Groffman
Peter M.
Groffman
Peter M.
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ArticleContinental-scale homogenization of residential lawn plant communities(Elsevier, 2017-05-20) Wheeler, Megan M. ; Neill, Christopher ; Groffman, Peter M. ; Avolio, Meghan L. ; Bettez, Neil D. ; Cavender-Bares, Jeannine ; Roy Chowdhury, Rinku ; Darling, Lindsay ; Grove, J. Morgan ; Hall, Sharon J. ; Heffernan, James B. ; Hobbie, Sarah E. ; Larson, Kelli L. ; Morse, Jennifer L. ; Nelson, Kristen ; Ogden, Laura ; O'Neil-Dunne, Jarlath ; Pataki, Diane E. ; Trammell, TaraResidential lawns are highly managed ecosystems that occur in urbanized landscapes across the United States. Because they are ubiquitous, lawns are good systems in which to study the potential homogenizing effects of urban land use and management together with the continental-scale effects of climate on ecosystem structure and functioning. We hypothesized that similar homeowner preferences and management in residential areas across the United States would lead to low plant species diversity in lawns and relatively homogeneous vegetation across broad geographical regions. We also hypothesized that lawn plant species richness would increase with regional temperature and precipitation due to the presence of spontaneous, weedy vegetation, but would decrease with household income and fertilizer use. To test these predictions, we compared plant species composition and richness in residential lawns in seven U.S. metropolitan regions. We also compared species composition in lawns with understory vegetation in minimally-managed reference areas in each city. As expected, the composition of cultivated turfgrasses was more similar among lawns than among reference areas, but this pattern also held among spontaneous species. Plant species richness and diversity varied more among lawns than among reference areas, and more diverse lawns occurred in metropolitan areas with higher precipitation. Native forb diversity increased with precipitation and decreased with income, driving overall lawn diversity trends with these predictors as well. Our results showed that both management and regional climate shaped lawn species composition, but the overall homogeneity of species regardless of regional context strongly suggested that management was a more important driver.
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ArticleThe changing landscape : ecosystem responses to urbanization and pollution across climatic and societal gradients(Ecological Society of America, 2008-06) Grimm, Nancy B. ; Foster, David R. ; Groffman, Peter M. ; Grove, J. Morgan ; Hopkinson, Charles S. ; Nadelhoffer, Knute J. ; Pataki, Diane E. ; Peters, Debra P. C.Urbanization, an important driver of climate change and pollution, alters both biotic and abiotic ecosystem properties within, surrounding, and even at great distances from urban areas. As a result, research challenges and environmental problems must be tackled at local, regional, and global scales. Ecosystem responses to land change are complex and interacting, occurring on all spatial and temporal scales as a consequence of connectivity of resources, energy, and information among social, physical, and biological systems. We propose six hypotheses about local to continental effects of urbanization and pollution, and an operational research approach to test them. This approach focuses on analysis of “megapolitan” areas that have emerged across North America, but also includes diverse wildland-to-urban gradients and spatially continuous coverage of land change. Concerted and coordinated monitoring of land change and accompanying ecosystem responses, coupled with simulation models, will permit robust forecasts of how land change and human settlement patterns will alter ecosystem services and resource utilization across the North American continent. This, in turn, can be applied globally.
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ArticleSatisfaction, water and fertilizer use in the American residential macrosystem(IOPScience, 2016-02-29) Groffman, Peter M. ; Grove, J. Morgan ; Polsky, Colin ; Bettez, Neil D. ; Morse, Jennifer L. ; Cavender-Bares, Jeannine ; Hall, Sharon J. ; Heffernan, James B. ; Hobbie, Sarah E. ; Larson, Kelli L. ; Neill, Christopher ; Nelson, Kristen ; Ogden, Laura ; O'Neil-Dunne, Jarlath ; Pataki, Diane E. ; Roy Chowdhury, Rinku ; Locke, Dexter H.Residential yards across the US look remarkably similar despite marked variation in climate and soil, yet the drivers of this homogenization are unknown. Telephone surveys of fertilizer and irrigation use and satisfaction with the natural environment, and measurements of inherent water and nitrogen availability in six US cities (Boston, Baltimore, Miami, Minneapolis-St. Paul, Phoenix, Los Angeles) showed that the percentage of people using irrigation at least once in a year was relatively invariant with little difference between the wettest (Miami, 85%) and driest (Phoenix, 89%) cities. The percentage of people using fertilizer at least once in a year also ranged narrowly (52%–71%), while soil nitrogen supply varied by 10x. Residents expressed similar levels of satisfaction with the natural environment in their neighborhoods. The nature and extent of this satisfaction must be understood if environmental managers hope to effect change in the establishment and maintenance of residential ecosystems.
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ArticleClimate and lawn management interact to control C4 plant distribution in residential lawns across seven U.S. cities.(Ecological Society of America, 2019-04-01) Trammell, Tara ; Pataki, Diane E. ; Still, Christopher J. ; Ehleringer, James R. ; Avolio, Meghan L. ; Bettez, Neil D. ; Cavender-Bares, Jeannine ; Groffman, Peter M. ; Grove, J. Morgan ; Hall, Sharon J. ; Heffernan, James B. ; Hobbie, Sarah E. ; Larson, Kelli L. ; Morse, Jennifer L. ; Neill, Christopher ; Nelson, Kristen ; O'Neil-Dunne, Jarlath ; Pearse, William D. ; Roy Chowdhury, Rinku ; Steele, Meredith K. ; Wheeler, Megan M.In natural grasslands, C4 plant dominance increases with growing season temperatures and reflects distinct differences in plant growth rates and water use efficiencies of C3 vs. C4 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 (δ13C, index of C3/C4 relative abundance) and C4 cover in residential lawns across seven U.S. cities to determine how climate, lawn plant management, or interactions between climate and plant management influenced C4 lawn cover. We also calculated theoretical C4 carbon gain predicted by a plant physiological model as an index of expected C4 cover due to growing season climatic conditions in each city. Contrary to theoretical predictions, plant δ13C and C4 cover in urban lawns were more strongly related to mean annual temperature than to growing season temperature. Wintertime temperatures influenced the distribution of C4 lawn turf plants, contrary to natural ecosystems where growing season temperatures primarily drive C4 distributions. C4 cover in lawns was greatest in the three warmest cities, due to an interaction between climate and homeowner plant management (e.g., planting C4 turf species) in these cities. The proportion of C4 lawn species was similar to the proportion of C4 species in the regional grass flora. However, the majority of C4 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, C4 plants were predominantly imported and cultivated. Elevated CO2 and temperature in cities can influence C3/C4 competitive outcomes; however, this study provides evidence that climate and plant management dynamics influence biogeography and ecology of C3/C4 plants in lawns. Their differing water and nutrient use efficiency may have substantial impacts on carbon, water, energy, and nutrient budgets across cities.
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ArticleMineralization of ancient carbon in the subsurface of riparian forests(American Geophysical Union, 2008-05-10) Gurwick, Noel P. ; McCorkle, Daniel C. ; Groffman, Peter M. ; Gold, Arthur J. ; Kellogg, D. Q. ; Seitz-Rundlett, PeterMicrobial activity in saturated, subsurface sediments in riparian forests may be supported by recent photosynthate or ancient (>500 ybp) soil organic carbon (SOC) in buried horizons. Metabolism of ancient SOC may be particularly important in riparian zones, considered denitrification hot spots, because denitrification in the riparian subsurface is often C-limited, because buried horizons intersect deep flow paths, and because low C mineralization rates can support ecosystem-relevant rates of denitrification. Buried horizons are common where alluvial processes (stream migration, overbank flow) have dominated riparian evolution. Our objectives were to determine: (1) the extent to which ancient SOC directly supports subsurface microbial activity; (2) whether different C sources support microbial activity in alluvial versus glaciofluvial riparian zones; and (3) how microbial use of ancient SOC varies with depth. In situ groundwater incubations and 14C dating of dissolved inorganic carbon revealed that ancient SOC mineralization was common, and that it constituted 31–100% of C mineralization 2.6 m deep at one site, at rates sufficient to influence landscape N budgets. Our data failed to reveal consistent spatial patterns of microbially available ancient C. Although mineralized C age increased with depth at one alluvial site, we observed ancient C metabolism 150 cm deep at a glaciofluvial site, suggesting that subsurface microbial activity in riparian zones does not vary systematically between alluvial and glaciofluvial hydrogeologic settings. These findings underscore the relevance of ancient C to contemporary ecosystem processes and the challenge of using mappable surface features to identify subsurface ecosystem characteristics or riparian zone N-sink strength.
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ArticleHomogenization of plant diversity, composition, and structure in North American urban yards(John Wiley & Sons, 2018-02-15) Pearse, William D. ; Cavender-Bares, Jeannine ; Hobbie, Sarah E. ; Avolio, Meghan L. ; Bettez, Neil D. ; Roy Chowdhury, Rinku ; Darling, Lindsay ; Groffman, Peter M. ; Grove, J. Morgan ; Hall, Sharon J. ; Heffernan, James B. ; Learned, Jennifer ; Neill, Christopher ; Nelson, Kristen ; Pataki, Diane E. ; Ruddell, Benjamin L. ; Steele, Meredith K. ; Trammell, TaraUrban ecosystems are widely hypothesized to be more ecologically homogeneous than natural ecosystems. We argue that urban plant communities assemble from a complex mix of horticultural and regional species pools, and evaluate the homogenization hypothesis by comparing cultivated and spontaneously occurring urban vegetation to natural area vegetation across seven major U.S. cities. There was limited support for homogenization of urban diversity, as the cultivated and spontaneous yard flora had greater numbers of species than natural areas, and cultivated phylogenetic diversity was also greater. However, urban yards showed evidence of homogenization of composition and structure. Yards were compositionally more similar across regions than were natural areas, and tree density was less variable in yards than in comparable natural areas. This homogenization of biodiversity likely reflects similar horticultural source pools, homeowner preferences, and management practices across U.S. cities.
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PreprintMethods for measuring denitrification : diverse approaches to a difficult problem( 2005-07-15) Groffman, Peter M. ; Altabet, Mark A. ; Bohlke, John K. ; Butterbach-Bahl, Klaus ; David, Mark B. ; Firestone, Mary K. ; Giblin, Anne E. ; Kana, Todd M. ; Nielsen, Lars Peter ; Voytek, Mary A.Denitrification, the reduction of the nitrogen (N) oxides, nitrate (NO3-) and nitrite (NO2-), to the gases nitric oxide (NO), nitrous oxide (N2O) and dinitrogen (N2), is important to primary production, water quality and the chemistry and physics of the atmosphere at ecosystem, landscape, regional and global scales. Unfortunately, this process is very difficult to measure, and existing methods are problematic for different reasons in different places at different times. In this paper, we review the major approaches that have been taken to measure denitrification in terrestrial and aquatic environments and discuss the strengths, weaknesses and future prospects for the different methods. Methodological approaches covered include; 1) acetylene-based methods, 2) 15N tracers, 3) direct N2 quantification, 4) N2/Ar ratio quantification, 5) mass balance approaches, 6) stoichiometric approaches, 7) methods based on stable isotopes, 8) in situ gradients with atmospheric environmental tracers and 9) molecular approaches. Our review makes it clear that the prospects for improved quantification of denitrification vary greatly in different environments and at different scales. While current methodology allows for the production of accurate estimates of denitrification at scales relevant to water and air quality and ecosystem fertility questions in some systems (e.g., aquatic sediments, well defined aquifers), methodology for other systems, especially upland terrestrial areas, still needs development. Comparison of mass balance and stoichiometric approaches that constrain estimates of denitrification at large scales with point measurements (made using multiple methods), in multiple systems, is likely to propel more improvement in denitrification methods over the next few years.
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ArticleIdeas and perspectives: biogeochemistry - some key foci for the future(European Geosciences Union, 2021-05-19) Bianchi, Thomas S. ; Anand, Madhur ; Bauch, Chris T. ; Canfield, Donald E. ; De Meester, Luc ; Fennel, Katja ; Groffman, Peter M. ; Pace, Michael L. ; Saito, Mak A. ; Simpson, Myrna J.Biogeochemistry has an important role to play in many environmental issues of current concern related to global change and air, water, and soil quality. However, reliable predictions and tangible implementation of solutions, offered by biogeochemistry, will need further integration of disciplines. Here, we refocus on how further developing and strengthening ties between biology, geology, chemistry, and social sciences will advance biogeochemistry through (1) better incorporation of mechanisms, including contemporary evolutionary adaptation, to predict changing biogeochemical cycles, and (2) implementing new and developing insights from social sciences to better understand how sustainable and equitable responses by society are achieved. The challenges for biogeochemists in the 21st century are formidable and will require both the capacity to respond fast to pressing issues (e.g., catastrophic weather events and pandemics) and intense collaboration with government officials, the public, and internationally funded programs. Keys to success will be the degree to which biogeochemistry can make biogeochemical knowledge more available to policy makers and educators about predicting future changes in the biosphere, on timescales from seasons to centuries, in response to climate change and other anthropogenic impacts. Biogeochemistry also has a place in facilitating sustainable and equitable responses by society.
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ArticleEcological homogenization of urban USA(Ecological Society of America, 2014-02) Groffman, Peter M. ; Cavender-Bares, Jeannine ; Bettez, Neil D. ; Grove, J. Morgan ; Hall, Sharon J. ; Heffernan, James B. ; Hobbie, Sarah E. ; Larson, Kelli L. ; Morse, Jennifer L. ; Neill, Christopher ; Nelson, Kristen ; O'Neil-Dunne, Jarlath ; Ogden, Laura ; Pataki, Diane E. ; Polsky, Colin ; Roy Chowdhury, Rinku ; Steele, Meredith K.A visually apparent but scientifically untested outcome of land-use change is homogenization across urban areas, where neighborhoods in different parts of the country have similar patterns of roads, residential lots, commercial areas, and aquatic features. We hypothesize that this homogenization extends to ecological structure and also to ecosystem functions such as carbon dynamics and microclimate, with continental-scale implications. Further, we suggest that understanding urban homogenization will provide the basis for understanding the impacts of urban land-use change from local to continental scales. Here, we show how multi-scale, multi-disciplinary datasets from six metropolitan areas that cover the major climatic regions of the US (Phoenix, AZ; Miami, FL; Baltimore, MD; Boston, MA; Minneapolis–St Paul, MN; and Los Angeles, CA) can be used to determine how household and neighborhood characteristics correlate with land-management practices, land-cover composition, and landscape structure and ecosystem functions at local, regional, and continental scales.
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ArticleClimate change decreases nitrogen pools and mineralization rates in northern hardwood forests(John Wiley & Sons, 2016-03-22) Durán, Jorge ; Morse, Jennifer L. ; Groffman, Peter M. ; Campbell, John L. ; Christenson, Lynn M. ; Driscoll, Charles T. ; Fahey, Timothy J. ; Fisk, Melany C. ; Likens, Gene E. ; Melillo, Jerry M. ; Mitchell, Myron J. ; Templer, Pamela H. ; Vadeboncoeur, Matthew A.Nitrogen (N) supply often limits the productivity of temperate forests and is regulated by a complex mix of biological and climatic drivers. In excess, N is linked to a variety of soil, water, and air pollution issues. Here, we use results from an elevation gradient study and historical data from the long-term Hubbard Brook Ecosystem Study (New Hampshire, USA) to examine relationships between changes in climate, especially during winter, and N supply to northern hardwood forest ecosystems. Low elevation plots with less snow, more soil freezing, and more freeze/thaw cycles supported lower rates of N mineralization than high elevation plots, despite having higher soil temperatures and no consistent differences in soil moisture during the growing season. These results are consistent with historical analyses showing decreases in rates of soil N mineralization and inorganic N concentrations since 1973 that are correlated with long-term increases in mean annual temperature, decreases in annual snow accumulation, and a increases in the number of winter thawing degree days. This evidence suggests that changing climate may be driving decreases in the availability of a key nutrient in northern hardwood forests, which could decrease ecosystem production but have positive effects on environmental consequences of excess N.
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ArticleSteering operational synergies in terrestrial observation networks : opportunity for advancing Earth system dynamics modelling(Copernicus Publications on behalf of the European Geosciences Union, 2018-05-23) Baatz, Roland ; Sullivan, Pamela L. ; Li, Li ; Weintraub, Samantha R. ; Loescher, Henry W. ; Mirtl, Michael ; Groffman, Peter M. ; Wall, Diana H. ; Young, Michael ; White, Tim ; Wen, Hang ; Zacharias, Steffen ; Kühn, Ingolf ; Tang, Jianwu ; Gaillardet, Jerome ; Braud, Isabelle ; Flores, Alejandro N. ; Kumar, Praveen ; Lin, Henry ; Ghezzehei, Teamrat ; Jones, Julia ; Gholz, Henry L. ; Vereecken, Harry ; Van Looy, KrisAdvancing our understanding of Earth system dynamics (ESD) depends on the development of models and other analytical tools that apply physical, biological, and chemical data. This ambition to increase understanding and develop models of ESD based on site observations was the stimulus for creating the networks of Long-Term Ecological Research (LTER), Critical Zone Observatories (CZOs), and others. We organized a survey, the results of which identified pressing gaps in data availability from these networks, in particular for the future development and evaluation of models that represent ESD processes, and provide insights for improvement in both data collection and model integration. From this survey overview of data applications in the context of LTER and CZO research, we identified three challenges: (1) widen application of terrestrial observation network data in Earth system modelling, (2) develop integrated Earth system models that incorporate process representation and data of multiple disciplines, and (3) identify complementarity in measured variables and spatial extent, and promoting synergies in the existing observational networks. These challenges lead to perspectives and recommendations for an improved dialogue between the observation networks and the ESD modelling community, including co-location of sites in the existing networks and further formalizing these recommendations among these communities. Developing these synergies will enable cross-site and cross-network comparison and synthesis studies, which will help produce insights around organizing principles, classifications, and general rules of coupling processes with environmental conditions.
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ArticleTime lags: insights from the U.S. Long Term Ecological Research Network(Ecological Society of America, 2021-05-17) Rastetter, Edward B. ; Ohman, Mark D. ; Elliott, Katherine J. ; Rehage, Jennifer S. ; Rivera-Monroy, Victor H. ; Boucek, Ross E. ; Castaneda-Moya, Edward ; Danielson, Tess M. ; Gough, Laura ; Groffman, Peter M. ; Jackson, C. Rhett ; Ford Miniat, ChelcyEcosystems across the United States are changing in complex ways that are difficult to predict. Coordinated long-term research and analysis are required to assess how these changes will affect a diverse array of ecosystem services. This paper is part of a series that is a product of a synthesis effort of the U.S. National Science Foundation’s Long Term Ecological Research (LTER) network. This effort revealed that each LTER site had at least one compelling scientific case study about “what their site would look like” in 50 or 100 yr. As the site results were prepared, themes emerged, and the case studies were grouped into separate papers along five themes: state change, connectivity, resilience, time lags, and cascading effects and compiled into this special issue. This paper addresses the time lags theme with five examples from diverse biomes including tundra (Arctic), coastal upwelling (California Current Ecosystem), montane forests (Coweeta), and Everglades freshwater and coastal wetlands (Florida Coastal Everglades) LTER sites. Its objective is to demonstrate the importance of different types of time lags, in different kinds of ecosystems, as drivers of ecosystem structure and function and how these can effectively be addressed with long-term studies. The concept that slow, interactive, compounded changes can have dramatic effects on ecosystem structure, function, services, and future scenarios is apparent in many systems, but they are difficult to quantify and predict. The case studies presented here illustrate the expanding scope of thinking about time lags within the LTER network and beyond. Specifically, they examine what variables are best indicators of lagged changes in arctic tundra, how progressive ocean warming can have profound effects on zooplankton and phytoplankton in waters off the California coast, how a series of species changes over many decades can affect Eastern deciduous forests, and how infrequent, extreme cold spells and storms can have enduring effects on fish populations and wetland vegetation along the Southeast coast and the Gulf of Mexico. The case studies highlight the need for a diverse set of LTER (and other research networks) sites to sort out the multiple components of time lag effects in ecosystems.