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311.
Cecilia Polansky 《国际发展与全球生态学杂志》2013,20(2):109-118
A workshop held in Tanzania in early 2002 brought practitioners of Participatory Forest Management (PFM) from 25 African countries together with donors and other interested organizations. One objective was to search for ways forward to improve and streamline implementing PFM. It was agreed that forest legislation permitting PFM is currently widespread and that many countries are somewhere on the path of implementation. It was also agreed that more needs to be done to further the definition and sharing of benefits from PFM forests in order for the practice to be successful and sustainable. The alarming rate of deforestation in many countries has not been sufficiently monitored or addressed by PFM. Lessons not yet learned from at least 30 years of experience include how to write satisfactory management plans and conduct inventories that would help define PFM benefits and monitoring aspects. This paper suggests ways to improve on these aspects of PFM planning. It also proposes a greater emphasis on inclusion of pitsawyer organization as a key component in sustaining forests for a longer time. 相似文献
312.
Ringrose S Chipanshi AC Matheson W Chanda R Motoma L Magole I Jellema A 《Environmental management》2002,30(1):98-109
For purposes of suggesting adaptive and policy options regarding the sustained use of forestry resources in Botswana, an analysis
of the whole countrywide satellite data (showing the mean present distribution of vegetation in terms of species abundance
and over all density) and the projection of vegetation cover changes using a simulation approach under different climatic
scenarios were undertaken. The analysis revealed that changes in vegetation cover types due to human and natural causes have
taken place since the first vegetation map was produced in 1971. In the southwest, the changes appear to be more towards an
increasing prevalence of thorn trees; in the eastern part of the country where widespread bush encroachment is taking place,
the higher population density suggests more human induced (agrarian-degradation) effects, while in the sparsely settled central
Kalahari region, changes from tree savanna to shrubs may be indicative of the possible influence of climate with the associated
effects of fires and local adaptations. Projection of future vegetation changes to about 2050 indicates degeneration of the
major vegetation types due to the expected drying. Based on the projected changes in vegetation, current adaptive and policy
arrangements are not adequate and as such a shift from the traditional adaptive approaches to community-based types is suggested.
Defining forestry management units and adopting different management plans for the main vegetation stands that are found in
Botswana are the major policy options. 相似文献
313.
The authors demonstrate the difficulties inherent in predicting vegetation changes in floodplains affected by hydroelectric
developments. The results are based on phytoecological studies in the Rhone River valley between Geneva and Lyon. The study
is based in a 200-km stretch of river where the floodplain can attain 10 km in width. Vegetation is described for the area
prior to the construction of four dams and compared with the situations 8 yr later. Research methods include systematic sampling
of geomorphological, soils, and floristic factors; collection of a data base of spatial information; and large-scale vegetation
mapping. 相似文献
314.
Many of todays agricultural landscapes once held vast amounts of wetland habitat for waterbirds and other wildlife. Successful restoration of these landscapes relies on access to accurate maps of the wetlands that remain. We used C-band (5.6-cm-wavelength), HH-polarized radar remote sensing (RADARSAT) at a 38° incidence angle (8-m resolution) to map the distribution of winter shorebird (Charadriiformes) habitat on agricultural lands in the Willamette Valley of western Oregon. We acquired imagery on three dates (10 December 1999, 27 January 2000, and 15 March 2000) and simultaneously collected ground reference data to classify radar signatures and evaluate map accuracy of four habitat classes: (1) wet with 50% vegetation (considered optimal shorebird habitat), (2) wet with > 50% vegetation, (3) dry with 50% vegetation, and (4) dry with > 50% vegetation. Overall accuracy varied from 45 to 60% among the three images, but the accuracy of focal class 1 was greater, ranging from 72 to 80%. Class 4 coverage was stable and dominated maps (40% of mapped study area) for all three dates, while coverage of class 3 decreased slightly throughout the study period. Among wet classes, class 1 was most abundant (about 30% coverage) in December and January, decreasing in March to approximately 15%. Conversely, class 2 increased dramatically from January to March, likely due to transition from class 1 as vegetation grew. This approach was successful in detecting optimal habitat for shorebirds on agricultural lands. For modest classification schemes, radar remote sensing is a valuable option for wetland mapping in areas where cloud cover is persistent.
Also, Department of Fisheries and Wildlife, Oregon State University, Corvallis, Oregon 97331, USA 相似文献
315.
Landscape changes over a period of 25 years were assessed for a catchment basin in Normandy, France. Landscape attributes, i.e. land use, land cover and natural habitat, were obtained from aerial photographs (1964, 1989) and soil maps, to define a landscape typology. Data were aggregated on a 500 m×500 m grid system and treated by multivariate analysis. Results of these analysis show that this rural landscape has undergone changes in landcover (mainly grassland receding to crop) as well as changes in spatial structure (mainly increase of plot size and uniformisation). These changes were related to a typology of farms (realised by multivariate analysis of a field survey on the 38 registered farms of the site). Results suggest that (i) farms with a narrow range of production, i.e. specialised farms, are located on a narrow range of environmental conditions and are associated with stable landscapes, while (ii) farms with a broader range of production (i.e. polyculture) are distributed more widely throughout the landscape, and are mostly associated with the landscape changes. 相似文献
316.
Irina Cech Ernst M. Davis Edward A. Gonzales Diana Brooks 《Journal of the American Water Resources Association》1979,15(6):1691-1706
ABSTRACT: Application of synographic techniques to four separate nonrelated research tasks demonstrated the usefulness of such an approach in interpreting and communicating hydrologic survey data especially when large geographic areas are involved. Nutrient exchange and biotic indicators in coastal estuaries were analyzed to determine residence times in different seasons of the year. Man induced changes in urban runoff patterns were shown to increase the probability of flooding with different recurrences of storm events. Nitrate and indicator bacteria in private wells were analyzed on a county-wide basis to determine the sources and extent of natural occurrence versus contamination origins. Water wells and the surface supply of metropolitan Houston were analyzed for sodium content to assist citizens and physicians with data which are needed for derivation of sodium restricted therapeutic diets. 相似文献
317.
Flash floods are characterized by their suddenness, fast and violent movement, rarity, small scale but high level of damage. They are particularly difficult to forecast accurately and there is little lead time for warning. This makes motorists especially vulnerable. Assuming that these flash flood hazard specificities may be the significant factors leading to difficulties for drivers to perceive danger, we used cognitive mapping combined with GIS data processing to assess motorists’ flash flood risk perception on their daily itineraries. The analysis of 200 mental maps collected allows planners to have maps highlighting dangerous areas where risk perception is weak and to identify reasons for this. 相似文献
318.
R. S. Kanwar H. P. Johnson T. E. Fenton 《Journal of the American Water Resources Association》1984,20(4):589-597
ABSTRACT Results of a field survey designed to assess the extent of crop production losses due to inadequate drainage in a large watershed of Iowa is presented. Information on the current status of drainage of the watershed, located in the Des Moines River basin, was collected through personal interviews with 256 farmers from 60 legal drainage districts. The results of the survey indicate that 95 percent of the area in upper Des Moines River basin has inadequate district mains or main outlet drains currently having a design capacity of ≤ 0.64 cm/day drainage coefficient. Outlet capacity of 1.27 cm/day d.c. would be required for full production. Inadequate drainage in the watershed is currently responsible for crop yield reduction equal to about one-third of the maximum yield potential for average weather conditions. 相似文献
319.
320.
作为一种国外被广泛用来评估噪声对居民的影响以及制定未来改善的工具,城市噪声地图在中国尚属于起步阶段,本文介绍了国外噪声地图发展和应用的情况以及如何建立噪声地图的有关技术,同时提出了一些关于发展噪声地图研究的建议,噪声地图的研究,不仅为城市规划和城市声环境控制提供了决策支持,同时也提供了一种与其他学科结合的途径,因此具有十分重要的意义。 相似文献