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971.
M.G. Morris 《Biological conservation》1975,7(4):311-319
Samples of Hemiptera were taken in September 1972, from areas of carboniferous limestone grassland which were burnt in April and May 1972, and from adjacent unburnt areas. Significantly larger numbers of species, of both Heteroptera and Auchenorhyncha, were recorded from the unburnt areas, and the species-diversity of the samples was significantly greater. The effects of burning on individual species are considered in relation to their biology and the effects of other kinds of management. The results are discussed in relation to the management of grassland for the conservation of wildlife, and a short review of the effects of burning on populations of invertebrate animals is made. 相似文献
972.
The evidence at present available, although incomplete, gives rise to fears for the future of the edible snail Helix pomatia L. The scale of exploitation is increasing, particularly in Eastern Europe, to meet growing demand, mainly from the West. The growth of legislation to control collecting supports the evidence of declining numbers, but the legislation does not appear to be backed by sufficiently detailed population ecology studies. The need for co-ordinated international action on farming, legislation and ecological study is urged. 相似文献
973.
The official final action acid hydrolysis method, 14.019, for the determination of fat in foods was successfully applied, with slight modifications, to the analysis of homogenates of food, feces, and animal tissues as well as dry samples of mixed foods. In samples containing sucrose or fructose, it was necessary to carry out a fermentation procedure before acid hydrolysis to avoid problems encountered when these sugars were present. 相似文献
974.
O W Van Auken W Hulse C L Durocher 《Journal of the Association of Official Analytical Chemists》1977,60(5):1087-1092
A method has been developed for the extraction, cleanup, derivatization, detection, and quantitation of hexachlorophene (HCP) residues from 2 types of plant storage tissue high in lipid content. Wet soybean or peanut tissue was homogenized and extracted with ethyl ether and chromatographed on silica gel to remove the neutral lipids. The cleaned up sample was methylated with diazomethane and the dimethoxyhexachlorophene was eluted from a second silical gel column and chromatographed on a 6' glass column packed with 3% OV-1 or 3% SE-30 on Gas-Chrom Q. The instrument detection limit for the 63Ni electron capture detector was less than 0.1 ng for dimethoxyhexachlorophene and about 1 ppb HCP residue in plant issue. Recovery of 10-420 ppb HCP added to tissue averaged 90.9 +/- 5.7%. Interfering substances were removed, column life was increased, peak sharpness was increased, and tailing of the parent compound was decreased by using appropriate column chromatography. 相似文献
975.
In 1970 and 1971 a high population of Rhyacionia buoliana (Denisand SchiffermÜller), the Pine shoot moth, appeared in aseed orchard of Pinus contorta Douglas ex Loud, in Wiltshire.The opportunity was taken to compare several alternative insecticideswith DDT. Field trials in March and August showed that fenitrothioncan be used as an alternative to DDT to control the Pine shootmoth. 相似文献
976.
The effects of five ameliorants for saline-sodic soil reclamation on certain chemical and physical soil properties over a four-year period of observation are reported. Of these ameliorants, three are conventionally used (gypsum, sulphur, manure); the other two are for this purpose either unusual (potassium sulphate) or relatively unknown (molasses meal). Results published in a previous paper demonstrated that molasses meal had a very rapid-acting favourable effect on most soil physical properties whilst soil chemical conditions remained essentially unchanged. The effect on physical properties was presumably due to soil aggregation by the polysaccharide component of molasses meal. As a follow-up this paper shows, however, that this aggregation does not last long; the rigidly arid climatic conditions under which this experiment was carried out apparently do not favour the preservation of structural bonds consisting of polysaccharide gums. Consequently, a gradual decline of structural conditions took place after the second year. Although initially not as effective as molasses meal, gypsum and sulphur retained their favourable influence on physical properties over a longer period. Potassium sulphate and farmyard manure provided virtually no benefits. 相似文献
977.
Soil Protozoa (primarily small naked amoebae and flagellates) were counted under control conditions and with stresses of nitrogen, water, or nitrogen and water under field conditions (Ecosystem Stress Area, Pawnee Site, northeastern Colorado, USA) in the summer of 1974. Protozoan populations were also measured in soil cores removed from the field and incubated under a wet-dry cycle. Protozoan numbers were higher in the top 1 cm of soil and overlying litter than at a depth of 5–6 cm in all treatments. After rainfall totaling 35 mm, the control and fertilized only treatments showed population increases with the fertilized only treatment showing the greater change. Protozoa showed marked responses to the addition of water to soil cores, with the largest numbers appearing after peak CO2 evolution. Numbers of active (trophic) forms ranged from about 20.000. g?1 dry soil in the control treatment under dry conditions to over 100,000. g?1 dry soil in the irrigated plus fertilized plot. There were few (<5%) cystic (dormant) forms in all treatments contrary to earlier studies in mesic climates. A rough estimate of protozoan production is presented. 相似文献
978.
A simple apparatus was developed to study metabolic gases in the rice rhizosphere. With this device, a positive rhizosphere effect of rice was demonstrated on three soil microbial activities: N2 fixation, CH4 formation and denitrification. 相似文献
979.
980.
A survey was made in 1972, of the status of Rhododendron pronticum L. at Winterton, Norfolk, and aerial photographs were used to assess its spread in recent years. The ecological implications of the continuing presence of this invsive alien shrub on the dunes are discussed. Comparisons with the highly successfull dune shrub Hippophaë rhamnoides L. help put into perspective the present and likely future role of Rhododendron at Winterton. The implications of controls are discussed together with methods by which this may be achieved. 相似文献