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541.
Paul Schroeder 《Environmental management》1991,15(4):475-481
A possible response to increasing atmospheric CO2 concentration is to attempt to increase the amount of carbon stored in terrestrial vegetation. One approach to increasing
the size of the terrestrial carbon sink is to increase the growth of forests by utilizing intensive forest management practices.
This article uses data from the literature and from forest growth and yield models to analyze the impact of three management
practices on carbon storage: thinning, fertilization, and control of competing vegetation. Using Douglas-fir (Pseudotsuga menziesii) and loblolly pine (Pinus taeda) as example species, results from experiments with computer simulation models suggest that, for these two species, thinning
generally does not increase carbon storage and may actually cause a decrease. The exception is thinning of very dense young
stands. Fertilization generally increases carbon storage, although the response can be quite variable. The largest gains in
carbon storage are likely to come from fertilizing lower-quality sites and from fertilizing thinned or less dense stands.
Forests usually show increased growth in response to fertilization over a wide range of ages. Simulation of the growth of
loblolly pine indicates that controlling competing vegetation at an early age helps to maximize stand growth and carbon storage.
The research described in this article has been funded by the US Environmental Protection Agency. This document has been prepared
at the EPA Environmental Research Laboratory in Corvallis, Oregon, through contract number 68-C8-0006 to NSI Technology Inc.
It has been subjected to the agency’s peer and administrative review and approved for publication. Mention of trade names
or commercial products does not constitute endorsement or recommendation for use. 相似文献
542.
The U.S. Environmental Protection Agency (EPA) has proposed regulations that would require corrective action (e.g., soil excavation and groundwater removal and treatment) at municipal solid waste landfills (MSWLFs) and hazardous waste treatment, storage, and disposal facilities (TSDFs). This paper presents an overview of the proposed corrective action regulations, and discusses their relationship to proposed or existing closure and post-closure care regulations. The paper then presents estimated corrective action cost curves for various MSWLF scenarios defined by landfill area, average waste thickness, and the presence or absence of a clay liner. The paper finally illustrates the economic benefits of sound closure and postclosure care by comparing estimated costs of corrective action to estimated costs of closure and postclosure care at MSWLFs. 相似文献
543.
Biotechnology applied to traditional foodanimals raises ethical issues in three distinctcategories. First are a series of issues that arise inthe transformation of pigs, sheep, cattle and otherdomesticated farm animals for purposes that deviatesubstantially from food production, including forxenotransplantation or production of pharmaceuticals.Ethical analysis of these issues must draw upon theresources of medical ethics; categorizing them asagricultural biotechnologies is misleading. The secondseries of issues relate to animal welfare. Althoughone can stipulate a number of different philosophicalfoundations for the ethical assessment of welfare,most either converge on Bernard Rollins principle ofwelfare conservation (Rollin, 1995), or devolve intodebates over the ethical significance of animaltelos or species integrity. The principle of welfareconservation prohibits disfunctional geneticengineering of food animals, but would permit alteringanimals biological functions, especially when (as inmaking animals less susceptable to pain or suffering)do so improves an individual animals well being.Objections to precisely this last form of geneticengineering stress telos or species integrity asconstraints on modification of animals, and thisrepresents the third class of ethical issues. Most whohave formulated such arguments have failed to developcoherent positions, but the notion of species being,derived from the 19th century German tradition,presents a promising way to analyze the basis forresisting the transformation of animal natures. 相似文献
544.
545.
Paul Edwin Potter 《Die Naturwissenschaften》1974,61(11):461-467
546.
Jiaen Liu Dr Willy Lissens Paul Devroey Andre Van Steirteghem Ingeborg Liebaers 《黑龙江环境通报》1993,13(9):873-880
The efficiency of the polymerase chain reaction (PCR) in detecting the cystic fibrosis (CF) ΔF508 mutation (which is the most common mutation of CF) was assessed in single human blastomeres. Twenty-one human immature oocytes (germinal-vesicle-stage oocytes) that had been donated for research were matured in vitro and a single spermatozoon from a carrier of the CF ΔF508 mutation was injected into the ooplasm. Fourteen embryos were obtained after intracytoplasmic sperm injection (ICSI). PCR analysis was carried out on 70 single blastomeres isolated from these 14 embryos. The results showed that the efficiency of DNA amplification by PCR in single nucleate blastomeres was 94 per cent (59/63). There were no false-positive results since none of the blank samples or the blastomeres without a nucleus showed an amplified signal. We found that nine embryos were homozygous for the unaffected genotype and that four embryos were heterozygous since they contained both the unaffected and the ΔF508 genotype. In a four-cell embryo, we observed the homozygous unaffected genotype in one blastomere and a heterozygous ΔF508/unaffected genotype in the other three blastomeres. 相似文献
547.
548.
应对不确定性:呼吁建立新的科学政策论坛 总被引:4,自引:1,他引:4
Ann Kinzig David starrett Kenneth Arrow Sara Aniyar Bert Bolin Partha Dasgupta Paul Ehrlich Carl Folke Michael Hanemann Geoff Heal Michael Hoel AnnMari Jansson Bengt-Owe Jansson Nils Kautsky Simon Levin Jane Lubchenco Karl-Gran Miler Stephen W.Pacala Stephen H.Schneider Domenico Siniscalco Brian Walker 《Ambio-人类环境杂志》2003,32(5):330-335
科学界和政策界具有不同的目标,这就自然导致了对构成某种变化或现象的"检验"标准的差异,以及用不同的方法去描述不确定性和风险的持性及传达不确定性和风险.这些差异可能损害科学家、决策者和公众之间的有效沟通,同时也限制了科学家所愿意研究的社会紧迫问题的类型.本文主要回顾了一系列处理不确定性问题的方法,阐述了当科学和政策不能很好协调时所可能引起的一些错误.并在此基础上,特别针对解决不确定性问题提出了一些具体建议,包括重构科学规范,建立由科学、政策两方面领导广泛参加的科学政策论坛. 相似文献
549.
Effects of Residential Development on Forest-Dwelling Neotropical Migrant Songbirds 总被引:13,自引:0,他引:13
Many bird species are in local or regional decline because of habitat loss or degradation. We attempted to disentangle the effects of residential development from the effects of forest size on forest-bird communities, with particular emphasis on Neotropical migrant species. Two variables were examined for their influence on avian diversity and abundance: forest size and the number of houses outside a forest within 100 m of the edge. We found that Neotropical migrants consistently increased in number and abundance as forest size increased. Of greater interest, we found that the number of houses surrounding a forest severely undermined its suitability for Neotropical migrants. Neotropical migrants consistently decreased in diversity and abundance as the level of adjacent development increased, regardless of forest size. The effects of development were striking: 4-ha woodlots without any nearby houses had on average a richer, more abundant Neotropical community than did 25-ha urban woodlots. No predictable pattern of change concerning development or forest size was observed for short-distance migrants or permanent residents. Current planning regulations generally permit housing right up to forest edges. This practice may prevent protection of ecological features within the forest. Threshold distances for housing developments around forests need to be determined to prevent or minimize adverse effects on features and functions within the forests. 相似文献
550.
Past reproductive success affects future habitat selection 总被引:4,自引:0,他引:4
Paul V. Switzer 《Behavioral ecology and sociobiology》1997,40(5):307-312
Correlational studies have shown that an individual's past reproductive success often increases its breeding site fidelity
(i.e., the tendency to return to a previously occupied location), suggesting that individuals use their reproductive experience
to assess habitat quality. However, the causality of the relationship between reproductive success and site fidelity is still
uncertain. In a field experiment, the effect of mating success on site fidelity was isolated from potential confounding variables
in a territorial dragonfly, the eastern amberwing (Perithemis tenera). The experiment controlled for site quality, intrinsic characteristics of males, previous territorial experience at the
site, arrival order, and territorial evictions. Males that were prevented from mating were much more likely to change sites
the following day than control males that were allowed to mate. This result was not affected by age, the amount of time a
male spent on the site, or mortality. These results imply that individuals use their own reproductive success to assess the
quality of the habitat. The benefit to an individual of using its reproductive success to determine habitat quality is discussed
relative to other sources of information.
Received: 31 May 1996 / Accepted: 31 January 1997 相似文献