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排序方式: 共有516条查询结果,搜索用时 484 毫秒
1.
Thomas J. Stohlgren Dan Binkley Thomas T. Veblen William L. Baker 《Environmental monitoring and assessment》1995,36(1):1-25
Monitoring long-term change in forested landscapes is an intimidating challenge with considerable practical, methodological, and theoretical limitations. Current field approaches used to assess vegetation change at the plot-to-stand scales and nationwide forest monitoring programs may not be appropriate at landscape scales. We emphasize that few vegetation monitoring programs (and, thus, study design models) are designed to detect spatial and temporal trends at landscape scales. Based primarily on advice from many sources, and trial and error, we identify 14 attributes of a reliable long-term landscape monitoring program: malpractice insurance for landscape ecologists. The attributes are to: secure long-term funding and commitment; develop flexible goals; refine objectives; pay adequate attention to information management; take an experimental approach to sampling design; obtain peer-review and statistical review of research proposals and publications; avoid bias in selection of long-term plot locations; insure adequate spatial replication; insure adequate temporal replication; synthesize retrospective, experimental, and related studies; blend theoretical and empirical models with the means to validate both; obtain periodic research program evaluation; integrate and synthesize with larger and smaller scale research, inventory, and monitoring programs; and develop an extensive outreach program. Using these 14 attributes as a guide, we describe one approach to assess the potential effect of global change on the vegetation of the Front Range of the Colorado Rockies. This self-evaluation helps identify strengthes and weaknesses in our program, and may serve the same role for other landscape ecologists in other programs. 相似文献
2.
Alan B. Bolten Peter Feinsinger Herbert G. Baker Irene Baker 《Die Naturwissenschaften》1990,77(9):452-452
3.
Harold N. Bass Joan B. Oliver Murali Srinivasan Ruth Petrucha Won Ng Jo Ellen S. Lee 《黑龙江环境通报》1986,6(1):33-35
Intrauterine fetal demise (IUFD) in one of twins at 12 weeks of gestation was accompanied by markedly elevated maternal serum alpha-fetoprotein (AFP) at 17 and 18 weeks. Amniotic fluid AFP from the healthy surviving twin's sac at 18·5 and 23 weeks was also greatly increased along with a positive acetylcholinesterase (AChE) band. Persistently elevated AFP and positive AChE so long after fetal demise–-6·5 and 11 weeks post IUFD–-has not, to our knowledge, been previously described. In similar cases, high level ultrasound and careful placental examination at birth should be utilized to search for fetal abnormalities or multiple pregnancy with IUFD. 相似文献
4.
Grant R. Sutherland Elizabeth Baker Stuart Purvis-Smith Athel Hockey Ed Krumins Sam Z. Eichenbaum 《黑龙江环境通报》1987,7(3):197-202
Eleven pregnancies in ten patients at risk for the fragile X were monitored by amniocentesis or chorion villus biopsy and induction of the fragile site using thymidine, methotrexate and FUdR. Three female fetuses and one male fetus were found to have the fragile X. The results obtained using thymidine induction were superior to those using methotrexate induction and probably better than those obtained using FUdR induction. 相似文献
5.
Dwight RH Fernandez LM Baker DB Semenza JC Olson BH 《Journal of environmental management》2005,76(2):95-103
A cost-of-illness framework was applied to health and income data to quantify the health burden from illnesses associated with exposure to polluted recreational marine waters. Using data on illness severity due to exposure to polluted coastal water and estimates of mean annual salaries and medical costs (adjusted to 2001 values) for residents of Orange County, California, we estimated that the economic burden per gastrointestinal illness (GI) amounts to 36.58 dollars, the burden per acute respiratory disease is 76.76 dollars, the burden per ear ailment is 37.86 dollars, and the burden per eye ailment is 27.31 dollars. These costs can become a substantial public health burden when millions of exposures per year to polluted coastal waters result in hundreds of thousands of illnesses. For example, exposures to polluted waters at Orange County's Newport and Huntington Beaches were estimated to generate an average of 36,778 GI episodes per year. At this GI illness rate, one can also expect that approximately 38,000 more illness episodes occurred per year of other types, including respiratory, eye, and ear infections. The combination of excess illnesses associated with coastal water pollution resulted in a cumulative public health burden of 3.3 million dollars per year for these two beaches. This paper introduces a public health cost variable that can be applied in cost-benefit analyses when evaluating pollution abatement strategies. 相似文献
6.
K.H. Roucoux I.T. Lawson T.R. Baker D. Del Castillo Torres F.C. Draper O. Lähteenoja M.P. Gilmore E.N. Honorio Coronado T.J. Kelly E.T.A. Mitchard C.F. Vriesendorp 《Conservation biology》2017,31(6):1283-1292
Large, intact areas of tropical peatland are highly threatened at a global scale by the expansion of commercial agriculture and other forms of economic development. Conserving peatlands on a landscape scale, with their hydrology intact, is of international conservation importance to preserve their distinctive biodiversity and ecosystem services and maintain their resilience to future environmental change. We explored threats to and opportunities for conserving remaining intact tropical peatlands; thus, we excluded peatlands of Indonesia and Malaysia, where extensive deforestation, drainage, and conversion to plantations means conservation in this region can protect only small fragments of the original ecosystem. We focused on a case study, the Pastaza‐Marañón Foreland Basin (PMFB) in Peru, which is among the largest known intact tropical peatland landscapes in the world and is representative of peatland vulnerability. Maintenance of the hydrological conditions critical for carbon storage and ecosystem function of peatlands is, in the PMFB, primarily threatened by expansion of commercial agriculture linked to new transport infrastructure that is facilitating access to remote areas. There remain opportunities in the PMFB and elsewhere to develop alternative, more sustainable land‐use practices. Although some of the peatlands in the PMFB fall within existing legally protected areas, this protection does not include the most carbon‐dense (domed pole forest) areas. New carbon‐based conservation instruments (e.g., REDD+, Green Climate Fund), developing markets for sustainable peatland products, transferring land title to local communities, and expanding protected areas offer pathways to increased protection for intact tropical peatlands in Amazonia and elsewhere, such as those in New Guinea and Central Africa which remain, for the moment, broadly beyond the frontier of commercial development. 相似文献
7.
Philippe Louâpre Stéphanie Llopis Véronique Martel Joan van Baaren 《Die Naturwissenschaften》2014,101(11):875-882
In many insect species, sperm-depleted males (SDMs, i.e. males that have exhausted their sperm after a given number of matings) remain sexually active and continue to mate females. Here, we investigated the behavioural modifications that occur in both sexes of the parasitoid Asobara tabida Nees (Hymenoptera: Braconidae), after matings by fertile males and sperm-depleted males. We show that (i) virgin females, mated females and females mated to a SDM exhibited different behaviours and that (ii) males responded differently to females depending on whether the females had previously mated with an SDM or not. Our findings demonstrate that SDM influenced the reproductive behaviour of both males and females, especially with regard to male responsiveness and female attractiveness. These findings are discussed in the context of adaptive behaviour and fitness maximization in both males and females. 相似文献
8.
Laura Joan Feyrer 《Marine Biology》2010,157(11):2461-2465
The ecological importance of mysid (Crustacea: Mysidacea) populations in coastal food webs is not well understood. Although the 10 or more species of epibenthic mysids found in Clayoquot
Sound, BC, Canada, form the primary prey resource for seasonally abundant gray whales (Eschrichtius robustus), little is known about their life history. Here, Holmesmysis sculpta dominates multi-species swarms, however there are several potential routes to this state, one of which is higher embryo production.
Reproductive capacity is key to the resiliency of local mysid populations and species diversity, in this study I compare one
aspect, brood size for the four most commonly found species, H. sculpta, Neomysis rayii, Exacanthomysis davisi, and Columbiaemysis ignota. The number of embryos per brood was found to vary significantly between species; however, individual length is a stronger
determinant of brood size. Here, I report previously unknown life history attributes of coastal mysid species, with important
consequences for community structure and local marine food webs. 相似文献
9.
M. W. Kress R. Baker S. J. Ursic 《Journal of the American Water Resources Association》1990,26(5):747-756
ABSTRACT: The deposition and chemistry of precipitation were estimated for one year in two forest ecosystems in the South-Central United States. Precipitation, throughfall, litter leachate, and soil leachate were analyzed for a small catchment of pine-hardwoods in southeastern Oklahoma and for a catchment of loblolly pines (Pinus taeda L.) in northern Mississippi. In the pine-hardwood forest, 98 percent of the acid deposition was neutralized, 50 percent in the forest canopy, and 48 percent in the forest floor. In the pine forest, 75 percent of the acid deposition was neutralized, all in the forest floor. The pine-hardwood ecosystem accumulated sulfate, nitrate, and ammonia ions, and lost base cations. During seasons of deficient precipitation, dry deposition appeared to enrich the concentrations of hydrogen, nitrate, sulfate, and ammonia ions in throughfall samples at both locations. 相似文献
10.
Liquid household hazardous wastes in the United States: Identification,disposal, and management plan
David K. Robertson Jude Akagha Jon Belasco Jane Bullis Gloria Byrne Joan Di Patria Wayne Fisher James Fonzino Jeffrey Hsu Lucy Merchan David Oster Jon Rosenberg Sabine Von Aulock Barry Vroeginday 《Environmental management》1987,11(6):735-742
Present methods of disposal of today's hazardous household chemicals in the United States are frequently not acceptable because of pathways to groundwater, surface water, and the atmosphere. This report identifies potentially hazardous liquid waste in the household, notes current disposal practices, and recommends an improved management plan that utilizes consumer education, manufacturer cooperation, and governmental intervention. Laws requiring uniform disposal labeling on packaging are critical. Local, county, and state governments must be encouraged to coordinate the necessary infrastructure. Managing hazardous household wastes now will mitigate potential disposal problems. 相似文献