Virginia R. Tolbert

Potential environmental effects of corn (Zea mays L.) stover removal with emphasis on soil organic matter and erosion

Abstract Recent concerns about CO2 emissions and global warming have prompted renewed interest in using corn stover for energy production. Lack of markets, concerns about sustained soil productivity, and lack of commercial conversion technologies have precluded the widespread harvest of corn residues for this purpose. This paper reviews existing literature to evaluate the major environmental impacts potentially associated with stover harvest from reduced tillage corn production sites. Issues of greatest concern are erosion and soil organic carbon (SOC) dynamics, the latter both for its role in soil quality and yield and for global carbon cycle implications. About half of the literature examined concerned research in the United States, many publications described research activities conducted for decades, and major soil types in corn producing regions were well represented. Regional differences were primarily temperature and rainfall effects on stand establishment and yield, with potential feedback effects on SOC. Several research papers discussing the effects of residue harvest were found, but few field studies were found that explicitly studied the effects of corn stover harvest and most discussions acknowledge potential tradeoffs among beneficial and adverse effects. It was concluded that more information is needed on several topics to determine potential long-term effects of residue harvest, including (1) erosion and water quality, especially pesticides and nitrate, (2) rates of transformation of different forms of SOC, (3) effects on soil biota, and (4) SOC dynamics in the subsoil.

Changes in soil quality and below-ground carbon storage with conversion of traditional agricultural crop lands to bioenergy crop production

Berm-isolated (0.5 ha) plots have been used since 1995 to quantify changes in soil and water quality with conversion from agricultural to bioenergy crops. Soil quality improvements, including increases in soil carbon storage, have occurred on sites planted to woody or herbaceous species, and no-till corn compared with tilled corn or cotton. Initial increases in soil carbon occurred within the upper 10 cm of the soil profile. Soil carbon on plantings of switchgrass, no-till corn, and sweetgum with a cover crop between the rows increased over the first 3 years. Soil carbon decreased by 6% on the sweetgum plantings without a cover crop and remained lower through the fifth growing season. Overall, the greatest increases in below ground carbon storage have occurred primarily within the upper 40 cm. Former land use, growth characteristics, management practices, and soil characteristics appear to be the primary factors determining the timing, depth. and extent of changes in soil carbon storage for bioenergy and no-till crops.

Soil Sustainability in Renewable Biomass Plantings

Abstract Sustainable use of natural resources continues to gain attention, especially in relation to energy and global carbon cycles. Biomass crops may offset fossil fuels and reduce CO2 contributions to greenhouse gases while improving soil and water quality. We review research on biomass crops, with emphasis on their specific characteristics and how their production can affect soil and water quality. Data from regions throughout the world are included, but the focus is primarily on recent research results from biomass crop production in the United States. Research to date shows promising short-term changes in soil and water quality, but responses vary. Short-term studies have demonstrated increases in surface soil organic-matter content, reduction in erosion and nutrient losses in surface runoff. We conclude that while the potential for benefits is present, data are not yet available to determine the long-term changes in soil quality associated with production of biomass crops.

Environmental enhancement of U.S. biomass crop technologies: research results to date

Abstract The U.S. continues efforts to develop genetically superior short-rotation woody crops (hybrid poplar and willow) and herbaceous crops (switchgrass). These biomass crops can provide multiple environmental benefits as well as energy and fiber. This paper focuses on results of site-specific studies that are quantifying the environmental potential and ramifications of converting agricultural croplands to biomass crop production. At research-scales, no differences have been found in erosion and movement of nutrients from annual row crops, switchgrass, and tree crops with and without a cover crop in the initial year of establishment. Research- and watershed-scale studies on different soil types, in different regions, and to match tree species with specific site characteristics and management regimes will help determine whether research-scale results can be used to predict effects at larger scales and to identify best management practices to minimize environmental effects while maximizing yields. Studies in different regions of the U.S. are evaluating the habitat value of biomass crops compared to agricultural row crops, grasslands, or natural forests. Results to date from both research- and larger-scale plantings show that SRWCs support greater bird diversity than row crops, but less diversity than natural forests. Switchgrass plantings extended habitat for grasslands birds compared to row crops. Surveys on industrial tree crop plantings in the south-eastern U.S. are addressing the relationship between site characteristics (planting acreage, species, landscape context, and age of plantings) and breeding bird use. The environmental studies of water and soil quality and wildlife diversity are being used to identify management strategies for biomass crops to increase productivity while increasing agricultural sustainability.

Comparison of growth, population structure, and food of the creek chub Semotilus atromaculatus in undisturbed and surface-mining-disturbed streams in Tennessee

Abstract Populations of the creek chub Semotilus atromaculatus from an undisturbed stream and from three streams disturbed by surface mining in East Tennessee were studied to determine surface-mining effects on growth, population structure and food. Comparison of chub populations among streams showed that 0+ and I+ age classes dominated the undisturbed stream, while I+ and II+ age classes dominated in the disturbed streams. Invividuals from the undisturbed stream were found to be significantly smaller but of similar condition compared with those of the same age class from the disturbed streams. Population densities in the disturbed streams were approximately one-third those of the undisturbed stream. Body fat in chubs from the undisturbed and the least-disturbed streams was significantly greater than that from fish in the two streams disturbed to the greatest extent by surface mining. With increased duration and extent of mining disturbance, both dependence on terrestrial food and the number of fish with empty stomachs increased.

Chattanooga shale exploitation and the aquatic environment: The critical issues

Abstract Early identification of the critical environmental issues arising from new energy technologies is needed to ensure adequate consideration of these issues in all phases of research and development. This study examines the potential hazards to aquatic ecosystems from large-scale exploitation (190,000 Mg/day) of the Chattanooga Shale Formation, an immense reserve of oil shale and uranium in Kentucky, Tennessee, and Alabama. Using existing data on regional ecology, hydrology, mining operations, and raw and spent shale chemistry, we identified two major, related environmental issues: (1) the potential for extensive adverse effects on aquatic communities through degradation of water quality and habitat; and (2) the potential conflict between the requirements for shale exploitation, and the habitat and water quality needs of threatened or endangered species. Specific hazards to aquatic ecosystems include erosion, sedimentation, acid mine drainage, raw and spent shale leachates, and surface disposal of immense quantities of solid wastes. Twelve of 19 federally designated, threatened or endangered fish and mollusks in the shale-bearing region were identified as known or recent inhabitants of the counties believed to be most favorable for the exploitation of shale. Of these, five species occur as single populations or are limited to a single river system. The potential for adverse effects on these species is greatest in the counties near the Tennessee-Alabama state line. Future research needs include physical, chemical, and toxicological characterizations of shale leachates and studies of the transport and fate of leachable contaminants. Such research can provide the guidance necessary to minimize impacts on aquatic communities resulting from extraction, retorting, and disposal of shale.

Environmental resources of selected areas of Hawaii: Ecological resources

Prepared for U.S. Department of Energy, Oak Ridge Operations Office by Oak Ridge National Laboratory. Report Number: ORNL/TM--12863; OSTI ID: 87000; Legacy ID: DE95014186; Other: ON: DE95014186; TRN: TRN: AHC29521%%56