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181.
182.
L P Lue C C Lewis V E Melchor 《Journal of environmental science and health. Part. B》1984,19(3):343-354
Aldicarb, Temik 15 G, was incorporated in furrows at 3.37 and 6.73 kg ai (active ingredient)/ha and carrots (Daucus carota L.) were directly seeded on the same day. The numbers of nematode larvae were significantly suppressed in the treated plots; averages were 249, 74, and 51/50 cc soil samples for control (0), 3.37 and 6.73 kg ai/ha, respectively. Aldicarb treatment resulted in a 28% yield increase as compared to the untreated. Aldicarb residue in carrots was 28 ppb for the low treatment and 46 ppb for the high. Residual levels in soil of high treatment declined from 61 to 31 ppb during two weeks prior to harvest, meanwhile, those in the low decreased slightly from 13 to 12 ppb. Carrots placed in hydroponic solution containing aldicarb 14.5 ppm for 6 days, had an aldicarb residue of 10.26 ppb and the hydroponic solution, 2.7 ppb. Persistence of aldicarb residue was in carrot greater than in soil greater than in hydroponic solution. 相似文献
183.
Paul W. Mielke Charles F. Chappell Lewis O. Grant 《Journal of the American Water Resources Association》1972,8(6):1219-1224
Principal component analysis is used to investigate density requirements of wintertime orographic cloud seeding experiment precipitation sensor networks. Three passes in the vicinity of Climax, Colorado are studied. The eighteen or more evenly spaced precipitation sensors of each pass are almost completely described by three principal components. These three principal components appear to represent (i) mean precipitation, (ii) slope orientation to storm systems, and (iii) elevation. Evaluation of these principal components is implemented with two distribution-free tests, a proportionality test and the runs test. The results of this study suggest that the loss of experimental information caused by low density precipitation sensor networks may be of little consequence. 相似文献
184.
The objective of the present study was to investigate the population genetic structure of the commercially important camouflage grouper, Epinephelus polyphekadion (Bleeker, 1849), in the western and central Pacific Ocean to improve existing management. Camouflage grouper are widely distributed in the Indo-Pacific and form brief, seasonal, spawning aggregations that are often heavily fished. The present study examined populations sampled in 1997-1998 at five sites in the western central Pacific spanning a geographic distance of ~5,000 km: New Caledonia, Great Barrier Reef, Palau, Marshall Islands, and Pohnpei (Micronesia). Primer pairs were developed to examine genetic variation at three polymorphic microsatellite loci. Cluster analysis, using genetic distance, revealed three regional groupings: (1) Palau, (2) Pohnpei and the Marshall Islands, and (3) the Great Barrier Reef and New Caledonia. Highly significant allele frequency differences were observed among sites. At Pohnpei, significant allele frequency differences in successive years were also apparent, possibly related to genetic variation among cohorts or between local spawning groups. The inter-annual differences at Pohnpei suggest that there may be further genetic structuring over relatively modest distances, a finding relative to determining management units for this commercially valuable species and suggests that future studies need to incorporate possible small-scale temporal or spatial components into study design. 相似文献
185.
186.
The chemical environment of pest species may be considered a habitat susceptible to management Management may be by means of manipulation of the environment of the pest for population suppression or for enhancement of natural enemies Examples of each are reviewed here Chemical stimuli influencing the behavior of phytophagous insects include host plant originated stimuli and pheromones The latter, especially sex pheromones, have proved most successful as tools for manipulation of pest population dynamics Factors influencing search behavior of natural enemies include habitat characteristics such as crop, associated plants and plant assemblages, host plant characteristics, influence of associated organisms, and characteristics of the searching entomophage Recent studies have shown potential for simultaneous management of a pest species and enhancement of natural enemies using pest pheromones 相似文献
187.
The article presents a holistic approach to studying and applying crop protection in agricultural systems A theoretical framework of integrated pest management (IPM) is presented that allows an understanding of pest population processes on a whole-agroecological-system basis The need for and emergence of holistic research on agroecosystems is discussed, as are the current trends in ecological theory and pest management 相似文献
188.
Allan G. Sangster Lewis Ling Frédéric Gérard Martin J. Hodson 《Water, Air, & Soil Pollution: Focus》2007,7(1-3):143-149
Douglas fir [Pseudotsuga menziesii (Mirb.) Franco] shoots from mature trees were collected from two sites of contrasting soil pH: the Glendon campus of York
University in Toronto, Canada (pH 6.7 at 40 cm) designated Can.; and Breuil Forest, Morvan, France (pH 4 to 4.5) designated
Fr.. Needles were removed from the shoots, frozen in liquid nitrogen, and kept in a cryo-biological storage system prior to
X-ray microanalysis on the cold stage (−170°C) of a cryo-SEM. Four elements detected, potassium, phosphorus, sulphur and chlorine,
were ubiquitous in the needle tissues from both sites. Manganese was infrequently found in needle tissues from the Fr. site.
Calcium was localized most heavily in the outer tangential wall of the hypodermis and also in the epidermal walls. Silicon
(Si) concentrations were higher in the Fr. site than in the Can. site. The epidermis, hypodermis and mesophyll of needles
from the Fr. site exhibited the highest Si content, with greater amounts in the tip and middle of the needle than in the base.
Aluminium was distributed fairly evenly throughout the tissues, and there were few major sites of concentration. 相似文献
189.
Sebastian Chakeredza Lewis Hove Festus K. Akinnifesi Steven Franzel Oluyede C. Ajayi Gudeta Sileshi 《Natural resources forum》2007,31(4):286-296
Livestock production is an integral part of smallholder farming systems in southern Africa. While goats and sheep play some role in the smallholder farmer household economy, cattle are the predominant livestock species supplying draught power, milk, manure and meat. Production of cattle is based on range grazing. However, the nutritive value of the range is generally low depending on vegetation type and season. With the rapid increase in human population in southern Africa and the increasing need to produce staple food on a sustainable basis, smallholder farmers are increasingly encroaching onto lands formerly reserved for livestock grazing. Therefore, livestock subsisting on the range require supplementation. Conventional bought‐in supplements are expensive. Fodder trees and shrubs have been integrated within some farming systems of southern Africa as fodder banks with varying degrees of success. Work carried out in Tanzania, Malawi and Zimbabwe is reviewed to provide evidence on how the fodder tree technology has impacted on livestock production with special reference to smallholder dairy production, human food production and smallholder farmers’ income. For the wider adoption of the technology, a synopsis of the different scaling up pathways and approaches adopted by research and development agencies is presented. 相似文献
190.
James Lewis 《The Environmentalist》1989,9(4):269-275
Summary Much current evidence suggests that global temperatures are slowly increasing. It is believed that this increase will be associated with a sea level rise. Tuvalu, approximately 1000 km north of Fiji in the South Pacific Ocean, is one of six countries, all of them island states, that could face total destruction when sea levels rise. If sea level rises occur anywhere near the extreme projections that have been made, we can write these nations off the map. (Pernetta, 1988). This paper examines possible implications to the people of Tuvalu.James Lewis is a Fellow in Development Studies at the University of Bath, UK. This paper is based on the report of a field mission by the author on behalf of The Commonwealth Expert Group on Climate Change and Sea Level Rise (Lewis, 1988).Since submission of this article, James Lewis has taken part as a resource person at the Small States Conference on Sea Level Rise at Male, capital of the Maldives, 14th to 18th, November, 1989. A report of the Conference will be submitted for a subsequent issue ofThe Environmentalist. 相似文献