Cation exchange capacity of density fractions from paired conifer/grassland soils     

Sarah I. Beldin  Bruce A. Caldwell  Phillip Sollins  Elizabeth W. Sulzman  Kate Lajtha  Susan E. Crow 《Biology and Fertility of Soils》2007,43(6):837-841

The cation exchange capacity (CEC) of a soil depends on the type and amount of both mineral and organic surfaces. Previous studies that have sought to determine the relative contribution of organic matter to total soil CEC have not addressed differences in soil organic matter (SOM) composition that could lead to differences in CEC. The objectives of this study were (1) to compare the CEC of two distinct SOM pools, the “light fraction (LF)” composed of particulate plant, animal, and microbial debris, and the “heavy fraction (HF)” composed of mineral-bound organic matter; and (2) to examine the effects of differences in aboveground vegetation on CEC. Soil samples were collected from four paired grassland/conifer sites within a single forested area and density fractionated. LF CEC was higher in conifer soils than in grassland soils, but there was no evidence of an effect of vegetation on CEC for the HF or bulk soil. LF CEC (but not HF CEC) correlated well with the C concentration in the fraction. The mean CEC of both fractions (per kg fraction) exceeded that of the bulk soil; thus, when the LF and HF CEC were combined mathematically by weighting values for each fraction in proportion to dry mass, the resulting value was nearly twice the measured CEC of bulk soil. On a whole soil basis, the HF contributed on average 97% of the CEC of the whole soil, although this conclusion must be tempered given the inflation of CEC values by the density fractionation procedure.  相似文献   

Impact of coal combustion waste on the microbiology of a model aquifer     

J. S. Brunning  D. E. Caldwell  J. R. Lawrence  R. D. Robarts 《Water, air, and soil pollution》1994,74(1-2):103-120

The effects of water infiltration into an alkaline coal combustion waste burial site on the chemical and microbiological aspects of a meso-scale (2.44 m diameter × 4.6 m, height, 65 tonne) model aquifer were analyzed. The spatial and temporal effects of the alkaline leachate on microbial activity, numbers and diversity were examined in the model and compared with uncontaminated control materials. Within the saturated zone below the waste there was a pH gradient from 12.4 at the water table, immediately below the waste, to 6.0 at 3.5 meters from the waste, and elevated levels of arsenic and strontium in the pore waters. Microtox testing of the contaminated pore waters indicated high toxicity (a gamma value of 1 at dilutions of 45 to 110 fold). The leachate contamination was associated with a reduction in bacterial [³H] leucine incorporation from a high of 267 fmol g^?1 h^?1 in sediments below the contaminant plume to undetectable in the contaminated zone. In comparison, leucine incorporation rates in control column sediments were 899 fmol g^?1 h^?1. Similar toxic effects were evident in reduced total direct and culturable counts of bacteria. Observations also indicated a reduction in microbial diversity and development of alkaline-tolerant microbial communities. These results indicated that any failure of confinement technologies at disposal sites would adversely affect both the chemistry and microbiology of the underlying saturated zone.  相似文献   

Effects of vegetation regime on denitrification potential in two tropical volcanic soils     

Robert P. Griffiths  Bruce A. Caldwell  Phillip Sollins 《Biology and Fertility of Soils》1993,16(3):157-162

Effects of vegetation and nutrient availability on potentail denitrification rates were studied in two volcanic, alluvial-terrace soils in lowland Costa Rica that differ greatly in weathering stage and thus in availability of P and base cations. Potential denitrification rates were significantly higher in plots where vegetation had been left undisturbed than in plots where all vegetation had been removed continuously, and were higher on the less fertile of the two soils. The potential denitrification rates were correlated strongly with respiration rates, levels of mineralizable N, microbial biomass, and moisture content, and moderately well with concentrations of extractable NH _inf4 ^sup+ , Kjeldahl N, and total C. In all plots, denitrification rates were stimulated by the removal of O₂ and by the addition of glucose but not by the addition of water or NO _inf3 ^sup- .This is Paper 2772 of the Forest Research Laboratory, Oregon State University  相似文献   

Ecological effects of a major oil spill on panamanian coastal marine communities   总被引：1，自引：0，他引：1  

Jackson JB  Cubit JD  Keller BD  Batista V  Burns K  Caffey HM  Caldwell RL  Garrity SD  Getter CD  Gonzalez C  Guzman HM  Kaufmann KW  Knap AH  Levings SC  Marshall MJ  Steger R  Thompson RC  Weil E 《Science (New York, N.Y.)》1989,243(4887):37-44

In 1986 more than 8 million liters of crude oil spilled into a complex region of mangroves, seagrasses, and coral reefs just east of the Caribbean entrance to the Panama Canal. This was the largest recorded spill into coastal habitats in the tropical Americas. Many population of plants and animals in both oiled and unoiled sites had been studied previously, thereby providing an unprecedented measure of ecological variation before the spill. Documenation of the spread of oil and its biological begun immediately. Intertidal mangroves, algae, and associated invertebrates were covered by oil and died soon after. More surprisingly, there was also extensive mortality of shallow subtidal reef corals and infauna of seagrass beds. After 1.5 years only some organisms in areas exposed to the open sea have recovered.  相似文献   

Energized configurations of heart mitochondria in situ   总被引：3，自引：0，他引：3  

R A Harris  C H Williams  M Caldwell  D E Green  E Valdivia 《Science (New York, N.Y.)》1969,165(894):700-703

Changes in the configurational state of the cristal membranes of rat heart mitochondria within the living cell can be induced by imposing energizing conditions. An exact correlation has been established between the configurational states of the cristal membrane and the energy states of the mitochondrion. The configurational changes observed in mitochondria in situ are comparable to those established for beef heart mitochondria in vitro and are consistent with the postulate of the conformational basis of energy transductions in membrane systems. The formation of paracrystalline arrays is one of the noteworthy features of configurational changes of mitochondria in situ.  相似文献   

Revision of the Association's Constitution: A Statement by the Special Committee on Constitution and Bylaws     

Caldwell OW  Livingston BE  Moulton FR 《Science (New York, N.Y.)》1946,103(2670):245-250

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A NEW AND IMPROVED METHOD FOR OBTAINING PECTIN FROM FRUITS AND VEGETABLES     

Magoon CA  Caldwell JS 《Science (New York, N.Y.)》1918,47(1224):592-594

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RESOLUTION OF THE EXECUTIVE COMMITTEE     

Barker JW  Caldwell OW  Cannon WB  Carlson AJ  Compton AH  Livingston BE  Mather KF  Moulton FR  Stakman EC  Wrather WE 《Science (New York, N.Y.)》1944,99(2565):159-160

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Evidence of early pyrometallurgy in the kerman range in iran     

Dougherty RC  Caldwell JR 《Science (New York, N.Y.)》1966,153(3739):984-985

Physical and chemical anal ysis of pottery fragments, including a crucible shard and ore samples from Tal-i-Iblis, Iran, suggests that copper smelting may have been well advantced late in the fifth millennium B.C.  相似文献   

Oceans. Mitigating local causes of ocean acidification with existing laws     

Kelly RP  Foley MM  Fisher WS  Feely RA  Halpern BS  Waldbusser GG  Caldwell MR 《Science (New York, N.Y.)》2011,332(6033):1036-1037

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