共查询到20条相似文献，搜索用时 656 毫秒
1.
Amrita G. de Soyza Justin W. Van Zee Walter G. Whitford Anne Neale Nita Tallent-Hallsel Jeffrey E. Herrick Kris M. Havstad 《Journal of Arid Environments》2000,45(4):289
Early-warning indicators of rangeland health can be used to estimate the functional integrity of a site and may allow sustainable management of desert rangelands. The utility of several vegetation canopy-based indicators of rangeland health at 32 Great Basin rangeland locations was investigated. The indicators were originally developed in rangelands of the Chihuahuan Desert. Soil resources are lost through wind and water-driven erosion mainly from areas unprotected by plant canopies (i.e. bare soil). Study sites in Idaho had the smallest bare patches, followed by sites in Oregon. The more arid Great Basin Sagebrush Zone sites in Utah had the largest bare patches. Several vegetational indicators including percent cover by vegetation, percent cover by life-form, percent cover by sagebrush, and percent cover by resilient species were negatively related to mean bare patch size and are potential indicators of Great Basin rangeland condition. Plant community composition and the range of bare patch sizes were different at sites in the three locations in Idaho, Oregon and Utah. Therefore, expected indicator values are location specific and should not be extrapolated to other locations. The condition of study sites were often ranked differently by different indicators. Therefore, the condition of rangeland sites should be evaluated using several indicators. 相似文献
2.
T. K. Alexandridis T. Katagis I. Z. Gitas N. G. Silleos K. M. Eskridge G. Gritzas 《International journal of geographical information science》2013,27(4):507-521
Monitoring vegetation condition is an important issue in the Mediterranean region, in terms of both securing food and preventing fires. Vegetation indices (VIs), mathematical transformations of reflectance bands, have played an important role in vegetation monitoring, as they depict the abundance and health of vegetation. Instead of storing raster VI maps, aggregated statistics can be derived and used in long-term monitoring. The aggregation schemes (zonations) used in Greece are the forest service units, the fire service units, and the administrative units. The purpose of this work was to explore the effect of the modifiable areal unit problem (MAUP) in vegetation condition monitoring at the above-mentioned aggregation schemes using 16 days Normalized Difference Vegetation Index (NDVI) composites acquired by the moderate resolution imaging spectroradiometer satellite sensor. The effects of aggregation in the context of MAUP were examined by analyzing variance, from which the among polygon variation (objects' heterogeneity) and the within polygon variation (pixels' homogeneity) were derived. Significant differences in objects' heterogeneity were observed when aggregating at the three aggregation schemes; therefore there is a MAUP effect in monitoring vegetation condition on a nationwide scale in Greece with NDVI. Monitoring using the fire service units has significantly higher pixels' homogeneity; therefore there is indication that it is the most appropriate for monitoring vegetation condition on a nationwide scale in Greece with NDVI. Results were consistent between the two major types of vegetation, natural and agricultural. According to the statistical validation, conclusions based on the examined years (2003 and 2004) are justified. 相似文献
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Robert G. Cromley Jie Lin David A. Merwin 《International journal of geographical information science》2013,27(3):495-517
A common problem in location-allocation modeling is the error associated with the representation and scale of demand. Numerous researchers have investigated aggregation errors associated with using different scaled data, and more recently, error associated with the geographic representation of model objects has also been studied. For covering problems, the validity of using polygon centroid representations of demand has been questioned by researchers, but the alternative has been to assume that demand is uniformly distributed within areal units. The spatial heterogeneity of demand within areal units thus has been modeled using one of two extremes – demand is completely concentrated at one location or demand is uniformly distributed. This article proposes using intelligent areal interpolation and geographic information systems to model the spatial heterogeneity of demand within spatial units when solving the maximal covering location problem. The results are compared against representations that assume demand is either concentrated at centroids or uniformly distributed. Using measures of scale and representation error, preliminary results from the test study indicate that for smaller scale data, representation has a substantial impact on model error whereas at larger scales, model error is not that different for the alternative representations of the distribution of demand within areal units. 相似文献
6.
Participatory selection process for indicators of rangeland condition in the Kalahari 总被引：2，自引：0，他引：2
To develop indicator–based management tools that can facilitate sustainable natural resource management by non–specialists, meaningful participation of stakeholders is essential. A participatory framework is proposed for the identification, evaluation and selection of rangeland condition indicators. This framework is applied to the assessment of rangeland degradation processes and sustainable natural resource management with pastoralists in the southern Kalahari, Botswana. Farmer knowledge focused on vegetation and livestock, with soil, wild animal and socio–economic indicators playing a lesser role. Most were indicators of current rangeland condition; however 'early warning' indicators were also identified by some key informants. This demonstrates that some local knowledge is process–based. Such knowledge could be used to improve indicator–based management tools and extension advice on the livelihood adaptations necessary to prevent or reduce ecological change, capable of threatening livelihood sustainability. There is evidence that social background influences indicator use. Communal farmers rely most heavily on vegetation and livestock indicators, whilst syndicate and land–owning pastoralists cite wild animal and soil–based indicators most frequently. These factors must be considered if indicator–based management tools are to meet the requirements of a diverse community. 相似文献
7.
Spatio-temporal analysis of the geographical centroids for three major crops in China from 1949 to 2014 总被引：3，自引：1，他引：2
Lingling Fan Shefang Liang Hao Chen Yanan Hu Xiaofei Zhang Zhenhuan Liu Wenbin Wu Peng Yang 《地理学报(英文版)》2018,28(11):1672-1684
Spatial distribution changes in major crops can reveal important information about cropping systems. Here, a new centroid method that applies physics and mathematics to spatial pattern analysis in agriculture is proposed to quantitatively describe the historical centroids of rice, maize and wheat in China from 1949 to 2014. The geographical centroids of the rice area moved 413.39 km in a 34.32° northeasterly (latitude 3.08°N, longitude 2.10°E) direction at a speed of 6.36 km/year from central Hunan province to Hubei province, while the geographical centroids of rice production moved 509.26 km in the direction of 45.44° northeasterly (latitude 3.22°N, longitude 3.27°E) at a speed of 7.83 km/year from central Hunan province to Henan province. The geographical centroids of the maize area and production moved 307.15 km in the direction of 34.33° northeasterly (latitude 2.29°N, longitude 1.56°E) and 308.16 km in the direction of 30.79° northeasterly (latitude 2.39°N, longitude 1.42°E), respectively. However, the geographical centroids of the wheat area and production were randomly distributed along the border of Shanxi and Henan provinces. We divided the wheat into spring wheat and winter wheat and found that the geographical centroids of the spring wheat area and production were distributed within Inner Mongolia, while the geographical centroids of winter wheat were distributed in Shanxi and Henan provinces. We found that the hotspots of crop cultivation area and production do not always change concordantly at a larger, regional scale, suggesting that the changing amplitude and rate of each crops’ yield differ between different regions in China. Thus, relevant adaptation measures should be taken at a regional level to prevent production damage in those with increasing area but decreasing production. 相似文献
8.
民勤土地利用格局时空变化研究 总被引：6，自引：2，他引：4
应用1987年和2010年两期TM遥感数据,在GIS技术的支撑下,解译提取民勤县土地利用类型空间分布信息,用FRAGSTATS3.3软件计算斑块类型和景观两个层次的7个景观格局指数,分析民勤县土地利用类型空间转化特点和质心转移趋势。结果表明：（1）23年间,民勤县土地利用类型转换明显,戈壁、耕地面积增加,草地面积减少,林地部分退化。（2）土地类型多样性和均匀度减小、聚集度增加,表明人类活动对民勤县土地利用影响大,土地利用结构受个别土地类型影响程度加深、稳定性下降。（3）民勤县土地利用质心整体向西南方向偏移,沙漠、耕地质心向西南方向偏移明显,沙进人退的趋势显著。 相似文献
9.
Thomas G. Measham 《The Australian geographer》2007,38(2):145-159
Community-based natural resource management (CBNRM) continues to attract interest as a way of achieving social and environmental outcomes at the local and regional scale. Central to the success of CBNRM is the importance of capacity building and participatory approaches to research and management. This paper discusses an initiative in East Gippsland which involved a facilitated process to assist local residents build their capacity to manage their landscape. Through conducting a community survey, the project facilitated landholders to voice, develop and refine their understanding of remnant vegetation management, dieback and revegetation on private land. In doing so, landholders have improved not only their understanding of the issues but also their ability to act upon them. The empirical findings of the study highlight two issues of relevance to dieback on the East Gippsland Red Gum Plains. First, there is a perception that dieback has remained stable for at least 10 years. Second, scattered trees and small patches of trees are more vulnerable to dieback than clumped trees in larger patch sizes, as well as roadside vegetation. The research demonstrates the value of a community-based approach to NRM in terms of harnessing local knowledge, fostering human and social capital and engaging with interested landholders. 相似文献
10.
自然灾害对重庆土地资源可持续利用的影响及对策 总被引：8，自引：1，他引：7
重庆作为多种自然灾害主要是气象和山地灾害的多发区,其土地资源可持续利用中存在着许多自然灾害限制因子。伴随着经济的发展、人口的激增与城市化的加速．人类对土地资源的粗放式、掠夺式利用也不断变本加厉,从而诱发和加剧了潜在的自然灾害,而自然灾害的发生又反作用于土地利用,使其现有的生产力下降。文章在分析自然灾害与土地资源利用的相互作用机制的基础上,针对重庆市土地资源利用现状与自然灾害特征,提出了土地资源可持续利用对策。 相似文献
11.
随着社会经济的快速发展,资源短缺对中国经济的瓶颈作用越来越强烈。作为世界上最大的发展中国家,中国的资源环境现状面临严峻挑战。中国虽然资源总量丰富,但是人均资源量少、结构失衡,多年来以资源环境的大量投入不仅严重破坏了资源基础,更加重了环境恶化的趋势。总体来看,目前中国在资源生产和消费过程中主要存在资源利用效率低下、产品质量不过关、生产集约程度不足、生产和消费失衡以及生产与资源分布不吻合、资源管理不完善等方面的问题,要维持未来中国资源的有效供给,需要建立自然资源开发利用从宏观到微观的统一管理机制,强化机制的综合协调功能,因此我国资源节约型经济的基本模式应是：（（消费节省+生产集约）×（政府干预+市场调节））×科技教育。为此,中国资源节约战略可以考虑通过发展循环经济、推进国家资源加工深度化进程、加强资源管理和提高环保意识等措施进行。 相似文献
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《Singapore journal of tropical geography》2018,39(1):45-61
Decentralization of governance and natural resource management is an ongoing process in many parts of Africa and Asia. Natural resource management requires spatial land resource data for planning. However, currently the financial and human capacity for natural resource mapping, monitoring and modelling remains low in local governments. In this context, this paper explores how new opportunities provided by the increasing availability of free satellite imagery, digital elevation data and open source spatial analysis software, can be applied by local government and NGOs to conduct sophisticated natural resource mapping and modelling in ways that meet their needs and incorporates local knowledge. Reported are cases of a local government using free geospatial data and GIS software to improve evidence‐based natural resource management in the developing world with a focus on raster data applications for satellite image analysis and terrain modelling. It is argued that, through removing barriers to uptake, such applications provide a means of decentralizing landscape analysis skills to improve local natural resource management. This hypothesis is supported through examples of a local government applying these tools in eastern Indonesia, and within this context barriers to wider adoption are explored. 相似文献
13.
三江平原别拉洪河流域湿地农田化过程研究 总被引：10，自引：6，他引：10
自20世纪50年代以来,三江平原的别拉洪河流域在经历了3次大规模开荒后,大面积的湿地被农田所替代,耕地面积迅速增加,湿地农田化过程干扰和破坏了原有的湿地环境。在遥感和地理信息系统技术支持下,应用景观生态学方法,利用1954年、1976年、1986年、2000年和2005年的土地利用数据,分析了研究区近50 a来的湿地农田化过程。结果显示,湿地农田化过程中大面积的湿地斑块被农田斑块所取代,破碎化的小耕地斑块又逐渐合并为大的耕地斑块,并导致斑块形状复杂度指数逐渐增大,景观均匀度指数呈现波动变化;耕地面积在1954~1986年期间增长幅度较大,特别是在20世纪70年代末和80年代初的改革开放初期,研究区景观动态度为0.201,远高于其它时期;目前,农田景观已成为主要景观类型,农田面积占研究区总面积的63.69%,湿地面积占研究区总面积的比例由1954年的64.83%减小到2005年的19.44%。质心模型的分析结果显示,近50 a来研究区耕地景观质心平移幅度明显大于湿地景观,湿地景观质心不断地向东北方向移动,偏移了约20.5 km,而农田景观质心逐渐向东平移,平移了约44.7 km。农业开垦是研究区湿地大面积消退的主要原因。 相似文献
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GIS goes nano: Vegetation studies in Victoria Land, Antarctica 总被引：1，自引：0，他引：1
Abstract: Vegetation in Antarctica consists mainly of algae, moss and lichen and is interesting to research because of the isolation and extreme growing conditions. An understanding of this vegetation is important for both the management of tourism in Antarctica, and because it provides a potential barometer of global climate and environmental change. This paper demonstrates two applications of GIS to mapping vegetation in Victoria Land, Antarctica. The first application computes the changes that have occurred to the vegetation within a 120 m by 28 m plot between 1962 and 2004. The second application maps and analyses the growth of a lichen specimen (Buellia frigida) during the same period. These applications demonstrate that GIS is a multiscale technology that can be used to detect detailed change in vegetation growth. 相似文献
15.
多边形是GIS研究和应用中使用最频繁的几何对象,该文描述了基于简单要素模型的任意多边形分割算法。从计算几何出发,结合GIS空间数据的特点,将基于简单要素模型的多边形分割算法设计为:1)对多边形及分割线的边界排序,基于扫描线及外包矩形检测查找可能相交的线段,提高相交线段的搜索效率;2)计算交点生成结点信息(包括交点坐标、线号及交点的出入),并存储在独立的单向链表中;3)根据结点链表和原多边形坐标搜索结果多边形。该算法能够分割任意简单多边形(凹凸、曲线边界和带洞的多边形)以及有共享边的多边形。最后在MapGIS7.0平台上,实现了基于简单要素类的多边形分割功能。 相似文献
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Simon Bolwig Derek Pomeroy Herbert Tushabe David Mushabe 《Geografisk tidskrift / udgivet af Bestyrelsen for Det Kongelige danske geografiske selskab》2013,113(2):115-130
Geografisk Tidsskrift, Danish Journal of Geography 106(2): 115–130, 2006 This paper examines the relationship between the intensity of agricultural land use and the abundance and richness of trees and birds in a humid tropical developing region where natural vegetation is being rapidly converted into farmland under market and population pressures. We analysed survey data on land use, birds and woody plants collected in 14 study sites situated within smallholder cropland and commercial plantations in southern Uganda. Commercial plantations had very few trees and only 10% of the original bird species. Land use intensification in smallholder systems also showed losses in bird abundance and species richness, but not nearly as much as in plantations. In both systems the impact of intensification was much bigger on the specialised and threatened birds compared to the less specialised species. This argues strongly for ‘species-sensitive’ conservation policies combining protected areas with land use regulation in areas undergoing intensification. We also found a much higher loss in bird biodiversity during the first phases of land use intensification (when larger tracts of forest are cleared) than in later phases characterised by clearing of smaller patches of vegetation and improved management of farm trees. This suggests high pay-offs to geographical targeting of conservation efforts in farmed landscapes. 相似文献
17.
Floodplains are multi-state systems in which vegetation distribution is associated with the presence or absence of water as a resource. Less is known about the associations between the presence and absence of water and vegetation productivity. We examined patterns of vegetation productivity in a large (10 519 km2) unconfined floodplain during flood, rain and dry resource states. Mosaics of vegetation greenness were derived at two scales using the Normalized Difference Vegetation Index: a whole-of-landscape scale and a geomorphic unit scale with a riparian and floodplain unit. The NDVI was also calculated within a-priori vegetation community types within the floodplain. In all resource states over 50% of the floodplain showed no discernible vegetation greenness. When water is added as rain or flooding vegetation greenness increases, but the highest greenness occurs in the flood state. Trees situated in the riparian geomorphic unit maintain greenness during the dry resource state, whereas grasses situated in the floodplain contribute greenness during rain and flood resource states, with the highest greenness in the flood resource state. Aligned with views that dryland floodplains are boom-bust ecosystems, we suggest that flooding is a fundamental driver of vegetation productivity in this unconfined floodplain, contributing functional heterogeneity to the landscape. 相似文献
18.
We recover the gross space–time characteristics of high-frequency (HF) radiator of the great Sumatra-Andaman islands earthquake of 2004 December 26 ( M w = 9.1–9.3) using the time histories of the power of radiated HF P waves. To determine these time histories we process teleseismic P waves at 36 BB stations, using, in sequence: (1) bandpass filtering (four bands: 0.4–1.2, 1.2–2, 2–3 and 3–4 Hz); (2) squaring wave amplitudes, making 'power signals' for each band and (3) stripping the propagation-related distortion ( P coda, etc.) from the power signal and thus recovering source time function for HF power. In step (3) we employ an inverse filter constructed from an empirical Green's function, which is estimated as the power signal from an aftershock. For each ray we thus obtain signals with relatively well-defined end and no coda. From these signals we extract: total duration (joint estimate for all four bands) and temporal centroid of signal power for each band. Through linear inversion, the set of duration values for a set of rays delivers estimates of the rupture stopping point and stopping time. Similarly, the set of temporal centroids can be inverted to obtain the position of the space–time centroid of HF energy radiator. The quality of inversion for centroid is acceptable for lower-frequency bands but deteriorates for higher-frequency bands where only a fraction of stations provide useful data. For the source length and duration the following joint estimates were obtained: 1241 ± 224 km, 550 ± 10 s. The estimated stopping point position corresponds to the northern extremity of the aftershock zone. Spatial HF radiation centroids are located at distances 350–700 km from the epicentre, in a systematic way: the higher is the frequency, the farther is the centroid from the epicentre. Average rupture propagation velocity is estimated as 2.25 km s–1 . 相似文献
19.
Symbols, not data: rare trees and vegetation history in Mali 总被引：1，自引：0，他引：1
Chris S Duvall 《The Geographical journal》2003,169(4):295-312
Historical analysis of botanical literature concerning the trees Gilletiodendron glandulosum and Guibourtia copallifera in Mali's Manding Plateau reveals that the dominant representation of these plants has helped to perpetuate colonial-era theories of vegetation history, African land management, and natural resource politics in West Africa. The French botanist Aubréville described these plants as proof of the theory of vegetation history that blamed poor land management by rural Africans for a steady and continuing destruction of vegetation from its presumed original forest climax. Although Aubréville's representation of these trees was justified within the 1930s scientific context he worked, subsequent researchers uncritically maintained his conclusions even though the changed scientific context in which they worked did not justify such representation. Subsequent ecological research also failed to substantiate Aubréville's representation of these trees, yet several influential modern botanical works have uncritically accepted colonial-era botanical literature founded on his ideas. Thus, modern botanical works have perpetuated a simplistic and inaccurate narrative of resource use under an appearance of objectivity. As a result, policy recommendations based on the modern botanical sources remain almost identical to colonial-era policies. Based on the similarity of colonial-era and modern portrayals of these trees, this paper argues that a regional discursive formation recently described by other authors may be expanded to include southern Mali, which carries negative implications for decentralization reform in Mali. 相似文献
20.
Hui Xu Daniel G. Brown 《International journal of geographical information science》2017,31(4):738-762
Land-use/cover change (LUCC) projections can be generated by a variety of land-cover change models (LCMs) and applied to a range of ecological and environmental studies. Most existing spatially explicit LCMs represent land use or cover using either pixel or polygon/patch spatial units. However, the effects of the choice to use pixel versus polygonal land units on the outputs from any given model have not yet been systematically assessed. We evaluated the impacts of alternative land units on the performance of a LCM. A stochastic LCM based on a geostatistical algorithm was developed and applied using both pixel and polygons, which were derived from parcel maps. Nine possible parcel-change scenarios were generated to evaluate the effects of geometric change in management boundaries. The approach was tested through the simulation of multiple land-cover transitions in Medina County, Ohio, between 1992 and 2011. Performance of the simulations was assessed using a metric for the accuracy of spatial allocations (figure of merit (FoM)) and several landscape pattern metrics describing the shapes and sizes of resulting land-cover patches. Results support the notion that there is a clear trade-off between pixel and polygon land units: using polygon boundaries is helpful in obtaining more realistic spatial patterns, but at the cost of location accuracy. Significant differences were found among different parcel-change scenarios on both location accuracy and spatial patterns, with the primary effects being dependent on the type of land-cover transition and the resolution at which validation was assessed. 相似文献