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731.
Johnson U. Kitheka George S. Ongwenyi Kenneth M. Mavuti 《Ambio-人类环境杂志》2002,31(7):580-587
本文主要研究了肯尼亚姆瓦彻湾(属于浅潮滩红树林湿地)泥沙交换的动力机制.该港湾属于半日潮,大、小潮的潮差分别为.2m和1.4m,大潮高水位的水面面积为17km2. 相似文献
732.
Policy making at the level of international environmental problems appears to lack a transparent, multi criteria based, decision support ‘tool’. This is due mainly to the highly political, volatile, and contextual nature of issues at this level. The environmental problem of how to regulate emissions from international civil aviation due to their transboundary nature, and the participation of international and domestic players, makes it a ‘wicked’ international environmental problem where policy making has proved problematic. This problem has been used as the basis for developing and pilot testing a tool for contributing to international policymaking, the Multi Criteria Decision Support System (MCDSS). This tool is based on simplifying and integrating key components of Multi Criteria Analysis with a Decision Support System. A preliminary application of the tool explored three options for progressing the reduction of aviation emissions. Testing was based on the allocation of weights to environmental, social, economic and institutional categories, which were each then internally weighted to reflect key criteria in the policy process. Finally, likely performances of each option, against the criteria, were evaluated against Likert scale measures. The outputs from each of these steps were combined to generate a summed best policy option. Conclusions have been drawn and they indicate that the tool is potentially useful especially in the initial stages of policy development. The MCDSS is not an alternative to the international policy process, but rather complements, and makes explicit key tradeoffs in, that process. 相似文献
733.
William J Lindberg Thomas K Frazer Kenneth M Portier Frederic Vose James Loftin Debra J Murie Doran M Mason Brian Nagy Mary K Hart 《Ecological applications》2006,16(2):731-746
Many exploited reef fish are vulnerable to overfishing because they concentrate over hard-bottom patchy habitats. How mobile reef fish use patchy habitat, and the potential consequences on demographic parameters, must be known for spatially explicit population dynamics modeling, for discriminating essential fish habitat (EFH), and for effectively planning conservation measures (e.g., marine protected areas, stock enhancement, and artificial reefs). Gag, Mycteroperca microlepis, is an ecologically and economically important warm-temperate grouper in the southeastern United States, with behavioral and life history traits conducive to large-scale field experiments. The Suwannee Regional Reef System (SRRS) was built of standard habitat units (SHUs) in 1991-1993 to manipulate and control habitat patchiness and intrinsic habitat quality, and thereby test predictions from habitat selection theory. Colonization of the SRRS by gag over the first six years showed significant interactions of SHU size, spacing, and reef age; with trajectories modeled using a quadratic function for closely spaced SHUs (25 m) and a linear model for widely spaced SHUs (225 m), with larger SHUs (16 standardized cubes) accumulating significantly more gag faster than smaller 4-cube SHUs (mean = 72.5 gag/16-cube SHU at 225-m spacing by year 6, compared to 24.2 gag/4-cube SHU for same spacing and reef age). Residency times (mean = 9.8 mo), indicative of choice and measured by ultrasonic telemetry (1995-1998), showed significant interaction of SHU size and spacing consistent with colonization trajectories. Average relative weight (W(r)) and incremental growth were greater on smaller than larger SHUs (mean W(r) = 104.2 vs. 97.7; incremental growth differed by 15%), contrary to patterns of abundance and residency. Experimental manipulation of shelter on a subset of SRRS sites (2000-2001) confirmed our hypothesis that shelter limits local densities of gag, which, in turn, regulates their growth and condition. Density-dependent habitat selection for shelter and individual growth dynamics were therefore interdependent ecological processes that help to explain how patchy reef habitat sustains gag production. Moreover, gag selected shelter at the expense of maximizing their growth. Thus, mobile reef fishes could experience density-dependent effects on growth, survival, and/or reproduction (i.e., demographic parameters) despite reduced stock sizes as a consequence of fishing. 相似文献
734.
我们的研究首次发现一种耐寒的、适应性强的、速生的欧洲蕨,能在短时间内将土壤中有大量砷吸收并积累到其复叶之中,它不仅能祛除土壤中不同浓度的砷,还能祛除土壤中不同形态的砷,且欧洲蕨体内高达93%的砷被富集到复叶,从而使欧洲蕨成为修复土壤砷污染的救星。 相似文献
735.
736.
作为美国人,我对我们国家在处理全球气候变暖问题上缺乏领导作用感到惊讶、羞愧以及尴尬。有关气候变暖风险的科学证据与日俱增。最近,英国权威的斯特恩报告也作出了记载。但是,尽管在全球人造碳排放中美国占大约25%,美国人对改变他们的消费并没有表现出什么意愿或倾向。尽管出于错误的理由,布什当局在第一个任期拒绝签署 相似文献
737.
To determine whether life history differences can occur in salt marsh fishes that occupy different habitats within the same
marsh, we compared reproductive allocation in female mummichog (Fundulus heteroclitus) inhabiting creeks and ponds of a coastal salt marsh in southern New Jersey, USA during the spring and summer of 2001 and
2002. Females were collected in phase with the lunar spawning cycle from four sites of each habitat type, and assessed for
gonad-to-body-mass ratio and growth increment. Annual reproductive allocation, expressed as a percent of somatic mass, was
estimated for each site and year from the gonadosomatic indices of individuals collected during each spawning period. Mummichogs
from creeks showed little change in annual reproductive allocation from 2001 to 2002, whereas those inhabiting ponds showed
a significant increase between these years. Seasonal reproductive patterns indicated that pond females cease spawning at least
one lunar cycle earlier than creek fish. While ponds experienced considerably higher maximum summer temperatures than creeks
as well as near-anoxic pre-dawn conditions, neither of these variables explained a significant amount of variation in annual
reproductive allocation. In contrast, annual reproductive allocation of mummichogs in a pond correlated with its flood frequency
in both years of study. Our results suggest that while the length of the spawning season differs in mummichogs inhabiting
marsh creeks and ponds, annual reproductive allocation depends more upon the hydrodynamic conditions of the particular waterbody
than its habitat type per se. 相似文献
738.
Kenneth B. Armitage 《Behavioral ecology and sociobiology》1982,11(1):33-36
Summary A population of eight juvenile female yellow-bellied marmots (Marmota flaviventris) was introduced into a marmot locality from which all other marmots were removed. Social interactions were monitored in the field and the individual behavioral profile of each animal was determined by mirror image stimulation. Social interactions were unequally distributed among the eight juveniles. Neither body size nor kinship were significantly related to frequencies of social interactions. Social interactions were significantly related to individual differences. 相似文献
739.
740.
David R. Anderson Gary C. White Kenneth P. Burnham 《Environmental and Ecological Statistics》1995,2(2):91-115
We present three empirical methods for risk assessment in field studies of free-ranging vertebrates. First, we advocate statistical inference concerning population recruitment or mortality in response to ecological hazards. Second, if inferences about both recruitment and mortality are available, one can use a Leslie- Lefkovitch matrix to estimate the finite rate of population change () as a function of ecological hazards. Third, designed experiments can be conducted on samples of marked animals in natural environments to assess impacts and risks. These methods rely on either sophisticated capture-recapture or radio-tracking models, and on well-developed analysis theory. The use of uniquely marked animals is somewhat analogous to the use of tracers in other areas of risk assessment. We present examples of each approach and discuss some limitations. 相似文献