长武黄土塬区土地利用变化对潜水补给的影响   总被引：2，自引：0，他引：2       下载免费PDF全文

程立平  刘文兆  李志  韩晓阳 《水科学进展》2016,27(5):670-678

通过长武黄土塬区不同土地利用方式下深剖面土壤水分的长期定位监测以及氢氧稳定同位素示踪技术的使用,分析了该区域土地利用变化对地下潜水补给的影响。结果表明:① 降水补给地下水过程中存在着活塞流和优先流两种机制,由活塞流补给的地下水量,以休闲地居高,低产农田次之,最后是高产农田;② 随着该区域农田生产力大幅提升以及大面积农田转换为果园,地下水活塞流补给量逐年减少,加之地下水开采量增加,导致地下水位逐年下降,年均降幅达0.3 m;③ 同位素证据表明,目前长武塬区地下水补给以优先流形式为主。为了实现黄土塬区潜水资源的有效补给与可持续利用,需要合理调控土地利用结构,保持适度生产力水平。  相似文献   

基于BDI决策的MAS-CA模型黄海海滨城镇格局模拟研究——以大连金石滩为例   总被引：3，自引：1，他引：2  

杨俊  裴颖  席建超  葛全胜  李雪铭 《地理科学》2016,36(3):410-416

基于BDI决策MAS-CA模型,利用1998年、2003年、2008年和2013年土地利用数据,对大连金石滩2020年和2030年城镇区域面积进行模拟,Kappa系数达到0.635。研究结果表明：① BDI决策补充了MAS-CA模型决策的不足,使得模型整体框架进一步完善,模拟结果具体准确,精度达到89.1%。② 金石滩城镇用地呈现出依附海岸线和交通线的格局,向海岸线靠拢,城镇用地在中部区域比较集中且城镇用地有向周围区域扩张的趋势,葡萄沟村、河咀子村、庙上村、什字街村转变最大。③ 从金石滩城镇格局的模拟结果发现,海岸线因素引导着城镇格局的转变方向。滨海地区的生态环境容易被破坏,政府应该采取措施寻找土地利用与生态环境保护的完美平衡点。  相似文献   

A method for assessing generalized data accuracy with linear object resolution verification     

Tadeusz Chrobak  Stanisław Szombara  Krystian Kozoł 《国际地球制图》2017,32(3):238-256

The article is composed of two sections. In the first section, the authors describe the application of minimum line dimensions which are dependent on line shape, width and the operational scale of the map. The proposed solutions are based on the Euclidean metric space, for which the minimum dimensions of Saliszczew’s elementary triangle (Elementary triangle – is the term pertaining to model, standard triangle of least dimensions securing recognizability of a line. Its dimensions depend on scale of the map and width of the line representing it. The use of a triangle in the simplification process is as follows: triangles with sides (sections) on an arbitrary line and bases (completing the sides) are compared with lengths of the shorter side and the base of the elementary triangle.) were adapted. The second part of the article describes an application of minimum line dimensions for verifying and assessing generalized data. The authors also propose a method for determining drawing line resolution to evaluate the accuracy of algorithm simplification. Taking advantage of the proposed method, well-known simplification algorithms were compared on the basis of qualitative and quantitative evaluation. Moreover, corresponding with the methods of simplified data accuracy assessment the authors have extended these solutions with the rejected data. This procedure has allowed the identification of map areas where graphic conflicts occurred.  相似文献   

The role of soybean production as an underlying driver of deforestation in the South American Chaco     

《Global Environmental Change》2017

South America’s tropical dry forests and savannas are under increasing pressure from agricultural expansion. Cattle ranching and soybean production both drive these forest losses, but their relative importance remains unclear. Also unclear is how soybean expansion elsewhere affects deforestation via pushing cattle ranching to deforestation frontiers. To assess these questions, we focused on the Chaco, a 110 million ha ecoregion extending into Argentina, Bolivia, and Paraguay, with about 8 million ha of deforestation in 2000–2012. We used panel regressions at the district level to quantify the role of soybean expansion in driving these forest losses using a wide range of environmental and socio-economic control variables. Our models suggest that soybean production was a direct driver of deforestation in the Argentine Chaco only (0.08 ha new soybean area per ha forest lost), whereas cattle ranching was significantly associated with deforestation in all three countries (0.02 additional cattle per hectare forest loss). However, our models also suggested Argentine soybean cultivation may indirectly be linked to deforestation in the Bolivian and Paraguayan Chaco. We furthermore found substantial time-delayed effects in the relationship of soybean expansion in Argentina and Paraguay (i.e., soybean expansion in one year resulted in deforestation several years later) and deforestation in the Chaco, further suggesting that possible displacement effects within and between Chaco countries may at least partly drive forest loss. Altogether, our study showed that deforestation in the Chaco appears to be mainly driven by the globally surging demand for soybean, although regionally other proximate drivers are sometimes important. Steering agricultural production in the Chaco and other tropical dry forests onto sustainable pathways will thus require policies that consider these scale effects and that account for the regional variation in deforestation drivers within and across countries.  相似文献   

Resource use conflicts in Mabini and Tingloy,the Philippines     

Terhi Majanen 《Marine Policy》2007

This paper presents the results of an analysis of resource use conflicts in areas near marine protected areas in Mabini–Tingloy, the Philippines. The author found large differences between groups of stakeholders in terms of perceived benefits and costs of conservation and tourism, and these inequalities have led to conflicts between various stakeholder groups. Marked by unequal power relationships, the conflicts place subsistence fishers as the weakest stakeholders. Fishers also have the lowest rates of knowledge of and participation in conservation activities. The study concludes that in order for conservation programs to be effectively transitioned onto the social and legal fabric of Mabini–Tingloy, resource use conflicts need immediate attention.  相似文献   

Predicting oxygen in small estuaries of the Baltic Sea: a comparative approach     

Pirkko Kauppila  Jessica J. Meeuwig  Heikki Pitknen 《Estuarine, Coastal and Shelf Science》2003,57(5-6):1115-1126

Coastal eutrophication, manifested as hypoxia and anoxia, is a global problem. Only a few empirical models, however, exist to predict bottom oxygen concentration and percentage saturation from nutrient load or morphometry in coastal waters, which are successfully used to predict phytoplankton biomass both in lakes and in estuaries. Furthermore, hardly any empirical models exist to predict bottom oxygen from land-use. A data set was compiled for 19 estuaries in the northern Baltic Sea, which included oxygen concentration and percentage saturation, water chemistry, estuary morphometry, and land-use characteristics. In regression analyses, bottom oxygen was predicted both as a function of the percentage of watershed under agriculture and of mean depth. These models accounted for ca. 55% of the variation in oxygen. Additionally, oxygen was linked to fetch (diameter of the area in the direction of the prevailing wind), which accounted for 30% of the variation in oxygen. This suggests that shallow Finnish estuaries are wind-sensitive. In ‘pits’ (sub-thermocline waters of deep basins), near-bottom total nitrogen strongly correlated with oxygen percentage saturation (R²=0.81). Neither chlorophyll a, total phosphorus nor nutrient loading explained oxygen variation in entire estuaries or in ‘pits’, probably mainly due to annual sedimentation/sediment–water flux dynamics. On the basis of the results of cross-validation, the models have general applicability among Finnish estuaries.  相似文献   

The Wild Life of Pesticides: urban agriculture,institutional responsibility,and the future of biodiversity in Sydney's Hawkesbury-Nepean River     

Roel Plant  Jeremy Walker  Scott Rayburg  Jacqueline Gothe  Teresa Leung 《The Australian geographer》2012,43(1):75-91

Agricultural chemicals are a notoriously intractable source of environmental pollution. Offering enhanced agricultural productivity, they simultaneously risk degrading the ecological basis upon which agriculture depends. This paper considers chemicalisation as a cause of the erosion of aquatic biodiversity and ecosystem resilience, focusing on the Hawkesbury-Nepean River and the small-scale horticulturalists who supply the city's fresh vegetable markets, working under the pressure of urbanisation, retail monopolies, indifferent land-use planning, and often without access to information about pesticide use in the languages they understand. Arguing that standard practices of ‘risk management’ are unable to adequately control chemical contamination, the paper presents findings from interviews with actors within the ‘assemblage’ of institutions with responsibility for agriculture, water quality, and environmental protection, in order to assess the effectiveness of pesticide governance in the Greater Sydney Basin. It appears that pesticide pollution is far from being tamed: it is rarely measured nor monitored, neither is it a priority of any particular agency. Arguing that public health, the long-term viability of local farming and the ecological well-being of the Hawkesbury-Nepean River are mutually consistent goals, we conclude that these vital elements of the common-weal are currently subject to a system of ‘organised irresponsibility’. The paper concludes by proposing several ways forward.  相似文献   

Economic diversification and second‐tier political conflict: Assessing bitumen political ecologies in southwest Nigeria     

Godwin Uyi Ojo 《Singapore journal of tropical geography》2012,33(1):49-62

Since its emergence as a research field in the 1980s, political ecology has provided a useful tool to explicate violent environments, notably as hallmarks of natural resource‐dependent economies. Practitioners regularly address what might be called ‘charismatic’ natural resources such as oil and other precious minerals to describe contestation over access and control of natural resources. Yet, where this focus exists, the political ecology of less economically valuable or ‘noncharismatic’ resources is thereby obscured. Thus, Nigeria's dependency on oil production has generated much scholarly attention with its unstable political economy described as a rentier state. In contrast, this paper draws on extensive field experience and knowledge about the country to assess in a preliminary manner some of the dimensions and ramifications of a less well known second‐tier natural resource commodity that is gaining attention as part of a possible national economic diversification strategy. Using the case of bitumen, a viscous hydrocarbon mainly used in road surfacing and roofing work, I assess the trajectory of this relatively overlooked resource, thereby opening a window onto the political ecology of a noncharismatic resource. In contrast to the ubiquitous violence in the oil‐based Niger Delta, I suggest that bitumen political ecologies, while also provoking political conflict and debate, nonetheless seem to being marked by new power dynamics that might augur a less violence prone path in terms of Nigeria's political economy of natural resource production.  相似文献   

1947～2007年上海中心城区居住空间分异变化——基于居住用地类型视角   总被引：4，自引：2，他引：2  

廖邦固  徐建刚  梅安新 《地理研究》2012,31(6):1089-1102

采用4种分异度测度模型,在街坊尺度和乡镇尺度下,对上海中心城区1947～2007年11个时相的各类居住用地空间分异程度进行计算。发现1949年后各类居住用地分异度呈现不同的波动过程。不同时期居住用地总体分异程度的计算表明,1949年前空间分异严重,计划经济时期有所降低,转型期则又明显上升。不同时期居住用地等级高低与其分异度大小呈现不同的结构特征,1949年前高等级居住用地分异度高、中低等级居住用地分异度较低,形成"一高两低"结构;计划经济时期则是居住用地等级越高,分异度越大的"正相关"结构;90年代后则是最高和最低等级的居住用地分异度高,而中等居住用地分异度最低的"V"型结构。不同时期居住用地空间分异结构特征间的演进,直接原因是新式住宅的建设和旧城的改造,深层次原因则是土地使用制度的变迁和城市空间组织模式的转变。  相似文献   

Calibration and validation of a model of forest disturbance in the Western Ghats,India 1920–1990     

Robert?Gilmore PontiusJr.Email author  Pablo?Pacheco 《GeoJournal》2004,61(4):325-334

This paper introduces a new statistical method that we recommend should become standard procedure to quantify the goodness-of-fit of calibration and validation for land-use change models. We present a multiple-resolution Relative Operating Characteristic (ROC) that measures the goodness-of-fit between a reference map, which is considered reality, and a simulated map, which is a model’s output. This proposed ROC is based on: (1) multiple-resolutions, (2) soft classification, (3) sampling without replacement, and 4) explicit separation of factors of quantity versus location of land-use change. We illustrate the method with a case study in India’s Western Ghats, a biodiversity hotspot, where we have maps of cumulative forest disturbance for 1920 and 1990. We use a predictive modeling approach similar to GEOMOD in which we calibrate the model with the map of 1920, then predict the map of 1990, at which point we subject the model to validation. We show that the fit of calibration tends to be much larger than the fit of validation. Thus if a modeler assess a model by goodness-of-fit of calibration only, then the modeler will likely be over confident in the model’s predictive ability.  相似文献