通榆县2000-2014年沙质及盐碱质荒漠化监测     

邵婷婷  姜琦刚 《世界地质》2018,37(1):296-301

利用landsat7、landsat5和landsat8三期遥感影像,对通榆县2000-2014年沙质及盐碱质土地荒漠化变化进行监测。研究结果表明：①研究区荒漠化程度有减轻趋势,荒漠化等级与面积以及破碎程度虽个别有小幅度改变与上升,但整体呈现优化与下降趋势;②整体破碎度指数在2000-2007年由4.57 km2变为5.46 km2,2014年降为3.17 km2,说明研究区2014年荒漠化分布较为破碎零散,连通性较差,而2007年分布较为集中;③质心分布图表明通榆县研究年限内各类型荒漠化质心的位移轨迹呈现出先向东北平移再向南平移的趋势。  相似文献   

Community structure of epibenthic meiofauna in the St. Lucia Estuarine Lake (South Africa) during a drought phase     

D. Pillay  R. Perissinotto 《Estuarine, Coastal and Shelf Science》2009

The St. Lucia Estuary is Africa's largest estuarine system. It is a major component of the iSimangaliso (formerly Greater St. Lucia) Wetland Park, which was declared a World Heritage Site in 1999. The system has been severely affected by drought conditions which have culminated in the mouth of the system being cut off from the Indian Ocean since June 2002, for a period of almost five years. This study aimed to document the dynamics of meiofauna of the system during a drought phase, since (1) the effects of droughts on estuaries are poorly documented and understood and (2) because studies of meiofauna have never been undertaken in this system before. Meiofauna samples as well as physico-chemical data were collected at representative sites in February, April, August and October 2005. The drought had a major effect on the estuary, resulting in the development of hypersaline conditions (maximum 126 at Hells Gate), and to the complete evaporation of pelagic habitats, especially in the northern regions. The meiofauna of the St. Lucia Estuary was statistically separated into two distinct spatial clusters under drought conditions. The first cluster comprised sites in the Narrows and the southern region of South Lake, while the second comprised sites in the northern regions of South Lake and False Bay. Meiofauna of cluster 1, which was least affected by the drought, comprised nematodes, polychaetes, copepods, amphipods and ostracods, all of which accounted for 97% of meiofauna in this cluster. Cluster 2 on the other hand, which was more severely affected by the drought, was dominated by nematodes and copepods, which cumulatively contributed 97% to meiofauna in this group. Taxonomic richness and diversity of meiofauna were positively correlated with water depth, while abundance was inversely correlated with water temperature. The major effects of low water levels on the meiofauna of the system occurred through a negative impact on diversity and taxonomic richness, resulting in assemblages dominated by taxa most physiologically suited to such conditions. Secondly, at the peak of the drought, there was discontinuous water flow in the St. Lucia Estuary, resulting in parts of the northern and southern regions of the system being fragmented. This could have prevented the spread of meiofaunal taxa between the different basins of the system, and also explains the spatial separation of meiofauna into distinct clusters within the estuary.  相似文献   

Fragmentation of Leonids in space and a model of spatial distribution of meteoroids within the Leonid stream     

J. Tóth  J. Klačka 《Earth, Moon, and Planets》2004,95(1-4):181-186

The contribution presents an analysis of the Leonids 1999 HDTV Leonid MAC data. The observed grouping of the Leonids over a random level is explained by progressive fragmentation of meteoroids in space. The observed data are compared with a spatial distribution model. Possible fragmentation processes of meteoroids in space are presented and discussed.  相似文献   

THE MODELING OF BOLIDE TERMINAL EXPLOSIONS     

G. A. Tirskiy  D.Yu. Khanukaeva 《Earth, Moon, and Planets》2004,95(1-4):513-520

The phenomenon of terminal thermal explosions of bolides is considered and mathematically modeled, using the mechanisms of ablation and fragmentation due to mechanical and thermal stresses. The definition and criterion of thermal explosions are given. An analytical solution is obtained for the model of ablating and mechanically fragmenting meteoroid motion in the atmosphere. Numerical calculations including the terminal stage of the motion are fulfilled for the Tunguska parameters. They demonstrated a very rapid energy loss, corresponding to the terminal flare and full mass loss, explaining the absence meteorites.  相似文献   

湿地景观结构遥感动态变化分析     

张志锋  王丽华  石爱军  李建军  陶蕾  董雷 《地球信息科学学报》2006,8(2):17-23

景观镶嵌结构是景观异质性的重要表现,同时又是各种生态过程在不同尺度上作用的结果。本文以北京市野鸭湖湿地自然保护区为区域背景,以RS、GIS和GPS为技术手段,监测获取了1996-2002年研究区域湿地土地利用／土地覆盖景观空间格局变化,探讨了土地利用/土地覆盖景观空间格局变化对湿地环境的影响。故此,对1998-2000年和2000-2002年湿地资源景观镶嵌结构的动态变化进行详细分析。结果表明:(1)利用遥感信息多尺度、多时相、多波段的特点,在GIS、GPS技术的支持下,能够快速及时准确地反映湿地景观类型的动态变化,为湿地资源监测、保护与利用提供科学依据。(2)借助景观生态学中的相关原理,通过景观空间格局计算模型解释不同类型湿地景观的分布、变化,剖析湿地景观演化机制,为湿地景观规划与评价服务。(3)分析认为,野鸭湖湿地景观格局发生了较大的变化,水域面积减少严重,耕地面积增长幅度不高,旅游用地和堤坝面积明显增加。(4)湖泊和沼泽草甸是控制和影响湿地景观格局的主体。野鸭湖整个湿地景观的破碎化程度降低,人类活动干扰湿地在不断减弱,湿地景观异质性在逐渐降低,斑块之间的连通性提高,生境斑块相互之间的隔离度大大减少,湿地景观趋向稳定。  相似文献   

地理探测器方法下甘肃白龙江流域景观破碎化与驱动因子分析   总被引：6，自引：0，他引：6  

张金茜  巩杰  柳冬青 《地理科学》2018,38(8):1370-1378

基于GIS技术、景观格局指数、主成分分析和地理探测器的方法,定量分析了1990~2014年甘肃白龙江流域的景观破碎化及其驱动因子。结果表明：1990~2014年甘肃白龙江流域景观破碎化程度先增加后降低;研究期间流域东南部的景观指数变化最为剧烈和复杂,主要是文县和武都区;人类干扰（人类活动强度和土地利用类型）和地形因子（高程、坡度和坡向）对景观破碎化空间分异的影响显著不同,其中人类干扰是景观破碎化空间分异的主要驱动因子。  相似文献   

Determinants of microregional agricultural labour productivity – Evidence from Czechia     

《Applied geography (Sevenoaks, England)》2016

In this paper we aimed to explain differences in agricultural labour productivity at microregional level. We tested the effects of three major independent variables – farmland fragmentation, urbanization economies and farm size structure with particular emphasis on the relationship between land-use fragmentation and microregional differences in agricultural labour productivity. Our principal question therefore was if higher agricultural labour productivity at microregional level is associated with internal scale economies resulting from large average farm size (in terms of employment), proximity to large cities as a proxy for urbanization economies and lower levels of land-use fragmentation. We also asked if productivity gains from large average size of plots is higher than potential losses resulting from land tenure (tenants are generally less productive than farmland owners). Drawing on a case study of Czechia – a country with extremely fragmented farmland ownership, but the largest average size of plots in the EU and a strong role of farmland rental market – we confirmed our initial expectation that land-use fragmentation affects negatively microregional agricultural labour productivity. Larger average size of plots is positively related to microregional agricultural labour productivity despite potentially negative effects of land tenure. At the same time, no significant effects of urbanization economies and farm size structure were documented.  相似文献   

基于农户视角的耕地细碎化程度评价——以湖北省“江夏区—咸安区—通山县”为例   总被引：4，自引：1，他引：3  

文高辉  杨钢桥  汪文雄  赵微 《地理科学进展》2016,35(9):1129-1143

农户是耕地最主要的经营主体,基于农户视角构建耕地细碎化程度评价指标体系更为合理。本文选取湖北省“江夏区—咸安区—通山县”作为研究区域,采用改进的TOPSIS法,利用农户问卷调查数据,对耕地细碎化程度评价进行了实证研究。结果表明：①耕地细碎化程度衡量指标的选取应基于耕地细碎化的属性特征,从农户微观视角,选取地块平均面积、地块数量、地块间的平均距离3个指标,衡量某一区域的耕地细碎化程度;②耕地细碎化在岗地平原地区与低山丘陵地区间存在显著差异,岗地平原地区的耕地细碎化程度低于低山丘陵地区;③研究区域地形地貌呈现出“北部岗地平原—南部低山丘陵”的分布特征,耕地细碎化的综合程度基本上呈现出“北部低—南部高”的分布规律;④在不同经济发展水平地区耕地细碎化存在显著差异,在岗地平原地区,经济发展水平越高的地区,耕地细碎化程度越高;而在低山丘陵地区,经济发展水平越高的地区,耕地细碎化程度越低。  相似文献   

Linked to Landscape: Assessing Urbanization in Germany through Landscape and Economic Factors     

Rose Keller  Colin Vance 《The Professional geographer》2017,69(3):424-437

The ongoing encroachment of urban land into natural landscapes has resulted in the degradation of ecosystems throughout Europe. Understanding why the share of urban land has increased is important for managing urban growth and maintaining ecosystem services. We estimate a model of landscape change that integrates geospatial and socioeconomic data in a spatial autoregressive model to explain the variance in urban growth observed in Germany between 2000 and 2006. In doing so, we test several determinants of urbanization identified by theoretical frameworks from landscape ecology and economics, including landscape pattern and transit infrastructure. The results show that despite planning guidelines and policies to promote dense development, urban growth has been extensive. Regions with a high degree of fragmented land and the prevalence of environmental amenities are characterized by particularly strong growth, pointing to challenges in crafting landscape policies that balance economic development with environmental conservation.  相似文献   

Planning restoration in human-modified landscapes: New insights linking different scales     

《Applied geography (Sevenoaks, England)》2017

The transformation of tropical ecosystems by humans have resulted in forest loss, which, in turn, have caused negative impacts on biodiversity and the provisioning of ecosystem services. There is an urgent need to plan the restoration of these human-modified landscapes, using methodological approaches that consider key processes occurring at different spatial scales while engage local community participation, offering them the best possibilities of tangible benefits. In this study, was evaluated the landscape spatial pattern and local conservation status of existing forest remnants, showing an analysis of possible restoration scenarios for a human-modified landscape in La Montaña, an indigenous region in southwestern Mexico. Therefore, landscape and local scale approaches were linked to identify specific landscape elements where efforts to improve connectivity must be concentrated. Also, this approach allowed finding a set of species from reference sites that showed the best socioecological characteristics to be used in different restoration strategies. As expected, La Montaña region showed a spatial pattern typical of highly human-modified landscapes, i.e., several small (<21 ha) and irregular forest remnants with strong forest edge effects. Furthermore, these small and irregular forest fragments displayed forest structure, diversity and composition characteristics similar to those communities disturbed by selective harvesting or in an early successional phase. However, about 100 of woody species were found inside the fragments, some with important potential to provide ecosystem services. The landscape connectivity was very low, and an analysis of possible restoration scenarios showed that is equally important to restore the productive areas as well as open forest, to recover up to 47% of landscape connectivity. In this sense, it was proposed a productive restoration strategy to enrich open forests and create biodiversity-friendly habitat in agricultural areas, using species with high socioecological potential. We believe that the same approach could be applied to other highly human-modified tropical landscapes with similar socioecological problems.  相似文献