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This data set presents attributes of floodplain ecosystem characteristics including floodplain soil denitrification, floodplain soil biogeochemistry, floodplain vegetation, floodplain sedimentation, floodplain and channel morphometry, stream discharge and water quality, floodplain climate, floodplain physiographic region, and catchment land cover. Attributes are associated with 18 floodplains of the Chesapeake Bay watershed. For many of these attributes, mean values are summaries of multiple measurements made within each floodplain site.
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This study evaluated the contribution of winter rain-on-snow (ROS) events to annual and seasonal nitrate (N-NO3) export and identified the regional meteorological drivers of inter-annual variability in ROS N-NO3 export (ROS-N) at 9 headwater streams located across Ontario, Canada and the northeastern United States. Although on average only 3.3 % of annual precipitation fell as ROS during winter over the study period, these events contributed a significant proportion of annual and winter N-NO3 export at the majority of sites (average of 12 and 42 %, respectively); with the exception of the most northern catchment, where total winter precipitation was exceptionally low (average 77 mm). In years with a greater magnitude...
Categories: Publication; Types: Citation; Tags: Biogeochemistry
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Atmospheric depostion and stream discharge and solutes were measured for three years (September 1984 - August 1987) in two mixed conifer watersheds in Sequoia National Park, in the southern Sierra Nevada of California. The Log Creek watershed (50 ha, 2067-2397 m elev.) is drained by a perennial stream, while Tharp's Creek watershed (13 ha, 2067-2255 m elev.) contains an intermittent stream. Dominant trees in the area include Abies concolor (white fir), Sequoiadendron giganteum (giant sequoia), A. magnifica (red fir), and Pinus lambertiana (sugar pine). Bedrock is predominantly granite and granodiorite, and the soils are mostly Pachic Xerumbrepts. Over the three year period, sulfate (SO42-), nitrate (NO3-), and chloride...
Categories: Publication; Types: Citation; Tags: Biogeochemistry
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Dissolved organic carbon (DOC) dynamics in streams is important, yet few studies focus on DOC dynamics in Midwestern streams during storms. In this study, stream DOC dynamics during storms in two Midwestern watersheds with contrasting land uses, the change in character of stream DOC during storms, and the usability of DOC as a hydrologic tracer in artificially drained landscapes of the Midwest are investigated. Major cation/DOC concentrations, and DOC specific UV absorbance (SUVA) and fluorescence index (FI) were monitored at 2-4 h intervals during three spring storms. Although DOC is less aromatic in the mixed land use watershed than in the agricultural watershed, land use has little impact on stream DOC concentration...
Categories: Publication; Types: Citation; Tags: Biogeochemistry
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The chemical relationships among particulate and colloidal organic material and dissolved fulvic acid were examined in an alpine and subalpine lake and two streams in Loch Vale Watershed, Rocky Mountain National Park. The alpine lake, Sky Pond, had the lowest dissolved organic carbon (DOC) (0.37 mgC/L), the highest particulate carbon (POC) (0.13 mgC/L), and high algal biomass. The watershed of Sky Pond is primarily talus slope, and DOC and POC may be autochthonous. Both Andrews Creek and Icy Brook gain DOC as they flow through wet sedge meadows. The subalpine lake, The Loch, receives additional organic material from the surrounding forest and had a higher DOC (0.66 mgC/L). Elemental analysis, stable carbon isotopic...
Categories: Publication; Types: Citation; Tags: Biogeochemistry
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Recent work in seasonally snow covered ecosystems has identified thawed soil and high levels of heterotrophic activity throughout the winter under consistent snow cover. We performed measurements during the winter of 1994 to determine how the depth and timing of seasonal snow cover affect soil microbial populations, surface water NO3/- loss during snowmelt, and plant N availability early in the growing season. Soil under early accumulating, consistent snow cover remained thawed during most of the winter and both microbial biomass and soil inorganic N pools gradually increased under the snowpack. At the initiation of snowmelt, microbial biomass N pools increased from 3.0 to 5.9 g N m-2, concurrent with a decrease...
Categories: Publication; Types: Citation; Tags: Biogeochemistry
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In-stream nitrogen processing in the Mississippi River has been suggested as one mechanism to reduce coastal eutrophication in the Gulf of Mexico. Aquatic macrophytes in river channels and flood plain lakes have the potential to temporarily remove large quantities of nitrogen through assimilation both by themselves and by the attached epiphyton. In addition, rooted macrophytes act as oxygen pumps, creating aerobic microsites around their roots where coupled nitrification-denitrification can occur. We used in situ 15N-NO3- tracer mesocosm experiments to measure nitrate assimilation rates for macrophytes, epiphyton, and microbial fauna in the sediment in Third Lake, a backwater lake of the upper Mississippi River...
Categories: Publication; Types: Citation; Tags: Biogeochemistry
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Coastal zone managers need to factor submarine groundwater discharge (SGD) in their integration. SGD provides a pathway for the transfer of freshwater, and its dissolved chemical burden, from the land to the coastal ocean. SGD reduces salinities and provides nutrients to specialized coastal habitats. It also can be a pollutant source, often undetected, causing eutrophication and triggering nuisance algal blooms. Despite its importance, SGD remains somewhat of a mystery in most places because it is usually unseen and difficult to measure. SGD has been directly measured at only about a hundred sites worldwide. A typology generated by the Land-Ocean Interaction in the Coastal Zone (LOICZ) Project is one of the few...
Categories: Publication; Types: Citation; Tags: Biogeochemistry
The objectives of my current research are to 1. Understand the water quality effects of fire, 2. Measure the effects of fire on the carbon cycle and other biogeochemical cycles, 3. Characterize the combustion products of wildfire, mainly ash and charcoal, and 4. Link post-fire responses and the composition, physical characteristics, and reactivity of ash and charcoal to measures of burn severity detected on the ground or using remotely-sensed data. The overarching objective of my research is to understand runoff, erosion, deposition, and water quality effects after wildfire.
To study the mechanisms, pathways, and rates of transformation of carbon and nitrogen compounds (natural and contaminant) mediated by microorganisms in aquatic habitats and identify factors controlling these transformations and to examine the effect that these transformations have upon other biogeochemical processes.
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We studied the chemical and optical changes inthe dissolved organic matter (DOM) from twofreshwater lakes and a Sphagnum bog afterexposure to solar radiation. Stable carbonisotopes and solid-state 13C-NMR spectraof DOM were used together with optical andchemical data to interpret results fromexperimental exposures of DOM to sunlight andfrom seasonal observations of two lakes innortheastern Pennsylvania. Solar photochemicaloxidation of humic-rich bog DOM to smaller LMWcompounds and to DIC was inferred from lossesof UV absorbance, optical indices of molecularweight and changes in DOM chemistry. Experimentally, we observed a 1.2‰ enrichment in δ13$C and a 47% loss in aromaticC functionality in bog DOM samples exposed...
Categories: Publication; Types: Citation; Tags: Biogeochemistry
Abstract (from http://onlinelibrary.wiley.com/doi/10.1002/2014GL060199/abstract): While recent work demonstrates that glacial meltwater provides a substantial and relatively labile flux of the micronutrient iron to oceans, the role of high-latitude estuary environments as a potential sink of glacial iron is unknown. Here we present the first quantitative description of iron removal in a meltwater-dominated estuary. We find that 85% of “dissolved” Fe is removed in the low-salinity region of the estuary along with 41% of “total dissolvable” iron associated with glacial flour. We couple these findings with hydrologic and geochemical data from Gulf of Alaska (GoA) glacierized catchments to calculate meltwater-derived...
Our research seeks to evaluate and understand the processes that control and respond to changes in the level of CO 2 in the atmosphere. Our interests include the natural cycling of CO 2 and carbon through plants, soils, seawater, rocks, and sediments. We study the causes and effects of past geologic changes in atmospheric CO 2 levels, and the ongoing effects of human actions on CO 2 and climate.
The purpose of my research group is to develop new methods and applications of environmental isotopes to solve problems of national importance. In specific, the overall goal is to use environmental isotopes, combined with other biogeochemical measurements and hydrologic and biogeochemical modeling, to increase our understanding of biogeochemical and hydrological processes, nutrient and organic matter sources, subsurface flowpaths, and water age distributions in diverse environments. Many of our studies piggyback on the sampling efforts of major monitoring programs to investigate causes of hypoxia and food web problems. Our work provides critical scientific support for these monitoring programs. A long-term career...
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Arid and semiarid ecosystems (drylands) may dominate the trajectory of biosphere-to-atmosphere carbon (C) flux over the coming century. Accordingly, understanding dryland CO2 efflux controls is important for understanding C cycling at the global-scale: key unknowns regarding how temperature and moisture interact to regulate dryland C cycling remain. Further, the patchiness of dryland vegetation can create ‘islands of fertility’, with spatially heterogeneous rates of soil respiration (Rs). At our study site in southeastern Utah, USA we added or removed litter (0 to 650% of control) in paired plots that were either associated with a shrub or with interspaces between vascular plants. We measured Rs, soil temperature,...
Categories: Publication; Types: Citation; Tags: Biogeochemistry
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The relationships between the abundance and activity of planktonic, heterotrophic microorganisms and the quantity and characteristics of dissolved organic carbon (DOC) in a Rocky Mountain stream were evaluated. Peak values of glucose uptake, 2.1 nmol L-1 hr-1, and glucose concentration, 333 nM, occurred during spring snowmelt when the water temperature was 4.0??C and the DOC concentration was greatest. The turnover time of the in situ glucose pool ranged seasonally from 40-1110 hours, with a mean of 272 hr. Seasonal uptake of3H-glucose, particulate ATP concentrations, and direct counts of microbial biomass were independent of temperature, but were positively correlated with DOC concentrations and negatively correlated...
Categories: Publication; Types: Citation; Tags: Biogeochemistry
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Major ion and mercury (Hg) inputs to terrestrial ecosystems include both wet and dry deposition (total deposition). Estimating total deposition to sensitive receptor sites is hampered by limited information regarding its spatial heterogeneity and seasonality. We used measurements of throughfall flux, which includes atmospheric inputs to forests and the net effects of canopy leaching or uptake, for ten major ions and Hg collected during 35 time periods in 1999–2005 at over 70 sites within Acadia National Park, Maine to (1) quantify coherence in temporal dynamics of seasonal throughfall deposition and (2) examine controls on these patterns at multiple scales. We quantified temporal coherence as the correlation between...
Categories: Publication; Types: Citation; Tags: Biogeochemistry
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Microbial community metabolism relies on external digestion, mediated by extracellular enzymes that break down complex organic matter into molecules small enough for cells to assimilate. We analyzed the kinetics of 40 extracellular enzymes that mediate the degradation and assimilation of carbon, nitrogen and phosphorus by diverse aquatic and terrestrial microbial communities (1160 cases). Regression analyses were conducted by habitat (aquatic and terrestrial), enzyme class (hydrolases and oxidoreductases) and assay methodology (low affinity and high affinity substrates) to relate potential reaction rates to substrate availability. Across enzyme classes and habitats, the scaling relationships between apparent Vmax...
Categories: Publication; Types: Citation; Tags: Biogeochemistry
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Carbon cycling associated with biological soil crusts, which occupy interspaces between vascular plants in drylands globally, may be an important part of the coupled climate-carbon cycle of the Earth system. A major challenge to understanding CO2 fluxes in these systems is that much of the biotic and biogeochemical activity occurs in the upper few mm of the soil surface layer (i.e., the ‘mantle of fertility’), which exhibits highly dynamic and difficult to measure temperature and moisture fluctuations. Here, we report a multi-sensor approach to simultaneously measuring temperature and moisture of this biocrust surface layer (0–2 mm), and the deeper soil profile, concurrent with automated measurement of surface soil...
Categories: Publication; Types: Citation; Tags: Biogeochemistry
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Dissolved organic carbon (DOC) in Lake Fryxell, 10 streams flowing into the lake, and the moat surrounding the lake was studied to determine the influence of sources and biogeochemical processes on its distribution and chemical nature. Lake Fryxell is an amictic, permanently ice-covered lake in the McMurdo Dry Valleys which contains benthic and planktonic microbial populations, but receives essentially no input of organic material from the ahumic soils of the watershed. Biological activity in the water column does not appear to influence the DOC depth profile, which is similar to the profiles for conservative inorganic constituents. DOC values for the streams varied with biomass in the stream channel, and ranged...
Categories: Publication; Types: Citation; Tags: Biogeochemistry


map background search result map search result map Atmospheric deposition and solute export in giant sequoia: mixed conifer watersheds in the Sierra Nevada, California Data on denitrification and ecological characteristics of nontidal floodplains, Chesapeake Bay watershed, USA, 2013-2016 Atmospheric deposition and solute export in giant sequoia: mixed conifer watersheds in the Sierra Nevada, California Data on denitrification and ecological characteristics of nontidal floodplains, Chesapeake Bay watershed, USA, 2013-2016