bluuebunny/crossref_metadata_2025_split huggingface dataset:
Bioavailability and toxicity of soil particle-associated copper as determined by two bioluminescent Pseudomonas fluorescens biosensor strains
Authors: Brandt Kristian K. , Holm Peter E. , Nybroe Ole 
Published: July 2006

Abstract
We report the development and application of a novel, solid phase–contact bioassay based on two whole-cell bacterial biosensor strains. Our data indicate that a significant fraction of particle-associated Cu may be available to bacteria in dilute soil suspensions but also support the conventional view that mainly the soluble fraction of Cu is directly available to bacteria under more realistic soil conditions.
A biomarker approach to measure biological effects of contaminant exposure in largemouth bass from Lake Conestee, South Carolina, USA
Authors: Schreiber Erika A. , Otter Ryan R. , van den Hurk Peter 
Published: July 2006

AbstractSediments from Lake Conestee, a former reservoir now filled with pollutant-enriched sediments, located south of Greenville, South Carolina, USA, and other nearby reservoirs were collected and analyzed for lead and polycyclic aromatic hydrocarbons (PAHs). Hepatic ethoxyresorufin-O-deethylase (EROD), glutathione S-transferase (GST), UDP-glucuronosyltransferase (UGT), sulfotransferase (SULT), and erythrocyte δ-aminolevulinic acid dehydratase (ALAD) were measured in largemouth bass (Micropterus salmoides) to characterize biological effects of these contaminants over three seasons. Results showed that total PAH concentrations in Lake Conestee sediments were significantly greater than the control during each season. An average 10-fold induction in EROD activity was observed at Lake Conestee compared with the control over all three seasons, indicating that PAHs present in sediment were bioavailable to fish. Significant gender effects were observed in EROD activity during the spring, in which activity in reproductively active female fish was significantly suppressed compared with the male fish. Sediments from Lake Conestee had elevated lead concentrations, but the lack of ALAD inhibition in bass indicated that lead was not biologically available. Total GST activity, UGT activity, and SULT activity were not significantly induced in fish from any of the affected sites compared with the reference site. Both EROD and UGT activities were highest during the winter, as were sediment PAH concentrations in Lake Conestee, possibly linked to seasonal resuspension events. The biomarkers measured in this study were useful as a first investigation into the biological effects of contaminant exposure, as well as in determining the bioavailability of contaminants in Lake Conestee.
Carbon Sequestration in Dryland Soils and Plant Residue as Influenced by Tillage and Crop Rotation
Authors: Sainju Upendra M. , Lenssen Andrew , Caesar‐Thonthat Thecan , Waddell Jed 
Published: July 2006

ABSTRACTLong‐term use of conventional tillage and wheat (Triticum aestivum L.)–fallow systems in the northern Great Plains have resulted in low soil organic carbon (SOC) levels. We examined the effects of two tillage practices [conventional till (CT) and no‐till (NT)], five crop rotations [continuous spring wheat (CW), spring wheat–fallow (W–F), spring wheat–lentil (Lens culinaris Medic.) (W–L), spring wheat–spring wheat–fallow (W–W–F), and spring wheat–pea (Pisum sativum L.)–fallow (W–P–F)], and Conservation Reserve Program (CRP) planting on plant C input, SOC, and particulate organic carbon (POC). A field experiment was conducted in a mixture of Scobey clay loam (fine‐loamy, mixed, Aridic Argiborolls) and Kevin clay loam (fine, montmorillonitic, Aridic Argiborolls) from 1998 to 2003 in Havre, MT. Total plant biomass returned to the soil from 1998 to 2003 was greater in CW (15.5 Mg ha−1) than in other rotations. Residue cover, amount, and C content in 2004 were 33 to 86% greater in NT than in CT and greater in CRP than in crop rotations. Residue amount (2.47 Mg ha−1) and C content (0.96 Mg ha−1) were greater in NT with CW than in other treatments, except in CT with CRP and W–F and in NT with CRP and W–W–F. The SOC at the 0‐ to 5‐cm depth was 23% greater in NT (6.4 Mg ha−1) than in CT. The POC was not influenced by tillage and crop rotation, but POC to SOC ratio at the 0‐ to 20‐cm depth was greater in NT with W–L (369 g kg−1 SOC) than in CT with CW, W–F, and W–L. From 1998 to 2003, SOC at the 0‐ to 20‐cm depth decreased by 4% in CT but increased by 3% in NT. Carbon can be sequestered in dryland soils and plant residue in areas previously under CRP using reduced tillage and increased cropping intensity, such as NT with CW, compared with traditional practice, such as CT with W–F system, and the content can be similar to that in CRP planting.
Forest Environmental Investments and Implications for Climate Change Mitigation
Authors: Alig Ralph J. , Bair Lucas S. 
Published: July 2006

ABSTRACTForest environmental conditions are affected by climate change, but investments in forest environmental quality can be used as part of the climate change mitigation strategy. A key question involving the potential use of forests to store more carbon as part of climate change mitigation is the impact of forest investments on the timing and quantity of forest volumes that affect carbon storage. Using an economic optimization model, we project levels of U.S. forest volumes as indicators of carbon storage for a wide range of private forest investment scenarios. Results show that economic opportunities exist to further intensify timber management on some hectares and reduce the average timber rotation length such that the national volume of standing timber stocks could be reduced relative to projections reflecting historical trends. The national amount of timber volume is projected to increase over the next 50 yr, but then is projected to decline if private owners follow an economic optimization path, such as with more forest type conversions and shorter timber rotations. With perfect foresight, future forest investments can affect current timber harvest levels, with intertemporal linkages based on adjustments through markets. Forest investments that boost regenerated timber yields per hectare would act to enhance ecosystem services (e.g., forest carbon storage) if they are related to the rate of growth and extent of growing stock inventory.
Carbon Sequestration Potential in Reclaimed Mine Sites in Seven East‐Central States
Authors: Sperow Mark 
Published: July 2006

ABSTRACTTerrestrial systems represent a significant potential carbon (C) sink to help mitigate or offset greenhouse gas emissions. Nearly 3.2 Mha are permitted for mining activities in the United States, which are required to be reclaimed with vegetative cover. While site‐specific studies have assessed C accumulation on reclaimed mine sites, regional analyses to estimate potential C increases have not been conducted. For this analysis, potential C sequestration is analyzed on 567 000 ha of mine land in a seven‐state region reclaimed to cropland, pasture, or forest. Carbon accumulation is estimated for cropland, pasture, and forest soils, forest litter layer, and aboveground biomass by estimating average annual rates of C accumulation from site‐specific and general C sequestration studies. The average annual rate of C storage is highest when mine land is reclaimed to forest, where the potential sequestration is 0.7 to 2.2 Tg yr−1 The C from soils, litter layer, and biomass from mine lands reclaimed to forest represents 0.3 to 1.0% of the 1990 CO2 emissions from the study region (919 Tg CO2). To achieve the greenhouse gas (GHG) emission reduction goal of 7% below the 1990 level as proposed by the Kyoto Treaty requires CO2 emissions in the study area to be reduced by just over 64 Tg CO2 The potential carbon storage in mine sites reclaimed to forest could account for 4 to 12.5% of these required reductions.
Forest Carbon Management in the United States
Authors: Birdsey Richard , Pregitzer Kurt , Lucier Alan 
Published: July 2006

ABSTRACTThis paper reviews the effects of past forest management on carbon stocks in the United States, and the challenges for managing forest carbon resources in the 21st century. Forests in the United States were in approximate carbon balance with the atmosphere from 1600–1800. Utilization and land clearing caused a large pulse of forest carbon emissions during the 19th century, followed by regrowth and net forest carbon sequestration in the 20th century. Recent data and knowledge of the general behavior of forests after disturbance suggest that the rate of forest carbon sequestration is declining. A goal of an additional 100 to 200 Tg C/yr of forest carbon sequestration is achievable, but would require investment in inventory and monitoring, development of technology and practices, and assistance for land managers.
Effects of Elevated Atmospheric Carbon Dioxide on Biomass and Carbon Accumulation in a Model Regenerating Longleaf Pine Community
Authors: Runion G. B. , Davis M. A. , Pritchard S. G. , Prior S. A. , Mitchell R. J. , Torbert H. A. , Rogers H. H. , Dute R. R. 
Published: July 2006

ABSTRACTPlant species vary in response to atmospheric CO2 concentration due to differences in physiology, morphology, phenology, and symbiotic relationships. These differences make it very difficult to predict how plant communities will respond to elevated CO2 Such information is critical to furthering our understanding of community and ecosystem responses to global climate change. To determine how a simple plant community might respond to elevated CO2, a model regenerating longleaf pine community composed of five species was exposed to two CO2 regimes (ambient, 365 μmol mol−1 and elevated, 720 μmol mol−1) for 3 yr. Total above‐ and belowground biomass was 70 and 49% greater, respectively, in CO2–enriched plots. Carbon (C) content followed a response pattern similar to biomass, resulting in a significant increase of 13.8 Mg C ha−1 under elevated CO2 Responses of individual species, however, varied. Longleaf pine (Pinus palustris Mill.) was primarily responsible for the positive response to CO2 enrichment. Wiregrass (Aristida stricta Michx.), rattlebox (Crotalaria rotundifolia Walt. Ex Gmel.), and butterfly weed (Asclepias tuberosa L.) exhibited negative above‐ and belowground biomass responses to elevated CO2, while sand post oak (Quercus margaretta Ashe) did not differ significantly between CO2 treatments. As with pine, C content followed patterns similar to biomass. Elevated CO2 resulted in alterations in community structure. Longleaf pine comprised 88% of total biomass in CO2–enriched plots, but only 76% in ambient plots. In contrast, wiregrass, rattlebox, and butterfly weed comprised 19% in ambient CO2 plots, but only 8% under high CO2 Therefore, while longleaf pine may perform well in a high CO2 world, other members of this community may not compete as well, which could alter community function. Effects of elevated CO2 on plant communities are complex, dynamic, and difficult to predict, clearly demonstrating the need for more research in this important area of global change science.
Long‐Term Trends in Nitrous Oxide Emissions, Soil Nitrogen, and Crop Yields of Till and No‐Till Cropping Systems
Authors: Grandy A. Stuart , Loecke Terrance D. , Parr Sara , Robertson G. Philip 
Published: July 2006

ABSTRACTNo‐till cropping can increase soil C stocks and aggregation but patterns of long‐term changes in N2O emissions, soil N availability, and crop yields still need to be resolved. We measured soil C accumulation, aggregation, soil water, N2O emissions, soil inorganic N, and crop yields in till and no‐till corn–soybean–wheat rotations between 1989 and 2002 in southwestern Michigan and investigated whether tillage effects varied over time or by crop. Mean annual NO3−concentrations in no‐till were significantly less than in conventional till in three of six corn years and during one year of wheat production. Yields were similar in each system for all 14 years but three, during which yields were higher in no‐till, indicating that lower soil NO3−concentrations did not result in lower yields. Carbon accumulated in no‐till soils at a rate of 26 g C m−2yr−1over 12 years at the 0‐ to 5‐cm soil depth. Average nitrous oxide emissions were similar in till (3.27 ± 0.52 g N ha d−1) and no‐till (3.63 ± 0.53 g N ha d−1) systems and were sufficient to offset 56 to 61% of the reduction in CO2equivalents associated with no‐till C sequestration. After controlling for rotation and environmental effects by normalizing treatment differences between till and no‐till systems we found no significant trends in soil N, N2O emissions, or yields through time. In our sandy loam soils, no‐till cropping enhances C storage, aggregation, and associated environmental processes with no significant ecological or yield tradeoffs.
Nitrous Oxide Emissions from Corn–Soybean Systems in the Midwest
Authors: Parkin Timothy B. , Kaspar Thomas C. 
Published: July 2006

ABSTRACTSoil N2O emissions from three corn (Zea mays L.)–soybean [Glycine max (L.) Merr.] systems in central Iowa were measured from the spring of 2003 through February 2005. The three managements systems evaluated were full‐width tillage (fall chisel plow, spring disk), no‐till, and no‐till with a rye (Secale cereale L. ‘Rymin’) winter cover crop. Four replicate plots of each treatment were established within each crop of the rotation and both crops were present in each of the two growing seasons. Nitrous oxide fluxes were measured weekly during the periods of April through October, biweekly during March and November, and monthly in December, January, and February. Two polyvinyl chloride rings (30‐cm diameter) were installed in each plot (in and between plant rows) and were used to support soil chambers during the gas flux measurements. Flux measurements were performed by placing vented chambers on the rings and collecting gas samples 0, 15, 30, and 45 min following chamber deployment. Nitrous oxide fluxes were computed from the change in N2O concentration with time, after accounting for diffusional constraints. We observed no significant tillage or cover crop effects on N2O flux in either year. In 2003 mean N2O fluxes were 2.7, 2.2, and 2.3 kg N2O‐N ha−1 yr−1 from the soybean plots under chisel plow, no‐till, and no‐till + cover crop, respectively. Emissions from the chisel plow, no‐till, and no‐till + cover crop plots planted to corn averaged 10.2, 7.9, and 7.6 kg N2O‐N ha−1 yr−1, respectively. In 2004 fluxes from both crops were higher than in 2003, but fluxes did not differ among the management systems. Fluxes from the corn plots were significantly higher than from the soybean plots in both years. Comparison of our results with estimates calculated using the Intergovernmental Panel on Climate Change default emission factor of 0.0125 indicate that the estimated fluxes underestimate measured emissions by a factor of 3 at our sites.
Carbon Supply and Storage in Tilled and Nontilled Soils as Influenced by Cover Crops and Nitrogen Fertilization
Authors: Sainju Upendra M. , Singh Bharat P. , Whitehead Wayne F. , Wang Shirley 
Published: July 2006

ABSTRACTSoil carbon (C) sequestration in tilled and nontilled areas can be influenced by crop management practices due to differences in plant C inputs and their rate of mineralization. We examined the influence of four cover crops {legume [hairy vetch (Vicia villosa Roth)], nonlegume [rye (Secale cereale L.)], biculture of legume and nonlegume (vetch and rye), and no cover crops (or winter weeds)} and three nitrogen (N) fertilization rates (0, 60 to 65, and 120 to 130 kg N ha−1) on C inputs from cover crops, cotton (Gossypium hirsutum L.), and sorghum [Sorghum bicolor (L.) Moench)], and soil organic carbon (SOC) at the 0‐ to 120‐cm depth in tilled and nontilled areas. A field experiment was conducted on Dothan sandy loam (fine‐loamy, siliceous, thermic Plinthic Paleudults) from 1999 to 2002 in central Georgia. Total C inputs to the soil from cover crops, cotton, and sorghum from 2000 to 2002 ranged from 6.8 to 22.8 Mg ha−1 The SOC at 0 to 10 cm fluctuated with C input from October 1999 to November 2002 and was greater from cover crops than from weeds in no‐tilled plots. In contrast, SOC values at 10 to 30 cm in no‐tilled and at 0 to 60 cm in chisel‐tilled plots were greater for biculture than for weeds. As a result, C at 0 to 30 cm was sequestered at rates of 267, 33, −133, and −967 kg C ha−1 yr−1 for biculture, rye, vetch, and weeds, respectively, in the no‐tilled plot. In strip‐tilled and chisel‐tilled plots, SOC at 0 to 30 cm decreased at rates of 233 to 1233 kg C ha−1 yr−1 The SOC at 0 to 30 cm increased more in cover crops with 120 to 130 kg N ha−1 yr−1 than in weeds with 0 kg N ha−1 yr−1, regardless of tillage. In the subtropical humid region of the southeastern United States, cover crops and N fertilization can increase the amount of C input and storage in tilled and nontilled soils, and hairy vetch and rye biculture was more effective in sequestering C than monocultures or no cover crop.
Effect of Land‐Cover Change on Terrestrial Carbon Dynamics in the Southern United States
Authors: Chen Hua , Tian Hanqin , Liu Mingliang , Melillo Jerry , Pan Shufen , Zhang Chi 
Published: July 2006

ABSTRACTLand‐cover change has significant influence on carbon storage and fluxes in terrestrial ecosystems. The southern United States is thought to be the largest carbon sink across the conterminous United States. However, the spatial and temporary variability of carbon storage and fluxes due to land‐cover change in the southern United States remains unclear. In this study, we first reconstructed the annual data set of land‐cover of the southern United States from 1860 to 2003 with a spatial resolution of 8 km. Then we used a spatially explicit process‐based biogeochemical model (Terrestrial Ecosystem Model [TEM] 4.3) to simulate the effects of cropland expansion and forest regrowth on the carbon dynamics in this region. The pattern of land‐cover change in the southern United States was primarily driven by the change of cropland, including cropland expansion and forest regrowth on abandoned cropland. The TEM simulation estimated that total carbon storage in the southern United States in 1860 was 36.8 Pg C, which likely was overestimated, including 10.8 Pg C in the southeast and 26 Pg C in the south‐central. During 1860–2003, a total of 9.4 Pg C, including 6.5 Pg C of vegetation and 2.9 Pg C of soil C pool, was released to the atmosphere in the southern United States. The net carbon flux due to cropland expansion and forest regrowth on abandoned cropland was approximately zero in the entire southern region between 1980 and 2003. The temporal and spatial variability of regional net carbon exchange was influenced by land‐cover pattern, especially the distribution of cropland. The land‐use analysis in this study is incomplete and preliminary. Finally, the limitations, improvements, and future research needs of this study were discussed.
Use of Physical Properties to Predict the Effects of Tillage Practices on Organic Matter Dynamics in Three Illinois Soils
Authors: Yoo Gayoung , Nissen Todd M. , Wander Michelle M. 
Published: July 2006

ABSTRACTThis work builds on a previous study of long‐term tillage trials that found use of no‐tillage (NT) practices increased soil organic carbon (SOC) sequestration at Monmouth, IL (silt loam soil) by increasing the soil's protective capacity, but did not alter SOC storage in DeKalb, IL (silty clay loam), where higher clay contents provided a protective capacity not affected by tillage. The least limiting water range (LLWR), a multi‐factor index of structural quality, predicted observed soil CO2 efflux patterns. Here we consider whether LLWR can predict sequestration trends at a third site, Perry, IL (silt loam soil) where SOC content is lower and bulk density is higher than in previously considered sites, and determine whether pore size characteristics can help explain the influence use of NT practices has had on SOC sequestration at all three locations. At Perry, LLWR was again related with differences in specific soil organic carbon mineralization rates (RESPsp) (2000–2001). Reduced RESPsp rates explain increases in SOC storage under NT management observed only after 17 yr. Trends in RESPsp suggest use of NT practices only enhance physical protection of SOC where soil bulk density is relatively high (approximately 1.4 g cm−3). In those soils (Monmouth and Perry), use of NT management reduced the volume of small macropores (15–150 μm) thought to be important for microbial activity. Physical properties appear to determine whether or not use of NT practices will enhance C storage by increasing physical protection of SOC. By refining the functions used to compute the LLWR and our understanding of the interactions between management, pore structure, and SOC mineralization, we should be able to predict the influence of tillage practices on SOC sequestration.
Nutrient Transport from Livestock Manure Applied to Pastureland Using Phosphorus‐Based Management Strategies
Authors: Soupir M. L. , Mostaghimi S. , Yagow E. R. 
Published: July 2006

ABSTRACTLand applications of manure from confined animal systems and direct deposit by grazing animals are both major sources of nutrients in streams. The objectives of this study were to determine the effects of P‐based manure applications on total suspended solids (TSS) and nutrient losses from dairy manures and poultry litter surface applied to pasturelands and to compare the nutrient losses transported to the edge of the field during overland flow events. Two sets of plots were established: one set for the study of in‐field release and another set for the study of edge‐of‐the‐field nutrient transport. Release plots were constructed at three pastureland sites (previous poultry litter applications, previous liquid dairy manure application, and no prior manure application) and received four manure treatments (turkey [Meleagris gallopavo] litter, liquid dairy manure, standard cowpies, and none). Pasture plots with a history of previous manure applications released higher concentrations of TSS and higher percentages of total P (TP) in the particulate form. Transport plots were developed on pasture with no prior manure application. The average flow‐weighted TP concentrations were highest in runoff samples from the plots treated with cowpies (1.57 mg L−1). Reducing excess P in dairy cow diets and surface applying manure to the land using P‐based management practices did not increase N concentrations in runoff. This study found that nutrients are most transportable from cowpies; thus a buffer zone between pastureland and streams or other appropriate management practices are necessary to reduce nutrient losses to waterbodies.