Spatial variation of wetlands and flux of dissolved organic carbon in boreal headwater streams

In order to investigate the relation between water chemistry and functional landscape elements, spatial data sets of characteristics for 68 small (0·2–1·5 km²) boreal forest catchments in western central Sweden were analysed in a geographical information system (GIS). The geographic data used were extracted from official topographic maps. Water sampled four times at different flow situations was analysed chemically. This paper focuses on one phenomenon that has an important influence on headwater quality in boreal, coniferous forest streams: generation and export of dissolved organic carbon (DOC). It is known that wetland cover (bogs and fens) in the catchment is a major source of DOC. In this study, a comparison was made between a large number of headwater catchments with varying spatial locations and areas of wetlands. How this variation, together with a number of other spatial variables, influences the DOC flux in the streamwater was analysed by statistical methods. There were significant, but not strong, correlations between the total percentages of wetland area and DOC flux measured at a medium flow situation, but not at high flow. Neither were there any significant correlations between the percentage of wetland area connected to streams, nor the percentage of wetland area within a zone 50 m from the stream and the DOC flux. There were, however, correlations between catchment mean slope and the DOC flux in all but one flow situations. This study showed that, considering geographical data retrieved from official sources, the topography of a catchment better explains the variation in DOC flux than the percentage and locations of distinct wetland areas. This emphasizes the need for high‐resolution elevation models accurate enough to reveal the sources of DOC found in headwater streams. Copyright © 2007 John Wiley & Sons, Ltd.     

差分主成分分析法在辽河三角洲景观变化中的应用

差分主成分分析法是应用遥感数据检测景观变化的一种新方法。为了提高检测精度,我们利用TM卫星遥感数据,改进了主成分分析法和图像差值法,提出了差分主成分分析法。并以辽河三角洲地区为例,对该方法进行了验证。研究结果表明：(1) 与传统的检测法-分类后比较法相比,差分主成分分析法具有较高的检测精度,总检测精度为0.89,Kappa指数为0.82;(2) 在1984~2000年的16年间,辽河三角洲地区有近22%的景观发生了变化,主要包括芦苇湿地的减少、水稻田的增加以及城镇用地的增加。     

三江平原湿地景观结构的时空变化

基于湿地是流域中重要的景观和生态系统的思想,结合已有历史资料和遥感资料进行不同时段景观制图和GIS分析,对三江平原挠力河流域湿地景观结构和50年 (1949~2000) 来时空变化进行了系统研究,得出的主要结论为：(1) 流域湿地具有特殊的纵向结构、横向结构的景观梯度特征和内部结构特征,并且景观梯度特征与流域地形梯度、水文梯度以及地貌结构特征相协调;(2) 流域湿地景观结构在人类活动干扰下发生了巨大变化：景观纵向结构从连续的基质景观变化为河岸带景观,横向结构从明显的景观类型梯度特征变化为单一类型景观,而景观内部结构特征则表现为镶嵌斑块体的不断丧失;(3) 大规模土地开发活动和水利工程建设是流域湿地景观结构变化的主要驱动力。     

贵州岩溶区镶嵌景观上覆土层的粒度分布特征及其指示意义

通过对贵州岩溶区喀斯特镶嵌景观中碳酸盐岩与碎屑岩相互接触部位剖面的粒度分布特征综合对比、分析研究,结果表明:不同岩石上覆土层之间的粒度频率曲线和粒度参数存在明显的差异,仅在两种岩石类型的接触过渡带显示出一定混合特征,且与区域其它岩类上覆土层没有关联性;各土层粒度分布特征与下伏基岩有着密切的联系,显示出继承性。同时,进一步肯定了粒度分布特征在贵州岩溶区上覆土层的物源指示意义。      

黑河流域中游张掖绿洲景观格局研究

在解译的张掖绿洲土地利用/土地覆盖图的基础上, 进行相关的景观类型综合处理, 计算了绿洲景观格局的多个指数. 结果表明, 绿洲景观的组成以戈壁、沙地、耕地和草地为主, 体现了荒漠基质受人工影响而形成的典型农业型绿洲的特点. 绿洲内居民点众多, 仅与少数类型邻接并且比较分散, 戈壁、平原旱地和沙地分布则比较集中. 盐碱地和裸岩石砾地的形状最复杂, 戈壁的形状则最简单; 同时, 平原旱地、戈壁和裸岩石砾地的连接性均较好, 在景观中占有较大比重, 类型间的物质和能量迁移比较通畅.     

青藏高原冻融荒漠化的若干问题——以藏西-藏北荒漠化区为例

冻融荒漠化是高海拔地区特有的土地退化过程,依据生态基准面理论将青藏高原冻融荒漠化划分为极重度、重度、中度和轻度4个等级.藏西-藏北区冻融荒漠化面积达44303.73km²,多呈斑块状零星分布和片状分散分布.高原冻土区具有冻融荒漠化形成的环境基质,近40a区域气候持续变暖,人为活动频率与强度加剧,鼠类活动猖獗,使浅层多年冻土的冻融过程加剧,从而形成冻融荒漠化土地.其形成过程主要有多年冻土季节融化层增厚-地下水位下降-地表土壤干燥化、地表覆盖改变或地下融水增加-冻土融冻界面热融-地表沉陷破碎、冻融作用过程和斜坡过程受到强化等.预测未来20~30a冻融荒漠化继续发展,程度加重.防治冻融荒漠化的对策主要是减轻草场压力、恢复草地植被,加强鼠害防治和合理布局开发工程、采用工程与生物措施等.     

Influences of watershed landscape composition and configuration on lake‐water quality in the Yangtze River basin of China

Lake‐water quality is highly dependent on the landscape characteristics in its respective watershed. In this study, we investigated the relationships between lake‐water quality and landscape composition and configuration within the watershed in the Yangtze River basin of China. Water quality variables, including pH, electrical conductivity (EC), dissolved oxygen (DO), Secchi depth (SD), NO₂^?, NO₃^?, NH₄⁺, TN, TP, chemical oxygen demand (COD_Mn), chlorophyll‐a (Chl‐a), and trophic state index (TSI), were collected from 16 lakes during the period of 2001–2003. Landscape composition (i.e. the percentage of vegetation, agriculture, water, urban, and bare land) and landscape configuration metrics, including number of patches (NP), patch density (PD), largest patch index (LPI), edge density (ED), mean patch area (MPA), mean shape index (MSI), contagion (CONTAG), patch cohesion index (COHESION), Shannon's diversity index (SHDI), and aggregation index (AI), were calculated for each lake's watershed. Results revealed that the percentage of agriculture was negatively related to NO₂^?, TN, TP, Chl‐a concentrations, and TSI, while the percentage of urban was significantly correlated with EC, NH₄⁺, and COD_Mn concentrations. Among landscape‐level configuration metrics, only ED showed significant relationships with TN, TP concentrations, and TSI. However, at the class level, the PD, LPI, ED, and AI of agriculture and urban land uses were significantly correlated with two or more water quality variables. This study suggests that, for a given total area, large and clustered agricultural or urban patches in the watershed may have a greater impact on lake‐water quality than small and scattered ones. Copyright © 2011 John Wiley & Sons, Ltd.     

Establishing rates of karst landscape evolution in the Tropics: a context for the formation of archaeological sites in western Flores,Indonesia

Tropical landscapes evolve at a rapid rate, creating stepped alluvial terraces, dense basin and cone topographies and multilevel cave systems. An understanding of the rate of landscape evolution is crucial for understanding how landscapes respond to tectonic instability and for reconstructing landscapes that have changed over archaeological timescales. The rate of landscape incision as a proxy for karst landscape evolution in Indonesia, a key region in the path of human dispersal, has been established using the rate of karstification – by estimating a chronology for stages of cave development using thermal ionisation mass spectrometry U‐series dating on flowstones, and the rate of downcutting – by establishing a chronology for a series of alluvial terraces using red thermoluminescence dating. Using these techniques we have determined that the estimated rate of karstification (113 ± 26 mm ka^?1) is slower than the average rate of downcutting (305 ± 24 mm ka^?1), and the combined rate of landscape incision (217 ± 18 mm ka^?1) is slower than the known rate of tectonic uplift for this region derived from raised coral terraces (450 ± 50 mm ka^?1). This suggests that rivers are quicker to respond to tectonic instability, but both cave and river systems display a slower rate of incision and karstification than uplift. Correlations between these components of the landscape system reveal a strong, interacting relationship where defined phases of uplift are reflected in the pattern of karstification and cycles of downcutting. An understanding of this relationship has been pivotal in reconstructing the formation and geomorphic history of archaeological caves such as Liang Bua. Copyright © 2010 John Wiley & Sons, Ltd.     

哈尔滨市景观生态风险时空变化驱动力及分布预测

本文以哈尔滨市为研究对象,首先构建了景观生态风险及预测模型;然后对1998—2018年景观生态风险时空变化驱动力进行分析;最后对研究区域2023年景观生态风险空间分布进行预测。结果表明：①研究区域近20年景观生态风险先降低后升高,空间格局变化较为显著。②道路距离、第二产业、农业、高程为景观生态风险变化主要驱动力。1998—2008年,主城区周围道路距离系数逐年减小,南部地区逐年增高,其他时间内未见明显变化;农业和高程对区域景观生态风险的总体影响显著,存在空间差异;第二产业对区域景观生态风险影响程度呈现先增后降的变化。③预测所得的2023年景观生态风险空间差别不明显,降低区域比升高区域面积大。     

陕北干旱区景观生态风险空间分异特征及驱动因素分析

陕北黄土高原属于生态脆弱区,是国家生态修复重点项目区。本文以陕北榆林市2000—2020年3期土地利用数据为数据源,用网格法构建基于景观格局的综合生态风险指数模型,定量分析了榆林市景观生态风险时空分布,并采用地理探测器、R和Origin软件等工具定量分析了土地利用与生态风险的耦合关系。结果表明:2000—2020年该地区生态风险整体趋于下降,低生态风险区面积增加、高生态风险区面积逐渐较少且向西北方向偏移;中风险区域面积逐年增加,该区域仍存在较强潜在生态风险;在人类活动影响下的林地、草地面积变化,以及自然胁迫是驱动景观生态风险变化的主要因素。