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931.
Out of administrative control: Absentee owners, resident elk and the shifting nature of wildlife management in southwestern Montana 总被引:1,自引:0,他引:1
This paper describes the historical roots of an ongoing wildlife management dilemma involving decreasing opportunities for elk management via public hunting on private land in the context of an expanding elk presence on private land in southwest Montana. Our main focus is on the role of private ranchland in elk ecology, and the ability of land owners to set elk migration in new directions through cumulative decisions about hunting and tolerating elk. This takes elk management, traditionally the purview of the state, out of administrative control. We document connections between the region’s historical and emerging land tenure patterns, and analyze associated changes in hunter access. Elk numbers expanded rapidly in the Upper Yellowstone Valley at a moment of significant transition in ranchland tenure. New owners more interested in natural amenities than in livestock production encouraged the elk and discouraged hunting. This reinforced the spread of elk, and further weakened the ability of the state and other ranchers to manage elk (which interfere with livestock production in numerous ways). Though elk and cattle use the landscape in similar ways, elk became more effective agents of landscape change in a reflexive relationship with ideas of land that stress natural amenities over production. 相似文献
932.
Lawrence V. Stanislawski Kornelijus Survila Jeffrey Wendel Yan Liu Barbara P. Buttenfield 《制图学和地理信息科学》2018,45(4):319-328
This paper describes a workflow for automating the extraction of elevation-derived stream lines using open source tools with parallel computing support and testing the effectiveness of procedures in various terrain conditions within the conterminous United States. Drainage networks are extracted from the US Geological Survey 1/3 arc-second 3D Elevation Program elevation data having a nominal cell size of 10 m. This research demonstrates the utility of open source tools with parallel computing support for extracting connected drainage network patterns and handling depressions in 30 subbasins distributed across humid, dry, and transitional climate regions and in terrain conditions exhibiting a range of slopes. Special attention is given to low-slope terrain, where network connectivity is preserved by generating synthetic stream channels through lake and waterbody polygons. Conflation analysis compares the extracted streams with a 1:24,000-scale National Hydrography Dataset flowline network and shows that similarities are greatest for second- and higher-order tributaries. 相似文献
933.
吸引研发人员是推动国家高新区创新发展的关键举措之一。本文采用区位熵和地理探测器等方法,刻画国家高新区研发人员集聚的空间特征,探究其影响因子及作用机理。研究发现(:1)国家高新区研发人员数量呈现出以城市群为核心的空间分布格局,而研发人员集聚程度的空间分布较均衡。(2)整体上,高新区因子的解释力比城市因子更强,这说明以往只关注城市因子的研究存在不足。但在不同地区,两个层面因子解释力有所差异。东、中部地区,国家高新区研发人员集聚由城市因子和高新区因子共同作用,而高新区因子在西部地区影响更为显著。(3)高新区经济规模和高新区容纳人才能力是所有国家高新区研发人员集聚的核心因子。此外,城市住房成本、城市科研重视度和高新区外贸水平分别是主导东、中、西部国家高新区研发人员集聚的核心因子。(4)不同因子之间交互作用均呈现出增强关系,且具有区域差异性,具体表现为:高新区先进程度、高新区经济规模、城市交通便捷度分别是东、中、西部地区与其他因子的交互强化作用较为显著的因子。 相似文献
934.
Evaluating channel response to an extreme sedimentation event in the context of historical range of variability: Upper Colorado River,USA 总被引:1,自引:0,他引:1
In May 2003, a breach in a large irrigation ditch within Rocky Mountain National Park (RMNP) initiated a debris flow that entered Lulu Creek and the Colorado River, where 36 000 m3 of sediment substantially altered channel forms and processes. We present a proof of concept to understand whether the 2003 disturbance is within the historical range of variability (HRV), and whether the recovery potential of the system is sufficient to adapt to the disturbance. Flow and sediment regimes, and channel morphology and stability were monitored on Lulu Creek and the Colorado River from 2004 to 2011. Dominant channel response following the debris flow within Lulu Creek included step development, bed armoring, and channel widening. Step height‐to‐length ratios (H/L) for three reaches on Lulu Creek are outside the HRV of reference channels, with one reach approaching reference conditions. Erosion of approximately 23% of the debris fan volume occurred as a result of the long duration 2011 peak flow. Sediment within the Lulu Creek fan will persist for ~30–190 years, assuming current maximum and mean removal rates. Planform changes on the Colorado River since the debris flow include an increase in single‐thread geometries, with braided reaches where bar deposition occurred. Bedload transport and grain‐size analysis of bedload indicate translational spreading of a sand wave front with a dispersive component in steeper reaches. Lulu Creek is returning to a condition of natural variability, but the Colorado River is outside the HRV expected for steep‐gradient, pool‐riffle channels. Applying HRV to a situation where management questions require a longer term perspective, and pre‐disturbance baseline data are limited, is a useful approach. The HRV analysis facilitates a better understanding of site variability and delineates the range of possibilities of channel form and process to achieve management goals. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
935.
We show a mechanism whereby the jets result during the development of β-plumes (i.e., low-frequency Rossby waves that establish gyre circulations) in a model of ocean-basin circulation. The energy originates in baroclinic meanders of circulation at the eastern boundary of the ocean. Eddies are intimately related and occur as a result of the instability of this process. This mechanism does not rely on the existence of the small-scale turbulence to establish zonal flows. Zonal jets can then be amplified by eddies arranged in certain order in the flow. The underlying dynamics include the propagation of linear and nonlinear basin scale Rossby waves. The related barotropic theory for these waves is developed here. We demonstrate the radiative development of jets and β-plumes in a laboratory experiment using a rotating fluid with a paraboloidal free surface. The dynamical fields are measured by the laboratory analog of the satellite altimetry. 相似文献
936.
937.
DOM是国情普查内容的重要组成部分,是地理国情普查中调查的重要数据源。本文通过卫星影象纠正,控制点选取,全色波段影像正射纠正,多光谱影像与全色波段影像配准,多光谱影像与全色波段影像融合等技术手段,确保了DOM的精度,为国情普查的后续工作提供精确的基础资料。 相似文献
938.
The vegetation communities and spatial patterns on the Fire Island National Seashore are dynamic as the result of interactions with driving forces such as sand deposition, storm-driven over wash, salt spray, surface water, as well as with human disturbances. We used high spatial resolution QuickBird-2 satellite remote sensing data to map both terrestrial and submerged aquatic vegetation communities of the National Seashore. We adopted a stratified classification and unsupervised classification approach for mapping terrestrial vegetation types. Our classification scheme included detailed terrestrial vegetation types identified by previous vegetation mapping efforts of the National Park Service and three generalized categories of high-density seagrass, low-density seagrass coverages, and unvegetated bottom to map the submerged aquatic vegetation habitats. We used underwater videography, GPS-guided field reference photography, and bathymetric data to support remote sensing image classification and information extraction. This study achieved approximately 82% and 75% overall classification accuracy for the terrestrial and submnerged aquatic vegetations, respectively, and provided an updated vegetation inventory and change analysis for the Northeast Coastal and Barrier Network of the National Park Service. 相似文献
939.
《African Journal of Marine Science》2013,35(3):401-410
Elf Pomatomus saltatrix account for between 28% and 80% of the annually recorded recreational shore-angling catch in KwaZulu-Natal, South Africa, and have been subjected to various management regimes over the past 33 years. Management of the elf fishery was amended in 2005 to reduce fishing mortality and enhance egg production, following an assessment in 1997, which considered the elf stock to be overexploited and in need of rebuilding. A compromise was reached whereby the bag limit was reduced from five to four elf per angler per day, but the closed season was shortened, allowing an extra month of fishing for elf. A total of 33 years of recreational elf catches recorded on the National Marine Linefish System was investigated for any long-term trends and how they related to management of this species. Over 3 million angler-outings from the recreational shore-fishery in KZN were analysed, including more than 1.5 million elf in the catch. Despite the fast growth of elf and the latest management intervention seven years ago, which was based on a rigorous investigation of life-history parameters, the present study showed no evidence of an improvement in catch rate. It could not be determined whether this was due to a reduction in the bag limit, which would naturally reduce catch rates or whether other factors, including the shortened closed season, had been detrimental to elf stocks. Some shortfalls in the management of elf are discussed and possible reasons for the great variability in catches, which complicated the assessment of trends, are explored. 相似文献
940.
A novel toxicity method to determine sublethal and lethal effects of manmade contaminants on the bioluminescence output from marine dinoflagellates has been developed and tested over the course of 16 years. The toxicity system, QwikLite™, was developed for the sole purpose of evaluating the potential toxicity of various materials used in bay sediments, storm water discharges, industrial discharges from Naval facilities, and antifoulant paints. Bioluminescence inhibition was observed in the following dinoflagellates: Lingulodinium polyedrum (formerly known as Gonyaulax polyedra), Ceratocorys horrida, Pyrocystis noctiluca, Pyrocystis lunula, Pyrocystis fusiformis, and Pyrophacus steinii. Cultured cells were exposed to various concentrations of contaminants from hours through 10 days. Further application with bioluminescent dinoflagellates in a variety of toxicity testing schemes have shown that these species can be used as a screening assay organism in lieu of the more costly, labor intensive bioassays presently in use. 相似文献