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621.
622.
Barbara A. Cellarius 《GeoJournal》2001,55(2-4):599-606
Recent legislation for the restitution of ownership rights to, and subsequent management of, formerly privately owned forests
in postsocialist Bulgaria has focused largely albeit not exclusively on the restored forests from the perspective of timber
production, that is, `forest' equals `harvestable timber resource'. Using ethnographic data collected in rural Rhodope Mountain
communities, this paper presents a local-level perspective on forests and forest use, including the meaning that forests hold
for local residents as a source of non-timber forest products such as mushrooms and medicinal plants, of animal pasture, and
of firewood for household heating and cooking. This local social perspective is then contrasted with the timber-resource focus
of the forestry legislation and subsequent planning for forest use. The scale of forest ownership – in part a function of
the restitution legislation – is also addressed in relation to the practicalities of resource management. Generally, the paper
demonstrates a mismatch between the postsocialist forestry legislation and local practice and conditions with regard to forests
and the natural resources therein.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
623.
624.
Physical profile data (salinity, temperature, oxygen, and downwelling irradiance) and in situ incubations of light and dark bottles were used to characterize vertical structure and elucidate mechanisms controlling summertime hypoxia in western Long Island Sound. The period of oxygen depletion corresponded with the period of thermally-controlled stratification. Bulk density differences between surface and bottom waters were only 1.2 to 2.7 sigma-t units; but they were apparently sufficient to resist destratification by winds and tides. Thus oxygen depletion was a cumulative process through the summer. During the stratification period, net oxygen production (measured using light BOD bottles) was confined to a narrow surface zone of 1.8–4.5 m. Below this zone was an intermediate zone of high net oxygen uptake, beneath which was a subpycnoclinic zone where oxygen uptake was very low. Rates of total oxygen uptake (dark bottles) were greatest in the surface layer and diminished with depth. There was close coupling between physical conditions and metabolic structure. Vertical patterns of oxygen production and removal were strongest in calm weather. The location of the intermediate zone corresponded with that of the oxycline. The thickness of the zone and the steepness of the oxycline were determined by the depth and intensity of both physical stratification and biological production and respiration. The biological structure was weakened by physical mixing in the upper water column, and the intermediate zone disappeared with fall destratification. We hypothesize that biological uptake within the water column influences oxygen depletion through two mechanisms. (1) In bottom waters, uptake rates per unit volume are low, but bulk uptake is a significant factor in oxygen depletion because of the large volume of water involved. (2) The intermediate zone, where respiratory uptake is also significant, is strategically located between the surface zone of oxygen renewal and the bottom zone of depletion, where it constitutes an active filter which reinforces the pycnocline as a barrier to vertical oxygen dispersion. The magnitude of direct oxygen removal in the water column relative to removal by sediment oxygen demand and the potential effects of this biological filtering mechanism are important considerations for understanding eutrophication dynamics and managing Long Island Sound. Dynamic models which (1) underestimate the role of water column uptake and (2) incorporate only the two-zone characteristics of physical stratification will tend to (a) overestimate the contribution of sediments to summertime oxygen deficits and (b) overestimate rates of vertical dispersion and reventilation of bottom waters. 相似文献
625.
626.
Barbara J. Morehouse 《The Professional geographer》1996,48(1):46-57
Geographical spaces and boundaries are neither simple nor naively given. An examination of selected disputes over territory in the greater Grand Canyon area reveals the importance of considering the implications of absolute, relative, and representational spaces for how contests are framed and negotiated. Efforts to move toward a more ecologically based regime of natural resource management at Grand Canyon require a better understanding of how the existing spaces came to have their present location, size, configuration, definition, and jurisdictional structure. 相似文献
627.
Microcosms containing defaunated, fine estuarine sediments were field deployed to assess the effects of microcosm size on the rate of benthic macroinvertebrate recolonization and resulting community structure. Four sizes of microcosms (square acrylic plastic boxes: 7 cm side?1, 12 cm side?1, 20 cm side?1, and 32 cm side?1, all 6-cm deep) were deployed in upper Perdido Bay, Florida, and colonized for 6 wk. Absolute mean total number of organisms (TNO) differed (α=0.05) among all sizes, while normalized mean TNO (adjusted to 12 cm side?1 area) did not. Mean total number of taxa (TNT) was different among sizes: 7 cm side?1, 12 cm side?1, and 20 cm side?1, but not between sizes 20 cm side?1 and 32 cm side?1. Seven dominant taxa occurred in all size microcosms. Scaling of physical design features (size of microcosm) affected numbers of taxa in recolonization of fine-grained sediments in our study area, but effects on abundance and dominance were minimal. 相似文献
628.
An examination of the feasibility of passive transport from coastal spawning grounds to estuarine nursery areas for English sole 总被引:1,自引:0,他引:1
Christopher N. Rooper Donald R. Gunderson Barbara M. Hickey 《Estuarine, Coastal and Shelf Science》2006,68(3-4):609
English sole recruitment has been linked to environmental conditions occurring during their 6–10 week pelagic egg and larval stages, prior to their appearance in nursery estuaries during their first summer. The purpose of this study was to predict the spawning locations of juvenile English sole observed in estuaries to assess the feasibility of passive transport of egg and larval stages. Current meter data were used to back-calculate the transport trajectories of 19 cohorts of English sole observed as juveniles during estuarine trawl surveys. Only six of these cohorts were predicted to be spawned outside the Oregon–Washington shelf system, assuming passive transport of eggs and larvae. Predicted egg and larval trajectories indicate that most of the English sole found in Oregon and Washington estuaries were spawned off the coast of Washington, with some spawning off northern California and central Oregon. Although these results are not consistent with the presumed spawning locations for the Oregon and Washington shelf, they indicate that passive transport assumptions may be adequate to preserve the larvae in the coastal system until settlement. 相似文献
629.
630.