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101.
Different arrangements of decentralized forest management have been promoted as alternatives to centralized and top down approaches to halt tropical deforestation and forest degradation. Ethiopia is one of the countries piloting one of these approaches. To inform future programs and projects it is essential to learn from existing pilots and experiences. This paper analyses five of the pilot participatory forest management (PFM) programs undertaken in Ethiopia. The study is based on the Forest User Group (FUG) members’ analyses of the programs using selected outcome variables: forest income, change in forest conditions, forest ownership feelings and effectiveness of FUGs as forest managing institutions. These variables were assessed at three points in time—before the introduction of PFM, during the project implementation and after the projects ended. Data were collected using group discussions, key informant interviews and transect walks through the PFM forests. The results show that in all of the five cases the state of the forest is perceived to have improved with the introduction of PFM, and in four of the cases the improvement was maintained after projects ended. Regulated access to the forests following introduction of PFM was not perceived to have affected forest income negatively. There are, however, serious concerns about the institutional effectiveness of the FUGs after projects ended, and this may affect the success of the PFM approach in the longer term. 相似文献
102.
Sanne Vammen Larsen 《Regional Environmental Change》2011,11(1):111-122
Climate change is one of the risks that society faces today. Among other things, it has the potential to interfere with the
water environment, and thus it can be a relevant factor in current work with river basin management plans (RBMPs) in Denmark.
At the same time, climate change in theory has characteristics that can pose challenges, if included in such a planning process.
In this article, it is investigated what the attitudes towards climate change are among actors in the planning process, and
what the main drivers, barriers and challenges related to including climate change in the RBMPs are, compared to the theoretical
challenges. The investigation consists of a document study of hearing responses, interviews, and a survey among Danish municipalities.
The overall results are that there are many attitudes towards the inclusion of climate change as a factor in RBMPs and that
this diversity theoretically can be a challenge in the planning process. The main theoretical and practical barriers and challenges
in connection with inclusion of climate change in RBMPs relate to lacking knowledge and uncertainty. 相似文献
103.
Submicron aerosol deposition to outdoor vegetation was evaluated by measuring vegetation and air concentrations of 212Pb, 214Pb, and 7Be attached to atmospheric aerosols. A biomass-normalized deposition velocity (VD), with units of m3 kg?1 s?1, was used to compare species and isotopes with respect to air-to-vegetation transfer rates. For 212Pb (), higher night-time air concebtrations dominate deposition, while for 214Pb (), deposition measurements over shorter time periods relative to changing atmospheric conditions were possible. Calculated VD values were usually higher for 214Pb, possibly reflecting wind-enhanced deposition during the afternoon period of sampling. Evergreen species, including pines, were not appreciably different from deciduous species. Most striking was the narrow range of results (factor of 6 for 34 212Pb measurements of 20 species). Beryllium-7 () was used to evaluate time-integrated deposition by sampling vegetation in California near the end of dry summers. Similar deposition rates were found for this isotope. The results of the study indicated that naturally radioactive atmospheric aerosols can be used to understand the dynamics of submicron aerosol deposition to ecosystems. 相似文献
104.
Marvin J Dainoff Arne Aar?s Gunnar Horgen Maria Konarska Stig Larsen Magne Thoresen Barbara G F Cohen 《International journal of occupational safety and ergonomics》2005,11(1):9-23
This special issue of the International Journal of Occupational Safety and Ergonomics (JOSE) reports the results from an extensive multinational and multidisciplinary collaborative investigation of the impacts on visual display terminal (VDT) work of musculoskeletal, visual, ergonomic, and psychosocial factors. For brevity, this effort has been referred to as the MEPS project (musculoskeletal--eyestrain--psychosocial--stress). This paper lays out the basic methodological structure of the study. The study was conducted in 4 countries utilizing VDT data entry workers as the primary subject population. A battery of objective and subject assessment measures, including muscle load, visual function, physical and visual strain, postural, ergonomic and psychosocial factors, were assessed at 3 different points in time. A pre-test was given prior to an ergonomic intervention. Two post-tests were given 1 month and 1 year after the ergonomic intervention. 相似文献
105.
Arne Aar?s Gunnar Horgen Ola Ro Ellen L?ken Geir Mathiasen Hans-Henrik Bj?rset Stig Larsen Magne Thoresen 《International journal of occupational safety and ergonomics》2005,11(1):25-47
The Norwegian MEPS (musculoskeletal--visual--psychosocial--stress) study included 3 groups: data entry, data dialogue (female) and data dialogue (male). Before intervention, the data entry group reported significantly more symptoms and signs of musculoskeletal illness and had longer periods in front of the video display terminal (VDT) without a break. The ergonomic intervention consisted mainly of ergonomic information and training. After intervention, the data dialogue female group reported a significant reduction in shoulder pain in parallel with a reduction in trapezius load. Increasing the understanding in how to adjust the work stand and chair may have been contributing factors to reducing the pain level. There was a significant reduction in eye problems in all groups; the greatest reduction in eye symptoms was seen in the groups who had new optometric corrections. 相似文献
106.
Potent estrogenic hormones are consistently detected in the environment at low concentration, yet these chemicals are strongly sorbed to soil and are labile. The objective of this research was to improve the understanding of the processes of sorption, mobility, and transformation for estrogens in natural soils, and their interaction. Equilibrium and kinetic batch sorption experiments, and a long-term column study were used to study the fate and transport of 17beta-estradiol and its primary metabolite, estrone, in natural soil. Kinetic and equilibrium batch experiments were done using radiolabeled 17beta-estradiol and estrone. At the concentrations used, it appeared that equilibrium sorption for both estrogens was achieved between 5 and 24 h, and that the equilibrium sorption isotherms were linear. The log K(oc) values for 17beta-estradiol (2.94) and estrone (2.99) were consistent with previously reported values. Additionally, it was found that there was rate-limited sorption for both 17beta-estradiol (0.178 h(-1)) and estrone (0.210 h(-1)). An approximately 42 h long, steady-flow, saturated column experiment was used to study the transport of radiolabeled 17beta-estradiol, which was applied in a 5.00 mg L(-1) solution pulse for 44 pore volumes. 17beta-estradiol and estrone were the predominant compounds detected in the effluent. The effluent breakthrough curves were asymmetric and the transport modeling indicated that sorption was rate-limited. Sorption rates and distributions of the estrogens were in agreement between column and batch experiments. This research can provide a better link between the laboratory results and observations in the natural environment. 相似文献
107.
Commercial Medicinal Plant Extraction in the Hills of Nepal: Local Management System and Ecological Sustainability 总被引:1,自引:0,他引:1
Helle Overgaard Larsen 《Environmental management》2002,29(1):88-101
This paper presents a case study from Jumla District, Nepal, investigating local management systems and ecological sustainability
of commercial collection of a medicinal plant, spikenard (Nardostachys grandiflora DC, Valerianaceae), growing in alpine meadows. Interviews were undertaken with local collectors, traders, and district forest
office staff, and the dynamics of people–plant interactions are analyzed using the Oakerson model. In all, 110 sample plots
1m square were laid out in three areas with differing collection and grazing pressures for recording of floristic composition
and abundance of spikenard root biomass. Comparisons show significantly more root biomass in uncollected than collected areas
with local management and the interpretation of differences in abundance is discussed. The combination of qualitative and
quantitative investigations can provide a framework for the study of people–plant interactions, and this study can serve as
first step in a compilation of cases to create a more detailed picture of local management systems of Nepali nontimber forest
products in general and commercially collected medicinal and aromatic plants in particular. 相似文献
108.
A regional framework for establishing recovery criteria 总被引:6,自引:0,他引:6
Robert M. Hughes Thomas R. Whittier Christina M. Rohm David P. Larsen 《Environmental management》1990,14(5):673-683
Effective assessments of aquatic ecosystem recovery require ecologically sound endpoints against which progress can be measured.
Site-by-site assessments of end points and potential recovery trajectories are impractical for water resource agencies. Because
of the natural variation among ecosystems, applying a single set of criteria nationwide is not appropriate either. This article
demonstrates the use of a regional framework for stratifying natural variation and for determining realistic biological criteria.
A map of ecoregions, drawn from landscape characteristics, formed the framework for three statewide case studies and three
separate studies at the river basin scale. Statewide studies of Arkansas, Ohio, and Oregon, USA, streams demonstrated patterns
in fish assemblages corresponding to ecoregions. The river basin study in Oregon revealed a distinct change at the ecoregion
boundary; those in Ohio and Montana demonstrated the value of regional reference sites for assessing recovery. Ecoregions
can be used to facilitate the application of ecological theory and to set recovery criteria for various regions of states
or of the country. Such a framework provides an important alternative between site-specific and national approaches for assessing
recovery rates and conditions. 相似文献
109.
Bjørn Mejdell Larsen Odd Terje Sandlund Hans Mack Berger Trygve Hesthagen 《Water, Air, & Soil Pollution: Focus》2007,7(1-3):285-291
We describe the development of the fish community in the acidified and limed river Litleåna in southern Norway, and describe how chemical restoration, compensatory introductions of exotics, and accidental invasion of exotics interact to influence the population of the naturally occurring brown trout (Salmo trutta). The river Litleåna is a tributary to the river Kvina in Vest-Agder County, southern Norway. During the years 1996–2004, annual mean pH was 4.9–5.0 and 6.1–6.4 above and below the liming facility, which was installed in 1994. Originally, brown trout was the only fish species in the river, but brook trout (Salvelinus fontinalis) have been intentionally introduced, whereas European minnow (Phoxinus phoxinus) was introduced by accident. Fish densities were recorded by means of electrofishing annually over the ten year period 1995–2004. Although close to extinction before liming was initiated, brown trout fry densities increased from 1995 to 1999, with subsequent varying densities. There has been a simultaneous major increase in the occurrence and density of European minnow since 1997. Our results show that both brown trout and European minnow increase after liming. Minnow densities are negatively affected by low pH episodes in the river. The growth rates of brown trout fry are negatively correlated to minnow densities, indicating competition between the species. Brook trout densities have decreased since liming started, and during the brown trout recovery. 相似文献
110.
Eric W. Larsen Alexander K. Premier Steven E. Greco 《Journal of the American Water Resources Association》2006,42(4):1077-1097
ABSTRACT: Bank erosion along a river channel determines the pattern of channel migration. Lateral channel migration in large alluvial rivers creates new floodplain land that is essential for riparian vegetation to get established. Migration also erodes existing riparian, agricultural, and urban lands, sometimes damaging human infrastructure (e.g., scouring bridge foundations and endangering pumping facilities) in the process. Understanding what controls the rate of bank erosion and associated point bar deposition is necessary to manage large alluvial rivers effectively. In this study, bank erosion was proportionally related to the magnitude of stream power. Linear regressions were used to correlate the cumulative stream power, above a lower flow threshold, with rates of bank erosion at 13 sites on the middle Sacramento River in California. Two forms of data were used: aerial photography and field data. Each analysis showed that bank erosion and cumulative effective stream power were significantly correlated and that a lower flow threshold improves the statistical relationship in this system. These correlations demonstrate that land managers and others can relate rates of bank erosion to the daily flow rates of a river. Such relationships can provide information concerning ecological restoration of floodplains related to channel migration rates as well as planning that requires knowledge of the relationship between flow rates and bank erosion rates. 相似文献