Glenn Guntenspergen, Ph.D.
Glenn is a Research Ecologist at the Eastern Ecological Science Center in Laurel, MD.
Science and Products
Filter Total Items: 19
Environmental and Vegetation Data from Marsh-Forest Transgression Experiment at Blackwater National Wildlife Refuge, MD, USA Environmental and Vegetation Data from Marsh-Forest Transgression Experiment at Blackwater National Wildlife Refuge, MD, USA
We conducted a field experiment at the Moneystump Swamp in the Blackwater National Wildlife Refuge in Dorchester, MD, USA to simulate a natural forest disturbance event (e.g., storm-induced flooding) by inducing the death of established trees (coastal loblolly pine, Pinus taeda) at the marsh-upland forest ecotone. There were three treatment components: Cut- where the trees were cut and...
Changes in Organic Carbon Source and Storage with Sea Level Rise-Induced Transgression in a Chesapeake Bay Marsh Changes in Organic Carbon Source and Storage with Sea Level Rise-Induced Transgression in a Chesapeake Bay Marsh
This data set includes a variety of bulk organic carbon, lignin-phenol biomarker, and sedimentation rate data from a set of sites in the Blackwater Marsh in Chesapeake Bay. At each site, a short core was taken, and all data is organized according to depth below the marsh surface. Data includes: Bulk %OC, bulk %N, atomic carbon:nitrogen ratios, stable carbon isotopes (d13C) Lignin-phenol...
Water levels (November 11 2016 through November 11 2017) for four wells and Light intensity data (October 1 2015 through September 2019): from marsh to upland forest, for Moneystump Marsh, Blackwater National Wildlife Refuge, Maryland Water levels (November 11 2016 through November 11 2017) for four wells and Light intensity data (October 1 2015 through September 2019): from marsh to upland forest, for Moneystump Marsh, Blackwater National Wildlife Refuge, Maryland
Water levels in meters from four wells in Moneystump marsh at Blackwater National Wildlife Refuge, MD. Two wells are located in the upland forest; one well is located in the marsh-forest transition zone (ecotone); and one well is located in the marsh. Water depth of the adjacent creek is reported in meters. Data covers the time span from November 11 2016 - November 11 2017. Pressure...
Sediment Radiochemical Data from Georgia, Massachusetts and Virginia Coastal Marshes Sediment Radiochemical Data from Georgia, Massachusetts and Virginia Coastal Marshes
This data release is an archive of sedimentary laboratory analytical data produced by scientists from the U.S. Geological Survey St. Petersburg Coastal and Marine Science Center (USGS SPCMSC) for sediment cores and surface samples collected from coastal marshes in Georgia (GA), Virginia (VA), and Massachusetts (MA). Collaborators from USGS Patuxent Wildlife Research Center (PWRC) and the...
Experimental recovery rates of tidal marsh vegetation Experimental recovery rates of tidal marsh vegetation
We measured the response of plants to disturbance across a gradient in inundation times by transplanting tussocks of Schoenoplectus americanus into mesocosms of different elevation in two marsh organ platforms. Both organs were planted on April 11, 2012 and harvested on August 21, 2012. Plants in one organ were disturbed by clipping all above ground vegetation on June 20 2012 (62 days)...
Development of a Multimetric Index for Integrated Assessment of Salt Marsh Ecosystem Condition Development of a Multimetric Index for Integrated Assessment of Salt Marsh Ecosystem Condition
Data Release for journal publication describing development of a multimetric index for assessing salt marsh condition in northeastern National Parks. This is the first application of an empirical, metric-selection algorithm to metrics from multiple trophic groups (vegetation and nekton). While MMIs derived from nekton or vegetation metrics alone were strongly correlated with human...
Decomposition of plant litter in Pacific coast tidal marshes, 2014-2015 Decomposition of plant litter in Pacific coast tidal marshes, 2014-2015
Decomposition of plant matter is one of the key processes affecting carbon cycling and storage in tidal wetlands. In this study, we evaluated the effects of factors related to climate change (temperature, inundation) and vegetation composition on rates of litter decay in seven tidal marsh sites along the Pacific coast. In 2014 we conducted manipulative experiments to test inundation...
Filter Total Items: 132
Examining inequality in aquatic ecosystem services: Evidence from large-scale monitoring programs Examining inequality in aquatic ecosystem services: Evidence from large-scale monitoring programs
We hypothesize that aquatic ecosystem services are likely to be inequitably accessible and addressing this hypothesis requires systematic assessment at regional and national scales. We used existing data from large-scale aquatic monitoring programs (National Coastal Condition Assessment, National Lakes Assessment) to examine relationships between ecosystem condition, approximating a...
Authors
Katya E. Kovalenko, Sergey Ilyushkin, Holly Wellar-Kelly, Justine Neville, Glenn Guntenspergen
Understanding marsh elevation and accretion processes and vulnerability to rising sea levels across climatic and geomorphic gradients in California, USA Understanding marsh elevation and accretion processes and vulnerability to rising sea levels across climatic and geomorphic gradients in California, USA
Tidal marshes build elevations by below- and aboveground organic and mineral soil processes. Marsh elevation and accretion data can be used to determine if marshes are keeping pace with sea-level rise. Using a network of 54 deep rod surface elevation tables with paired feldspar marker horizon plots, we tracked elevation and accretion trends across 16 marshes in California, USA. All sites...
Authors
Karen M. Thorne, McKenna Bristow, Lyndsay Rankin, Katya E. Kovalenko, Justine Neville, Chase M. Freeman, Glenn Guntenspergen
Observing coastal wetland transitions using national land cover products Observing coastal wetland transitions using national land cover products
Over the coming century, climate change and sea-level rise are predicted to cause widespread change to coastal wetlands. Estuarine vegetated wetlands can adapt to sea-level rise through both vertical development (i.e., biophysical feedbacks and sedimentation) and upslope/horizontal migration. Quantifying changes to estuarine vegetated wetlands over time can help to inform current and...
Authors
Nicholas Enwright, Michael Osland, Karen M. Thorne, Glenn Guntenspergen, James Grace, Gregory Steyer, Nate Herold, Bogdan Chivoiu, Minoo Han
Foundations of modeling resilience of tidal saline wetlands to sea-level rise along the U.S. Pacific Coast Foundations of modeling resilience of tidal saline wetlands to sea-level rise along the U.S. Pacific Coast
Context Tidal saline wetlands (TSWs) are highly threatened from climate-change effects of sea-level rise. Studies of TSWs along the East Coast U.S. and elsewhere suggest significant likely losses over coming decades but needed are analytic tools gauged to Pacific Coast U.S. wetlands. Objectives We predict the impacts of sea-level rise (SLR) on the elevation capital (vertical) and...
Authors
Bruce Marcot, Karen M. Thorne, Joel A. Carr, Glenn Guntenspergen
Future marsh evolution due to tidal changes induced by human adaptation to sea level rise Future marsh evolution due to tidal changes induced by human adaptation to sea level rise
With sea level rise threatening coastal development, decision-makers are beginning to act by modifying shorelines. Previous research has shown that hardening or softening shorelines may change the tidal range under future sea level rise. Tidal range can also be changed by natural factors. Coastal marshes, which humans increasingly depend on for shoreline protection, are ecologically...
Authors
Celina Balderas-Guzman, Kevin Buffington, Karen M. Thorne, Glenn Guntenspergen, Michelle Hummel, Mark T. Stacey
Spatial distribution of elevation change monitoring in coastal wetlands across protected lands of the lower 48 United States Spatial distribution of elevation change monitoring in coastal wetlands across protected lands of the lower 48 United States
Introduction Tidally influenced coastal wetlands, both saline and fresh, appear where terrestrial and marine environments meet and are considered important ecosystems for identifying the impacts of climate change. Coastal wetlands provide valuable benefits to society and the environment in the form of flood protection, water-quality improvements, and shoreline erosion reduction, making...
Authors
Justine Neville, Glenn Guntenspergen
Nonlinear patterns of surface elevation change in coastal wetlands: The value of generalized additive models for quantifying rates of change Nonlinear patterns of surface elevation change in coastal wetlands: The value of generalized additive models for quantifying rates of change
In the face of accelerating climate change and rising sea levels, quantifying surface elevation change dynamics in coastal wetlands can help to develop a more complete understanding of the implications of sea-level rise on coastal wetland stability. The surface elevation table-marker horizon (SET-MH) approach has been widely used to quantify and characterize surface elevation change...
Authors
Laura Feher, Michael Osland, Darren Johnson, James Grace, Glenn Guntenspergen, David R. Stewart, Carlos Coronado-Molina, Fred Sklar
Widespread retreat of coastal habitat is likely at warming levels above 1.5 °C Widespread retreat of coastal habitat is likely at warming levels above 1.5 °C
Several coastal ecosystems—most notably mangroves and tidal marshes—exhibit biogenic feedbacks that are facilitating adjustment to relative sea-level rise (RSLR), including the sequestration of carbon and the trapping of mineral sediment1. The stability of reef-top habitats under RSLR is similarly linked to reef-derived sediment accumulation and the vertical accretion of protective coral...
Authors
Neil Saintilan, Benjamin Horton, Torbjörn Törnqvist, Erica Ashe, Nicole Khan, Mark Schuerch, Chris Perry, Robert Kopp, Gregory Garner, Nicholas Murray, Kerrylee Rogers, Simon Albert, Jeffrey Kelleway, Timothy Shaw, Colin Woodroffe, Catherine Lovelock, Madeline Goddard, Lindsay Hutley, Katya Kovalenko, Laura Feher, Glenn Guntenspergen
Comparing wetland elevation change using a surface elevation table, digital level, and total station Comparing wetland elevation change using a surface elevation table, digital level, and total station
The surface elevation table (SET) approach and two survey instruments, a digital level (DL) and a total station (TS), were used to evaluate elevation change at a 1-ha, micro-tidal, back-barrier salt marsh at Assateague Island National Seashore (Berlin, MD, USA) from 2016 to 2022. SET data were collected at 3 sampling stations along the perimeter of the plot, 36 pins per station, and the...
Authors
James Lynch, Neil Winn, Katya Kovalenko, Glenn Guntenspergen
Maintaining wetland ecosystem services in a changing climate Maintaining wetland ecosystem services in a changing climate
A changing climate is causing challenges for soil and water management in many parts of the world. Current soil management practices need to be redesigned to effectively address present and future fluctuating climates. Soil Hydrology in a Changing Climate explores how soil management practices impact soil hydrological characteristics, and how we can improve our understanding of soil and...
Authors
W. Johnson, Glenn Guntenspergen
Constraints on the adjustment of tidal marshes to accelerating sea level rise Constraints on the adjustment of tidal marshes to accelerating sea level rise
Much uncertainty exists about the vulnerability of valuable tidal marsh ecosystems to relative sea level rise. Previous assessments of resilience to sea level rise, to which marshes can adjust by sediment accretion and elevation gain, revealed contrasting results, depending on contemporary or Holocene geological data. By analyzing globally distributed contemporary data, we found that...
Authors
Neil Saintilan, Katya E. Kovalenko, Glenn Guntenspergen, Kerrylee Rogers, James Lynch, Donald Cahoon, Catherine Lovelock, Daniel Friess, Erica Ashe, Ken Krauss, Nicole Cormier, Tom Spencer, Janine Adams, Jacqueline Raw, Carles Ibanez, Francesco Scarton, Stijn Temmerman, Patrick Meire, Tom Maris, Karen M. Thorne, John Brazner, Gail L. Chmura, Tony Bowron, Vishmie Gamage, Kimberly Cressman, Charlie Endris, Christina Marconi, Pamela Marcum, Kari St. Laurent, William Reay, Kenneth Raposa, Jason Garwood, Nicole Kahn
Migration and transformation of coastal wetlands in response to rising seas Migration and transformation of coastal wetlands in response to rising seas
Coastal wetlands are not only among the world’s most valued ecosystems but also among the most threatened by high greenhouse gas emissions that lead to accelerated sea level rise. There is intense debate regarding the extent to which landward migration of wetlands might compensate for seaward wetland losses. By integrating data from 166 estuaries across the conterminous United States, we...
Authors
Michael Osland, Bogdan Chivoiu, Nicholas Enwright, Karen M. Thorne, Glenn Guntenspergen, James Grace, Leah Dale, William Brooks, Nathaniel Herold, John Day, Fred Sklar, Christopher Swarzenski
By
Ecosystems Mission Area, Water Resources Mission Area, Ecosystems Land Change Science Program, Land Management Research Program, Eastern Ecological Science Center, Lower Mississippi-Gulf Water Science Center, Western Ecological Research Center (WERC), Wetland and Aquatic Research Center , Gulf of America
Science and Products
Filter Total Items: 19
Environmental and Vegetation Data from Marsh-Forest Transgression Experiment at Blackwater National Wildlife Refuge, MD, USA Environmental and Vegetation Data from Marsh-Forest Transgression Experiment at Blackwater National Wildlife Refuge, MD, USA
We conducted a field experiment at the Moneystump Swamp in the Blackwater National Wildlife Refuge in Dorchester, MD, USA to simulate a natural forest disturbance event (e.g., storm-induced flooding) by inducing the death of established trees (coastal loblolly pine, Pinus taeda) at the marsh-upland forest ecotone. There were three treatment components: Cut- where the trees were cut and...
Changes in Organic Carbon Source and Storage with Sea Level Rise-Induced Transgression in a Chesapeake Bay Marsh Changes in Organic Carbon Source and Storage with Sea Level Rise-Induced Transgression in a Chesapeake Bay Marsh
This data set includes a variety of bulk organic carbon, lignin-phenol biomarker, and sedimentation rate data from a set of sites in the Blackwater Marsh in Chesapeake Bay. At each site, a short core was taken, and all data is organized according to depth below the marsh surface. Data includes: Bulk %OC, bulk %N, atomic carbon:nitrogen ratios, stable carbon isotopes (d13C) Lignin-phenol...
Water levels (November 11 2016 through November 11 2017) for four wells and Light intensity data (October 1 2015 through September 2019): from marsh to upland forest, for Moneystump Marsh, Blackwater National Wildlife Refuge, Maryland Water levels (November 11 2016 through November 11 2017) for four wells and Light intensity data (October 1 2015 through September 2019): from marsh to upland forest, for Moneystump Marsh, Blackwater National Wildlife Refuge, Maryland
Water levels in meters from four wells in Moneystump marsh at Blackwater National Wildlife Refuge, MD. Two wells are located in the upland forest; one well is located in the marsh-forest transition zone (ecotone); and one well is located in the marsh. Water depth of the adjacent creek is reported in meters. Data covers the time span from November 11 2016 - November 11 2017. Pressure...
Sediment Radiochemical Data from Georgia, Massachusetts and Virginia Coastal Marshes Sediment Radiochemical Data from Georgia, Massachusetts and Virginia Coastal Marshes
This data release is an archive of sedimentary laboratory analytical data produced by scientists from the U.S. Geological Survey St. Petersburg Coastal and Marine Science Center (USGS SPCMSC) for sediment cores and surface samples collected from coastal marshes in Georgia (GA), Virginia (VA), and Massachusetts (MA). Collaborators from USGS Patuxent Wildlife Research Center (PWRC) and the...
Experimental recovery rates of tidal marsh vegetation Experimental recovery rates of tidal marsh vegetation
We measured the response of plants to disturbance across a gradient in inundation times by transplanting tussocks of Schoenoplectus americanus into mesocosms of different elevation in two marsh organ platforms. Both organs were planted on April 11, 2012 and harvested on August 21, 2012. Plants in one organ were disturbed by clipping all above ground vegetation on June 20 2012 (62 days)...
Development of a Multimetric Index for Integrated Assessment of Salt Marsh Ecosystem Condition Development of a Multimetric Index for Integrated Assessment of Salt Marsh Ecosystem Condition
Data Release for journal publication describing development of a multimetric index for assessing salt marsh condition in northeastern National Parks. This is the first application of an empirical, metric-selection algorithm to metrics from multiple trophic groups (vegetation and nekton). While MMIs derived from nekton or vegetation metrics alone were strongly correlated with human...
Decomposition of plant litter in Pacific coast tidal marshes, 2014-2015 Decomposition of plant litter in Pacific coast tidal marshes, 2014-2015
Decomposition of plant matter is one of the key processes affecting carbon cycling and storage in tidal wetlands. In this study, we evaluated the effects of factors related to climate change (temperature, inundation) and vegetation composition on rates of litter decay in seven tidal marsh sites along the Pacific coast. In 2014 we conducted manipulative experiments to test inundation...
Filter Total Items: 132
Examining inequality in aquatic ecosystem services: Evidence from large-scale monitoring programs Examining inequality in aquatic ecosystem services: Evidence from large-scale monitoring programs
We hypothesize that aquatic ecosystem services are likely to be inequitably accessible and addressing this hypothesis requires systematic assessment at regional and national scales. We used existing data from large-scale aquatic monitoring programs (National Coastal Condition Assessment, National Lakes Assessment) to examine relationships between ecosystem condition, approximating a...
Authors
Katya E. Kovalenko, Sergey Ilyushkin, Holly Wellar-Kelly, Justine Neville, Glenn Guntenspergen
Understanding marsh elevation and accretion processes and vulnerability to rising sea levels across climatic and geomorphic gradients in California, USA Understanding marsh elevation and accretion processes and vulnerability to rising sea levels across climatic and geomorphic gradients in California, USA
Tidal marshes build elevations by below- and aboveground organic and mineral soil processes. Marsh elevation and accretion data can be used to determine if marshes are keeping pace with sea-level rise. Using a network of 54 deep rod surface elevation tables with paired feldspar marker horizon plots, we tracked elevation and accretion trends across 16 marshes in California, USA. All sites...
Authors
Karen M. Thorne, McKenna Bristow, Lyndsay Rankin, Katya E. Kovalenko, Justine Neville, Chase M. Freeman, Glenn Guntenspergen
Observing coastal wetland transitions using national land cover products Observing coastal wetland transitions using national land cover products
Over the coming century, climate change and sea-level rise are predicted to cause widespread change to coastal wetlands. Estuarine vegetated wetlands can adapt to sea-level rise through both vertical development (i.e., biophysical feedbacks and sedimentation) and upslope/horizontal migration. Quantifying changes to estuarine vegetated wetlands over time can help to inform current and...
Authors
Nicholas Enwright, Michael Osland, Karen M. Thorne, Glenn Guntenspergen, James Grace, Gregory Steyer, Nate Herold, Bogdan Chivoiu, Minoo Han
Foundations of modeling resilience of tidal saline wetlands to sea-level rise along the U.S. Pacific Coast Foundations of modeling resilience of tidal saline wetlands to sea-level rise along the U.S. Pacific Coast
Context Tidal saline wetlands (TSWs) are highly threatened from climate-change effects of sea-level rise. Studies of TSWs along the East Coast U.S. and elsewhere suggest significant likely losses over coming decades but needed are analytic tools gauged to Pacific Coast U.S. wetlands. Objectives We predict the impacts of sea-level rise (SLR) on the elevation capital (vertical) and...
Authors
Bruce Marcot, Karen M. Thorne, Joel A. Carr, Glenn Guntenspergen
Future marsh evolution due to tidal changes induced by human adaptation to sea level rise Future marsh evolution due to tidal changes induced by human adaptation to sea level rise
With sea level rise threatening coastal development, decision-makers are beginning to act by modifying shorelines. Previous research has shown that hardening or softening shorelines may change the tidal range under future sea level rise. Tidal range can also be changed by natural factors. Coastal marshes, which humans increasingly depend on for shoreline protection, are ecologically...
Authors
Celina Balderas-Guzman, Kevin Buffington, Karen M. Thorne, Glenn Guntenspergen, Michelle Hummel, Mark T. Stacey
Spatial distribution of elevation change monitoring in coastal wetlands across protected lands of the lower 48 United States Spatial distribution of elevation change monitoring in coastal wetlands across protected lands of the lower 48 United States
Introduction Tidally influenced coastal wetlands, both saline and fresh, appear where terrestrial and marine environments meet and are considered important ecosystems for identifying the impacts of climate change. Coastal wetlands provide valuable benefits to society and the environment in the form of flood protection, water-quality improvements, and shoreline erosion reduction, making...
Authors
Justine Neville, Glenn Guntenspergen
Nonlinear patterns of surface elevation change in coastal wetlands: The value of generalized additive models for quantifying rates of change Nonlinear patterns of surface elevation change in coastal wetlands: The value of generalized additive models for quantifying rates of change
In the face of accelerating climate change and rising sea levels, quantifying surface elevation change dynamics in coastal wetlands can help to develop a more complete understanding of the implications of sea-level rise on coastal wetland stability. The surface elevation table-marker horizon (SET-MH) approach has been widely used to quantify and characterize surface elevation change...
Authors
Laura Feher, Michael Osland, Darren Johnson, James Grace, Glenn Guntenspergen, David R. Stewart, Carlos Coronado-Molina, Fred Sklar
Widespread retreat of coastal habitat is likely at warming levels above 1.5 °C Widespread retreat of coastal habitat is likely at warming levels above 1.5 °C
Several coastal ecosystems—most notably mangroves and tidal marshes—exhibit biogenic feedbacks that are facilitating adjustment to relative sea-level rise (RSLR), including the sequestration of carbon and the trapping of mineral sediment1. The stability of reef-top habitats under RSLR is similarly linked to reef-derived sediment accumulation and the vertical accretion of protective coral...
Authors
Neil Saintilan, Benjamin Horton, Torbjörn Törnqvist, Erica Ashe, Nicole Khan, Mark Schuerch, Chris Perry, Robert Kopp, Gregory Garner, Nicholas Murray, Kerrylee Rogers, Simon Albert, Jeffrey Kelleway, Timothy Shaw, Colin Woodroffe, Catherine Lovelock, Madeline Goddard, Lindsay Hutley, Katya Kovalenko, Laura Feher, Glenn Guntenspergen
Comparing wetland elevation change using a surface elevation table, digital level, and total station Comparing wetland elevation change using a surface elevation table, digital level, and total station
The surface elevation table (SET) approach and two survey instruments, a digital level (DL) and a total station (TS), were used to evaluate elevation change at a 1-ha, micro-tidal, back-barrier salt marsh at Assateague Island National Seashore (Berlin, MD, USA) from 2016 to 2022. SET data were collected at 3 sampling stations along the perimeter of the plot, 36 pins per station, and the...
Authors
James Lynch, Neil Winn, Katya Kovalenko, Glenn Guntenspergen
Maintaining wetland ecosystem services in a changing climate Maintaining wetland ecosystem services in a changing climate
A changing climate is causing challenges for soil and water management in many parts of the world. Current soil management practices need to be redesigned to effectively address present and future fluctuating climates. Soil Hydrology in a Changing Climate explores how soil management practices impact soil hydrological characteristics, and how we can improve our understanding of soil and...
Authors
W. Johnson, Glenn Guntenspergen
Constraints on the adjustment of tidal marshes to accelerating sea level rise Constraints on the adjustment of tidal marshes to accelerating sea level rise
Much uncertainty exists about the vulnerability of valuable tidal marsh ecosystems to relative sea level rise. Previous assessments of resilience to sea level rise, to which marshes can adjust by sediment accretion and elevation gain, revealed contrasting results, depending on contemporary or Holocene geological data. By analyzing globally distributed contemporary data, we found that...
Authors
Neil Saintilan, Katya E. Kovalenko, Glenn Guntenspergen, Kerrylee Rogers, James Lynch, Donald Cahoon, Catherine Lovelock, Daniel Friess, Erica Ashe, Ken Krauss, Nicole Cormier, Tom Spencer, Janine Adams, Jacqueline Raw, Carles Ibanez, Francesco Scarton, Stijn Temmerman, Patrick Meire, Tom Maris, Karen M. Thorne, John Brazner, Gail L. Chmura, Tony Bowron, Vishmie Gamage, Kimberly Cressman, Charlie Endris, Christina Marconi, Pamela Marcum, Kari St. Laurent, William Reay, Kenneth Raposa, Jason Garwood, Nicole Kahn
Migration and transformation of coastal wetlands in response to rising seas Migration and transformation of coastal wetlands in response to rising seas
Coastal wetlands are not only among the world’s most valued ecosystems but also among the most threatened by high greenhouse gas emissions that lead to accelerated sea level rise. There is intense debate regarding the extent to which landward migration of wetlands might compensate for seaward wetland losses. By integrating data from 166 estuaries across the conterminous United States, we...
Authors
Michael Osland, Bogdan Chivoiu, Nicholas Enwright, Karen M. Thorne, Glenn Guntenspergen, James Grace, Leah Dale, William Brooks, Nathaniel Herold, John Day, Fred Sklar, Christopher Swarzenski
By
Ecosystems Mission Area, Water Resources Mission Area, Ecosystems Land Change Science Program, Land Management Research Program, Eastern Ecological Science Center, Lower Mississippi-Gulf Water Science Center, Western Ecological Research Center (WERC), Wetland and Aquatic Research Center , Gulf of America