中国近地面PM2.5浓度与排放的时空分布及其关联分析

PM_2.5是威胁人体健康的主要大气污染物之一。大量研究关注近地面PM_2.5浓度的监测及其时空分布,但目前针对PM_2.5排放及其与近地面浓度之间的关联研究较为缺乏。本文通过2000—2014年近地面PM_2.5浓度格网数据和PM_2.5排放格网数据,采用长时间序列分析法对PM_2.5浓度和PM_2.5排放从定性和定量两个角度进行时空变化趋势对比研究,并进一步结合标准差椭圆法和趋势分析法,分析了我国近地面PM_2.5浓度和PM_2.5排放的时空变化特征及其关联。结果表明,从总体时间序列趋势上,近地面PM_2.5浓度和PM_2.5排放之间在空间分布上基本呈现一致性,集中在胡焕庸线以东的人口密集区,但在时间上,PM_2.5浓度和排放之间存在动态变化时间差。且PM_2.5浓度的变化更为明显,2000—2007年高于35 μg/m³的国土面积占比增加了14.26%,2007—2014年减少了2.84%;从标准差椭圆分析来看,PM_2.5浓度椭圆和排放椭圆在覆盖面积和方位角上与人口和经济分布吻合,但前者面积更大,长轴更接近于东西方向,二者存在约17°差异,而两类椭圆的中心位置随时间变化呈现出较一致的轨迹特征并呈现出滞后特点;此外,受大气扩散、点源排放等因素影响,PM_2.5浓度变化趋势与排放变化趋势在胡焕庸线以东并不完全一致,部分区域排放呈降低趋势而浓度则反而呈升高趋势。因此,从全国层面来看,减排政策对浓度降低在时间上虽存在滞后,但边际效益显著,并已显露成效;而从局地来看,受地形、气象条件和大气化学过程等复杂影响,二者的变化在空间上仍会存在差异,有待进一步深入研究;从防控措施来看,在继续加强落实本地减排政策的同时,应考虑污染物的扩散迁移规律,加强联防联控,有效改善空气质量。     

Land use regionalization of rural settlements in China

This paper compartmentalizes regional land use of rural settlements in China by employing a hierarchical clustering method.The statistic data are sourced from the National Bureau of Statistics of China(NBSC) and the data of land use change from the Ministry of Land and Resources of China(MLRC).The population of rural settlement decreases from the southeast to the northwest of China and the density of rural settlement decreases from the east to the west of China.Land-use scale of rural settlement,the proportion of one-storey houses and the average household area decrease from the north to the south of China.The ratio of area of cultivated land to rural settlement is high in the northeast and southwest of China but low in the southeast of China.The land use regionalization of rural settlement can be divided into four regions,namely:the northern region of China,Qinghai-Tibet,Yunnan-Guizhou,and the middle and eastern region of China.The northern region of China and the middle and eastern region of China can be further divided into nine sub-regions:Xinjiang,Northeast China,Ningxia and Inner Mongolia,North China,the south of the Changjiang(Yantze) River and Sichuan Basin,Jiangsu-Shanghai,South China,the Loess Plateau,and Guangxi.In consideration of the significant regional differences,it is proposed that different policies should be implemented regarding the utilization and management of rural settlements.     

Spatial-temporal pattern and population driving force of land use change in Liupan Mountains region, southern Ningxia, China

The Liupan Mountains is located in the southern Ningxia Hui Autonomous Region of China, which forms an important dividing line between landforms and bio-geographic regions. The populated part of the Liupan Mountains region has suffered tremendous ecological damages over time due to population pressure, excessive demand and inappropriate use of agricultural land resources. In this paper, datasets of land use between 1990 and 2000 were obtained from Landsat TM imagery, and then spatial models were used to characterize landscape conditions. Also, the relationship between the population density and land use/cover change （LUCC） was analyzed. Results indicate that cropland, forestland, and urban areas have increased by 44,186ha, 9001ha and 1550ha, respectively while the grassland area has appreciably decreased by 54,025ha in the study period. The decrease in grassland was most notable. Of the grassland lost, 49.4% was converted into cropland. The largest annual land conversion rate in the study area was less than 2%. These changes are attributed to industrial and agricultural development and population growth. To improve the eco-economic conditions in the study region, population control, urbanization and development of an ecological friendly agriculture were suggested.     

Spatial and temporal variability of farm size in China in context of rapid urbanization

During the last 30 years,China has witnessed rapid economic growth and dramatic urbanization,with about 1.2 × 107rural people migrating annually into urban areas.Meanwhile,especially since 1995,the rural population has been declining,which is closely linked to land circulation and the increase in farm size in many villages.Increasing scale of farming operations is often regarded as a key to avoiding the abandonment of farmland and to increasing the income of rural farmers.However,until now,there has been little research on the spatial and temporal variability of farm size at the national level in China.Using data from the national agricultural census and rural household surveys,this study examines the characteristics of land use circulation and the consequent changes in the area of farmland per household.The results show that: 1) 12.2% of rural households were involved in land circulation at the national level.The highest amounts of land circulation have occurred in those provinces where the farmland per capita is more than 0.2 ha or less than 0.1 ha;2) over 80% of households operate less than 0.6 ha of farmland;3) the proportion of mid-sized farms(between 0.2 ha and 0.6 ha per household) has decreased while the smallest and the largest farms have increased.This bears some similarity with the phenomenon known as the ′disappearing middle′,referring to the changes in farm size.This study establishes a framework for interpreting the factors affecting the changes in farm size in China,which include two promoting factors(urbanization and agriculture) and four hindering factors(agricultual land system,household registration,stable clan system,and farmland loss).     

Spatio-temporal characteristics of population and economy in transitional geographic space at the southern end of "Hu Huan-yong Line"

"Hu Huan-yong Line (Hu Line)" depicts a geographical pattern of China's population distribution.Its essence is the regionality of human-land relationship and re...     

Estimation of regional evapotranspiration in alpine area and its response to land use change: A case study in Three-River Headwaters region of Qinghai-Tibet Plateau, China

Three-River Headwaters(TRH) region involved in this paper refers to the source region of the Changjiang(Yangtze) River,the Huanghe(Yellow) River and the Lancang River in China.Taking the TRH region of the Qinghai-Tibet Plateau as a case,the annual evapotranspiration(ET) model developed by Zhang et al.(2001) was applied to evaluate mean annual ET in the alpine area,and the response of annual ET to land use change was analyzed.The plant-available water coefficient(w) of Zhang’s model was revised by using vegetation-temperature condition index(VTCI) before annual ET was calculated in alpine area.The future land use scenario,an input of ET model,was spatially simulated by using the conversion of land use and its effects at small regional extent(CLUE-S) to study the response of ET to land use change.Results show that the relative errors between the simulated ET and that calculated by using water balance equation were 3.81% and the index of agreement was 0.69.This indicates that Zhang’s ET model based on revised plant-available water coefficient is a scientific and practical tool to estimate the annual ET in the alpine area.The annual ET in 2000 in the study area was 221.2 mm,11.6 mm more than that in 1980.Average annual ET decreased from southeast to northwest,but the change of annual ET between 1980 and 2000 increased from southeast to northwest.As a vast and sparsely populated area,the population in the TRH region was extremely unbalanced and land use change was concentrated in very small regions.Thus,land use change had little effect on total annual ET in the study area but a great impact on its spatial distribution,and the effect of land use change on ET decreased with increasing precipitation.ET was most sensitive to the interconversion between forest and unused land,and was least sensitive to the interconversion between cropland and low-covered grassland.     

集成土地利用数据和夜间灯光数据优化人口空间化模型

人口统计数据空间化是解决统计数据与自然要素数据融合分析的有效途径。随着RS和GIS技术的发展,人口统计数据空间化方法推陈出新,其中,土地利用数据、夜间灯光数据是人口空间化研究中普遍利用的数据源,但各有优、缺点：土地利用数据中的城镇用地、农村居民点能准确表示人口分布的空间范围,却不能反映其内部的人口密度差异特征;夜间灯光数据的强度信息能体现人口分布的疏密程度,但其像元溢出问题显著夸大人口分布范围,像元过饱和现象也影响着人口数据空间化结果的精度。本研究以中国大陆沿海区域为例,尝试集成土地利用数据和夜间灯光数据优化人口空间化方法,设计了基于精度阈值和动态样本的渐进回归与分区建模的方法,获得了中国沿海2000、2005、2010年1 km分辨率人口空间化数据。结果表明,优化模型显著提高了研究区整体的精度,尤其适用于人口空间结构内部差异较为显著的区域。     

Land cover change in different altitudes of Guizhou-Guangxi karst mountain area,China: patterns and drivers

Topography, especially altitude, will influence the way, process and characteristics of land cover changes in mountainous area, simultaneously, the vertical difference of land cover changes will affect soil quality and regional ecological environment. Therefore, the gradient relationship analysis between land cover changes and altitude is very important for regional sustainability. This study investigated land cover dynamics based on land cover data from a typical mountainous area in the Guizhou-Guangxi karst mountain area, China, in 2000 and 2010, then explored the relationship between altitude and land cover change and analyzed different drivers of land cover change at different altitudes. Our findings are as follows. 1) From 2000 to 2010, the total area of land cover transition was 7167.04 km~2 or 2.8% of the region. The increasing area of build-up land(926.23 km~2) was larger than that of forest(859.38 km~2), suggesting that the urban construction speed was higher than that of reforestation. 2) Intensity of land cover transition in northwestern Guizhou-Guangxi karst mountain area was much larger than that of southeast part and their transition trend was also significantly different, which was consistent with regional population and economy. 3) Human activity was the most dramatic at altitudes between 0–500 m. For 500–1000 m, grassland mainly converted to forest and build-up land. Area of land cover transition was the greatest between 1000–1500 m, while above 1500 m, the transition of grassland was the most obvious. 4) The drivers of land cover change varied. Land cover change was positively correlated with gross domestic product and population density but was inversely related to relief amplitude. There were correlations between land cover change and distance to roads and rivers, and their correlations varied with altitude. By revealing patterns and causes of land cover changes in different altitudes, we hope to understand the vertical dependence of land cover changes, so as to improve land productivity and protect land ecological environment scientifically.     

Spatial pattern and influencing factor of county-level industrial development in Liaoning Province of China

County-level industrial development and structure upgrade is one of the most important issues of revitalizing old industrial base of China. After the cluster analysis on GDP per capita and GDP per area of each county in Liaoning Province, this paper finds the similarity of population size, land use intensity, and economic development of each county. Location quotient reflects the specialization intensity of industries in each county, and it also reflects the spatial differences of county-level industrial development. Economic development level is higher in the southeast than in the northwest of Liaoning, and the industry driving effect on county-level economy is apparent. The main influencing factors include location, industrial foundation and economic system reform, capital input level, knowledge and technology dissemination, conditions of domestic and overseas markets, population and labor force transfer. Industrialization is an important approach to urbanization for the counties in Liaoning Province. The proportion of agriculture is much higher in the northwest than in the southeast of Liaoning, so it will be take longer time for counties in the northwest of Liaoning to make industrialization, urbanization and modernization.     

City size distribution and its spatiotemporal evolution in China

Based on the National Land Use/Cover Database of China(NLUD-C) in the end of the 1980s(the 1980s,hereafter), 1995, 2000, 2005, and 2010, 665 cities were selected to study the size distribution and its changes of urban lands in China. In this study, the spatiotemporal evolutions of urban land size distribution as well as the influence of administrative-level on these cities were explored by combining urban spatial positions and administrative-levels. Results indicate that: 1) City size distribution using urban lands was more practical and reasonable than using non-agricultural population. 2) In the 1980s, cities with ascending urban land rank were centralized in Eastern China, specially the Changjiang(Yangtze) River Delta, the Zhujiang(Pearl) River Delta, and Beijing-Tianjin-Hebei region. Cities in Central, Western, and Northeast China mainly indicated descending urban land rank. 3) The transfer of national development focus resulted in cities with ascending urban land rank becoming evenly distributed nationwide; however, this trend was slightly centralized around Chengdu, Chongqing, and Wuhan in different periods. 4) During the 1980s to 2010, the proportion of cities with ascending urban land rank in provincial capitals, municipalities, and special administrative regions(high-level cities, hereafter) was consistently higher than those in prefecture- and county-level cities except for 2005–2010. The ranks of the majority of the prefecture- and county-level cities were mainly descending, supported by ascending; the proportion of cities with unchanged rank is small. This study breaks through the bottleneck of traditional research in the area of city size distribution by examining urban land replacing the non-agricultural population. The current study also provides scientific explanation for the healthy and reasonable development of urban land as well as the coordinated development of population urbanization and land urbanization.     

北京城市增长边界预测

为了遏制北京”摊大饼”式的城市发展模式,促进土地资源的集约、高效利用,引导国土空间合理布局,划定北京城市增长边界成为重要举措。本研究从城市内生发展动力角度,将遗传神经网络嵌入CA模型,建立北京城市增长边界预测模型,选定了自然、人口经济、区位、邻域、土地利用类型和政策规划6类因素共18个影响因子,预测北京市城市增长弹性边界。同时,从土地自身生态承载能力角度,用建设用地适宜性评价方法,选定了地形、地貌、公园水域、土地利用现状、自然保护区、城市用地距离为影响因子,划定北京市城市增长刚性边界。结果表明,利用该模型预测北京市2025年城市增长边界,总的面积匹配值为96%,模型精度较高;2025年北京市弹性增长边界总面积为1738.98 km²,刚性增长边界总面积为3297.01 km²。基于GANN-CA模型的城市增长边界划定方法对确定城市未来扩张方向有指导作用,可为城市规划和发展政策的制定提供依据。     

土地利用空间格局的置换变化与代换变化分析

为揭示土地利用空间格局的动态变化,本文基于土地利用转移矩阵,从类型间的空间转移过程出发,构建了置换变化与代换变化的计算模型,并对其2种变化进行了分析。置换变化是2种类型之间以相同面积发生空间位置的置换过程,且各种类型的数量结构保持不变;代换变化则是所研究类型的数量结构保持不变,而与之转换的其他类型数量上的增加或减少;从而将单一类型的总变化进一步细分为置换变化、代换变化与净变化。以晋江流域1985年与2006年2期土地利用格局的变化为例进行分析,结果显示：在1985-2006年间,晋江流域的土地利用空间格局发生了显著变化;园地、建设用地、未利用地呈现扩张态势,草地与旱地呈现萎缩变化,水域变化不大;这6种地类的交换变化面积相对较少,以置换变化为主。水田与林地则主要表现为空间位置的交换变化,其中,水田呈现出与林地、旱地2种类型之间的置换变化,而林地则主要是园地-林地与林地-草地这2对类型间的代换变化。结果表明,通过置换变化与代换变化的分析,更细化了各种类型之间的动态变化过程。     

城市地铁站点商业价值数字化评价方法

地铁站点商业价值是地铁改变城市交通方式基础上城市商业业态价值的体现,对其科学和量化的评价是地铁站点建设重要的方面。本文首先对地铁站点商业价值的评价从商业等级与商业规模两个方面进行了体系构建,然后以广州地铁八号线为研究对象基于此体系进行了商业价值的评估。在地铁站点商业等级评价中,选取5个空间因子与2个非空间因子进行多因子评价。在进行空间因子评价中的商圈因子分析时,基于市级和区级商圈周边商业用地基准地价具有一致性的距离衰减特征,创新性的构建了商业地价的空间衰减函数,并据此将这一衰减函数转换为商圈距离衰减因子评价值的函数与量化定义,有效解决专家赋值存在的主观性问题。以此方法对八号线地铁站点商业等级进行评价,在完成空间因子评价以及非空间因子校核后,发现上下九-文化公园区域的商业等级最高,次一级则分布在荔湾区中部。对于商业规模的评价,则以商业建筑面积需求平衡方法,基于地铁站点服务半径内人口规模的评估以预测潜在的商业人口数量,并据此估算未来的商业建筑面积需求。以此方法,对地铁八号线以陈家祠站为例对该站点进行了商业建筑面积需求的预测。本研究提出了基于地价距离衰减与量化评价的因子评价方法完善的相关的方法体系,以数字化模型构建商业等级与商业规模的量化评价提高了地铁站点商业价值评估方法的合理性和科学性。     

闽南金三角地区城市扩展及其驱动分析——以漳州市主城区为例

城市空间扩展是衡量城市化进程的重要指标。本文以闽南金三角地区的福建省漳州市主城区作为研究区,选取2000、2006和2013年的Landsat遥感影像,利用IBI建筑指数分别提取了3个年份的建筑用地信息,然后对其变化进行GIS分析。结果表明,13 a间漳州市主城区面积净增13.69 km²,净增面积为2000年的66.9%。主城区主要沿交通主干道往西北方向呈带状和面状扩展。缓冲区分析表明,道路对主城区扩展起到很大的引导和促进作用。综合社会经济数据可知,主城区的城市扩展历程与第二产业的发展密切相关,属工业导向型的城市扩展模式。另外,城市人口的增加也起到了一定的促进作用,不同区位人口增长速率的差异,对城市扩展的方向也产生了一定的引导作用。     

基于遥感和BP人工神经网络的城乡气象站点划分分析

城市热岛是城市环境和全球变化研究的重要组成部分,利用气象观测资料研究城市热岛的影响一般采用城市和乡村气象站的同步实测气温,并计算其平均气温差,因此,城乡气象站点划分的准确性,将直接影响城市热岛研究的科学性。鉴于以行政单元统计人口为依据的划分方式未考虑人口在行政单元内的实际空间分布,本文以安徽省为例,利用从遥感影像上提取的土地利用信息,采用BP人工神经网络方法,建立站点缓冲区内土地利用类型比例的城乡站点划分模型,并利用空间化后的人口格网数据对该模型的精度进行了验证。结果表明,该模型有效地建立了气象站点周边缓冲区内的土地利用类型比例与城乡站点类型之间的定量关系,避免直接采用行政单元统计人口数据的不足,客观地模拟了缓冲区内土地利用对气象站点的综合作用,科学地划分出城市和乡村气象站点,为城市热岛研究提供科学、可靠的数据保障,并可用于大区域研究。另外,本文利用划分出的乡村站点建立背景温度场,得出2000年安徽省各城市站点平均热岛强度为0.4℃。     

Soil erosion and its basic characteristics at karst rocky-desertified land consolidation area: A case study at Muzhe Village of Xichou County in Southeast Yunnan,China

Xichou County of Wenshan Zhuang and Miao Autonomous Prefecture in southeast Yunnan is one of the karst mountainous areas in southwest China showing typical rock desertification. During this study, we set up three soil erosion contrast test spots at Muzhe Village, Benggu Township, Xichou County, which was the birthplace of the Xichou rock-desertified land consolidation mode. The three spots included the terrace land spot (already consolidated land), sloping land spot (unconsolidated sloping land under rock desertification), and standard runoff spot (bare land spot). In 2007, a whole-year complete observation was conducted during the rainy season and "rainfall-erosion" data were obtained for 32 times. Our analysis showed that during the entire observation period, the number of the rainfalls that led to soil erosion accounted for 34.04% of the number of all rainfalls and the amount of the rainfalls that led to soil erosion accounted for 84.17% of the total amount of all rainfalls. The average erosive rainfall standard in the three test spots was 11.0 mm, slightly higher than the 10 mm standard that has been adopted all over China, but lower than the 12.7 mm standard of the US and the 13.0 mm standard of Japan. According to single-factor analysis, the soil loss in the sloping land spot (L2) and that in the bare land spot (L3) are correlated to certain extent to many other factors, including the single precipitation (P), rainfall intensity during the maximum ten minutes (I10), rainfall intensity during the maximum 20 minutes (I20), rainfall intensity during the maximum 30 minutes (I30), rainfall intensity during the maximum 40 minutes (I40), and rainfall intensity during the maximum 60 minutes (I60). Among these factors, they are of the highest relativity with I60. According to double-factor analysis, both L2 and L3 are of good relativity with P and I60. According to multi-factor analysis, L2 and L3 are also of good relativity with seven rainfall indexes, namely, P, Ia (average rainfall intensity), I10, I20, I30, I40, and I60, with their related coefficient R reaching 0.906 and 0.914, respectively. The annual soil losses in the three test spots are widely different: 1030.70 t/km2·a in the terrace land spot, which indicates a low-level erosion; 12913.22 t/km2·a in the sloping land spot (unconsolidated spot), some 12.5 times than that in the terrace land spot, which indicates an ultra-high-level erosion; and 19511.67 t/km2·a in the bare land spot, some 18.9 times than that in terrace land spot, indicating an acute erosion. These figures fully show that the Xichou rock-desertified land consolidation mode plays a significant role in soil conservation.     

Ecosystem Health: Assessment Framework,Spatial Evolution,and Regional Optimization in Southwest China

Regional ecological health,the core of comprehensive ecosystem assessments,is an important foundation for regional exploration,environmental conservation,and sustainable development.The mountainous areas in southwest China are backward in economy,but industrialization and urbanization have been rapid in recent years.This study assessed the ecosystem health of the Sichuan and Yunnan provinces in China using a pressure-state-response(PSR)model.Spatiotemporal patterns of regional ecosystem health were analyzed from 2000 to 2016,including overall characteristics as well as local characteristics.Ecosystem health in most regions was improved over time(Y=0.0058 X–11.0132,R2=0.95,P<0.001),and areas with poorer ecosystem health decreased from half to one-third of the total area.Analysis of the primacy ratio and the variation coefficient confirmed that the gap in health scores between regions has gradually expanded since 2007,but there are more high quality regions overall(Z of Moran’s index<1.96,P>0.05).Overall,the regional ecosystems to the east of the Hu line-an imaginary line dividing east and west China into roughly equivalent parts-were healthier than those to the west.The pressure and state scores of ecosystems were determined by physiographic condition,and the response scores by government policies and social concern.The spatiotemporal patterns of ecosystem health were dominated to a greater extent by natural than anthropogenic factors,which explains why the shift in the patterns aligned with the direction of the Hu line.Dividing regions into key management areas based on natural geographical conditions and socioeconomic development could contribute to the formulation of a reasonable ecological and environmental protection policy,guaranteeing ecosystem services in the long run.     

Relief degree of land surface and population distribution of mountainous areas in China

Evaluation on the population pressure in the mountainous areas is a necessary condition for the protection and good governance. The evaluation depends on accurate population density assessment. Traditional methods used to calculate population density often adopt the administrative region as a scale for statistical analysis. These methods did not consider the effects of the relief degree of land surface(RDLS) on the population distribution. Therefore they cannot accurately reflect the degree of population aggregation, especially in mountainous areas. To explore this issue further, we took the mountainous areas of China as the research area. China has A total area of 666 km2 can be classified as mountainous area,accounting for 69.4% of the country’s total landmass. The data used in this research included the digital elevation model(DEM) of China at a scale of 1:1,000,000, National population density raster data, the DEM and the national population density raster data. First, we determined the relief degree of land surface(RDLS). Next, we conducted a correlation analysis between the population distribution and the RDLS using the Statistical Package for Social Science(SPSS). Based on the correlation analysis results and population distribution, this new method was used to revise the provincial population density of themountainous areas. The revised results were used to determine the population pressure of different mountainous areas. Overall, the following results were obtained:(1) The RDLS was low in most mountainous areas(with a value between 0 and 3.5) and exhibited a spatial pattern that followed the physiognomy of China;(2) The relationship between the RDLS and population density were logarithmic, with an R2 value up to 0.798(p<0.05), and the correlation decreased from east to west;(3) The difference between the revised population density(RPD) and the traditional population density(PD) was larger in the southeastern region of China than in the northwestern region;(4) In addition, compared with traditional results, the revised result indicated that the population pressure was larger. Based on these results, the following conclusions were made:(1) the revised method for estimating population density that incorporates the RDLS is reasonable and practical,(2) the potential population pressure in the southeastern mountainous areas is substantial,(3) the characteristics of the terrain in the high mountainous areas are important for the scattered distribution of the population, and(4) the population distribution of mountainous areas in China should be guided by local conditions, such as social, economic, and topographic conditions.     

Comparison and analysis of agricultural and forest land changes in typical agricultural regions of northern mid-latitudes

The northeastern China, the United States, and the western Europe are important agricultural regions both on the global and regional scales. The western Europe has a longer history of agricultural land development than the eastern United States. These two regions have changed from the deforestation and reclamation phase in the past to the current land abandonment and reforestation phase. Compared with the two regions, large-scale land exploitation has only been practiced in the northeastern China during the last century. After a short high-intensity deforestation and reclamation period, agricultural and forest lands are basically in a dynamic steady state. By comparing domestic and international agro-forestry development and considering the ecological environment and socio-economic benefits that can be derived from agro-forestry, this paper suggests that large area of reforestation would be inevitable in future though persistent and large agricultural demand in coming decades even more. And local reforestation at slope farmland with ecological vulnerability should be imperative at present to avoid severer damage. At the same time, from the perspective of Land Change Science, the results demonstrate that the research on land use change in the agro-forestry ecotone is typical and critical, particularly those dealing with the analysis of spatial and temporal characteristics and the simulation of climate, hydrology, and other environmental effects.     

西藏一江两河地区人口分布与地形要素关系分析

地形条件是影响区域人口分布的最基本的因素之一,本文基于1 km×1 km人口空间分布公里网格数据定量分析一江两河地区人口分布基本特征及其与高程、坡度、坡向、地形起伏度等地形要素之间的关系,有助于揭示西藏高原人口分布现状的本质、理解人口空间分布结构特征,对于今后宜居地选址、改善农牧民人居环境、制定区域经济发展政策,促进区域内人口、资源与环境可持续发展具有重要意义。研究结果表明：① 一江两河地区90%的区域人口密度不足10人/km²,80%的人口分布在不足5%的土地上,人口分布比较集中。当前一江两河地区有2个主要的人口集中区,分别是拉萨市城关区和日喀则地区日喀则市,拉萨市城关区尤其显著。② 一江两河地区人口沿河分布,80.46%的人口居住在距离河流10 km以内区域,人口总数、人口密度与距河流距离呈明显的指数关系,距离河流2 km以内的区域人口密度高于50人/km²;③ 近99%的人口分布在海拔4500 m以下,当高程超过3800 m时,人口密度随海拔升高呈下降趋势;④ 近70%的人口分布在坡度小于15°的区域,而且随着坡度越大,人口密度越小,人口分布受坡向的影响不明显;⑤ 地形起伏度对人口分布的影响显著,近85%的人口分布在地形起伏度小于800 m的区域,人口密度与地形起伏度之间为倒指数关系。