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• 1. [Article] Plant Nitrogen Concentration and Isotopic Composition in Residential Lawns Across Seven US Cities

  Human drivers are often proposed to be stronger than biophysical drivers in influencing ecosystem structure and function in highly urbanized areas. In residential land cover, private yards are influenced ...

  Citation × Citation Citation Abstract Copy Title: Plant Nitrogen Concentration and Isotopic Composition in Residential Lawns Across Seven US Cities Author: Trammell, Tara, Pataki, Diane E., Cavender-Bares, Jeannine, Groffman, Peter M., Hall, Sharon J. Year: 2016 Human drivers are often proposed to be stronger than biophysical drivers in influencing ecosystem structure and function in highly urbanized areas. In residential land cover, private yards are influenced by individual homeowner preferences and actions while also experiencing large-scale human and biophysical drivers. We studied plant nitrogen (%N) and N stable isotopic composition (δ15N) in residential yards and paired native ecosystems in seven cities across the US that span major ecological biomes and climatic regions: Baltimore, Boston, Los Angeles, Miami, Minneapolis-St. Paul, Phoenix, and Salt Lake City. We found that residential lawns in three cities had enriched plant δ15N (P < 0.03) and in six cities higher plant N (%) relative to the associated native ecosystems (P < 0.05). Plant δ15N was progressively depleted across a gradient of urban density classes in Baltimore and Boston (P < 0.05). Lawn fertilization was associated with depleted plant δ15N in Boston and Los Angeles (P < 0.05), and organic fertilizer additions were associated with enriched plant δ15N in Los Angeles and Salt Lake City (P < 0.04). Plant δ15N was significantly enriched as a function of housing age in Baltimore (r2 = 0.27, P < 0.02), Boston (r2 = 0.27, P < 0.01), and Los Angeles (r2 = 0.34, P < 0.01). These patterns in plant δ15N and plant N (%) across these cities suggests that N sources to lawns, as well as greater rates of N cycling combined with subsequent N losses, may be important drivers of plant N dynamics in lawn ecosystems at the national scale. Title: Plant Nitrogen Concentration and Isotopic Composition in Residential Lawns Across Seven US Cities Author: Trammell, Tara, Pataki, Diane E., Cavender-Bares, Jeannine, Groffman, Peter M., Hall, Sharon J. Year: 2016 Human drivers are often proposed to be stronger than biophysical drivers in influencing ecosystem structure and function in highly urbanized areas. In residential land cover, private yards are influenced by individual homeowner preferences and actions while also experiencing large-scale human and biophysical drivers. We studied plant nitrogen (%N) and N stable isotopic composition (δ15N) in residential yards and paired native ecosystems in seven cities across the US that span major ecological biomes and climatic regions: Baltimore, Boston, Los Angeles, Miami, Minneapolis-St. Paul, Phoenix, and Salt Lake City. We found that residential lawns in three cities had enriched plant δ15N (P < 0.03) and in six cities higher plant N (%) relative to the associated native ecosystems (P < 0.05). Plant δ15N was progressively depleted across a gradient of urban density classes in Baltimore and Boston (P < 0.05). Lawn fertilization was associated with depleted plant δ15N in Boston and Los Angeles (P < 0.05), and organic fertilizer additions were associated with enriched plant δ15N in Los Angeles and Salt Lake City (P < 0.04). Plant δ15N was significantly enriched as a function of housing age in Baltimore (r2 = 0.27, P < 0.02), Boston (r2 = 0.27, P < 0.01), and Los Angeles (r2 = 0.34, P < 0.01). These patterns in plant δ15N and plant N (%) across these cities suggests that N sources to lawns, as well as greater rates of N cycling combined with subsequent N losses, may be important drivers of plant N dynamics in lawn ecosystems at the national scale. Close

• 2. [Article] Convergence of Microclimate in Residential Landscapes Across Diverse Cities in the United States

  Context The urban heat island (UHI) is a welldocumented pattern of warming in cities relative to rural areas. Most UHI research utilizes remote sensing methods at large scales, or climate sensors in single ...

  Citation × Citation Citation Abstract Copy Title: Convergence of Microclimate in Residential Landscapes Across Diverse Cities in the United States Author: Hall, Sharon J., Learned, J, Ruddell, Benjamin, Larson, Kelli L., Cavender-Bares, Jeannine, Bettez, Neil D., Groffman, Peter M., Grove, J. Morgan, Heffernan, James B., Hobbie, Sarah E., Larson, Kristen, Morse, Jennifer L., Neill, Christopher, Nelson, Kristen C., O'Neil-Dunne, Jarlath, Ogden, Laura A., Pataki, Diane E., Pearse, William D., Polsky, Colin, Chowdhury, Rinku Roy, Steele, Meredith K., Trammell, Tara Year: 2015 Context The urban heat island (UHI) is a welldocumented pattern of warming in cities relative to rural areas. Most UHI research utilizes remote sensing methods at large scales, or climate sensors in single cities surrounded by standardized land cover. Relatively few studies have explored continental-scale climatic patterns within common urban microenvironments such as residential landscapes that may affect human comfort. Objectives We tested the urban homogenization hypothesis which states that structure and function in cities exhibit ecological ‘‘sameness’’ across diverse regions relative to the native ecosystems they replaced. Methods We deployed portable micrometeorological sensors to compare air temperature and humidity in residential yards and native landscapes across six U.S. cities that span a range of climates (Phoenix, AZ; Los Angeles, CA; Minneapolis-St. Paul, MN; Boston, MA; Baltimore, MD; and Miami, FL). Results Microclimate in residential ecosystems was more similar among cities than among native ecosystems, particularly during the calm morning hours. Maximum regional actual evapotranspiration (AET) was related to the morning residential microclimate effect. Residential yards in cities with maximum AET \50–65 cm/year (Phoenix and Los Angeles) were generally cooler and more humid than nearby native shrublands during summer mornings, while yards in cities above this threshold were generally warmer (Baltimore and Miami) and drier (Miami) than native forests. On average, temperature and absolute humidity were *6 % less variable among residential ecosystems than among native ecosystems from diverse regions. Conclusions These data suggest that common residential land cover and structural characteristics lead to microclimatic convergence across diverse regions at the continental scale. Title: Convergence of Microclimate in Residential Landscapes Across Diverse Cities in the United States Author: Hall, Sharon J., Learned, J, Ruddell, Benjamin, Larson, Kelli L., Cavender-Bares, Jeannine, Bettez, Neil D., Groffman, Peter M., Grove, J. Morgan, Heffernan, James B., Hobbie, Sarah E., Larson, Kristen, Morse, Jennifer L., Neill, Christopher, Nelson, Kristen C., O'Neil-Dunne, Jarlath, Ogden, Laura A., Pataki, Diane E., Pearse, William D., Polsky, Colin, Chowdhury, Rinku Roy, Steele, Meredith K., Trammell, Tara Year: 2015 Context The urban heat island (UHI) is a welldocumented pattern of warming in cities relative to rural areas. Most UHI research utilizes remote sensing methods at large scales, or climate sensors in single cities surrounded by standardized land cover. Relatively few studies have explored continental-scale climatic patterns within common urban microenvironments such as residential landscapes that may affect human comfort. Objectives We tested the urban homogenization hypothesis which states that structure and function in cities exhibit ecological ‘‘sameness’’ across diverse regions relative to the native ecosystems they replaced. Methods We deployed portable micrometeorological sensors to compare air temperature and humidity in residential yards and native landscapes across six U.S. cities that span a range of climates (Phoenix, AZ; Los Angeles, CA; Minneapolis-St. Paul, MN; Boston, MA; Baltimore, MD; and Miami, FL). Results Microclimate in residential ecosystems was more similar among cities than among native ecosystems, particularly during the calm morning hours. Maximum regional actual evapotranspiration (AET) was related to the morning residential microclimate effect. Residential yards in cities with maximum AET \50–65 cm/year (Phoenix and Los Angeles) were generally cooler and more humid than nearby native shrublands during summer mornings, while yards in cities above this threshold were generally warmer (Baltimore and Miami) and drier (Miami) than native forests. On average, temperature and absolute humidity were *6 % less variable among residential ecosystems than among native ecosystems from diverse regions. Conclusions These data suggest that common residential land cover and structural characteristics lead to microclimatic convergence across diverse regions at the continental scale. Close