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1.
Soil organic carbon sequestration in cotton production systems of the southeastern United States: a review 总被引:1,自引:0,他引:1
Causarano HJ Franzluebbers AJ Reeves DW Shaw JN 《Journal of environmental quality》2006,35(4):1374-1383
Past agricultural management practices have contributed to the loss of soil organic carbon (SOC) and emission of greenhouse gases (e.g., carbon dioxide and nitrous oxide). Fortunately, however, conservation-oriented agricultural management systems can be, and have been, developed to sequester SOC, improve soil quality, and increase crop productivity. Our objectives were to (i) review literature related to SOC sequestration in cotton (Gossypium hirsutum L.) production systems, (ii) recommend best management practices to sequester SOC, and (iii) outline the current political scenario and future probabilities for cotton producers to benefit from SOC sequestration. From a review of 20 studies in the region, SOC increased with no tillage compared with conventional tillage by 0.48 +/- 0.56 Mg C ha(-1) yr(-1) (H(0): no change, p < 0.001). More diverse rotations of cotton with high-residue-producing crops such as corn (Zea mays L.) and small grains would sequester greater quantities of SOC than continuous cotton. No-tillage cropping with a cover crop sequestered 0.67 +/- 0.63 Mg C ha(-1) yr(-1), while that of no-tillage cropping without a cover crop sequestered 0.34 +/- 47 Mg C ha(-1) yr(-1) (mean comparison, p = 0.04). Current government incentive programs recommend agricultural practices that would contribute to SOC sequestration. Participation in the Conservation Security Program could lead to government payments of up to Dollars 20 ha(-1). Current open-market trading of C credits would appear to yield less than Dollars 3 ha(-1), although prices would greatly increase should a government policy to limit greenhouse gas emissions be mandated. 相似文献
2.
Kelly M Burnett Gordon H Reeves Daniel J Miller Sharon Clarke Ken Vance-Borland Kelly Christiansen 《Ecological applications》2007,17(1):66-80
The geographic distribution of stream reaches with potential to support high-quality habitat for salmonids has bearing on the actual status of habitats and populations over broad spatial extents. As part of the Coastal Landscape Analysis and Modeling Study (CLAMS), we examined how salmon-habitat potential was distributed relative to current and future (+100 years) landscape characteristics in the Coastal Province of Oregon, USA. The intrinsic potential to provide high-quality rearing habitat was modeled for juvenile coho salmon (Oncorhynchus kisutch) and juvenile steelhead (O. mykiss) based on stream flow, valley constraint, and stream gradient. Land ownership, use, and cover were summarized for 100-m analysis buffers on either side of stream reaches with high intrinsic potential and in the overall area encompassing the buffers. Past management seems to have concentrated nonindustrial private ownership, agriculture, and developed uses adjacent to reaches with high intrinsic potential for coho salmon. Thus, of the area in coho salmon buffers, 45% is either nonforested or recently logged, but only 10% is in larger-diameter forests. For the area in steelhead buffers, 21% is either non-forested or recently logged while 20% is in larger-diameter forests. Older forests are most extensive on federal lands but are rare on private lands, highlighting the critical role for public lands in near-term salmon conservation. Agriculture and development are projected to remain focused near high-intrinsic-potential reaches for coho salmon, increasing the importance of effectively addressing nonpoint source pollution from these uses. Percentages of larger-diameter forests are expected to increase throughout the province, but the increase will be only half as much in coho salmon buffers as in steelhead buffers. Most of the increase is projected for public lands, where policies emphasize biodiversity protection. Results suggest that widespread recovery of coho salmon is unlikely unless habitat can be improved in high-intrinsic-potential reaches on private lands. Knowing where high-intrinsic-potential stream reaches occur relative to landscape characteristics can help in evaluating the current and future condition of freshwater habitat, explaining differences between species in population status and risk, and assessing the need for and feasibility of restoration. 相似文献
3.
Cu,Cr and As distribution in soils adjacent to pressure-treated decks,fences and poles 总被引:1,自引:0,他引:1
Chirenje T Ma LQ Clark C Reeves M 《Environmental pollution (Barking, Essex : 1987)》2003,124(3):407-417
Chromated copper arsenate (CCA)-treated wood has been widely used in the Southeastern United States to protect wood products from microbial and fungal decay. The aims of this study were to (1). determine the distribution of arsenic (As), chromium (Cr), and copper (Cu), in soils surrounding CCA-treated wood structures such as decks, fences and poles; and (2). evaluate the impacts of these structures on As, Cr and Cu loading of the soils. Profile and lateral soil samples were collected under CCA-treated decks and adjacent to poles and fences. The results showed elevation of As, Cr and Cu concentrations close to and under the structures, with mean As concentrations as high as 23 mg x kg(-1) close to utility poles compared with less than 3 mg x kg (-1) at distances of about 1.5 m away. Concentrations of As, Cr, and Cu decreased with depth in areas close to CCA-treated poles. However, these results were only apparent in relatively new structures. A combination of weathering and leaching with time may have reduced the impact in older poles. Increased concentrations of As, Cu and Cr were also observed close to CCA-treated decks and fences, with age showing a similar impact. These results are helpful for CCA-treated wood product users to determine the safe use of these structures. 相似文献
4.
Manganese uptake and accumulation by the hyperaccumulator plant Phytolacca acinosa Roxb. (Phytolaccaceae) 总被引:9,自引:0,他引:9
Xue SG Chen YX Reeves RD Baker AJ Lin Q Fernando DR 《Environmental pollution (Barking, Essex : 1987)》2004,131(3):393-399
The perennial herb Phytolacca acinosa Roxb. (Phytolaccaceae), which occurs in Southern China, has been found to be a new manganese hyperaccumulator by means of field surveys on Mn-rich soils and by glasshouse experiments. This species not only has remarkable tolerance to Mn but also has extraordinary uptake and accumulation capacity for this element. The maximum Mn concentration in the leaf dry matter was 19,300 microg/g on Xiangtan Mn tailings wastelands, with a mean of 14,480 microg/g. Under nutrient solution culture conditions, P. acinosa could grow normally with Mn supplied at a concentration of 8000 micromol/l, although with less biomass than in control samples supplied with Mn at 5 micromol/l. Manganese concentration in the shoots increased with increasing external Mn levels, but the total mass of Mn accumulated in the shoots first increased and then decreased. At an Mn concentration of 5000 micromol/l in the culture solution, the Mn accumulation in the shoot dry matter was highest (258 mg/plant). However, the Mn concentration in the leaves reached its highest value (36,380 microg/g) at an Mn supply level of 12,000 micromol/l. These results confirm that P. acinosa is an Mn hyperaccumulator which grows rapidly, has substantial biomass, wide distribution and a broad ecological amplitude. This species provides a new plant resource for exploring the mechanism of Mn hyperaccumulation, and has potential for use in the phytoremediation of Mn-contaminated soils. 相似文献
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6.
Fracturing, either pneumatic or hydraulic, is a method to improve the performance of soil vapor extraction (SVE) in relatively low permeability soils (< 10(-5) cm/s). A two-dimensional model is presented to simulate trichloroethylene (TCE) soil vapor extraction modified by fracturing. Flow and transport is modeled using mobile macropore and micropore networks, which also have been identified in the literature as dual porosity, dual permeability, or heterogeneous flow models. In this model, fluids can flow in both the macropore and micropore networks. This represents a more general model compared to immobile micropore, mobile macropore models presented thus far in the literature for vapor flow and transport in two dimensions. The model considers pressure- and concentration-driven exchange between the macropore and micropore networks, concentration-driven exchange between the gas and sorbed phases within each network, and equilibrium exchange between the gas and water and a sorbed phase within each network. The parameters employed in an example simulation are based on field measurements made at a fractured site. Considered in the simulations were the influence of the volume percentage of fractures, the length of fractures, the relative location of the water table, and the influence of pulsed pumping. For these simulations, internetwork concentration-driven exchange most significantly affected mass removal. The volume percentage of fractures more significantly influence flow and mass removal than the length of fractures. The depth of the water table below the contamination plume only significantly influenced flow and mass removal when the water table was within 60 cm of the bottom of the contaminated soil in the vadose zone for the parameters considered in this study. Pulsed pumping was not found to increase the amount of mass removed in this study. 相似文献
7.
The potential of diffuse reflectance spectroscopy for the determination of carbon inventories in soils 总被引:1,自引:0,他引:1
Investigations have shown that near- and mid-infrared reflectance spectroscopy can accurately determine organic-C in soil. Efforts have also demonstrated that both can differentiate between organic and inorganic-C in soils, but the mid-infrared produces more accurate calibrations. Nevertheless, the greatest benefit would come with in situ determinations where factors such as particle size, sample heterogeneity and moisture can be important. While the variations in large (> 20 mesh) particle size can adversely effect calibration accuracy, efforts have demonstrated that the scanning of larger amounts of sample can overcome this, but the effects of moisture have not been fully explored. While under in situ conditions C distribution and sample heterogeneity are a problem for any analytical method, the rapid analysis possible with spectroscopic techniques will allow many more samples to be analyzed. In conclusion, near- and mid-infrared spectroscopy have great potential for providing the C values needed for C sequestration studies. 相似文献
8.
Cumulative ecological and socioeconomic effects of forest policies in coastal Oregon. 总被引:1,自引:0,他引:1
Thomas A Spies K Norman Johnson Kelly M Burnett Janet L Ohmann Brenda C McComb Gordon H Reeves Pete Bettinger Jeffrey D Kline Brian Garber-Yonts 《Ecological applications》2007,17(1):5-17
Forest biodiversity policies in multi-ownership landscapes are typically developed in an uncoordinated fashion with little consideration of their interactions or possible unintended cumulative effects. We conducted an assessment of some of the ecological and socioeconomic effects of recently enacted forest management policies in the 2.3-million-ha Coast Range Physiographic Province of Oregon. This mountainous area of conifer and hardwood forests includes a mosaic of landowners with a wide range of goals, from wilderness protection to high-yield timber production. We projected forest changes over 100 years in response to logging and development using models that integrate land use change and forest stand and landscape processes. We then assessed responses to those management activities using GIS models of stand structure and composition, landscape structure, habitat models for focal terrestrial and aquatic species, timber production, employment, and willingness to pay for biodiversity protection. Many of the potential outcomes of recently enacted policies are consistent with intended goals. For example, we project the area of structurally diverse older conifer forest and habitat for late successional wildlife species to strongly increase. 'Other outcomes might not be consistent with current policies: for example, hardwoods and vegetation diversity strongly decline within and across owners. Some elements of biodiversity, including streams with high potential habitat for coho salmon (Oncorhynchus kisutch) and sites of potential oak woodland, occur predominately outside federal lands and thus were not affected by the strongest biodiversity policies. Except for federal lands, biodiversity policies were not generally characterized in sufficient detail to provide clear benchmarks against which to measure the progress or success. We conclude that land management institutions and policies are not well configured to deal effectively with ecological issues that span broad spatial and temporal scales and that alternative policies could be constructed that more effectively provide for a mix of forest values from this region. 相似文献
9.
L. Shivashankar E. Whitney G. Colmorgen T. Young G. Munshi D. Wilmoth K. Byrne G. Reeves Dr. D. S. Borgaonkar S. R. Picciano P. A. Marttn-Deleon 《黑龙江环境通报》1988,8(2):85-91
A case of tetrasomy i(12p) detected prenatally is reported. The patient, a black, 33-year-old G3P2002 at 24 weeks' gestation with an unremarkable family history presented herself for prenatal care. Ultrasound examination showed a fetus with diminished femoral and humeral lengths, and hydramnios. A level II scan confirmed the presence of an omphalocele. Amniocentesis at 31 weeks showed 47,XY, + i(12p) karyotype. An infant with multiple congenital anomalies was delivered at 34 weeks. The infant died after 5 h. Genetic and ultrasonographic examinations in the third trimester were helpful in the investigation of this fetus with multiple congenital anomalies. The careful, complete team counselling afforded by this approach enabled the mother and family to be well adjusted to the strong possibility (and subsequent reality) of an abnormal infant. 相似文献
10.
Guth JA Reischmann FJ Allen R Arnold D Hassink J Leake CR Skidmore MW Reeves GL 《Chemosphere》2004,57(8):871-887
Volatilisation of crop protection chemicals from soil and crop surfaces is one of a number of processes that may contribute to their dissipation in the environment. Therefore, information on the potential of a chemical to volatilise from these surfaces is required by international and national registration authorities. This paper reports the results of more than 190 experiments, which were carried out with 80 different crop protection chemicals under controlled conditions (laboratory and/or greenhouse) according to the BBA guideline. Percent loss values observed during 24 h after application are reported for 123 soil and 71 crop volatility studies. Generally, volatile losses from crop surfaces were found to be greater than from soil surfaces under comparable experimental conditions. It has been previously proposed that volatile losses from soil surfaces, from crops, and from aqueous systems can be estimated from physico-chemical parameters. The data are therefore analysed to determine whether a correlation exists between volatilisation and physico-chemical parameters, such as vapour pressure, Henry's law constant, water/air and soil/air distribution coefficients. It was found that these parameters can be used to make reasonable predictions of volatile losses from crop and soil surfaces, which can be expected for crop protection chemicals under controlled conditions. Vapour pressure was the best predictor of losses from soil and crops. The use of the soil/air distribution coefficient is an alternative for predicting/estimating the volatility potential of a chemical from soil. Based on direct measurements, no noticeable volatility can be expected from compounds with a vapour pressure below 10(-3) Pa from soil and 10(-4) Pa from crops, this is fully confirmed by indirect measurements. A tiered volatility testing scheme including appropriate trigger values is proposed. 相似文献