首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   10篇
  免费   1篇
测绘学   1篇
大气科学   1篇
地球物理   1篇
地质学   3篇
海洋学   1篇
自然地理   4篇
  2017年   1篇
  2016年   1篇
  2015年   1篇
  2014年   2篇
  2013年   1篇
  2008年   1篇
  2006年   1篇
  2003年   1篇
  2002年   1篇
  1997年   1篇
排序方式: 共有11条查询结果,搜索用时 62 毫秒
1.
We synthesize the study of coupled natural and human systems across sites and cultures through a process of simplification and abstraction based on multiple dimensions of human-nature connectedness: satisfaction of basic needs, psycho-cultural connectedness and regulation of use of natural resources. We thus provide both a place-based and general understanding of value-driven anthropogenic environmental change and response. Two questions guide this research: what are the crucial stakeholder values that drive land use decisions and thus land cover change? And how can knowledge of these values be used to make decisions and policies that sustain both the human and natural systems in a place? To explore these questions we build simulation models of four study sites, two in the State of Texas, United States, and two in Venezuela. All include protected areas, though they differ in the specifics of vegetation and land use. In the Texas sites, relatively affluent individuals are legally converting forests to residential, commercial, and industrial uses, while in Venezuela landless settlers are extra-legally converting forests for purposes of subsistence agriculture. Contemporary modeling techniques now facilitate simulations of stakeholder and ecosystem dynamics revealing emergent patterns. Such coupled human and natural systems are currently recognized as a form of biocomplexity. Our modeling framework is flexible enough to allow adaptation to each of the study sites, capturing the essential features of the respective natural and anthropogenic land use changes and stakeholder reactions. The interactions between human stakeholders are simulated using multi-agent models that act on forest landscape models, and receive feedback of the effects of these actions on ecological habitats and hydrological response. The multi-agent models employ a formal logic-based method for the Venezuelan sites and a decision analysis approach using multi-attribute utility functions for the Texas sites, differing more in style and emphasis than in substance. Our natural-systems models are generic and can be tailored according to site-specific conditions. Similar models of tree growth and patch transitions are used for all the study sites and the differing responses to environmental variables are specified for each local species and terrain conditions.  相似文献   
2.
3.
Apple varieties boom and bust as the vogue for new flavors cycle through the market. Dwarfing rootstocks, an old but freshly blossoming orchard technology, allows growers to intervene in trees in new ways and keep up with shifts in consumer demand. They cultivate customization in apple orchards and facilitate emerging neoliberal trends in food systems. However, the rootstocks do more than entrench actors further into the whims of the market—they also shape economic agency in ways that have multiple expressions. Drawing on work on actor-networks and assemblages, this paper considers how technologies play a role in contemporary food politics through their material characteristics and the performances they inspire. Using apple production in the American Midwest as a case study, this paper discusses the ways that rootstock technologies both reproduce current power structures and conventional organizational forms in food, while providing a platform for an alternative type of assemblage. In doing so, it contributes theoretically to conversations about the role of materials in economic politics and substantively to an optimistic vision of the future of food.  相似文献   
4.
Because food web regimes control the biomass of primary producers (e.g., plants or algae), intermediate consumers (e.g., invertebrates), and large top predators (tuna, killer whales), they are of societal as well as academic interest. Some controls over food web regimes may be internal, but many are mediated by conditions or fluxes over large spatial scales. To understand locally observed changes in food webs, we must learn more about how environmental gradients and boundaries affect the fluxes of energy, materials, or organisms through landscapes or seascapes that influence local species interactions. Marine biologists and oceanographers have overcome formidable challenges of fieldwork on the high seas to make remarkable progress towards this goal. In river drainage networks, we have opportunities to address similar questions at smaller spatial scales, in ecosystems with clear physical structure and organization. Despite these advantages, we still have much to learn about linkages between fluxes from watershed landscapes and local food webs in river networks. Longitudinal (downstream) gradients in productivity, disturbance regimes, and habitat structure exert strong effects on the organisms and energy sources of river food webs, but their effects on species interactions are just beginning to be explored. In fluid ecosystems with less obvious physical structure, like the open ocean, discerning features that control the movement of organisms and affect food web dynamics is even more challenging. In both habitats, new sensing, tracing and mapping technologies have revealed how landscape or seascape features (e.g., watershed divides, ocean fronts or circulation cells) channel, contain or concentrate organisms, energy and materials. Field experiments and direct in situ observations of basic natural history, however, remain as vital as ever in interpreting the responses of biota to these features. We need field data that quantify the many spatial and temporal scales of functional relationships that link environments, fluxes and food web interactions to understand how they will respond to intensifying anthropogenic forcing over the coming decades.  相似文献   
5.
Up until very recently--and in marked contrast to such countries as Spain, Denmark and Germany--Australia generated hardly any electricity from the wind. Driven largely by the mandatory targets embodied in the Renewable Energy (Electricity) Act 2000 (Commonwealth) this situation is now changing. Australia has several operational small- to medium-sized wind energy power stations in Western Australia, Victoria, New South Wales and Queensland. But--in the face of often strong local opposition--the Australian Wind Energy Association is keen to increase the number and scale of such projects. This paper outlines recent overseas developments in wind energy and then focuses on the environmental and planning dilemmas posed by this form of electricity production. Particular attention is focused on a highly controversial wind energy proposal in south-western Victoria, the Portland Wind Energy Project (PWEP). The argument presented is that wind is only one of a number of possible renewable energy options, that coastal landscapes are an 'endangered species', and that it is time for geographers to revisit methodologies concerned with evaluating landscape beauty and debating the place of landscape values within the ecologically sustainable development paradigm.  相似文献   
6.
广州市大力开展"数字绿化"管理平台建设,依托其中的广州市林业和园林局3维实景展示项目,以仿真应用为目的,研究基于CAD设计施工图和普查获取的城市园林景观GIS数据的3维可视化技术,具体叙述了相关的技术方法和流程。  相似文献   
7.
The Future Midwestern Landscapes (FML) project is part of the U.S. Environmental Protection Agency's Ecosystem Services Research Program. The goal of the FML project is to quantify changes in ecosystem services across the Midwestern region as a result of the growing demand for biofuels. Watershed models are an efficient way to quantify ecosystem services of water quality and quantity. By calibrating models, we can better capture watershed characteristics before they are applied to make predictions. The Kaskaskia River watershed in Illinois was selected to investigate the effectiveness of different calibration strategies (single‐site and multi‐site calibrations) for streamflow, total suspended sediment (TSS) and total nitrogen (TN) loadings using the Soil and Water Assessment Tool. Four USGS gauges were evaluated in this study. Single‐site calibration was performed from a downstream site to an upstream site, and multi‐site calibration was performed and fine‐tuned based on the single‐site calibration results. Generally, simulated streamflow and TSS were not much affected by different calibration strategies. However, when single‐site calibration was performed at the most downstream site, the Nash–Sutcliffe efficiency (NSE) values for TN ranged between ?0.09 and 0.53 at the other sites; and when single‐site calibration was performed at the most upstream site, the NSE values ranged between ?8.38 and ?0.07 for the other sites. The NSE values for TN were improved to 0.5 – 0.59 for all four sites when multi‐site calibration was performed. The results of the multi‐site calibration and validation showed an improvement on model performance on TN and highlighted that multi‐site calibrations are needed to assess the hydrological and water quality processes at various spatial scales. Copyright © 2012 John Wiley & Sons, Ltd.  相似文献   
8.
南沙群岛景观分5种类型:礁丘热带海洋生物繁生景观,环礁带海洋生物繁生景观,灰沙岛热带常绿刮灌林磷积石灰土景观,大陆架热带海海海洋生物繁生景观,深海热带大洋性和深海性海洋生物景观,这5种景观归纳为两类,一类为热带海洋景观,包括浅海和深海;另一类为热带珊瑚礁景观,下分礁丘,环礁和灰沙岛3种,南沙群岛景观类型分布和演化与古地理和现代化环境条件有关。  相似文献   
9.
The Hydrogeological Landscape (HGL) Framework is a landscape-characterisation tool that is used to discern areas of similar physical, hydrogeological, hydrological, chemical and biological properties, referred to as HGL Units. The HGL Framework facilitates prioritisation of natural-resource management investment by identifying current and potential hazards in the landscape. Within prioritised regions, on-ground management actions are tailored for specific Management Areas within individual HGL Units. The HGL Unit boundaries are determined through expert interpretation of spatial and field based datasets, such as climate, landform, geology, regolith, soil, stream network, groundwater flow systems, water quality and vegetation assemblages. The resulting HGL Units are validated by an interdisciplinary team using field assessment and biophysical testing. The use of the HGL Framework for new applications creates opportunities for refinement of the existing methodology and products for end users. This paper uses an application in the Australian Capital Territory as a case study to illustrate two enhanced techniques for the landscape characterisation component of the HGL Framework: use of an unsupervised statistical learning algorithm, Self-Organising Maps (SOM), to further validate HGL Units; and landform modelling to assist in delineation of Management Areas. The combined use of SOM and landform modelling techniques provides statistical support to the existing expert and field-based techniques, ensuring greater rigour and confidence in determination of landscape patterns. This creates a more refined HGL Framework landscape-characterisation tool, facilitating more precise hazard assessment and strategic natural-resource management by end users.  相似文献   
10.
In Amazonia, our knowledge of the trade-offs and possible thresholds in the relationships among social, economic and environmental parameters remains quite limited and hinders the design of sustainable socio-environmental systems. To fill this gap, we analyzed relationships among landscape metrics, socio-economic patterns, biodiversity and soil-based ecosystem services within a total of 51 farms located at 6 sites of the Colombian and Brazilian Amazon. Farms were representative of an initial set of 274 and they represented colonization ages from 10 to 80 years and a range of public policies found in the region.Cluster analysis separated farms in 7 types of production systems according to 5 main criteria (size of the farm, human capital, incomes, farm products and production intensity) selected from an initial set of 18 criteria. Biodiversity was summarized into a composite index Bd built with data from 8 different groups: trees, shrubs, grasses and forbs, birds, Saturnidae and Sphingidae moths, Drosophilidae, earthworms and ants. Provision of ecosystem services was quantified by a composite indicator of 6 sub-indicators of soil hydrological functions, C storage and chemical fertility. Increasing intensity of production systems was linked to a significant decrease of indicators of natural capital biodiversity (Bd) and soil based ecosystem services (Es) with 20% and 37.3% variance explained, respectively. No relationship was observed between production systems and an indicator of human wellbeing (Sb) based on a set of 5 criteria identified with the farmers. Findings indicate that early colonizers migrate when a certain level of development has been achieved (as a result of their activities) and are replaced by wealthier populations.An overall indicator of sustainability (Su) – that combines production efficiency (Ep), Sb, Bd and Es indices (ranging from 0.1–1.0) – decreases significantly with the landscape intensification (Li) with 18.7% variance directly explained by this relationship. Su was also significantly related to production systems (36.4% variance explained): while this indicator remained relatively stable with a value of 0.5 across the early and intermediate phases following deforestation, it dropped down considerably (0.2) for production systems based on cattle ranching on highly degraded pastures with less than 2% forest cover remaining. Restoration with sylvopastoral systems allowed some farms of this former group to increase sustainability to a value of 0.35 after less than 5 years. Agroforestry systems on sites deforested at the same time maintained values around 0.5, as they allowed the maximum production efficiencies and maintained relatively high values of the Biodiversity (Bd) and Ecosystem services (Es) indexes. This is evidence that beyond the general negative trade-off between human development and natural capital observed in Amazonia, agro ecological options to revert the trend are quite promising. A general methodological approach for the reconstruction of sustainable landscapes in farms of the deforested Amazonian region is proposed as a conclusion.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号