乌兰布和沙漠不同土地覆被类型粒度特征及空间分异

对中国沙尘暴源区之一的乌兰布和沙漠进行系统采样,分析不同土地覆被类型的地表沉积物粒度特征及其空间分异规律。结果表明：乌兰布和沙漠地表沉积物以中沙和细沙为主,平均粒径为2.84 φ。沙漠地表沉积物的粒度特征在不同土地覆被类型和不同空间存在明显的分异规律,表明该沙漠的地表沉积物粒度分布是由物源、地形和搬运营力共同作用的结果。乌兰布和沙漠内部最可能成为沙尘暴尘源的有沙漠中部的盐碱地、东北部的耕地和广泛存在于沙漠中的沙丘。根据不同区域的土地覆被类型因地制宜地选取先锋植物种群改善区域地表覆盖状况和地表沉积物粒度组分,是该区域尘源治理的主要手段。     

广州市城乡交错带土地覆被景观格局时空分异

基于1990、1995、2000和2005年覆盖广州市南部拓展区的LandsatTM遥感影像,经监督分类和人工目视解译获得研究区各时相土地覆被景观图。选取景观指数指标对研究区的景观格局和动态变化进行研究,并利用缓冲区技术研究分析各时期内景观特征的梯度方向分异。结果表明:广州市南部拓展区在15年间景观格局发生了重大变化,该时期内景观的破碎化程度逐年增大,景观异质性先增后减,优势斑块呈分散趋势;耕地面积先减后增,总体呈下降趋势,而建筑用地面积则逐年上升;景观格局梯度分析显示区域景观格局存在方向上的梯度分异,反映大城市中心区不同辐射距离范围内城乡交错带的城市化发展差异。     

快速城市化过程中城市土地覆被的时空动态特征

1990—2005年间，是广州市经济快速发展和城市景观变化最大的时期，以同时段TM影像解译得到广州市的土地覆被类型图，从数量结构、空间信息及位置转移和景观等方面，分析了广州市土地覆被的动态特征．数量结构的研究结果显示：在快速城市化过程中广州市的耕地、林地等自然资源的利用程度在加大，自1995年起，这种变化的趋势开始减缓；土地覆被类型之间的信息与位置的转移变化频繁，并且表现出空间位置分异的特征．景观特征指数分析结果表明：广州市城市土地覆被向破碎化方向发展，城市建设用地呈扩展之势．     

1990 年以来广州市土地覆被景观的时空梯度分异

取1990 年、1995 年、2000 年和2005 年4 个时相覆盖广州市的TM 遥感影像为数据源, 经非监督分类及人工目视解译, 获得研究区各时相土地覆被类型图。以高速公路为轴线 应用缓冲区技术, 形成南北和东西两条样带, 同时以城市中心区域向外等距扩展而形成辐射状梯度圈。通过样带和梯度圈剪裁形成土地覆被类型图, 计算土地覆被类型图的景观指数, 分析广州市15 年间土地覆被动态过程, 揭示区域景观动态的方向和梯度分异特征。数量结构与样带研究结果表明: 广州市因经济发展而使土地覆被景观恶化的趋势已得到一定程度的遏制, 城市发展逐步进入理性控制阶段, 但是存在方向分异, 东西样带上的土地覆被景观的多样性持续下降, 斑块破碎化程度加剧; 辐射梯度圈研究结果显示, 向外围扩展的城市化过程使广州市呈现出多个次级中心的格局, 对城市土地覆被景观的干扰强度自中心城区向郊区递减, 方向分异不显著; 东南方向的辐射梯度圈内土地覆被景观的分维数和多样性指数变化特征表明, 自2000 年始, 经济发展已开始侵占南部海域。     

重庆喀斯特地区土地覆被类型对土壤特征的影响

1 Introduction The karst region of Southwest China, with Guizhou Province as the center, extends across Yunnan Province, Guangxi Zhuang Autonomous Region, Sichuan Province, Chongqing, western Hunan Province, Hubei Province, and Guangdong Province, coveri…     

快速城市化过程中城市土地覆被的时空动态特征

1990～2005年间,是广州市经济快速发展和城市景观变化最大的时期,以同时段TM影像解译得到广州市的土地覆被类型图,从数量结构、空间信息及位置转移和景观等方面,分析了广州市土地覆被的动态特征.数量结构的研究结果显示:在快速城市化过程中广州市的耕地、林地等自然资源的利用程度在加大,自1995年起,这种变化的趋势开始减缓;土地覆被类型之间的信息与位置的转移变化频繁,并且表现出空间位置分异的特征.景观特征指数分析结果表明:广州市城市土地覆被向破碎化方向发展,城市建设用地呈扩展之势.     

快速城市化过程中城市土地覆被的时空动态特征

1990~2005年间,是广州市经济快速发展和城市景观变化最大的时期,以同时段TM影像解译得到广州市的土地覆被类型图,从数量结构、空间信息及位置转移和景观等方面,分析了广州市土地覆被的动态特征.数量结构的研究结果显示:在快速城市化过程中广州市的耕地、林地等自然资源的利用程度在加大,自1995年起,这种变化的趋势开始减缓;土地覆被类型之间的信息与位置的转移变化频繁,并且表现出空间位置分异的特征.景观特征指数分析结果表明:广州市城市土地覆被向破碎化方向发展,城市建设用地呈扩展之势.     

黄河三角洲土地利用与土地覆被的质量变化

土地利用／土地覆被变化（LUCC）在全球环境变化与可持续发展研究中占有重要地位。其质量变化尤能反映人类开发活动的环境效应。运用遥感信息土地分类和植被指数提取、土壤定点采样实测和统计分析相结合的方法，研究了黄河三角洲地区数年至20余年的土地利用／土地覆被的质量变化。其在区域总体上向好的方向发展，但在内部地段间存在着差异和不平衡。盐渍土改造的任务仍然十分艰巨。地力下降的隐患不可忽视。进而分析了变化的驱动力并提出土地持续利用对策。     

USGCRP土地覆被研究的最新动向

本文根据美国全球变化研究委员会提出的“美国全球变化研究计划”（ＵＳＧＣＲＰ）,概要介绍了土地覆被研究的目标、内容和设想。由于美国在这一领域研究中的领先地位,因此本文基本反映了国际上的最新趋势。     

流域土地利用／土地覆被变化的生态效应

土地利用／土地覆被变化改变了地表生态系统组成结构,影响着生态系统功能,威胁着区域生态安全。本文以辽河流域的浑河-太子河流域为研究区,探讨了流域空间尺度上的LUCC特征及其所带来的生态效应。研究表明,不同的生态指标对LUCC的响应程度略有不同：（1）从景观生态格局角度看,反映生态系统斑块形状特征的景观指数对LUCC的响应...     

Vertical differentiation of land cover in the central Himalayas

Characterized by obvious altitudinal variation, habitat complexity, and diversity in land cover, the Mt. Qomolangma region within the central Himalayas is one of the most sensitive areas to climate change in the world. At the same time, because the Mt. Qomolangma region possesses the most complete natural vertical spectrum in the world, it is also an ideal place to study the vertical structure of alpine land cover. In this study, land cover data for 2010 along with digital elevation model data were used to define three methods for dividing the northern and southern slopes in the Mt. Qomolangma region, i.e., the ridgeline method, the sample transect method, and the sector method. The altitudinal distributions of different land cover types were then investigated for both the northern and southern slopes of the Mt. Qomolangma region by using the above three division methods along with Arc GIS and MATLAB tools. The results indicate that the land cover in the study region was characterized by obviously vertical zonation with the south-six and north-four pattern of vertical spectrum that reflected both the natural vertical structure of vegetation and the effects of human activities. From low to high elevation, the main land cover types were forests, grasslands, sparse vegetation, bare land, and glacier/snow cover. The compositions and distributions of land cover types differed significantly between the northern and southern slopes; the southern slope exhibited more complex land cover distributions with wider elevation ranges than the northern slope. The area proportion of each land cover type also varied with elevation. Accordingly, the vertical distribution patterns of different land cover types on the southern and northern slopes could be divided into four categories, with glaciers/snow cover, sparse vegetation, and grasslands conforming to unimodal distributions. The distribution of bare land followed a unimodal pattern on the southern slope but a bimodal pattern on the northern slope. Finally, the use of different slope division methods produced similar vertical belt structures on the southern slope but different ones on the northern slope. Among the three division methods, the sector method was better to reflect the natural distribution pattern of land cover.     

Vertical distribution changes in land cover between 1990 and 2015 within the Koshi River Basin,Central Himalayas

The study of mountain vertical natural belts is an important component in the study of regional differentiation.These areas are especially sensitive to climate change and have indicative function,which is the core of three-dimensional zonality research.Thus,based on high precision land cover and digital elevation model (DEM) data,and supported by MATLAB and ArcGIS analyses,this paper aimed to study the present situation and changes of the land cover vertical belts between 1990 and 2015 on the northern and southern slopes of the Koshi River Basin (KRB).Results showed that the vertical belts on both slopes were markedly dif-ferent from one another.The vertical belts on the southern slope were mainly dominated by cropland,forest,bare land,and glacier and snow cover.In contrast,grassland,bare land,sparse vegetation,glacier and snow cover dominated the northern slope.Study found that the main vertical belts across the KRB within this region have not changed substantially over the past 25 years.In contrast,on the southern slope,the upper limits of cropland and bare land have moved to higher elevation,while the lower limits of forest and glacier and snow cover have moved to higher elevation.The upper limit of alpine grassland on the northern slope retreated and moved to higher elevation,while the lower limits of glacier and snow cover and vegetation moved northward to higher elevations.Changes in the vertical belt were influenced by climate change and human activities over time.Cropland was mainly controlled by human activities and climate warming,and the reduced precipitation also led to the abandonment of cropland,at least to a certain extent.Changes in grassland and forest ecosystems were predominantly influenced by both human activities and climate change.At the same time,glacier and snow cover far away from human activities was also mainly influenced by climate warming.     

基于多期数据集的中亚五国土地利用/覆盖变化分析

针对目前中亚地区土地利用变化和分布格局方面的信息相对匮乏,现有资料较为陈旧且零散,无法满足中亚生态与环境变化研究需求的现状,利用全球的UMD, DISCover,GLC2000,GlobCover2005和GlobCover2009的5期土地覆被遥感数据集,提取中亚地区长时间序列土地覆被信息。并针对上述4个土地覆被分类系统无法进行直接对比和变化分析的问题,分别将其综合为4类土地覆被类型：耕地、自然植被、水体和其他,以分析近30 a中亚土地利用/土地覆被变化趋势。中亚土地利用类型多样,草地、裸地、农田、灌丛占绝对优势。自前苏联解体以后,20世纪90年代初至2000年期间,耕地面积大幅度减少,至2010年尽管有所恢复,但仍无法达到20世纪90年代初水平。而自然植被表现出了相反的趋势,这说明在此时间段内,由于社会政治制度的变化和市场经济的建立,耕地发生了较大规模的弃耕,弃耕地通常转换为草地、灌丛等自然植被。近10 a由于社会经济条件的变化,前苏联解体后所弃耕的土地又被收复和重新开发为耕地。90年代初至2000年期间,水体呈现先减少后增加的趋势。利用全球基于多期不同信息源获得的中亚土地覆被数据,尽管分类体系不统一,但均可较好地表征当时地表覆被状况。这在一定程度上弥补了中亚地区土地覆被数据不足的现状。通过对耕地、自然植被、水体及其他土地覆被类型进行大类合并,可基本体现中亚土地覆被的宏观特征和变化趋势。     

Land Cover Status in the Koshi River Basin,Central Himalayas

The Koshi River Basin is in the middle of the Himalayas, a tributary of the Ganges River and a very important cross-border watershed. Across the basin there are large changes in altitude, habitat complexity, ecosystem integrity, land cover diversity and regional difference and this area is sensitive to global climate change. Based on Landsat TM images, vegetation mapping, field investigations and 3S technology, we compiled high-precision land cover data for the Koshi River Basin and analyzed current land cover characteristics. We found that from source to downstream, land cover in the Koshi River Basin in 2010 was composed of water body (glacier), bare land, sparse vegetation, grassland, wetland, shrubland, forest, cropland, water body (river or lake) and built-up areas. Among them, grassland, forest, bare land and cropland are the main types, accounting for 25.83%, 21.19%, 19.31% and 15.09% of the basin’s area respectively. The composition and structure of the Koshi River Basin land cover types are different between southern and northern slopes. The north slope is dominated by grassland, bare land and glacier; forest, bare land and glacier are mainly found on northern slopes. Northern slopes contain nearly seven times more grassland than southern slopes; while 97.13% of forest is located on southern slopes. Grassland area on northern slope is 6.67 times than on southern slope. The vertical distribution of major land cover types has obvious zonal characteristics. Land cover types from low to high altitudes are cropland, forest, Shrubland and mixed cropland, grassland, sparse vegetation, bare land and water bodies. These results provide a scientific basis for the study of land use and cover change in a critical region and will inform ecosystem protection, sustainability and management in this and other alpine transboundary basins.     

NCEP/NCAR 再分析资料在喜马拉雅山-青藏高原气象研究中的可行性分析

Due to the difficult logistics in the extreme high elevation regions over the Himalayas and Tibetan Plateau, the observational meteorological data are very few. In 2003, an automatic weather station was deployed at the northeastern saddle of Mt. Nyainqentanglha (NQ) (30°24′44.3″ N, 90°34′13.1″ E, 5850 m a.s.l.), the southern Tibetan Plateau. In 2005, another station was operated at the East Rongbuk Glacier Col (28°01′0.95″ N, 86°57′48.4″ E, 6523 m a.s.l.) of Mt. Qomolangma. Observational data from the two sites have been compared with the reanalysis data from the National Centers for Environmental Prediction/National Center for Atmospheric Research (NCEP/NCAR), reliability of NCEP/NCAR reanalysis data has been investigated in the Himalayas/Tibetan Plateau region. The reanalysis data can capture much of the synoptic-scale variability in temperature and pressure, although the reanalysis values are systematically lower than the observation. Furthermore, most of the variability magnitude is, to some degree, underestimated. In addition, the weather event extracted from the NCEP/NCAR reanalyzed pressure and temperature prominently appears one day ahead of the observational data on Mt. Qomolangma, while on Mt. NQ it occurs basically in the same day.     

Reliability of NCEP/NCAR reanalysis data in the Himalayas/Tibetan Plateau

Due to the difficult logistics in the extreme high elevation regions over the Himala-yas and Tibetan Plateau, the observational meteorological data are very few. In 2003, an automatic weather station was deployed at the northeastern saddle of Mt. Nyainqentanglha (NQ) (30°24′44.3″ N, 90°34′13.1″ E, 5850 m a.s.l.), the southern Tibetan Plateau. In 2005, another station was operated at the East Rongbuk Glacier Col (28°01′0.95″ N, 86°57′48.4″ E, 6523 m a.s.l.) of Mt. Qomolangma. Observational data from the two sites have been com-pared with the reanalysis data from the National Centers for Environmental Predic-tion/National Center for Atmospheric Research (NCEP/NCAR), reliability of NCEP/NCAR reanalysis data has been investigated in the Himalayas/Tibetan Plateau region. The reanaly-sis data can capture much of the synoptic-scale variability in temperature and pressure, al-though the reanalysis values are systematically lower than the observation. Furthermore, most of the variability magnitude is, to some degree, underestimated. In addition, the weather event extracted from the NCEP/NCAR reanalyzed pressure and temperature prominently appears one day ahead of the observational data on Mt. Qomolangma, while on Mt. NQ it occurs basically in the same day.     

Incorporating spectral data into logistic regression model to classify land cover: a case study in Mt. Qomolangma (Everest) National Nature Preserve

Only few models for land-cover classification incorporated spectral data into ordinary logistic regression (OL model) in the Mt. Qomolangma (Everest) National Nature Preserve (QNNP) in China. In this study, spectral variables were incorporated into OL model and autologistic regression (AL) model to classify six main land covers. Twelve environmental variables and seven spectral variables of 10,000 stratified random sites in the QNNP were quantified and analyzed; OL model, AL model, OL model with spectral data (OLM model), and AL model with spectral data (ALM model) were estimated. The OLM and ALM models produced better estimates of regression coefficients and significantly improved model performance and overall accuracy for the grassland, sparsely vegetated land, and bare land compared with OL and AL models.     

Glacial change in the vicinity of Mt. Qomolangma (Everest), central high Himalayas since 1976

Glaciers are one of the most important land covers in alpine regions and especially sensitive to global climate change. Remote sensing has proved to be the best method of investigating the extent of glacial variations in remote mountainous areas. Using Landsat thematic mapping (TM) and multi-spectral-scanner (MSS) images from Mt. Qomolangma (Everest) National Nature Preserve (QNNP), central high Himalayas for 1976, 1988 and 2006, we derived glacial extent for these three periods. A combination of object-oriented image interpretation methods, expert knowledge rules and field surveys were employed. Results showed that (1) the glacial area in 2006 was 2710.17 ± 0.011 km2 (about 7.41% of the whole study area), and located mainly to the south and between 4700 m to 6800 m above sea level; (2) from 1976 to 2006, glaciers reduced by 501.91 ± 0.035 km2 and glacial lakes expanded by 36.88 ± 0.035 km2; the rate of glacier retreat was higher in sub-basins on the southern slopes (16.79%) of the Himalayas than on the northern slopes (14.40%); most glaciers retreated, and mainly occurred at an elevation of 4700–6400 m, and the estimated upper limit of the retreat zone is between 6600 m and 6700 m; (3) increase in temperature and decrease in precipitation over the study period are the key factors driving retreat.     

Glacial change in the vicinity of Mt. Qomolangma （Everest）, central high Himalayas since 1976

Glaciers are one of the most important land covers in alpine regions and especially sensitive to global climate change. Remote sensing has proved to be the best method of investigating the extent of glacial variations in remote mountainous areas. Using Landsat thematic mapping (TM) and multi-spectral-scanner (MSS) images from Mt. Qomolangma (Everest) National Nature Preserve (QNNP), central high Himalayas for 1976, 1988 and 2006, we derived glacial extent for these three periods. A combination of object-oriented image interpretation methods, expert knowledge rules and field surveys were employed. Results showed that (1) the glacial area in 2006 was 2710.17 ± 0.011 km² (about 7.41% of the whole study area), and located mainly to the south and between 4700 m to 6800 m above sea level; (2) from 1976 to 2006, glaciers reduced by 501.91 ± 0.035 km² and glacial lakes expanded by 36.88 ± 0.035 km²; the rate of glacier retreat was higher in sub-basins on the southern slopes (16.79%) of the Himalayas than on the northern slopes (14.40%); most glaciers retreated, and mainly occurred at an elevation of 4700–6400 m, and the estimated upper limit of the retreat zone is between 6600 m and 6700 m; (3) increase in temperature and decrease in precipitation over the study period are the key factors driving retreat.     

Quantifying successional land cover after clearing of tropical rainforest along forest frontiers in the Congo Basin

State-of-the-art impact-modeling studies in environmental and climatological sciences require detailed future deforestation scenarios that allow forest to be replaced by a mosaic of multiple successional land-cover types, rather than the simple conversion of forest to a single land-cover type, such as bare soil or cropland. Therefore, not only the amount and location of forest removal has to be known (as is typically provided by scenarios), but also knowledge about the successional land-cover types and their relative areal proportions is needed. The main objective of this study was to identify these successional land-cover types and quantify their areal proportions in regions deforested during the past 37 years around the city of Kisangani, D.R. Congo. The fallow vegetation continuum was categorized in different stages, adapted from existing classifications. Ground-truth points describing the present-day vegetation were obtained during a field campaign and used for supervised and validated land-cover classification of these categories, using the Landsat image of 2012. Areal proportions of successional land-cover types were then derived from the resulting land-cover map. The second objective of this study was to relate these areal proportions to time since deforestation, which is expected to influence fallow landscapes. Landsat images of 1975, 1990, and 2001 were analyzed. Present-day mature tree fallow is less abundant on areas deforested during 1975–1990. The relative areal proportions were used to refine a deforestation scenario and apply it to existing data-sets of LAI and canopy height (CH). Assuming a simple conversion of forest to cropland, the deforestation scenario projected a reduction of grid-cell-averaged CH from 25.5 to 7.5 m (within deforested cells), whereas the refined scenarios that we propose show more subtle changes, with a reduced CH of 13 m. This illustrates the importance of taking successional land cover correctly into account in environmental and climatological modeling studies.