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181.
Stephen J. Lawrence Parker J. Wigington 《Journal of the American Water Resources Association》1987,23(6):1069-1076
ABSTRACT: Oxidized nitrogen (nitrite + nitrate N) concentrations were measured from bulk precipitation, bulk through-fall, and streamflow in a 7.86 hectare forested watershed in southeastern Oklahoma during the wet season from March through June 1983. Oxidized nitrogen inputs comparable to results of other studies were recorded during the 19 rainstorms sampled. Oxidized nitrogen concentrations appeared to increase after rainfall interacted with the pine and hardwood canopies and were inversely related to both rainfall and through-fall depth. Oxidized N concentrations in streamflow were greatest during the rising limb of storm flow with subsequent decreases during the falling limb of storm hydrographs and lowest during base flow. The oxidized N inputs from bulk precipitation were considerably greater than outputs from streamflow resulting in a net retention of oxidized nitrogen within the watershed during the study period. 相似文献
182.
A quantitative succession model was developed both to meet resource management needs in Montana's Lewis and Clark National Forest and to develop a modeling methodology. It builds upon previous concepts and incudes three new features: quantitative prediction of all tree species and seedlings; quantitative predictions of important understory species; and successional pathways determined by fire intensity and scorch height. The method is described and demonstrated for selected Montana habitat (community) types. It is also available in managerial guidelines and has been programmed as a new module in theforplan simulator. Weaknesses of this and other models are discussed. Conclusions relate succession modeling to resource management needs. 相似文献
183.
184.
Ecotourism: The Santa Elena rainforest project 总被引:1,自引:0,他引:1
Stephen Wearing 《The Environmentalist》1993,13(2):125-135
Summary This paper outlines an ecotourism project undertaken in the Santa Elena community in the Monteverde region of Costa Rica. The community is seeking to establish a rainforest reserve on a parcel of land that has been permanently leased to their high school by the Costa Rican Government. The Community and Youth Challenge International are developing an ecotourism project that will provide a wider economic basis for the area and employment for students graduating from the high school. This project seeks to achieve sustainable development and fulfil the development requirements of the population surrounding the project. This is in the belief that it is only when conservation projects benefit local communities, and are set up with an infrastructure that vests control within local communities, that genuine ecotourism is achieved.Stephen Wearing is a lecturer in the School of Leisure and Tourism Studies at the University of Technology, Sydney, Australia, and he lectures and consults in the area of Tourism and Environmental Planning, and Parks Protected Area Management. His particular interest is in ecotourism projects with local communities. He is linked with Youth Challenge International and people interested in becoming involved or looking for assistance in projects can contact him at the above address. 相似文献
185.
Assessment of Soil Erodibility Indices for Conservation Reserve Program Lands in Southwestern Kansas Using Satellite Imagery and GIS Techniques 总被引:2,自引:0,他引:2
The soil erodibility index (EI) of Conservation Reserve Program (CRP) lands, which was the major criterion for CRP enrollment,
was assessed for six counties in southwestern Kansas using USGS seamless digital elevation model data and Geographical Informational
System techniques. The proportion of land areas with EI values of 8 or lower was less than 1% of the entire study area and
most of the land areas (72.5%) were concentrated on EI values between 8 and 24. Although land acreage with EI values of 24
or higher decreased dramatically, the proportion of CRP lands to the other land-use types did not change much from low to
high EI levels. The soil EI and physical soil characteristics of the CRP lands were compared to those of other land-use types.
In general, the mean EI values of the land-use types were strongly correlated with physical soil properties, including organic
matter content, clay content, available water capacity, permeability, and texture. CRP lands were compared in detail with
cropland in terms of their soil characteristics to infer the pivotal cause of the land transformation. Although there was
no significant statistical difference in EI between cropland and CRP soils, soil texture, soil family, and permeability were
statistically different between the two. Statistical analyses of these three variables showed that CRP soils had coarser texture
and higher permeability on average than cropland soils, indicating that CRP lands in the study area are drier than cropland
soils. Therefore, soil moisture characteristics, not necessarily soil erosion potential, might have been the key factor for
CRP enrollment in the study area. 相似文献
186.
This paper explores the apparent contradiction between the 'linearity' of most Sustainable Development projects, with time-bound and defined outputs achieved at a fixed cost, and an implied 'circularity' of the theory whereby there is no 'end'. Projects usually have clear parameters within which they are implemented, and the inclusion of elements such as the need for accountability, measurable impact and 'value for money' have grown in importance. It could be argued that we live in a 'projectified' and therefore linear world. The paper explores the potential contradiction between 'linearity' and 'circularity', and suggests that one way around this is to frame the project within a form of the Kolb Learning Cycle heuristic. This will facilitate a rationalisation from those implementing the sustainable development project as to why decisions are being made and for whom. If these questions are opened up to the project stakeholders, including beneficiaries, then the Kolb cycle could encourage learning and understanding by all involved. It could also provide Sustainability Therapy to those trapped in processes, which they find orthogonal to their own perceptions. It is suggested that such learning, therapy and reflective practice should be a valid output of the sustainable development project, although typically the focus is only upon the final outputs and how they feed into policy. Ironically funders would be well advised to take a broader perspective in order to achieve true 'value for money' within such projects, even if learning is not an easily measurable or tangible outcome. These points are explored within the context of the wider literature and experience with a sustainable development project undertaken in Malta. 相似文献
187.
Anaerobic microbial processes play particularly important roles in the biogeochemical functions of wetlands, affecting water quality, nutrient transport, and greenhouse gas fluxes. This study simultaneously examined nitrate and sulfate removal rates in sediments of five southwestern Michigan wetlands varying in their predominant water sources from ground water to precipitation. Rates were estimated using in situ push-pull experiments, in which 500 mL of anoxic local ground water containing ambient nitrate and sulfate and amended with bromide was injected into the near-surface sediments and subsequently withdrawn over time. All wetlands rapidly depleted nitrate added at ambient ground water concentrations within 5 to 20 h, with the rate dependent on concentration. Sulfate, which was variably present in porewaters, was also removed from injected ground water in all wetlands, but only after nitrate was depleted. The sulfate removal rate in ground water-fed wetlands was independent of concentration, in contrast to rates in precipitation-fed wetlands. Sulfate production was observed in some sites during the period of nitrate removal, suggesting that the added nitrate either stimulated sulfur oxidation, possibly by bacteria that can utilize nitrate as an oxidant, or inhibited sulfate reduction by stimulating denitrification. All wetland sediments examined were consistently capable of removing nitrate and sulfate at concentrations found in ground water and precipitation inputs, over short time and space scales. These results demonstrate how a remarkably small area of wetland sediment can strongly influence water quality, such as in the cases of narrow riparian zones or small isolated wetlands, which may be excluded from legal protection. 相似文献
188.
Jennifer E. Kay Stephanie K. Kampf Rebecca N. Handcock Keith A. Cherkauer Alan R. Gillespie Stephen J. Burges 《Journal of the American Water Resources Association》2005,41(5):1161-1175
Emitted thermal infrared radiation (TIR, λ= 8 to 14 μm) can be used to measure surface water temperatures (top approximately 100 μm). This study evaluates the accuracy of stream (50 to 500 m wide) and lake (300 to 5,000 m wide) radiant temperatures (15 to 22°C) derived from airborne (MASTER, 5 to 15 m) and satellite (ASTER 90 m, Landsat ETM+ 60 m) TIR images. Applied atmospheric compensations changed water temperatures by ?0.2 to +2.0°C. Atmospheric compensation depended primarily on atmospheric water vapor and temperature, sensor viewing geometry, and water temperature. Agreement between multiple TIR bands (MASTER ‐ 10 bands, ASTER ‐ 5 bands) provided an independent check on recovered temperatures. Compensations improved agreement between image and in situ surface temperatures (from 2.0 to 1.1°C average deviation); however, compensations did not improve agreement between river image temperatures and loggers installed at the stream bed (from 0.6 to 1.6°C average deviation). Analysis of field temperatures suggests that vertical thermal stratification may have caused a systematic difference between instream gage temperatures and corrected image temperatures. As a result, agreement between image temperatures and instream temperatures did not imply that accurate TIR temperatures were recovered. Based on these analyses, practical accuracies for corrected TIR lake and stream surface temperatures are around 1°C. 相似文献
189.
Summary. We investigated the hypothesis that aggregation signals produced by male webbing clothes moths (WCM), Tineola bisselliella (Hum.) (Lepidoptera: Tineidae), and close-range male attractant signals produced by females have a pheromonal basis, at least
in part. Gas chromatographic-electroantennographic detection (GC-EAD) and GC-mass spectrometric analyses of bioactive methanolic
extracts of male WCM disclosed three candidate pheromone components: hexadecanoic acid methyl ester (16:Ester), (Z)-9-hexadecenoic acid methyl ester (Z9—16:Ester), and octadecanoic acid methyl ester (18:Ester). In bioassay experiments in a large Plexiglas™ arena, a blend of
synthetic 16:Ester plus Z9—16:Ester was attractive to male and virgin (but not mated) female WCM; the 18:Ester was inactive.
GC-EAD analyses of pheromone gland extracts from female WCM revealed (E,Z)-2,13-octadecadienal (E2Z13—18:Ald) and (E,Z)-2,13-octadecadienol (E2Z13—18:OH) as candidate sex pheromone components. In arena bioassay experiments, 1—5 female equivalents of synthetic E2Z13—18:Ald (0.2 ng) and E2Z13—18:OH (0.1 ng) were more attractive to male WCM than were two virgin female WCM. We anticipate that the combination of
aggregation and sex pheromones, male-produced sonic aggregation signals, and habitat-derived semiochemicals will be highly
effective in attracting male and female WCM to commercial traps.
Received 12 January 2001; accepted 8 June 2001. 相似文献
190.
Kenneth C. Schiff Stephen B. Weisberg Valerie Raco-Rands 《Environmental management》2001,29(6):871-876
Monitoring of the ocean environment in southern California, USA, has been conducted by a diverse array of public and private organizations with different motivations, working on a variety of spatial and temporal scales. To create a basis from which to integrate information from these diverse programs, we conducted an inventory of ocean monitoring activities in the Southern California Bight to address the following questions: (1) How much money is being expended annually on marine monitoring programs? (2) Which organizations are conducting the most monitoring? (3) How are resources allocated among the different types of monitoring programs? This inventory focused on programs existing, or those expected to be in existence, for at least 10 years and that were active at any time between 1994 and 1997. For each program identified for inclusion in this study, information was collected on the number of sites, sampling intensity, parameters measured, and methods used. Levels of effort were translated into cost estimates based upon a market survey of local consulting firms. One hundred fourteen marine monitoring programs, conducted by 65 organizations and costing US $31 million annually, were identified. Most of the effort (81 programs, 65% of samples, 70% of costs) was expended by ocean dischargers as part of their compliance with National Pollutant Discharge Elimination System (NPDES) permit requirements. Federal programs (11 programs, 25% of samples, 10% of total expenditures) expended more than state or local government programs. More than one quarter of monitoring expenditures were conducted to measure concentrations and mass of effluent inputs to the ocean. The largest effort expended on receiving water monitoring was for measuring bacteria, followed by sediments, fish/shellfish, water quality, and intertidal habitats. The large level of expenditures by individual agencies has presented opportunities for integrating small, site-specific ocean monitoring programs into regional- and national-scale monitoring and assessment programs. 相似文献