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• 1. [Article] Response of Sagebrush Steppe Species to Elevated CO2 and Soil Temperature

  Elevated atmospheric CO2 may cause long-term changes in the productivity and species composition of the sagebrush steppe. Few studies, however, have evaluated the effects of increased CO2 on growth and ...

  Citation × Citation Citation Abstract Copy Title: Response of Sagebrush Steppe Species to Elevated CO2 and Soil Temperature Author: Lucash, Melissa S., Farnsworth, Blake, Winner, William E. Year: 2005 Elevated atmospheric CO2 may cause long-term changes in the productivity and species composition of the sagebrush steppe. Few studies, however, have evaluated the effects of increased CO2 on growth and physiology of species important to this ecosystem. Since the response of plants to elevated CO2 may be limited by environmental factors, soil temperature was also examined to determine if low soil temperatures limit CO2 response. To determine how CO2 and soil temperature affect the growth of species native to the sagebrush steppe, bottlebrush squirreltail [Elymus elymoides (Raf.) Swezey], Thurber needlegrass (Stipa thurberiana Piper), and Wyoming big sagebrush (Artemisia tridentata ssp. wyomingensis Beetle) were grown in ambient (374 mL L–1) or high (567 mL L–1) CO2 and low (13°C) or high (18°C) soil temperature for approximately 4 months. Although soil temperature affected the growth of squirreltail and needlegrass, temperature did not modify their response to elevated CO2. Total biomass of sagebrush was consistent across soil temperature and CO2 treatments, reflecting its slow-growing strategy. All 3 species had higher leaf water-use efficiency at elevated CO2 due to higher net photosynthesis and lower transpiration rates. We conclude that elevated CO2 and soil warming may increase the growth of grasses more than shrubs. Field studies in the sagebrush steppe are necessary to determine if differences in biomass, resulting from changes in CO2 and soil temperature, are exhibited in the field. Title: Response of Sagebrush Steppe Species to Elevated CO2 and Soil Temperature Author: Lucash, Melissa S., Farnsworth, Blake, Winner, William E. Year: 2005 Elevated atmospheric CO2 may cause long-term changes in the productivity and species composition of the sagebrush steppe. Few studies, however, have evaluated the effects of increased CO2 on growth and physiology of species important to this ecosystem. Since the response of plants to elevated CO2 may be limited by environmental factors, soil temperature was also examined to determine if low soil temperatures limit CO2 response. To determine how CO2 and soil temperature affect the growth of species native to the sagebrush steppe, bottlebrush squirreltail [Elymus elymoides (Raf.) Swezey], Thurber needlegrass (Stipa thurberiana Piper), and Wyoming big sagebrush (Artemisia tridentata ssp. wyomingensis Beetle) were grown in ambient (374 mL L–1) or high (567 mL L–1) CO2 and low (13°C) or high (18°C) soil temperature for approximately 4 months. Although soil temperature affected the growth of squirreltail and needlegrass, temperature did not modify their response to elevated CO2. Total biomass of sagebrush was consistent across soil temperature and CO2 treatments, reflecting its slow-growing strategy. All 3 species had higher leaf water-use efficiency at elevated CO2 due to higher net photosynthesis and lower transpiration rates. We conclude that elevated CO2 and soil warming may increase the growth of grasses more than shrubs. Field studies in the sagebrush steppe are necessary to determine if differences in biomass, resulting from changes in CO2 and soil temperature, are exhibited in the field. Close

• 2. [Article] Winter Climate Change Affects Growing-Season Soil Microbial Biomass and Activity in Northern Hardwood Forests

  Understanding the responses of terrestrial ecosystems to global change remains a major challenge of ecological research. We exploited a natural elevation gradient in a northern hardwood forest to determine ...

  Citation × Citation Citation Abstract Copy Title: Winter Climate Change Affects Growing-Season Soil Microbial Biomass and Activity in Northern Hardwood Forests Author: Durán, Jorge, Morse, Jennifer L., Groffman, Peter M., Campbell, John L., Christenson, Lynn M., Driscoll, Charles T., Fahey, Timothy J., Fisk, Melany C., Mitchell, Mryon J., Templer, Pamela H. Year: 2014 Understanding the responses of terrestrial ecosystems to global change remains a major challenge of ecological research. We exploited a natural elevation gradient in a northern hardwood forest to determine how reductions in snow accumulation, expected with climate change, directly affect dynamics of soil winter frost, and indirectly soil microbial biomass and activity during the growing season. Soils from lower elevation plots, which accumulated less snow and experienced more soil temperature variability during the winter (and likely more freeze/thaw events), had less extractable inorganic nitrogen (N), lower rates of microbial N production via potential net N mineralization and nitrification, and higher potential microbial respiration during the growing season. Potential nitrate production rates during the growing season were particularly sensitive to changes in winter snow pack accumulation and winter soil temperature variability, especially in spring. Effects of elevation and winter conditions on N transformation rates dif­ fered from those on potential microbial respiration, suggesting that N-related processes might respond differently to winter climate change in northern hardwood forests than C-related processes. Title: Winter Climate Change Affects Growing-Season Soil Microbial Biomass and Activity in Northern Hardwood Forests Author: Durán, Jorge, Morse, Jennifer L., Groffman, Peter M., Campbell, John L., Christenson, Lynn M., Driscoll, Charles T., Fahey, Timothy J., Fisk, Melany C., Mitchell, Mryon J., Templer, Pamela H. Year: 2014 Understanding the responses of terrestrial ecosystems to global change remains a major challenge of ecological research. We exploited a natural elevation gradient in a northern hardwood forest to determine how reductions in snow accumulation, expected with climate change, directly affect dynamics of soil winter frost, and indirectly soil microbial biomass and activity during the growing season. Soils from lower elevation plots, which accumulated less snow and experienced more soil temperature variability during the winter (and likely more freeze/thaw events), had less extractable inorganic nitrogen (N), lower rates of microbial N production via potential net N mineralization and nitrification, and higher potential microbial respiration during the growing season. Potential nitrate production rates during the growing season were particularly sensitive to changes in winter snow pack accumulation and winter soil temperature variability, especially in spring. Effects of elevation and winter conditions on N transformation rates dif­ fered from those on potential microbial respiration, suggesting that N-related processes might respond differently to winter climate change in northern hardwood forests than C-related processes. Close

• 3. [Article] Using Environmental Variables and Soil Processes to Forecast Denitrification Potential and Nitrous Oxide Fluxes in Coastal Plain Wetlands Across Different Land Uses

  We examined relationships between denitrification (DNF) and nitrous oxide (N2O) fluxes and potentially important chemical and physical predictors to build a predictive understanding of gaseous N losses ...

  Citation × Citation Citation Abstract Copy Title: Using Environmental Variables and Soil Processes to Forecast Denitrification Potential and Nitrous Oxide Fluxes in Coastal Plain Wetlands Across Different Land Uses Author: Morse, Jennifer L., Ardón, Marcelo, Bernhardt, Emily S. Year: 2012 We examined relationships between denitrification (DNF) and nitrous oxide (N2O) fluxes and potentially important chemical and physical predictors to build a predictive understanding of gaseous N losses from coastal plain wetlands. We collected soil, gas, and pore water samples from 48 sampling locations across a large (440 ha) restored wetland, an adjacent drained agricultural field, and nearby forested wetlands every two months over two years. In summer and fall 2007, we measured soil DNF potential (21.6-3560 mg N m-3 d-1) and N2O efflux (-4.36-8.81 mg N m -2 d-1), along with 17 predictor variables. We developed statistical models for the most comprehensive subset of the data set (fall 2007) and used another subset (summer 2007) for cross-validation. Soil pH and total soil nitrogen were the best predictors of DNF potential (Radj2 = 0.68). A regression using carbon dioxide flux and soil temperature together with soil extractable NH4+ and DNF potential explained 85% of the variation in fall N2O fluxes. The model for DNF performed reasonably well when cross-validated with summer data (R2 = 0.40), while the N2O model did not predict summer N2O fluxes (R2 < 0.1). Poor model performance was likely due to nonlinear responses to high temperatures and/or higher and more variable root respiration by plants during the growing season, leading to overprediction of N2O flux. Our results suggest that soil DNF potential may be modeled fairly effectively from a small number of soil parameters, that DNF potential is uncorrelated with N2O effluxes, and that successful estimation of wetland N2O effluxes will require finer-scale models that incorporate seasonal dynamics. Title: Using Environmental Variables and Soil Processes to Forecast Denitrification Potential and Nitrous Oxide Fluxes in Coastal Plain Wetlands Across Different Land Uses Author: Morse, Jennifer L., Ardón, Marcelo, Bernhardt, Emily S. Year: 2012 We examined relationships between denitrification (DNF) and nitrous oxide (N2O) fluxes and potentially important chemical and physical predictors to build a predictive understanding of gaseous N losses from coastal plain wetlands. We collected soil, gas, and pore water samples from 48 sampling locations across a large (440 ha) restored wetland, an adjacent drained agricultural field, and nearby forested wetlands every two months over two years. In summer and fall 2007, we measured soil DNF potential (21.6-3560 mg N m-3 d-1) and N2O efflux (-4.36-8.81 mg N m -2 d-1), along with 17 predictor variables. We developed statistical models for the most comprehensive subset of the data set (fall 2007) and used another subset (summer 2007) for cross-validation. Soil pH and total soil nitrogen were the best predictors of DNF potential (Radj2 = 0.68). A regression using carbon dioxide flux and soil temperature together with soil extractable NH4+ and DNF potential explained 85% of the variation in fall N2O fluxes. The model for DNF performed reasonably well when cross-validated with summer data (R2 = 0.40), while the N2O model did not predict summer N2O fluxes (R2 < 0.1). Poor model performance was likely due to nonlinear responses to high temperatures and/or higher and more variable root respiration by plants during the growing season, leading to overprediction of N2O flux. Our results suggest that soil DNF potential may be modeled fairly effectively from a small number of soil parameters, that DNF potential is uncorrelated with N2O effluxes, and that successful estimation of wetland N2O effluxes will require finer-scale models that incorporate seasonal dynamics. Close

• 4. [Article] Accelerated Thermokarst Formation in the McMurdo Dry Valleys, Antarctica

  Thermokarst is a land surface lowered and disrupted by melting ground ice. Thermokarst is a major driver of landscape change in the Arctic, but has been considered to be a minor process in Antarctica. ...

  Citation × Citation Citation Abstract Copy Title: Accelerated Thermokarst Formation in the McMurdo Dry Valleys, Antarctica Author: Levy, Joseph S., Fountain, Andrew G., Dickson, James L., Head, James W., Okal, Marianne, Marchant, David R., Watters, Jaclyn Year: 2013 Thermokarst is a land surface lowered and disrupted by melting ground ice. Thermokarst is a major driver of landscape change in the Arctic, but has been considered to be a minor process in Antarctica. Here, we use ground-based and airborne LiDAR coupled with timelapse imaging and meteorological data to show that 1) thermokarst formation has accelerated in Garwood Valley, Antarctica; 2) the rate of thermokarst erosion is presently,10 times the average Holocene rate; and 3) the increased rate of thermokarst formation is driven most strongly by increasing insolation and sediment/albedo feedbacks. This suggests that sediment enhancement of insolation-driven melting may act similarly to expected increases in Antarctic air temperature (presently occurring along the Antarctic Peninsula), and may serve as a leading indicator of imminent landscape change in Antarctica that will generate thermokarst landforms similar to those in Arctic periglacial terrains. Title: Accelerated Thermokarst Formation in the McMurdo Dry Valleys, Antarctica Author: Levy, Joseph S., Fountain, Andrew G., Dickson, James L., Head, James W., Okal, Marianne, Marchant, David R., Watters, Jaclyn Year: 2013 Thermokarst is a land surface lowered and disrupted by melting ground ice. Thermokarst is a major driver of landscape change in the Arctic, but has been considered to be a minor process in Antarctica. Here, we use ground-based and airborne LiDAR coupled with timelapse imaging and meteorological data to show that 1) thermokarst formation has accelerated in Garwood Valley, Antarctica; 2) the rate of thermokarst erosion is presently,10 times the average Holocene rate; and 3) the increased rate of thermokarst formation is driven most strongly by increasing insolation and sediment/albedo feedbacks. This suggests that sediment enhancement of insolation-driven melting may act similarly to expected increases in Antarctic air temperature (presently occurring along the Antarctic Peninsula), and may serve as a leading indicator of imminent landscape change in Antarctica that will generate thermokarst landforms similar to those in Arctic periglacial terrains. Close

• 5. [Article] Defining the Terroir of the Columbia Gorge Wine Region, Oregon and Washington, USA Using Geographic Information Systems (GIS)

  The Columbia Gorge Wine Region (CGWR) is an emerging wine producing area that extends for about 100km along the Columbia River in Oregon and Washington State in which the number of vineyards, wineries ...

  Citation × Citation Citation Abstract Copy Title: Defining the Terroir of the Columbia Gorge Wine Region, Oregon and Washington, USA Using Geographic Information Systems (GIS) Author: Whitney, Hilary Year: 2015 The Columbia Gorge Wine Region (CGWR) is an emerging wine producing area that extends for about 100km along the Columbia River in Oregon and Washington State in which the number of vineyards, wineries and physical terroir conditions have yet to be defined. To better understand the physical factors affecting Oregon and Washington wine, this project analyzes climate, topography, geology and soil at vineyards in the CGWR. This was accomplished using Geographic Information Systems, existing earth science databases and field work. The region, which includes the Columbia Gorge American Viticulture Area (AVA) and the southwest portion of the Columbia Valley AVA, is home to 82 vineyards, 513 hectares (1268 acres), 37 wineries and 41 different varieties of Vitus Vinifera. Vineyards range in elevation from 29 to 548 meters (95 to 1799 feet). Vintner responses to a grower's survey suggest that twenty-eight grape varieties account for 98% of the estimated grape variety acreage, with Pinot Noir being the most widely planted grape variety in both AVAs. The boundaries of each climatic regime were mapped based on 1981-2010 PRISM data, the Winkler Index (Amerine and Winkler, 1944) updated by Jones et al. (2010) and climatic maturity groupings designed for Oregon (Jones et al., 2002; Jones et al., 2010). Three Winkler climate regimes are represented within the CGWR, including regions Ia, Ib, and II from the Winkler Index (Jones et al., 2010). The diversity in regimes allows for a diversity of grape varieties to be planted within the regime. The average growing season temperatures and growing degree days, respectively, from 1981-2010 calculated for vineyards ranges from 13.7°C (55.7°F) to 17.7°C (63.9°F) and 871 for °C (1567 for °F) to 1664 for °C (2994 for °F) respectively. 58% of the vineyards are characterized in an intermediate climatic regime, 29% are within a cool climatic regime, 9% are within a warm climatic regime and 4% are on the boundaries between a cool, intermediate or warm regime. 80% of the vineyards are within Regions Ia and Ib characterized by the Winkler Index, and 20% are within Region II. The growing degrees days calculated for the CGWR are similar those measured in the Willamette Valley, Oregon, Burgundy, France, Umpqua Valley AVA in Oregon and Bordeaux wine region in France. All of the soils currently being used to grow grapes are well-drained and within a xeric moisture regime, which are favorable conditions for viticulture. 30 soil series are represented among the vineyard sites, with the Chemawa Series (Underwood Mountain) and Walla Walla Series (eastern portions) being the dominant soil series used to grow grapes. Majority of the soils contain a silt loam texture. Soil Survey data for Oregon and Washington suggest that loess is extensive in the CGWR, with 46.5% of the total vineyard acreage planted on soils formed in loess. The Missoula Floods also greatly influenced the texture and age of the soil in this region, with skeletal textures being close to the Columbia River. Other common geological deposits at vineyards in the CGWR include, Quaternary Basalt (19.6%), Missoula Flood deposits (9.1%), The Dalles Formation (8.0%), Columbia River Basalt Group (7.5%), Pliocene Basalt (3.0%), Quaternary Surficial deposits (3.0%), lahars (2.3%) and Quaternary Basaltic Andesite and Andesite (0.9%). Common geological deposits, soil series, and climate conditions at vineyard sites vary spatially in the region, and therefore it is suggested that future work focus on separating the region into separate climatic sub-AVA regimes to better reflect the diversity in terroir conditions. Title: Defining the Terroir of the Columbia Gorge Wine Region, Oregon and Washington, USA Using Geographic Information Systems (GIS) Author: Whitney, Hilary Year: 2015 The Columbia Gorge Wine Region (CGWR) is an emerging wine producing area that extends for about 100km along the Columbia River in Oregon and Washington State in which the number of vineyards, wineries and physical terroir conditions have yet to be defined. To better understand the physical factors affecting Oregon and Washington wine, this project analyzes climate, topography, geology and soil at vineyards in the CGWR. This was accomplished using Geographic Information Systems, existing earth science databases and field work. The region, which includes the Columbia Gorge American Viticulture Area (AVA) and the southwest portion of the Columbia Valley AVA, is home to 82 vineyards, 513 hectares (1268 acres), 37 wineries and 41 different varieties of Vitus Vinifera. Vineyards range in elevation from 29 to 548 meters (95 to 1799 feet). Vintner responses to a grower's survey suggest that twenty-eight grape varieties account for 98% of the estimated grape variety acreage, with Pinot Noir being the most widely planted grape variety in both AVAs. The boundaries of each climatic regime were mapped based on 1981-2010 PRISM data, the Winkler Index (Amerine and Winkler, 1944) updated by Jones et al. (2010) and climatic maturity groupings designed for Oregon (Jones et al., 2002; Jones et al., 2010). Three Winkler climate regimes are represented within the CGWR, including regions Ia, Ib, and II from the Winkler Index (Jones et al., 2010). The diversity in regimes allows for a diversity of grape varieties to be planted within the regime. The average growing season temperatures and growing degree days, respectively, from 1981-2010 calculated for vineyards ranges from 13.7°C (55.7°F) to 17.7°C (63.9°F) and 871 for °C (1567 for °F) to 1664 for °C (2994 for °F) respectively. 58% of the vineyards are characterized in an intermediate climatic regime, 29% are within a cool climatic regime, 9% are within a warm climatic regime and 4% are on the boundaries between a cool, intermediate or warm regime. 80% of the vineyards are within Regions Ia and Ib characterized by the Winkler Index, and 20% are within Region II. The growing degrees days calculated for the CGWR are similar those measured in the Willamette Valley, Oregon, Burgundy, France, Umpqua Valley AVA in Oregon and Bordeaux wine region in France. All of the soils currently being used to grow grapes are well-drained and within a xeric moisture regime, which are favorable conditions for viticulture. 30 soil series are represented among the vineyard sites, with the Chemawa Series (Underwood Mountain) and Walla Walla Series (eastern portions) being the dominant soil series used to grow grapes. Majority of the soils contain a silt loam texture. Soil Survey data for Oregon and Washington suggest that loess is extensive in the CGWR, with 46.5% of the total vineyard acreage planted on soils formed in loess. The Missoula Floods also greatly influenced the texture and age of the soil in this region, with skeletal textures being close to the Columbia River. Other common geological deposits at vineyards in the CGWR include, Quaternary Basalt (19.6%), Missoula Flood deposits (9.1%), The Dalles Formation (8.0%), Columbia River Basalt Group (7.5%), Pliocene Basalt (3.0%), Quaternary Surficial deposits (3.0%), lahars (2.3%) and Quaternary Basaltic Andesite and Andesite (0.9%). Common geological deposits, soil series, and climate conditions at vineyard sites vary spatially in the region, and therefore it is suggested that future work focus on separating the region into separate climatic sub-AVA regimes to better reflect the diversity in terroir conditions. Close