Relationships between soil and vegetation characteristics of tundra ecosystems and their use to assess soil resilience, degradation, and rehabilitation potentials     

V. D. Vasil’evskaya  V. Ya. Grigor’ev  E. A. Pogozheva 《Eurasian Soil Science》2006,39(3):314-323

Definitions of the notions of soil resilience and degradation of the soil-vegetation cover are suggested. These problems are considered with respect to vulnerable tundra ecosystems. The analysis of available experimental data made it possible to obtain empirical equations characterizing the relationships between the plant productivity and the soil properties. These equations can be used to predict the degree of soil degradation under particular types of technogenic loads and the soil and vegetation potential for the natural restoration or artificial rehabilitation of the soil-vegetation cover in tundra ecosystems. The results obtained can be applied for the development of optimal nature management strategies in the areas of oil and gas fields in the north.  相似文献   

An evaluation of the pesera soil erosion model and its application to a case study in Zakynthos, Greece     

M. Tsara  C. Kosmas  M.J. Kirkby  D. Kosma  N. Yassoglou 《Soil Use and Management》2005,21(4):377-385

Abstract. The Pan‐European Soil Erosion Risk Assessment (pesera ) model was evaluated using existing soil erosion data collected under various types of climate, vegetation, landscape and soil conditions. The data used represent a variety of typical Mediterranean land uses such as winter wheat, vines, olives and bare, stony land prevailing in hilly areas. Using this data, the model was calibrated for sediment transport by overland flow and results compared to measured soil erosion values from runoff plots and a watershed on a monthly basis. The performance of the model was assessed statistically, showing that it can be satisfactorily used for predicting soil erosion rates under the conditions included in the study. The overall model estimate including all the available experimental data was 0.69 t ha^?1 yr^?1 with a maximum error of 1.49 t ha^?1 yr^?1. After validation, the model was applied to a small watershed (60 ha) of great ecological importance for the sea turtle Caretta caretta. For this purpose, soil and vegetation maps were compiled from all the necessary data for applying the model. The model was run for three years using daily data from an existing nearby meteorological station. The predicted and measured soil erosion rates for a 7‐month period were 0.31 t and 0.18 t, respectively. Application of the model to each mapping unit showed the over‐riding importance of land use for sediment generation under the given climatic conditions. Bare land, occupying 5.5% of the watershed area, generated up to 69% of the total sediments estimated for the watershed. It is concluded that the pesera model can be used as a regional diagnostic tool under a range of soil, topographic and climatic conditions for identifying the best land use type and vegetation cover to protect hilly areas from soil erosion. The calculated overall root mean square error for the model is 0.06 t ha^?1 yr^?1, compared to a soil erosion rate of 0.04 t ha^?1 yr^?1, which can be tolerated for protecting the area for the sea turtle.  相似文献   

Feeding Frequency Affects Growth, Not Fillet Composition, of Juvenile Sunshine Bass Morone chrysops×M. saxatilis Grown in Cages     

Carl D.  Webster  Kenneth R.  Thompson  Ann M.  Morgan  Ebony J.  Grisby Siddhartha  Dasgupta 《Journal of the World Aquaculture Society》2001,32(1):79-88

Abstract.— In an effort to feed sunshine bass Morone chrysops × M. saxatilis efficiently, promote optimal growth, and reduce labor costs associated with feeding, sunshine bass were grown in cages and fed one of four feeding frequencies: once/d, twice/d, once every other day (I X/EOD), and twice every other day (2X/EOD) for 21 wk. Juvenile sunshine bass were fed a commercial floating diet containing 40% protein and 11.5% lipid. One hundred fish were hand-counted and stocked into each of 12 3.5-m³ cages with three replications per treatment. At the conclusion of the study, percentage weight gain of sunshine bass fed twice/d was significantly (P < 0.05) higher (1,850%) compared to fish fed all other feeding frequencies. Specific growth rate (SGR) of fish fed twice/d was significantly higher (2.1%/d) compared to fish fed all other feeding regimes, while fish fed once/d had a higher SGR (2.0%/d) compared to fish fed I X/EOD (1.6%/d) and 2X/EOD (1.8%/d). Percentage survival was not significantly different (P > 0.05) among all treatments and averaged 70.4%r. Feed conversion ratio (FCR) of fish fed twice/d was significantly higher (2.40) compared to fish fed all other feeding regimes. Percentage fillet weight of fish fed twice/d was significantly higher (27.8%) compared to all other treatments. Percentage moisture, protein, lipid, and ash in fillet were not significantly different among all treatments and averaged 75.7%, 19.4%, 3.5%, and 1.2%n, respectively (wet-weight basis). Based upon data from the present study, it appears that producers growing juvenile sunshine bass in cages may want to feed fish twice daily. This feeding regimen allows for higher growth rates, without adverse effects on body or fillet compositions. However, economic analysis needs to be conducted to determine if feeding twice/d is profitable.  相似文献   

Histopathological and hematological findings in myeloid leukemia induced by a new feline leukemia virus isolate   总被引：2，自引：0，他引：2  

S R Toth  D E Onions  O Jarrett 《Veterinary pathology》1986,23(4):462-470

Myeloid leukemia was induced by a new feline leukemia virus isolate FeLV-AB/GM-1 in a high proportion of cats. The latency period was short. Three to 5 weeks after infection early changes were detectable in the bone marrow, and cats developed leukemia 5 to 8 weeks after infection. The results of the present histological and cytological studies suggested that there were two stages in the development of leukemia. The first stage appeared to be equivalent to the syndrome of bone marrow dysplasia or preleukemia which, however, converted rapidly to leukemia. Cytopenia(s) were the main hematological findings in all preleukemic and leukemic cats. White blood cell counts were low or normal, but the number of leukemic and abnormal cells increased in the peripheral blood with the progression of the disease. This reliable model system lends itself to further studies to elucidate the pathogenesis of myeloproliferative disorders.  相似文献   

Canine distal renal tubular acidosis and urolithiasis   总被引：1，自引：0，他引：1  

D J Polzin  C A Osborne  F W Bell 《Veterinary Clinics of North America: Small Animal Practice》1986,16(2):241-250

Distal RTA is characterized by decreased distal renal tubular hydrogen ion secretion, decreased ability to acidify urine, hypercalciuria, hyperphosphaturia, hypocitraturia, and metabolic acidosis. Because of the resulting alterations in urine composition and pH, patients with distal RTA are predisposed to urolithiasis and renal calcification. Diagnosis of distal RTA is important because it is a potentially reversible disorder that, left untreated, may cause nephrocalcinosis, recurrent urolith formation, moderate to severe metabolic acidosis, and renal failure.  相似文献   

Survival of Leptosphaeria maculans in soil on residues of Brassica napus in South Australia     

M. R. Sosnowski  E. S. Scott  M. D. Ramsey 《Plant pathology》2006,55(2):200-206

The survival of Leptosphaeria maculans , which causes phoma stem canker (blackleg), on oilseed rape residues ( Brassica napus ) in South Australia was investigated. Using a quantitative polymerase chain reaction (PCR) assay for L. maculans DNA, the pathogen was mainly detected in the upper 5 cm of the soil profile, including residues on the soil surface. As the size of organic matter particles in the soil decreased, so did the quantity of L. maculans detected in them. To obtain representative data for a field, at least 30 subsamples needed to be collected over the 0·81 ha area studied. In a survey of 49 commercial fields in South Australia, most L. maculans was detected in fields 1 year after oilseed rape had been grown, with less detected after 2 years and negligible amounts 3 years or more after cropping. The diagnostic DNA-based assay for L. maculans reduced the time and cost of studying L. maculans survival in soil and increased the sensitivity and accuracy of results compared with estimates of propagule number of colony-forming units on a semiselective medium.  相似文献   

Coxofemoral Luxation in the Dog and Cat     

ANTHONY W. P. BASHER BVetMed  mrcvs  MARY C. WALTER dvm  CHARLES D. NEWTON dvm  ms  Diplomateacvs 《Veterinary surgery : VS》1986,15(5):356-362

The medical records from 95 cases of coxofemoral luxation in dogs and cats were reviewed. Unilateral craniodorsal luxation was most common, (78.1% of dogs, 72.7% of cats). Trauma from being struck by an automobile was the most frequent cause (59.0%). Treatment was closed (manual) or open (surgical) reduction. The failure rate following single closed reduction was 64.8%. The surgical reduction procedure included capsular repair (capsulorrhaphy) via a craniolateral approach to the hip or via trochanteric osteotomy or gluteal tenotomy. The success rate following reduction via the craniolateral approach was 82%; no failure was recorded with trochanteric transposition, but reluxa-tion followed the single gluteal tenotomy. The Ehmer sling was the most common external fixation and was kept in place an average of 12.5 days. Thirty-three animals were available for follow-up, and no difference was recorded in limb function between the two groups of animals treated by closed vs surgical reduction. Patients with degenerative joint disease at the time of luxation were less likely to be successfully reduced; 64.3% of these animals were eventually treated by femoral head and neck excision. Thirty-eight patients had associated major injuries. Long-term follow-up results were better in those patients with concomitant orthopedic injuries than in those without other injuries.  相似文献   

Effects of pesticides and fertilizer on invertebrate populations of grass and wheat plots in Kent in relation to productivity and yield     

BRIGITTE S. LINZELL  D. S. MADGE 《Grass and Forage Science》1986,41(2):159-174

At a site in Kent, perennial ryegrass (Lolium perenne) variety S24 and Italian ryegrass (L. multiflorum) variety RVP, wheat varieties Armada and Norman, and the original mixed grass ley were grown in small plots during 1982–84. Two toxic pesticides (phorate and aldicarb) were applied to half the total number of plots three times each year to eliminate soil invertebrate populations. Fertilizer was also applied to most plots. The yields of the crops, grown with and without pesticide, and the effects of the fertilizer were compared. Grass herbage yield was measured on three occasions during the summers of 1983 and 1984. Wheat grain yields were also determined in 1983. During the first year significant differences were not apparent in grass dry matter yield between pesticide-treated and non-treated plots, but significant differences were found in the second year. The perennial ryegrass was more susceptible to pest damage than the Italian ryegrass or the grass ley. Grass yields varied between cuts and in relation to variety and pesticide treatment, yields tending to be greater in untreated plots. Fertilizer treatment greatly increased grass dry matter yields, particularly with the Italian ryegrass. The effects of pesticide treatment on both wheat varieties varied although some yield enhancement was evident. Invertebrate animal populations in pesticide and fertilizer-treated plots were also assessed in autumn 1982, spring and autumn 1983 and spring 1984. In contrast to pesticide treatment, fertilizer treatment had little effect on soil invertebrate populations. Nematode populations were reduced at each sampling occasion by the pesticide treatment. Slug populations were initially unaffected but were subsequently reduced. Leatherjackets, by far the most abundant pest in both grass and wheat plots, were markedly affected by pesticides on all sampling occasions. Generally, fewer soil-dwelling dipterous larvae were recovered in spring than in autumn. Stem-boring dipterous larvae were virtually absent.  相似文献   

AN APPARATUS FOR ROLLER TUBE TISSUE CULTURE     

Coman DR  Stabler NG 《Science (New York, N.Y.)》1941,94(2450):569-570

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PRESENTATION OF THE PENROSE MEDAL OF THE GEOLOGICAL SOCIETY OF AMERICA TO DR. N. H. DARTON     

Johnson D 《Science (New York, N.Y.)》1941,93(2411):247-248

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