A5077072418- Soil Carbon and Nitrogen Dynamics
- Soil and Water Nutrient Dynamics
- Plant responses to elevated CO2
- Geology and Paleoclimatology Research
- Peatlands and Wetlands Ecology
- Research in Cotton Cultivation
- Seedling growth and survival studies
- Crop Yield and Soil Fertility
- Plant Water Relations and Carbon Dynamics
- Rangeland and Wildlife Management
- Clay minerals and soil interactions
- Soil and Unsaturated Flow
- Heavy metals in environment
- Soil erosion and sediment transport
- Hydrology and Sediment Transport Processes
- Forest ecology and management
- Groundwater and Isotope Geochemistry
- Heavy Metal Exposure and Toxicity
- Microbial Community Ecology and Physiology
- Mercury impact and mitigation studies
- Fire effects on ecosystems
- Atmospheric and Environmental Gas Dynamics
- Isotope Analysis in Ecology
- Water management and technologies
- Aluminum toxicity and tolerance in plants and animals
Vertex Pharmaceuticals (United States)
2024
Duke University
2011-2023
Australian National University
2021
Leipzig University
2019
University of Duisburg-Essen
2009
Louisiana State University
2004
North Carolina School of Science and Mathematics
2000-2003
Duke University Hospital
1995
Duke Medical Center
1995
University of Michigan
1985-1987
Airborne particles and vapors contributed significantly to the nutrient requirements pollutant load of a mixed hardwood forest in eastern United States. Dry deposition was an important mechanism atmospheric input foliar canopy, occurring primarily by vapor uptake for sulfur, nitrogen, free acidity particle calcium potassium. The canopy retained 50 70 percent deposited but released Atmospheric supplied 40 100 nitrogen sulfur requirements, respectively, annual woody increment. This...
Industrially produced N-fertilizer is essential to the production of cereals that supports current and projected human populations. We constructed a top-down global N budget for maize, rice, wheat 50-year period (1961 2010). Cereals harvested total 1551 Tg N, which 48% was supplied through fertilizer-N 4% came from net soil depletion. An estimated (737 Tg) crop equal 29, 38, 25 kg ha(-1) yr(-1) wheat, respectively, contributed by sources other than fertilizer- or soil-N. Non-symbiotic N2...
Soil profiles are rarely homogeneous. Resource availability and microbial abundances typically decrease with soil depth, but microbes found in deeper horizons still important components of terrestrial ecosystems. By studying 20 across the United States, we documented consistent changes bacterial archaeal communities depth. Deeper soils harbored distinct from those more commonly studied surface horizons. Most notably, that candidate phylum Dormibacteraeota (formerly AD3) was often dominant...
Abstract The term Anthropocene initially emerged from the Earth System science community in early 2000s, denoting a concept that Holocene Epoch has terminated as consequence of human activities. First associated with onset Industrial Revolution, it was then more closely linked Great Acceleration industrialization and globalization 1950s fundamentally modified physical, chemical, biological signals geological archives. Since 2009, been evaluated by Working Group, tasked examining for...
This is the Executive Summary of a report produced by membership Anthropocene Working Group as part submission to Subcommission on Quaternary Stratigraphy seek formalisation an epoch geological time. It summarises content two reports and their associated appendices which provide background to: history usage term Anthropocene, when proposed started, characterisation deposits stratigraphic value, recognition in different sedimentary environments, rank duration Global boundary Stratigraphic...
Abstract We linked a leaf‐level CO 2 assimilation model with that accounts for light attenuation in the canopy and measurements of sap‐flux‐based conductance into new conductance‐constrained carbon (4C‐A) model. estimated uptake ( A nC ) at Duke Forest free‐air enrichment (FACE) study. Rates from 4C‐A agreed well leaf gas exchange net both treatments. Under ambient conditions, monthly sums by were 13% higher than estimates based on eddy‐covariance chamber measurements. Annual only 3% (C)...
Terrestrial vegetation and soils may act as important carbon sinks if rising atmospheric CO2 stimulates plant production. We used free-air enrichment (FACE) technology to expose three 30 m diameter plots of a loblolly pine (Pinus taeda) forest elevated at 200 μL/L above ambient levels, while control were outfitted with FACE apparatus but fumigated air. quantified litterfall mass chemistry, fine root biomass increment turnover, efflux from soils, δ13C in soil CO2, microbial C N, potential net...
Canopy leaching or retention of all major ions was determined for three deciduous forests in eastern Tennessee that are currently receiving wet and dry acidic deposition. For canopies, the atmospherically deposited cations (H + [Formula: see text]) exceeded anions text] on a charge-equivalent basis. Charge balance maintained by ion exchange between K , Ca 2+ Mg canopy surfaces. It found 40–60% from these canopies results this process, with remainder attributable to coleaching plant-derived...
Sulfate was the dominant anion in throughfall and soil solutions from a chestnut oak (Quercuspinus L.) yellow poplar (Liriodendrontulipifera forest eastern Tennessee. Assuming much of this [Formula: see text] anthropogenic origin, cation-leaching rates foliage soils these forests would have to been accelerated by acid deposition two- three-fold. This acclerated leaching could, turn, cause changes K + , Ca 2+ or Mg cycling according any number possible scenarios explored paper. Subsoils...
Abstract In the 1981 water year, bulk precipitation was primarily a solution of dilute H 2 SO 4 , and 2‐ dominant anion in tbroughfall soil leachates two eastern Tennessee deciduous forests. Ecosystem inputs which included dry deposition forest canopies, may have been up to 40% greater than input estimates based on atmospheric sampling open areas. Volume‐weighted mean annual pH 4.3; throughfall 4.8; from O2, A1, B21 horizons about 6.0. At both sites, strong acids were largely neutralized...
We analyse the ‘three flaws’ to potentially defining a formal Anthropocene geological time unit as advanced by Ruddiman (2018). (1) recognize long record of pre-industrial human impacts, but note that these increased in relative magnitude slowly and were strongly time-transgressive comparison with extraordinarily rapid, novel near-globally synchronous changes post-industrial time. (2) The rules stratigraphic nomenclature do not ‘reject’ anthropogenic signals – have been key characteristic...
Data sharing not applicable – no new data generated.
This study analyzed the impact of urban-soil pedogenesis on soil lead (Pb) contamination from paint and gasoline in historic core Durham, North Carolina. Total Pb 1000 samples streetsides, residential properties, residual upland floodplains ranged 6 to 8825 mg/kg (mean = 211 mg/kg), with 50% between 50 200 Pb. The highest concentrations were within 1 m pre-1978 foundations, inversely correlated house age. Streetside elevated over geologic background <30 traffic flow. lower than Durham...
The Anthropocene Working Group (AWG) has concluded that the represents geological reality and should be linked with plethora of stratigraphic proxies initiate or show marked perturbations at around 1950s, defined using a Global boundary Stratotype Section Point (GSSP). We propose formalizing as series/epoch, terminating Holocene Series/Epoch single Crawfordian stage/age. GSSP located level where primary marker shows rapid increase in 239+240Pu concentrations (coinciding globally...