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• 1. [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

• 2. [Article] Greenhouse Gas Fluxes in Southeastern U.S. Coastal Plain Wetlands Under Contrasting Land Uses

  Whether through sea level rise or wetland restoration, agricultural soils in coastal areas will be inundated at increasing rates, renewing connections to sensitive surface waters and raising critical questions ...

  Citation × Citation Citation Abstract Copy Title: Greenhouse Gas Fluxes in Southeastern U.S. Coastal Plain Wetlands Under Contrasting Land Uses Author: Morse, Jennifer L., Ardón, Marcelo, Bernhardt, Emily S. Year: 2012 Whether through sea level rise or wetland restoration, agricultural soils in coastal areas will be inundated at increasing rates, renewing connections to sensitive surface waters and raising critical questions about environmental trade-offs. Wetland restoration is often implemented in agricultural catchments to improve water quality through nutrient removal. Yet flooding of soils can also increase production of the greenhouse gases nitrous oxide and methane, representing a potential environmental trade-off. Our study aimed to quantify and compare greenhouse gas emissions from unmanaged and restored forested wetlands, as well as actively managed agricultural fields within the North Carolina coastal plain, USA. In sampling conducted once every two months over a two-year comparative study, we found that soil carbon dioxide flux (range: 8000–64 800 kg CO2·ha-1· yr-1) comprised 66–100% of total greenhouse gas emissions from all sites and that methane emissions (range: -6.87 to 197 kg CH4·ha-1·yr-1) were highest from permanently inundated sites, while nitrous oxide fluxes (range: -1.07 to 139 kg N2O·ha-1·yr-1) were highest in sites with lower water tables. Contrary to predictions, greenhouse gas fluxes (as CO2 equivalents) from the restored wetland were lower than from either agricultural fields or unmanaged forested wetlands. In these acidic coastal freshwater ecosystems, the conversion of agricultural fields to flooded young forested wetlands did not result in increases in greenhouse gas emissions. Title: Greenhouse Gas Fluxes in Southeastern U.S. Coastal Plain Wetlands Under Contrasting Land Uses Author: Morse, Jennifer L., Ardón, Marcelo, Bernhardt, Emily S. Year: 2012 Whether through sea level rise or wetland restoration, agricultural soils in coastal areas will be inundated at increasing rates, renewing connections to sensitive surface waters and raising critical questions about environmental trade-offs. Wetland restoration is often implemented in agricultural catchments to improve water quality through nutrient removal. Yet flooding of soils can also increase production of the greenhouse gases nitrous oxide and methane, representing a potential environmental trade-off. Our study aimed to quantify and compare greenhouse gas emissions from unmanaged and restored forested wetlands, as well as actively managed agricultural fields within the North Carolina coastal plain, USA. In sampling conducted once every two months over a two-year comparative study, we found that soil carbon dioxide flux (range: 8000–64 800 kg CO2·ha-1· yr-1) comprised 66–100% of total greenhouse gas emissions from all sites and that methane emissions (range: -6.87 to 197 kg CH4·ha-1·yr-1) were highest from permanently inundated sites, while nitrous oxide fluxes (range: -1.07 to 139 kg N2O·ha-1·yr-1) were highest in sites with lower water tables. Contrary to predictions, greenhouse gas fluxes (as CO2 equivalents) from the restored wetland were lower than from either agricultural fields or unmanaged forested wetlands. In these acidic coastal freshwater ecosystems, the conversion of agricultural fields to flooded young forested wetlands did not result in increases in greenhouse gas emissions. Close