grasslands of this region. Vegetation cover and soil samples were collected from 8 sites, including two previously cultivated and two reference noncultivated sites. NMS was used to extract the strongest community gradients, which naturally separated out the seral stage classifications of the vegetation. To evaluate differences between the vegetation and the seed bank, between successional stages, and between cultivation histories, MRPP was used. Results from the seed bank study are consistent with many other studies around the world in perennial grasslands showing that the vegetation and seed bank are often dissimilar. Similarities between the vegetation and seed bank were highest in the annual grass dominated stage compared to the early seral stage. The effects of cultivation appear to still be evident in the seed bank, where cultivated sites have significantly more introduced grasses compared to noncultivated sites (p < 0.05). There was an overall greater abundance of introduced annual forb and grass species in the seed bank on these benchland sites, suggesting that they may be native seed limited and could easily shift to invasive species dominance after further disturbance, especially on previously cultivated areas. The results of both of these studies suggest that benchlands and lower sloped sites surrounding them in the canyon grasslands of the Lower Imnaha Subbasin may less resistant and resilient to disturbance. Priorities for future research and management may also need to focus on the plant communities of benchlands in these unique grasslands. Close

• 357. [Article] Forestry

  Posted by permission of Cambridge Scientific Abstracts (CSA). (c) CSA 2009. All rights reserved.

  Citation × Citation Citation Abstract Copy Title: Forestry Author: Avery, Bonnie E. Posted by permission of Cambridge Scientific Abstracts (CSA). (c) CSA 2009. All rights reserved. Title: Forestry Author: Avery, Bonnie E. Posted by permission of Cambridge Scientific Abstracts (CSA). (c) CSA 2009. All rights reserved. Close

• 358. [Article] The Role of Plant-soil Feedback in the Invasion of Brachypodium sylvaticum in Douglas-fir Forests

  Invasive plants have the capacity to transform landscapes and alter ecosystem function, causing significant economic and ecological damage. These effects include displacement and reduction of native flora ...

  Citation × Citation Citation Abstract Copy Title: The Role of Plant-soil Feedback in the Invasion of Brachypodium sylvaticum in Douglas-fir Forests Author: Esterson, Andrew Invasive plants have the capacity to transform landscapes and alter ecosystem function, causing significant economic and ecological damage. These effects include displacement and reduction of native flora and fauna, altered fire regimes, modification of biotic and abiotic soil properties, as well as local, regional, and global economic impacts. With such large impacts it is important that we better understand invasion dynamics to help with prevention, control and mitigation of invasive species. One process that has been associated with plant invasion is plant-soil feedback (PSF). A PSF occurs when plants alter biotic and abiotic soil properties through a variety of root exudates and litter decomposition such that subsequent plant growth is either positively or negatively affected. Positive conspecific and negative heterospecific responses have been theorized to be invasive species traits that promote invasion. Once an invasive species is removed from a system, there is a chance that PSFs generated by that species will persist in the soil, which is often referred to as 'plant legacies' or 'legacy effects' and may negatively influence restoration efforts. In the U.S. Pacific Northwest (PNW), Brachypodium sylvaticum (slender false brome), a perennial bunch grass native to Eurasia, is listed as a quarantined invasive species in California, Oregon, and Washington. Currently, B. sylvaticum is in the midst of rapid population growth and range expansion with populations in New York, Virginia, and Ontario, Canada. With a quickly expanding range research is critical for successful efforts to reduce the spread of B. sylvaticum. We developed two experiments to determine if PSF is a contributing factor to B. sylvaticum invasion in PNW forests. We hypothesized that 1) B. sylvaticum has positive conspecific and negative heterospecific PSF, 2) native species PSF has no effect on B. sylvaticum, and 3) PSF generated by B. sylvaticum will persist in the soil once removed, but over time, response of native species, soil nutrients and bacterial community composition will change from the invaded conditioned. To test our first two hypotheses, B. sylvaticum and five common native plants from the Oregon Coastal range, including the economically important tree, Pseudotsuga menziesii (Douglas-fir), were grown in a greenhouse on wild forest soils that had either been sterilized or kept live to condition the soil biotic community to the invader and the native species. Brachypodium sylvaticum was then grown on soil conditioned by itself and soil conditioned by natives; each of the five native species was grown on soil conditioned by B. sylvaticum and on their own conditioned soils. Plant biomass along with species specific measurements (number of leaves, stems, tillers, stem diameter and height) were recorded and a relative response (RR) index was used to determine the direction of PSF for the invader and native species. To test our third hypothesis, in March, 2015, ten plots were established in the McDonald-Dunn Research Forest located in Corvallis, OR where B. sylvaticum had at least 75% cover. Herbicide was applied to half of each plot to make two soil treatments: soil with B. sylvaticum and soil without B. sylvaticum. Over a nine-month period three soil collections took place where soil was collected from all plots and treatments. Plant response was evaluated by growing four native species and B. sylvaticum on both soil treatments and evaluating total biomass with a RR index; plant response (via growth), soil nutrients and bacterial communities were measured for each collection period. Bacterial communities were measured with phospholipid fatty acid (PLFA) analysis and high throughput 16s rRNA amplicon sequencing. Contrary to our hypotheses, the RR to PSF generated by B. sylvaticum was negative for the invader and P. menziesii and neutral for all other natives. Soils conditioned by Bromus vulgaris inhibited B. sylvaticum growth whereas soils conditioned by Prunella vulgaris and P. menziesii promoted B. sylvaticum growth. When testing for legacy effects, the RR of P. menziesii was negative when grown on soils where B. sylvaticum had been removed for six-months (six-month soils) but when grown on soils where B. sylvaticum had been removed for nine-months (nine-month soil) the RR of P. menziesii was neutral. The RR of P. vulgaris to six-month soils was positive while its RR to nine-month soils was negative. Nutrient and bacterial communities did not change in response to B. sylvaticum removal suggesting that the biotic and abiotic legacy requires longer than nine-months to be observed or B. sylvaticum does not affect the response variables measured. Overall, our data suggest that PSF generated by B. sylvaticum does not facilitate the invasion process but does differentially affect native species growth over time. PSF generated by native grasses may be a useful restoration tool to help prevent B. sylvaticum invasion and we suggest planting native species at least nine-months after B. sylvaticum removal. Title: The Role of Plant-soil Feedback in the Invasion of Brachypodium sylvaticum in Douglas-fir Forests Author: Esterson, Andrew Invasive plants have the capacity to transform landscapes and alter ecosystem function, causing significant economic and ecological damage. These effects include displacement and reduction of native flora and fauna, altered fire regimes, modification of biotic and abiotic soil properties, as well as local, regional, and global economic impacts. With such large impacts it is important that we better understand invasion dynamics to help with prevention, control and mitigation of invasive species. One process that has been associated with plant invasion is plant-soil feedback (PSF). A PSF occurs when plants alter biotic and abiotic soil properties through a variety of root exudates and litter decomposition such that subsequent plant growth is either positively or negatively affected. Positive conspecific and negative heterospecific responses have been theorized to be invasive species traits that promote invasion. Once an invasive species is removed from a system, there is a chance that PSFs generated by that species will persist in the soil, which is often referred to as 'plant legacies' or 'legacy effects' and may negatively influence restoration efforts. In the U.S. Pacific Northwest (PNW), Brachypodium sylvaticum (slender false brome), a perennial bunch grass native to Eurasia, is listed as a quarantined invasive species in California, Oregon, and Washington. Currently, B. sylvaticum is in the midst of rapid population growth and range expansion with populations in New York, Virginia, and Ontario, Canada. With a quickly expanding range research is critical for successful efforts to reduce the spread of B. sylvaticum. We developed two experiments to determine if PSF is a contributing factor to B. sylvaticum invasion in PNW forests. We hypothesized that 1) B. sylvaticum has positive conspecific and negative heterospecific PSF, 2) native species PSF has no effect on B. sylvaticum, and 3) PSF generated by B. sylvaticum will persist in the soil once removed, but over time, response of native species, soil nutrients and bacterial community composition will change from the invaded conditioned. To test our first two hypotheses, B. sylvaticum and five common native plants from the Oregon Coastal range, including the economically important tree, Pseudotsuga menziesii (Douglas-fir), were grown in a greenhouse on wild forest soils that had either been sterilized or kept live to condition the soil biotic community to the invader and the native species. Brachypodium sylvaticum was then grown on soil conditioned by itself and soil conditioned by natives; each of the five native species was grown on soil conditioned by B. sylvaticum and on their own conditioned soils. Plant biomass along with species specific measurements (number of leaves, stems, tillers, stem diameter and height) were recorded and a relative response (RR) index was used to determine the direction of PSF for the invader and native species. To test our third hypothesis, in March, 2015, ten plots were established in the McDonald-Dunn Research Forest located in Corvallis, OR where B. sylvaticum had at least 75% cover. Herbicide was applied to half of each plot to make two soil treatments: soil with B. sylvaticum and soil without B. sylvaticum. Over a nine-month period three soil collections took place where soil was collected from all plots and treatments. Plant response was evaluated by growing four native species and B. sylvaticum on both soil treatments and evaluating total biomass with a RR index; plant response (via growth), soil nutrients and bacterial communities were measured for each collection period. Bacterial communities were measured with phospholipid fatty acid (PLFA) analysis and high throughput 16s rRNA amplicon sequencing. Contrary to our hypotheses, the RR to PSF generated by B. sylvaticum was negative for the invader and P. menziesii and neutral for all other natives. Soils conditioned by Bromus vulgaris inhibited B. sylvaticum growth whereas soils conditioned by Prunella vulgaris and P. menziesii promoted B. sylvaticum growth. When testing for legacy effects, the RR of P. menziesii was negative when grown on soils where B. sylvaticum had been removed for six-months (six-month soils) but when grown on soils where B. sylvaticum had been removed for nine-months (nine-month soil) the RR of P. menziesii was neutral. The RR of P. vulgaris to six-month soils was positive while its RR to nine-month soils was negative. Nutrient and bacterial communities did not change in response to B. sylvaticum removal suggesting that the biotic and abiotic legacy requires longer than nine-months to be observed or B. sylvaticum does not affect the response variables measured. Overall, our data suggest that PSF generated by B. sylvaticum does not facilitate the invasion process but does differentially affect native species growth over time. PSF generated by native grasses may be a useful restoration tool to help prevent B. sylvaticum invasion and we suggest planting native species at least nine-months after B. sylvaticum removal. Close