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Our research focuses on assessing the components of the Net Ecoystem Carbon Balance using the eddy covariance approach to measure atmospheric fluxes of heat, energy, carbon dioxide and methane and testing equipment and techniques to measure the tidal exchange of dissolved organic (DOC) and inorganic carbon (DIC). The atmospheric flux tower is located south of Solano Land Trust's Rush Ranch, a working ranch encompassing 2,070 acres of marsh and rolling grasslands that provides both recreational and educational experiences for the public (http://www.solanolandtrust.org/RushRanch.aspx). Lateral fluxes are being collected at the San Francisco Bay National Estuarine Research Reserve First Mallard water quality station...
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Macroclimatic drivers, such as temperature and rainfall regimes, greatly influence ecosystem structure and function in tidal saline wetlands. Understanding the ecological influence of macroclimatic drivers is important because it provides a foundation for anticipating the effects of climate change. Tidal saline wetlands include mangrove forests, salt marshes, and salt flats, which occupy similar geomorphic settings but different climatic regimes. However, most global- or regional-scale analyses have treated these wetlands as independent systems. Here we used climate and literature-derived ecological data from all three systems, collected across targeted regional-scale macroclimatic gradients, to test hypotheses...
Phenol oxidase and peroxidase activities in desert grassland soils at the Sevilleta Long Term Ecological Research site in central New Mexico (USA) are far greater than those of temperate soils. Activity is uniformly distributed across particles ranging from >1 mm to <38 ?m and is unaffected by autoclaving, in contrast to hydrolase activities. The sorbed enzymes are readily extractable and inactivated by boiling. High soil pH, high stabilized oxidative enzyme activity, and carbonates create optimal conditions for degradation of phenols which increase decomposition potentials and limit soil organic matter accumulation. Published in Soil Biology and Biochemistry, volume 40, issue 2, on pages 550 - 553, in 2008.
Soil respiration in semiarid ecosystems responds positively to temperature, but temperature is just one of many factors controlling soil respiration. Soil moisture can have an overriding influence, particularly during the dry/warm portions of the year. The purpose of this project was to evaluate the influence of soil moisture on the relationship between temperature and soil respiration. Soil samples collected from a range of sites arrayed across a climatic gradient were incubated under varying temperature and moisture conditions. Additionally, we evaluated the impact of substrate quality on short-term soil respiration responses by carrying out substrate-induced respiration assessments for each soil at nine different...
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We examined the 10-day response of soil microbial biomass-N to additions of carbon (dextrose) and nitrogen (NH4NO3) to water-amended soils in a factorial experiment in four plant communities of the Chihuahuan desert of New Mexico (U.S.A.). In each site, microbial biomass-N and soil carbohydrates increased and extractable soil N decreased in response to watering alone. Fertilization with N increased microbial biomass-N in grassland soils; whereas, fertilization with C increased microbial biomass-N and decreased extractable N and P in all communities dominated by shrubs, which have invaded large areas of grassland in the Chihuahuan desert during the last 100 years. Our results support the hypothesis that the control...
Peatlands are a major reservoir of global soil carbon, yet account for just 3% of global land cover. Human impacts like draining can hinder the ability of peatlands to sequester carbon and expose their soils to fire under dry conditions. Estimating soil carbon loss from peat fires can be challenging due to uncertainty about pre-fire surface elevations. This study uses multi-temporal LiDAR to obtain pre- and post-fire elevations and estimate soil carbon loss caused by the 2011 Lateral West fire in the Great Dismal Swamp National Wildlife Refuge, VA, USA. We also determine how LiDAR elevation error affects uncertainty in our carbon loss estimate by randomly perturbing the LiDAR point elevations and recalculating elevation...
With recent concern over climate change, methods for decreasing atmospheric levels of greenhouse gasses such as CO<sub>2</sub> have been of particular interest, including carbon sequestration in soils that have depreciated levels of carbon from cultivated agricultural crop production. The Delmarva Peninsula contains many Delmarva Bay landforms, which commonly contain wetlands. Five pairs of Delmarva Bays were selected to examine change in carbon stocks following conversion to agriculture and to assess the potential for carbon sequestration if these soils were to be restored hydrologically and vegetatively. A loss of approximately 50 % of the stored soil carbon was observed following the conversion to agriculture....
Some single-factor experiments suggest that elevated CO2 concentrations can increase soil carbon, but few experiments have examined the effects of interacting environmental factors on soil carbon dynamics. We undertook studies of soil carbon and nitrogen in a multi-factor (CO2 × temperature × soil moisture) climate change experiment on a constructed old-field ecosystem. After four growing seasons, elevated CO2 had no measurable effect on carbon and nitrogen concentrations in whole soil, particulate organic matter (POM), and mineral-associated organic matter (MOM). Analysis of stable carbon isotopes, under elevated CO2, indicated between 14 and 19% new soil carbon under two different watering treatments with as...
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Macroclimatic drivers, such as temperature and rainfall regimes, greatly influence ecosystem structure and function in tidal saline wetlands. Understanding the ecological influence of macroclimatic drivers is important because it provides a foundation for anticipating the effects of climate change. Tidal saline wetlands include mangrove forests, salt marshes, and salt flats, which occupy similar geomorphic settings but different climatic regimes. However, most global- or regional-scale analyses have treated these wetlands as independent systems. Here we used climate and literature-derived ecological data from all three systems, collected across targeted regional-scale macroclimatic gradients, to test hypotheses...
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Plant-mediated processes are often important in determining carbon cycling and storage in ecosystems. With climate-induced changes in the environment, plant-associated processes may also shift. Salt marshes in particular are useful systems to investigate plant-mediated carbon cycling, as these systems experience both sea-level rise and increased carbon dioxide concentrations due to climate change, in addition to stochastically experiencing extreme drought and flood conditions. We measured biomass, soil, and gas carbon pools and the fluxes between those pools using a mesocosm approach in a salt marsh system, to investigate the response of plant-mediated carbon cycling to near-term climate change.
Global management of wetlands to suppress greenhouse gas (GHG) emissions, facilitate carbon (C) sequestration, and reduce atmospheric CO2 concentrations while simultaneously promoting agricultural gains is paramount. However, studies that relate variability in CO2 and CH4 emissions at large spatial scales are limited. We investigated three-year emissions of soil CO2 and CH4 from the primary wetland types of the Liaohe Delta, China, by focusing on a total wetland area of 3287 km2. One percent is Suaeda salsa, 24% is Phragmites australis, and 75% is rice. While S. salsa wetlands are under somewhat natural tidal influence, P. australis and rice are managed hydrologically for paper and food, respectively. Total C emissions...
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Macroclimatic drivers, such as temperature and rainfall regimes, greatly influence ecosystem structure and function in tidal saline wetlands. Understanding the ecological influence of macroclimatic drivers is important because it provides a foundation for anticipating the effects of climate change. Tidal saline wetlands include mangrove forests, salt marshes, and salt flats, which occupy similar geomorphic settings but different climatic regimes. However, most global- or regional-scale analyses have treated these wetlands as independent systems. Here we used climate and literature-derived ecological data from all three systems, collected across targeted regional-scale macroclimatic gradients, to test hypotheses...
Understanding of the organic layer thickness (OLT) and organic layer carbon (OLC) stocks in subarctic ecosystems is critical due to their importance in the global carbon cycle. Moreover, post-fire OLT provides an indicator of long-term successional trajectories and permafrost susceptibility to thaw. To these ends, we 1) mapped OLT and associated uncertainty at 30 m resolution in the Yukon River Basin (YRB), Alaska, employing decision tree models linking remotely sensed imagery with field and ancillary data, 2) converted OLT to OLC using a non-linear regression, 3) evaluate landscape controls on OLT and OLC, and 4) quantified the post-fire recovery of OLT and OLC. Areas of shallow (< 10 cm), moderate (≥ 10 cm and...
map background search result map search result map Factors Determining Soil Microbial Biomass and Nutrient Immobilization in Desert Soils Suisun Marsh, CA: Net Ecosystem Carbon Balance Linear and nonlinear effects of temperature and precipitation on ecosystem properties in tidal saline wetlands Cell data Point data Salt marsh carbon dynamics under altered hydrologic regimes and elevated CO2 conditions, Louisiana, USA (2014-2015) Suisun Marsh, CA: Net Ecosystem Carbon Balance Salt marsh carbon dynamics under altered hydrologic regimes and elevated CO2 conditions, Louisiana, USA (2014-2015) Factors Determining Soil Microbial Biomass and Nutrient Immobilization in Desert Soils Point data Linear and nonlinear effects of temperature and precipitation on ecosystem properties in tidal saline wetlands Cell data