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1.
How to assort with the relationship between the urban construction and the maintenance of ecological security is a hot issue during the process of urbanization. The purpose of this study is to identify the key ecological land maintaining ecological security and to put forward some measures for environmental management. Based on the GIS technology, from the view of water security, biodiversity conservation, disaster protection, natural recreation security, and human disturbance, an integrated index is put forward to evaluate the ecological importance of regional space. Then, a GIS-based approach for evaluating ecological importance was created, with Xingguo county of China as a case study. The results show that the area of core eco-space in the study area accounts for 30% of the total area. These areas mainly consist of the core areas of regional river systems, wetlands, nature reserves, forest parks, and scenic spots and the endangered and protected zone of geological hazards. According to the spatial characteristics of ecological importance for different regions, this study proposes some zoning regulations and measures for environmental management. 相似文献
2.
Fourteen commercial leek fields with first and second generation Leek moth, Acrolepiopsis assectella Z., (LM) injury were sampled during 1986 in The Netherlands. For both generations, plant injury was more prevalent in the perimeter of the field than in interior portions. A sequential sampling program for use in making treatment decisions for LM was developed. An economic analysis of the value of sampling information derived from the sequential sampling program was performed. The parameters used for the analysis were crop yield and value, expected level of LM infestation, potential loss of value due to LM infestation, effectiveness of insecticide application, and cost of sampling. Due mainly to the high value of the crop and low cost of treatment, analysis indicates that there is little difference between a sampling-based management plan and prophylactic application of insecticides in terms of pest control costs. Additionally, such a sampling-based management plan is relatively insensitive to changes in the parameters used in the model. Thus, development of a threshold linked to a sampling procedure will not reduce pest control costs. Use of the sampling-based management plan will also not significantly increase pest control costs and will likely result in reduced insecticide use compared with a prophylactic treatment program.
Zusammenfassung In den Niederlanden wurde 1986 der durch den Befall der ersten und zweiten Generation der Lauchmotte (Acrolepiosis assectella Z.) verursachte Schaden auf 14 kommerziell genutzten Porreefeldern ermittelt. Für beide Generationen wurde an den Feldrändern ein deutlich höherer Befall als in dem inneren Bereich eines Feldes festgestellt. Zur Bekämpfung der Lauchmotte wurde als Entscheidungsmodell ein sequentielles Probenahmeverfahren entwickelt. Der Informationsgehalt der sequentiellen Befallserhebung wurde einer ökonomischen Bewertung unterzogen. Hierbei wurden folgende Parameter zugrunde gelegt: Erntemenge und Ertrag, erwarteter Befallsgrad sowie hierdurch verursachter möglicher Ertragsverlust, Wirkungsgrad einer Insektizidbehandlung und Kosten der Stichprobennahme. Die Analyse der einzelnen Parameter ergab nur eine geringe Kostendifferenz zwischen einer gezielten Bekämpfung nach sequentieller Probenahme und prophylaktischen Insektizidspritzungen, bedingt durch den hohen Wert der Kultur und die niedrigen Kosten einer Bekämpfung. Darüber hinaus its das Verfahren einer gezielten Lauchmottenbekämpfung gegeüber Veränderungen der obengenannten Parameter relativ unempfindlich. Deshalb wird die Entwicklung eines Schwellenwertes der mit Probenahmeverfahren verbunden ist die Bekämpfungskosten nicht reduzieren. Die anwendung der Probenahmeplans würde Bekämpfungskosten auch nicht erhöhen und würde wahrscheinlich Insecktizidverbrauch reduzieren im Vergleich zu einen prophylaktischen Behandlungsprogramm.相似文献
3.
Patricia Lyons Johnson 《Human ecology: an interdisciplinary journal》1990,18(4):403-416
The European demographic transition of the nineteenth century is often proposed as a model for demographic change in twentieth century developing nations, and economic development is seen as leading to an inevitable reduction in total fertility in these nations. This paper examines data from the Gainj of Papua New Guinea, a natural fertility population with very low reproductive output, and suggests that the effects of development on fertility change are much more complex than a simple demographic transition model would suggest. Looking at two variables known to contribute significantly to low total fertility among the Gainj, late age at first birth for women and long interbirth intervals, the paper suggests that households, in their recruitment and allocation of labor, may exert a mediating influence in the relationship between economic development and fertility. 相似文献
4.
A total of 24 commercial fields of cabbages and Brussels sprouts were sampled in a grid fashion with 20–25 equally spaced
cells with four plants per cell. Using this data base of 80–100 plants, we conducted computer stimulations to compare the
treatment decisions that would be made for the major insect pests using published sequential sampling programs and a newly
developed variable-intensity sampling program. Additionally, we compared the number of samples required to make the decision.
At low thresholds (10–20%) for both Lepidoptera and cabbage aphids, variable intensity-sampling required a smaller sample
size and provided more reliable decisions, while at high thresholds (40–50%) sequential sampling provided more reliable decisions.
In both procedures, the occurrence of incorrect decisions was minimal. The number of cases in which a decision would not be
reached after a 40-plant sample was lower for variable-intensity sampling. Considering the number of samples required to make
a correct decision and the greater need for reliable decisions at lower thresholds, variable-intensity sampling was superior
to sequential sampling. Additionally, variable-intensity sampling has the advantage of requiring samples to be taken in a
greater area of the field and thus increases the probability of detecting localized infestations. Although variable-intensity
sampling was not designed to classify pest populations for treatment decisions but rather to achieve sampling precision around
the population mean, our present studies indicate that it can also be an effective method to aid in treatment decisions. 相似文献
5.
小麦叶蜂危害的产量损失与防治指标研究 总被引:2,自引:1,他引:1
当小麦叶蜂幼虫数量相等时,在较干旱的年份(1988)危害较重;而在气候较湿润的年份(1989)危害较轻。虫量与产量损失成正相关(r=0.9821**),其中以25头/m2幼虫危害的产量损失突增,达显著水平,可以认定为防治指标。 相似文献
6.
Clem Tisdell 《Biodiversity and Conservation》1994,3(5):419-436
The main characteristics of the dominant economic system, including the increasing use of markets and money are described. The global system has expanded trade, including international trade, and production tremendously. While this system has the potential to favour nature conservation, in practice the opposite has occurred. Difficulties raised for conservation of biodiversity by short-term economic crises such as deficits in a country's international payments, the adoption of policies for structural economic adjustment, international capital flows, international loans and foreign aid as well as debt-for-nature swaps are discussed. As explained, it is politically difficult in market economies to support nature conservation at the expense of economic growth and as more economies develop and become market economies this problem spreads. Given global interdependence of nations, an important issue is the distribution of net benefits from biodiversity conservation between developed and less developed countries. Possible distributions of benefits and related issues are discussed. In conclusion, the importance of political lobbying by nature conservation groups in developed market economies is emphasised as a means of ensuring correction of market failures. Unfortunately, no economic system is likely to prove satisfactory in itself in conserving biodiversity so political action by conservationists is always required. 相似文献
7.
David Cheal 《Human ecology: an interdisciplinary journal》1993,21(2):197-213
In Canada, there has been a marked increase in the relative frequency of dual earner families, and especially of dual career families, compared to breadwinner/homemaker families. Effects of this change on the handling of incomes inside the household are examined here. In this paper, quantitative survey data and qualitative data on strategies of financial management are described and analyzed for co-resident couples in Winnipeg. Findings are presented on control over income, financial possession, and access to household money. These findings are interpreted as evidence of a shift in the form of companionate marriage toward greater equality of economic agency. It is suggested that the most common household financial strategy among Canadian couples today is that of flexible shares. 相似文献
8.
Ricardo Godoy Nicholas Brokaw David Wilkie 《Human ecology: an interdisciplinary journal》1995,23(1):29-52
We use microeconomic theory to frame hypotheses about the effects of income on the use of non-timber rain forest products. We hypothesize that an increase in income: (a) encourages foraging specialization, resulting in the extraction of fewer goods; (b) increases the share of household income from occupations besides foraging; (c) produces a yearly value from the extraction of nontimber forest goods of about $50 per hectare; and (d) produces depletion of forest goods entering commercial channels and sustainable extraction of goods facing cheaper industrial substitutes. To examine these hypotheses we present worldwide ethnographic information and preliminary findings from field work carried out among the Sumu Indians of Nicaragua. Field work suggests that higher income produces: (a) foraging specialization with animals rather than with plants; (b) a decline in the economic importance of forest goods in household income; (c) and a rise in the value of non-timber goods removed from the forest to about $35/ha/year. We did not have time to test hypothesis d. 相似文献
9.
Robert Wasserstrom 《Human ecology: an interdisciplinary journal》1978,6(2):127-143
In a recent work on the Tzotzil (Maya) of Chiapas, Mexico, George Collier has suggested that indigenous groups frequently employ agricultural practices which are in obvious disequilibrium with their environment. As a result, he claims, such groups bring about the permanent destruction of their lands and forests. In this article, historical and demographic evidence is presented to demonstrate that the development of commencal agriculture outside of native communities, not overpopulation or technological conservatism within them, lies at the heart of such destruction. Finally, it is argued that anthropologists must consider the evolution of social classes in rural areas if they are to understand the difficulties which economic development entails. 相似文献
10.
Henry Hurd Rusby (1855–1940) is one of the outstanding personalities in the history of the New York Botanical Garden (NYBG).
He played a significant role, not only in the founding of NYBG in 1891, but also in establishing a strong precedent of research
and exploration in the field of economic botany at the new institution. As a result of Rusby’s influence and activity, the
study of useful plants formed an important part of NYBG’s original mandate, an institutional commitment that was rejuvenated
nearly a century later, with the formation of the Institute of Economic Botany. An indefatigable researcher both in the field
and in the herbarium, Rusby left behind a voluminous corpus of published work in systematic and economic botany that is a
legacy for modern botanists and pharmacologists. 相似文献