土地利用和覆被变化对岩溶区土壤CO2浓度的影响

通过选择3个具有不同地质背景、气候条件等环境特征的山西汾阳马跑-郭庄岩溶泉域、湖南湘西大龙洞地下河流域、广西桂江流域,对流域内具有代表性的不同土地利用方式和覆被类型下垫面土壤20~50cm深处CO2浓度进行检测。结果显示,土地利用方式和覆被变化对3个流域岩溶土壤中20cm、30cm、40cm和50cm深处CO2浓度具有明显的影响作用:湖南湘西大龙洞地下河流域多数样地土壤CO2表现为随土层的加深先增加后降低的双向梯度;山西马跑-郭庄泉域玉米地的土壤CO2浓度比种植马铃薯的高,且随着覆被条件由草地→灌丛→林地的改善,土壤的扰动性变小,CO2浓度差趋于减少,变幅趋于稳定。各个流域相同覆被类型,群落结构和优势种变化越小,土壤CO2浓度变幅越小。      

近百年来冷圈波动

本世纪CO_2的增温导致了冷圈波动。中纬度山地冰川的普遍退缩与加速消融引起了海面持续上升。格陵兰冰盖目前尚未处于显著的负平衡状态,边缘区在变薄,中心区在增厚。南极大陆冰盖还在增长,但基底可能发生退缩。北极海冰在1935—1960年期间退缩了10％,南极海冰面积在1973—1980年间减少了2.5×10~6km~2。大陆积雪的变化主要表现在中纬度地区,并呈现出区域性差异。而高纬度地区,大陆冰盖的降雪量有增加趋势。     

渗滤液浸泡对深度脱水污泥强度和渗透性能的影响

为探讨深度脱水污泥作为垃圾填埋场覆盖材料在湿润气候区的服役性能,将杭州主城区污水处理厂处理后的深度脱水污泥分别在蒸馏水、渗滤液中浸泡一个月和两个月,测试其强度和渗透特性的变化规律,并与填埋场覆盖层常用的黏性土进行了对比。试验结果表明,相对于一般污泥,深度脱水污泥的无侧限抗压强度较高,但在渗滤液和蒸馏水中浸泡两个月后分别降低5.4%和18.9%。在蒸馏水和渗滤液中浸泡两个月的深度脱水污泥黏聚力有所降低,而有效内摩擦角提高约7.5°;在浸泡水和渗滤液后,脱水污泥的渗透系数提高约3～5倍。该深度脱水污泥应用于填埋场覆盖材料时,其强度达到城镇污水处理厂污泥填埋控制要求。     

老挝万象土地利用变化分析

采用灰度比值法、归一化植被覆盖法(NDVI)及主成分分析法(PCA)和分类后比较法对老挝万象1999年和2006年的地表覆盖变化/土地利用变化进行了分析比较实验。实验表明,灰度比值法、归一化植被覆盖法(NDVI)及主成分分析法变化信息提取的组合结果明显优于分类后比较法,因此作者选取组合方法的变化信息提取结果,分析了老挝万象1999年和2006年土地利用变化情况,得到变化分布图和统计表。研究表明,老挝万象1999年和2006年城市得到大规模扩张(城市面积增长71%),而农业、林地、水体面积都明显减少。     

Common features and different trajectories of land cover changes in six Western Mediterranean urban regions

Land use and land cover change (LULCC) dynamics have been particularly strong in the Mediterranean region, due to its historical development and to agro-pedoclimatic conditions favorable to human settlement. This area has undergone in the 1950s and the 1980s intense urbanization processes that has followed different trajectories. Urban expansion commonly occurs at the expense of agricultural land, leading to the fragmentation of natural areas and conflicts over access to land resources. These dynamics mainly concern the fringe between urban and agricultural land, e.g. the peri-urban areas usually included within functional urban regions. Here, to identify common features of LULCC in Western Mediterranean urban regions, we investigated two main features: direct changes due to urbanization and indirect changes affecting non-artificial land uses. We compared LULCC dynamics in 6 case studies from the north and south of the Western Mediterranean region: the urban regions of Montpellier and Avignon (France), Pisa (Italy), Madrid (Spain), Meknes (Morocco), and Constantine (Algeria), using a 30-year multitemporal spatial analysis (1980–2010). Two series of Landsat TM images were acquired for each case study and land cover data were analyzed both for dynamics and for land patterns, using landscape and class metrics. We found no significant north-south differences in LULCC dynamics between the investigated Western Mediterranean urban regions. Differences are more pronounced between small–medium cities and large metropolitan areas in type of urban diffusion, which is more sprawled in small–medium cities and more compact in large metropolitan areas. Rather, differences occur in LULCC not directly affected by urbanization, since in Northern Mediterranean urban regions afforestation and abandonment of agricultural areas are prevalent and closer to the urban areas, whereas transformation of natural areas into agricultural ones occurs mainly in Southern Mediterranean urban regions at a similar distance from urban areas than it happens for afforested or abandoned areas. In attempting for the first time to assess LULCC in these Mediterranean urban regions, we provide a preliminary comprehensive analysis that can contribute to the active LULCC research in the Mediterranean basin and that can be easily applied to other Mediterranean urban regions.     

珠江三角洲城镇建筑覆盖近期变化研究

基于遥感与地理信息系统技术,从1988年与1998年两个时期研究区域的TM卫星影像提取各城镇的实际建筑覆盖区面积等专题信息,并利用Arc/Info802建立珠江三角洲乡镇级空间数据库。在此基础上重点对珠江三角洲城镇建筑覆盖近期变化的空间扩展特性,并就企业、交通设施、人口、区域经济与行政体制等驱动因子进行了初步综合分析。研究表明20世纪末珠江三角洲城镇建筑覆盖总体圈层格局相对稳定,核心增长与交通指向扩展非常显著,城镇建筑覆盖区增长总量与增长速率空间分布不一致,城镇扩展强度指数空间分布也显示出核心增长与交通轴向增长显著的特征     

土地利用/覆被历史重建方法(英文)

Understanding long-term human-environment interactions requires historical reconstruction of past land-use and land-cover changes. Most reconstructions have been based primarily on consistently available and relatively standardized information from historical sources. Based on available data sources and a retrospective research, in this paper we review the approaches and methods of the digital reconstruction and analyze their advantages and possible constraints in the following aspects:(1) Historical documents contain qualitative or semi-quantitative information about past land use, which also usually include land-cover data, but preparation of archival documents is very time-consuming.(2) Historical maps and pictures offer visual and spatial quantitative land-cover information.(3) Natural archive has significant advantages as a method for reconstructing past vegetation and has its unique possibilities especially when historical records are missing or lacking, but it has great limits of rebuilding certain land-cover types.(4) Historical reconstruction models have been gradually developed from empirical models to mechanistic ones. The method does not only reconstruct the quantity of land use/cover in historical periods, but it also reproduces the spatial distribution. Yet there are still few historical land-cover datasets with high spatial resolution.(5) Reconstruction method based on multiple-source data and multidisciplinary research could build historical land-cover from multiple perspectives, complement the missing data, verify reconstruction results and thus improve reconstruction accuracy. However, there are challenges that make the method still in the exploratory stage. This method can be a long-term development goal for the historical land-cover reconstruction. Researchers should focus on rebuilding historical land-cover dataset with high spatial resolution by developing new models so that the study results could be effectively applied in simulations of climatic and ecological effects.     

巢湖流域的土地利用变化及其生态系统功能损益

基于多时点TM影像解译数据,研究了巢湖流域近30年以来的土地利用/覆盖变化,并借助于生态系统服务价值理论,估算了研究区土地利用/覆盖类型变化所造成的生态系统服务价值损益。由于巢湖流域主要以水田为主,生态服务价值较高,同时考虑该区域水田一年两季的耕作特点,单位面积耕地生态系统服务价值是全国平均值的两倍,单位面积林草地的生态系统服务价值是全国平均价值的1.45倍。研究结果表明:巢湖流域近30年生态服务功能价值损失了831.68×10⁶元,年均损失27.7×10⁶元,并呈现逐年加剧趋势;流域生态服务价值损失量空间分布极不平衡,合肥每年生态服务价值损失量超过流域均值5倍,由此表明大城市扩张对巢湖流域生态服务价值损益作用明显。     

Overland flow generation and continuity on stone-covered soil surfaces

The influence of stone cover on the generation and continuity of overland flow is a function of several variables, primarily stone size, distance (spacing) between stones, and stone position (on top of the soil surface or partially embedded). The initial hypothesis of the present study were that stone size affects overland flow generation by inducing ‘concentration overland flow’ and that the distance between stones affects overland flow continuity. With respect to stone size and distance between stones, opposing results have been found in the literature. Accordingly, the present paper reports on laboratory experiments which were conducted to investigate, systematically, the effect on overland flow of stone size, distance between stones, and stone position. The main conclusions were:

• 1 Stone cover tended to induce overland flow, relative to bare soil. Small stones, however, especially in a low-cover percentage setting, and when resting on top of the soil surface, produced less overland flow than bare soil.
• 2 Overland flow was positively related to stone size, but inversely related to distance between stones.
• 3 Overland flow yield was always greater when stones were embedded than when on top of the soil surface.
• 4 The effect of stone size on increasing the degree of overland flow was of greater significance than the effect of the distance between stones on reducing overland flow.

     

Modeling sea dike breaching induced by breaking wave impact-laboratory experiments and computational model

Sea dikes are of crucial importance for the defense systems of low-lying coastal areas in countries such as Germany, The Netherlands, Denmark, etc. As sea dike breaching induced by storm surges is regarded as one of the main causes of coastal flood disasters, reliable predictions of both the breach initiation, formation and breach development is urgently needed. Although a simple preliminary model for the simulation of sea dike breaching initiated from the seaside was developed (Stanczak et al., 2006), its limitations showed the necessity for further research and for the development of a more detailed model. This paper therefore provides a summary of the results of laboratory experiments on the erosion of grass and clay revetment of a sea dike induced by breaking wave impact and describes the new detailed computational model, including an uncertainty analysis.