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The emerging multidisciplinary field of earth system science sets out to improve our understanding functioning ecosystems, at a global level across the entire planet. Stable Isotopes and Biosphere - Atmosphere Interactions looks to one of its most powerful tools the application of stable isotope analyses to understanding biosphere-atmosphere exchange of the greenhouse gases, and synthesizes much of the recent progress in this work. Stable Isotopes and Biosphere - Atmosphere Interactions describes recent progress in understanding the mechanisms, processes and applications of new techniques. It makes a significant contribution to the emerging, multidisciplinary study of the Earth as an interacting system. This book will be an important reference for students and researchers in biology, ecology, biogeochemistry, meteorology, and atmospheric science and will be invaluable for anyone with any interest in the future of the planet. * Describes applications of new stable isotope techniques to the emerging fields of earth system science and global change * Illustrates advances in scaling of physiological processes from leaf/soil to the global scale * Contains state-of-the-art, critical reviews written by international researchers and experts

Context As urban areas increase in extent globally, domestic yards play an increasingly important role as potential contributors to ecosystem services and well-being. These benefits largely depend on the plant species richness and composition of yards. Objectives We aim to determine the factors that drive plant species richness and phylogenetic composition of cultivated and spontaneous flora in urban yards at the continental scale, and how these potential drivers interact. Methods We analyzed plant species richness and phylogenetic composition of cultivated and spontaneous flora of 117 private yards from six major metropolitan areas in the US. Yard plant species richness and phylogenetic composition were expressed as a function of biophysical and socioeconomic variables and yard characteristics using linear mixed-effects models and spatially explicit structural equation modeling. Results Extreme temperatures largely determined yard species richness and phylogenetic composition at the continental scale. Precipitation positively predicted spontaneous richness but negatively predicted cultivated richness. Only the phylogenetic composition of the spontaneous flora was associated with precipitation. The effect of lower temperatures and precipitation on all yard diversity parameters was partly mediated by yard area. Among various socioeconomic variables, only education level showed a significant effect on cultivated phylogenetic composition. Conclusions Our results support the hypothesis that irrigation compensates for precipitation in driving cultivated yard plant diversity at the continental scale. Socioeconomic variables among middle and upper class families have no apparent influence on yard diversity. These findings inform the adaptation of US urban vegetation in cities in the face of global change. ; National Science Foundation Macrosystems Biology Program in the Emerging Frontiers Division of the Biological Sciences Directorate; Long Term Ecological Research Program; "Yard Futures'' project from the NSF Macrosystems Program [EF-1638519]; "Ecological Homogenization of Urban America'' project - NSF Macrosystems Program [EF-1065548, 1065737, 1065740, 1065741, 1065772, 1065785, 1065831, 121238320]; NSF Long Term Ecological Research ProgramNational Science Foundation (NSF) [DEB-0423476, BCS-1026865, DEB-0423704, DEB-9714833, OCE-1058747, 1238212, DEB-0620652, DBI-0620409] ; Research funding was provided by the National Science Foundation Macrosystems Biology Program in the Emerging Frontiers Division of the Biological Sciences Directorate and Long Term Ecological Research Program. The senior author was supported by the "Yard Futures'' project from the NSF Macrosystems Program (EF-1638519). Data collection was supported by the "Ecological Homogenization of Urban America'' project, funded by a series of collaborative grants from the NSF Macrosystems Program (EF-1065548, 1065737, 1065740, 1065741, 1065772, 1065785, 1065831 and 121238320); and additionally by grants from the NSF Long Term Ecological Research Program supporting work in Baltimore (DEB-0423476), Phoenix (BCS-1026865, DEB-0423704 and DEB-9714833), Plum Island (Boston) (OCE-1058747 and 1238212), Cedar Creek (Minneapolis-St. Paul) (DEB-0620652) and Florida Coastal Everglades (Miami) (DBI-0620409). We are grateful to the botanical field teams involved in yard sampling and data organization: BAL-Charlie Davis, Dan Dillon, Erin Mellenthin, Charlie Nicholson, Hannah Saunders, Avery Uslaner; BOS-Emma Dixon, Roberta Lombardiy, Pamela Polloni, Jehane Semaha, Elisabeth Ward, Megan Wheeler; LA-Aprille Curtis, La'Shaye Ervin; MIA-Bianca Bonilla, Stephen Hodges, Lawrence Lopez, Gabriel Sone; MSP-Chris Buyarksi, Emily Loberg, Alison Slaats, Kelsey Thurow; PHX-Erin Barton, Miguel Morgan. ; Public domain authored by a U.S. government employee

In urban areas, anthropogenic drivers of ecosystem structure and function are thought to predominate over larger-scale biophysical drivers. Residential yards are influenced by individual homeowner preferences and actions, and these factors are hypothesized to converge yard structure across broad scales. We examined soil total C and total delta C-13, organic C and organic delta C-13, total N, and delta N-15 in residential yards and corresponding reference ecosystems in six cities across the United States that span major climates and ecological biomes (Baltimore, Maryland; Boston, Massachusetts; Los Angeles, California; Miami, Florida; Minneapolis-St. Paul, Minnesota; and Phoenix, Arizona). Across the cities, we found soil C and N concentrations and soil delta N-15 were less variable in residential yards compared to reference sites supporting the hypothesis that soil C, N, and delta N-15 converge across these cities. Increases in organic soil C, soil N, and soil delta N-15 across urban, suburban, and rural residential yards in several cities supported the hypothesis that soils responded similarly to altered resource inputs across cities, contributing to convergence of soil C and N in yards compared to natural systems. Soil C and N dynamics in residential yards showed evidence of increasing C and N inputs to urban soils or dampened decomposition rates over time that are influenced by climate and/or housing age across the cities. In the warmest cities (Los Angeles, Miami, Phoenix), greater organic soil C and higher soil delta C-13 in yards compared to reference sites reflected the greater proportion of C-4 plants in these yards. In the two warm arid cities (Los Angeles, Phoenix), total soil delta C-13 increased and organic soil delta C-13 decreased with increasing home age indicating greater inorganic C in the yards around newer homes. In general, soil organic C and delta C-13, soil N, and soil delta N-15 increased with increasing home age suggesting increased soil C and N cycling rates and associated C-12 and N-14 losses over time control yard soil C and N dynamics. This study provides evidence that conversion of native reference ecosystems to residential areas results in convergence of soil C and N at a continental scale. The mechanisms underlying these effects are complex and vary spatially and temporally. ; U.S. National Science FoundationNational Science Foundation (NSF) [EF-1065548, 1065737, 1065740, 1065741, 1065772, 1065785, 1065831, 121238320] ; The authors thank La'Shaye Ervin, William Borrowman, Moumita Kundu, and Barbara Uhl for field and laboratory assistance. This research was funded by a series of collaborative grants from the U.S. National Science Foundation (EF-1065548, 1065737, 1065740, 1065741, 1065772, 1065785, 1065831, 121238320). The authors appreciate valuable comments by anonymous reviewers on a previous version of the manuscript. ; Public domain authored by a U.S. government employee

Although ecosystem services have been intensively examined in certain domains (e.g., forests and wetlands), little research has assessed ecosystem services for the most dominant landscape type in urban ecosystems-namely, residential yards. In this paper, we report findings of a cross-site survey of homeowners in six U.S. cities to 1) examine how residents subjectively value various ecosystem services, 2) explore distinctive dimensions of those values, and 3) test the urban homogenization hypothesis. This hypothesis posits that urbanization leads to similarities in the social-ecological dynamics across cities in diverse biomes. By extension, the thesis suggests that residents' ecosystem service priorities for residential landscapes will be similar regardless of whether residents live in the humid East or the arid West, or the warm South or the cold North. Results underscored that cultural services were of utmost importance, particularly anthropocentric values including aesthetics, low-maintenance, and personal enjoyment. Using factor analyses, distinctive dimensions of residents' values were found to partially align with the Millennium Ecosystem Assessment's categories (provisioning, regulating, supporting, and cultural). Finally, residents' ecosystem service priorities exhibited significant homogenization across regions. In particular, the traditional lawn aesthetic (neat, green, weed-free yards) was similarly important across residents of diverse U.S. cities. Only a few exceptions were found across different environmental and social contexts; for example, cooling effects were more important in the warm South, where residents also valued aesthetics more than those in the North, where low-maintenance yards were a greater priority. ; MacroSystems Biology Program in the Emerging Frontiers Division of the Biological Sciences Directorate at the National Science Foundation (NSF) [EF-1065548, 1065737, 1065740, 1065741, 1065772, 1065785, 1065831, 121238320]; NSFNational Science Foundation (NSF) [DEB-0423476, SES-0951366]; Phoenix [BCS-1026865]; Plum Island (Boston) [OCE-1058747]; Cedar Creek (Minneapolis-St Paul) [DEB-0620652]; Florida Coastal Everglades (Miami) [DBI-0620409] ; This work was supported by the MacroSystems Biology Program in the Emerging Frontiers Division of the Biological Sciences Directorate at the National Science Foundation (NSF) under grants EF-1065548, 1065737, 1065740, 1065741, 1065772, 1065785, 1065831, 121238320. The work arose from research funded by grants from the NSF Long-Term Ecological Research Program supporting work in Baltimore (DEB-0423476), Phoenix (BCS-1026865), Plum Island (Boston) (OCE-1058747), Cedar Creek (Minneapolis-St Paul) (DEB-0620652), and Florida Coastal Everglades (Miami) (DBI-0620409). This research was also supported by the NSF-funded Decision Center for a Desert City II: Urban Climate Adaptation (SES-0951366). Any opinions, findings, and conclusions or recommendations expressed in this material are those of the authors and do not necessarily reflect the views of NSF. ; Public domain authored by a U.S. government employee

In natural grasslands, C-4 plant dominance increases with growing season temperatures and reflects distinct differences in plant growth rates and water use efficiencies of C-3 vs. C-4 photosynthetic pathways. However, in lawns, management decisions influence interactions between planted turfgrass and weed species, leading to some uncertainty about the degree of human vs. climatic controls on lawn species distributions. We measured herbaceous plant carbon isotope ratios (delta C-13, index of C-3/C-4 relative abundance) and C-4 cover in residential lawns across seven U.S. cities to determine how climate, lawn plant management, or interactions between climate and plant management influenced C-4 lawn cover. We also calculated theoretical C-4 carbon gain predicted by a plant physiological model as an index of expected C-4 cover due to growing season climatic conditions in each city. Contrary to theoretical predictions, plant delta C-13 and C-4 cover in urban lawns were more strongly related to mean annual temperature than to growing season temperature. Wintertime temperatures influenced the distribution of C-4 lawn turf plants, contrary to natural ecosystems where growing season temperatures primarily drive C-4 distributions. C-4 cover in lawns was greatest in the three warmest cities, due to an interaction between climate and homeowner plant management (e.g., planting C-4 turf species) in these cities. The proportion of C-4 lawn species was similar to the proportion of C-4 species in the regional grass flora. However, the majority of C-4 species were nonnative turf grasses, and not of regional origin. While temperature was a strong control on lawn species composition across the United States, cities differed as to whether these patterns were driven by cultivated lawn grasses vs. weedy species. In some cities, biotic interactions with weedy plants appeared to dominate, while in other cities, C-4 plants were predominantly imported and cultivated. Elevated CO2 and temperature in cities can influence C-3/C-4 competitive outcomes; however, this study provides evidence that climate and plant management dynamics influence biogeography and ecology of C-3/C-4 plants in lawns. Their differing water and nutrient use efficiency may have substantial impacts on carbon, water, energy, and nutrient budgets across cities. ; U.S. National Science Foundation Macrosystems Biology Program [EF-1065548, 1065737, 1065740, 1065741, 1065772, 1065785, 1065831, 121238320] ; This research was funded by a series of collaborative grants from the U.S. National Science Foundation Macrosystems Biology Program (EF-1065548, 1065737, 1065740, 1065741, 1065772, 1065785, 1065831, 121238320). The authors thank La'Shaye Ervin, William Borrowman, Moumita Kundu, and Barbara Uhl for field and laboratory assistance. ; Public domain authored by a U.S. government employee

The urban heat island (UHI) is a well-documented 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. 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. 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). 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 similar to 6 % less variable among residential ecosystems than among native ecosystems from diverse regions. These data suggest that common residential land cover and structural characteristics lead to microclimatic convergence across diverse regions at the continental scale. ; Macrosystems Biology Program at NSF [EF-1065548, 1065737, 1065740, 1065741, 1065772, 1065785, 1065831, 1241960, 121238320]; Earth Systems Modeling program at NSF [EF-1049251]; NSF Long-term Ecological Research Program in Baltimore (BES LTER) [DEB-0423476]; NSF Long-term Ecological Research Program in Phoenix (CAP LTER) [BCS-1026865]; NSF Long-term Ecological Research Program in Plum Island (PIE LTER Boston) [OCE-1058747, 1238212]; NSF Long-term Ecological Research Program in Cedar Creek (CDR LTER, Minneapolis-St Paul) [DEB-1234162]; NSF Long-term Ecological Research Program in Florida Coastal Everglades (FCE LTER, Miami) [DBI-0620409] ; We are grateful to numerous technical staff, students, and volunteers who assisted with microclimate data collection, including Erin Barton, Matthew Camba, Emma Dixon, La'Shaye Ervin, Caitlin Holmes, Richard McHorney, Miguel Morgan, Joseph Rittenhouse, Anna Royar, Jehane Samaha, Sydney Schiffner, Julea Shaw, Anissa Vega, Elisabeth Ward, and Megan Wheeler. We also thank Darrel Jenerette for reviewing an earlier draft of this manuscript. This project was supported by several collaborative grants from the Macrosystems Biology Program at NSF (EF-1065548, 1065737, 1065740, 1065741, 1065772, 1065785, 1065831, 1241960, and 121238320), and by the Earth Systems Modeling program at NSF (EF-1049251). This work was also supported in part by the NSF Long-term Ecological Research Program in Baltimore (BES LTER, DEB-0423476), Phoenix (CAP LTER, BCS-1026865), Plum Island (PIE LTER Boston; OCE-1058747 and 1238212), Cedar Creek (CDR LTER, Minneapolis-St Paul; DEB-1234162), and Florida Coastal Everglades (FCE LTER, Miami; DBI-0620409). ; Public domain authored by a U.S. government employee

Societal Impact Statement: Globally, cities are planning for resilience through urban greening initiatives as governments understand the importance of urban forests in improving quality of life and mitigating climate change. However, the persistence of urban forests and the ecosystem benefits they provide are threatened by climate change, and systematic assessments of causes of tree dieback and mortality in urban environments are rare. Long-term monitoring studies and adaptive management are needed to identify and prevent climate change-driven failures and mortality. Research and monitoring when coupled with systematic forecasting will enable governments to incorporate climate change resilience into urban forestry planning. Future scenarios in which urban forests are resilient or in decline will depend on the management and planning actions we make today. Summary: The management of urban forests is a key element of resilience planning in cities across the globe. Urban forests provide ecosystem services as well as other nature-based solutions to 4.2 billion people living in cities. However, to continue to do so effectively, urban forests need to be able to thrive in an increasingly changing climate. Trees in cities are vulnerable to extreme heat and drought events, which are predicted to increase in frequency and severity under climate change. Knowledge of species' vulnerability to climate change, therefore, is crucial to ensure provision of desired ecosystem benefits, improve species selection, maintain tree growth and reduce tree mortality, dieback and stress in urban forests. Yet, systematic assessments of causes of tree dieback and mortality in urban environments are rare. We reviewed the state of knowledge of tree mortality in urban forests globally, finding very few frameworks that enable detection of climate change impacts on urban forests and no long-term studies assessing climate change as a direct driver of urban tree dieback and mortality. The effects of climate change on urban forests remain poorly understood and quantified, constraining the ability of governments to incorporate climate change resilience into urban forestry planning.