Drivers of phytoplankton,bacterioplankton, and zooplankton carbon biomass in tropical hydroelectric reservoirs

Studies of carbon sources in plankton communities are important because carbon content has become the main currency used in functional studies of aquatic ecosystems. We evaluated the contribution to the total organic carbon pool from different plankton communities (phytoplankton, bacterioplankton, and zooplankton – C-biota) and its drivers in eight tropical hydroelectric reservoirs with different trophic and hydrological status and different physical features. Our systems were separated into three groups based on trophic status and water residence time: (i) mesotrophic with low residence time (ML); (ii) mesotrophic with high residence time (MH); and (iii) eutrophic with low residence time (EL). Our hypothesis that reservoirs with low water residence times and low nutrient concentrations would show the lowest C-biota was supported. Phytoplankton carbon (C-phy) showed the highest concentrations in the EL, followed by MH and ML systems. The EL group also showed significantly higher zooplankton carbon (C-zoo). No significant difference was observed for bacteria carbon (C-bac) among the three system groups. In addition to trophic status and water residence time, regression analyses revealed that water temperature, light, pH, and dissolved organic carbon concentrations were the main drivers of plankton communities in these large tropical hydroelectric reservoirs.     

Land-cover and land-use change in a Mediterranean landscape: A spatial analysis of driving forces integrating biophysical and human factors

This article develops a spatial analysis applied to examine the main driving forces of land-cover and land-use (LCLU) change in a Mediterranean region. Three different tools have been used in order to differentiate LCLU changes, driving forces and landscape dynamics. LCLU changes have been quantified with remote sensing techniques, driving forces have been analysed with multiple logistic regressions combining biophysical and human variables, whereas landscape dynamics have been quantified using different metrics. Results show the intensification of subsidised herbaceous crops on the coastal agricultural plain, the abandonment of olive trees and vineyards in the transitional area and forest restoration in the mountainous subregion.     

Evaluating the Temporal and Spatial Urban Expansion Patterns of Guangzhou from 1979 to 2003 by Remote Sensing and GIS Methods

China has experienced and is experiencing expeditious urban expansion in the recent decades, especially in the coastal areas and big cities. Rapid urban expansion and dramatic changes of landscape have caused great economic, environmental and social impacts consequently. It is crucial to understand urban temporal, spatial expansion patterns and their related effects. In this paper, urban expansion of Guangzhou, a rapid growing city in south‐east China, from 1979 to 2003 is studied temporally and spatially. Four time ranges including 1979–1990, 1990–1995, 1995–2000 and 2000–2003 are designed and the urban expansion area, expansion rate and the spatial expansion pattern are discussed by using remote sensing data and Geographical Information System (GIS) tool. Two transects are designed along two axes of Guangzhou expansion and the structural of urban expansion patches at different orientations are compared in order to quantitively understand the urban expansion of Guangzhou during the past 24 years. The gradient analysis integrating multi‐temporal data is performed in order to analyze and compare the spatial and temporal dynamics of urban expansion. Two indices of compactness and fractal dimensional index are used to describe the urban developing pattern in the study time durations. And the influence of different types of traffic roads to urban expansion is evaluated using the buffer analysis of GIS. The results show that: (1) temporally, urban area of Guangzhou increase 296.54 km² from 141.15 km² in 1979 to 437.70 km² in 2003 and the increasing rate is up to 210.08%; (2) spatially, Guangzhou has different urban expanding directions in different stages and the general expanding directions are towards northeast, north, southeast and north in four studied time ranges; (3) transportation lines play a very important role in urban expansion of Guangzhou, but different types of road have different impacts. National roads and highways exhibit stronger control to urban expansion than provincial roads; and (4) expansion of Guangzhou has gradually changed from a compact pattern to leapfrogging and disordering patterns.     

浙江沿海20年土地利用变化分析

在资料收集的基础上,利用遥感(RS)和地理信息系统(GIS)技术,结合经济社会因子和数学模型,以浙江沿海地区1990年、2000年和2010年的土地利用数据为基础,对20年间土地利用变化动态进行研究。利用灰色动态系统建立模型分析浙江沿海地区各类土地利用的变化趋势,在此基础上探讨其变化驱动力,揭示其变化的主要方式、原因及发展方向,预测未来土地利用的发展趋势,以期能为浙江省沿海地区土地利用规划提供科学依据。     

湿地生态系统退化机制和驱动力的模型构建——以天津地区湿地为例

在评述目前关于湿地退化机制和驱动因素研究的基础上,以天津地区湿地为例,从湿地生态系统结构和功能的整体性角度,分析了湿地退化过程中各结构组分与生态功能的关系。湿地作为重要的生态系统,其退化机制与驱动力分析应该首先从生态学角度出发,分析造成湿地生态系统结构改变的因素,以及对湿地生态系统服务功能退化的影响,确定了湿地退化的驱动力因素。按照其内在的逻辑关系,构建了湿地生态系统退化机制和驱动力模型,对影响天津地区湿地退化的驱动因素进行了梳理,并根据分析结果提出了天津湿地生态恢复的对策建议。     

转型期广州大都市区户籍贫困人口特征和空间分布

20世纪90年代中后期以来,伴随着经济体制转型和国有企业改革的深化,广州市户籍贫困人口总量增加,贫困阶层种类由单一走向多元,新增种类中的下岗失业无业、在业低收入者成为救助对象主体.救助对象从基本没有收入的个体为主拓展到有少量收入的家庭为主,贫困深度降低.受到历史继承、单位制和工业企业改革、住房市场化和住房制度改革等因素的影响,户籍贫困人口区际空间分布和集聚的相对差异增加,贫困人口在内城外围区集聚程度明显增加,并在大都市区形成绝对改善区、相对缓解区、变化微小区、相对加重区和绝对加深区5种地域类型.对少数贫困     

深圳市土地利用变化机制分析

利用１９８０、１９８８、１９９４年的遥感影像,通过应用最大似然法和概率松弛法对深圳市土地利用进行了测量。在此基础上,运用分类结果求得研究区土地利用变化的转移矩阵,据此分析了深圳上１５年来土地利用变化的空间过程。结果表明：深圳市土地利用纺要表现为原有农田、果园用地显著减少,城镇用地沿海岸和主要公路干线迅速增加。这一土地利用变化的驱动力主要是深圳经济特区的开放政策、城镇人口迅速增长、外资大量涌入和以房     

区域土地利用变化驱动力研究前景展望

区域土地利用变化驱动力研究旨在从典型区域角度揭示土地利用变化背后的真正动因及其作用机理,进而动态模拟、预测区域土地利用变化过程。土地利用系统的自组织性及其内驱动因子作用的复杂性,决定了其研究必须与某一特定区域相联系,以便确定合适的可定量指标来体现外生驱动因子的驱动效果。系统地识别土地利用系统在不同控制状态下的驱动因子及其多种时空尺度效应,建立具有综合模拟的区域土地利用变化动态模型,能减少土地利用系统通常受临界值域和突变所左右的局面。区域土地利用变化驱动因子识别、区域土地利用变化驱动机制分析、区域土地利用变化驱动过程模拟等的研究现状表明,为更好地理解区域土地利用变化的机制和原因,测度现有及未来土地利用变化的速率、过程和地点,支持政府相关决策的制定与实施,促使区域土地利用变化向有利于人类的方向发展,区域土地利用变化驱动力分析应优先考虑以下研究领域：①驱动力因子识别及其作用效应的尺度依赖性;②驱动力因子的贡献量化及其在具体区域的非均一分布;③驱动力因子作用过程的自然反馈机制模型化。 [HT5H]关〓键〓词：[HT5K]     

北京城乡过渡区土地利用变化驱动力分析

在多时相遥感数据和实际调查数据的支持下，采用典型样带和样点相结合的研究方法，对北京西部城乡过渡区的土地利用/覆盖变化驱动力进行了研究。结果表明，研究区的土地利用/覆盖变化受到了不同层次、多种驱动力的综合作用，人类活动从整体上改变着城乡过渡区的景观特征，政策体制转变下的经济高速增长和快速的城市化过程是北京城乡过渡区土地利用/覆盖变化的根本原因。在这个过程中，城市投资和产业的转变与农村农业用地内部的结构调整相互结合，从城市和农村两个方向共同推动着北京城乡过渡区的土地利用/覆盖变化，而地形、交通等因素则从局部尺度上决定着土地利用/覆盖变化的方向。此外，人类个体的行为选择，尤其是就业和消费选择，也在一定程度上对北京城乡过渡区的土地利用/覆盖变化起着调整和修改作用。     

磁层-电离层-热层耦合的模式计算和分析

对磁层-电离层电动耦合和电离层发电机两种效应进行了模式计算,并对所得的一些耦合现象作了综合讨论.结果表明,在中低纬和赤道区的电离层和地磁研究中必须考虑磁层-电离层耦合效应向中低纬区的穿透和屏蔽;潮汐发电机效应对极光区（电导率增高时）的作用也值得重视.这两效应的特征和相对重要性随磁暴的发展阶段而异,在高低纬区也各不相同,但都有明显的晨昏不对称性.此外,弱磁扰对中低纬电离层形态的影响也不容忽视.