水沙变异对黄河三角洲湿地面积演变的影响

水沙过程是塑造湿地生态系统结构与功能的重要驱动力,控制着湿地的形成与演化。利用1976年-2014年近40年黄河三角洲湿地面积变化的遥感影像数据,系统分析湿地面积、湿地重心和南北区域湿地类型的动态变化进特征。研究结果显示:近40年来黄河三角洲人工湿地面积增加约1 000倍,自然湿地面积呈波动下降趋势,减少约41.9%;芦苇、滩涂、养殖及盐田湿地等典型湿地面积重心整体由西北向东南方向位移;南北部区域的湿地类型的演变出现呈现较为明显的差异特征,其中北部芦苇湿地、滩涂湿地面积呈减少趋势,南部芦苇湿地面积整体呈增加趋势,滩涂湿地面积先增加后减少。研究结果可为水沙变异条件下黄河三角洲湿地生态系统的保护与修复提供科学依据。     

基于RS和GIS的艾比湖湿地信息提取及面积动态分析

采用新疆艾比湖湿地保护区的1972年Landsat/MSS、1990年的Landsat/TM、2001年和2006年的Landsat/ETM+遥感数据,利用RS与GIS技术,对研究区的遥感影像进行处理及湿地信息提取。在图像预处理时通过分析Landsat/MSS／TM／ETM+各波段之间相关系数来选择最佳波段;在湿地信息提取技术方面,采用监督分类中的最大似然法进行分类提取湿地信息,并对湿地信息动态变化进行研究。结果表明:在30多年间,研究区湖泊湿地面积经历了迅速缩小、基本稳定、逐步增大3个阶段;1972—2001年沼泽湿地和河流湿地面积持续增加;2001—2006年沼泽湿地面积小幅减少,河流湿地面积保持稳定;1972—2006年人工湿地、绿洲、农业用地面积呈现逐渐增加趋势。     

基于遥感云计算的鄱阳湖湿地植被群落分类研究

针对大型通江湖泊湿地植被精细分类中精度不高、算法稳健性不强的问题，以鄱阳湖湿地植被为研究对象，基于遥感云平台GEE和Sentinel-2影像，着重研究不同训练样本数量、不同时相特征数据及不同机器学习算法对鄱阳湖湿地植被类型分类的影响。结果表明：(1)随着训练样本数量的增加，植被类型的分类精度呈现先上升后平稳的规律，当不同植被类型训练样本达到550个时，精度达到峰值平稳状态；(2)不同时相特征的数据集分类精度具有显著差异，具体为：月度时序>枯水期>四季多时相>单时相，其中，月度时序数据集的总体精度最高，总体精度及Kappa系数分别为82%和0.79;(3)不同遥感算法获得的分类结果精度不同，RF分类精度最高，SVM和CART次之；(4)当不同植被类型的训练样本达到550个时，使用Sentinel-2月时序影像和RF算法能取得最优的分类结果。研究成果可为鄱阳湖湿地精细分类提供方法借鉴，为鄱阳湖湿地保护提供技术支持。     

基于SPOT-VGT数据的洞庭湖水体面积变化分析

监测洞庭湖水体变化、全面了解其变化规律和演化趋势对于湖区治理和防洪减灾具有重要的现实意义.本文基于SPOT-VGT NDVI数据,采用动态阈值法提取了洞庭湖1998-2010年间逐旬水体信息,并结合历史数据分析了水体面积变化特征.主要结论如下:①动态阈值方法在长时间序列、大数据量的遥感信息提取中具有显著优越性.②洞庭湖水体面积在年内呈现明显季节性变化;在年际呈缩减趋势(丰水期);1825-2010年水体缩减呈现四个阶段,当前处于新一轮的锐减期.③基于累积降雨量数据建立的水面积预测经验模型,精度较为理想.     

基于MODIS数据的洞庭湖水面面积估算方法

利用美国Terra卫星上MODIS传感器提供的NDVI数据产品,采用两种方法分别在年和月时间尺度上对2000~2007年间洞庭湖的水面面积进行了估算。在年尺度上,采用ISODATA方法对NDVI时间序列进行非监督分类,区分水面及各种湿地类型,并分析了各类湿地的面积变化趋势。在月尺度上,采用16 d平均NDVI数据,通过NDVI阈值提取水面,在不同的季节选取不同的阈值,并将基于NDVI数据得到的水面面积与基于水位—面积曲线得到的水面面积进行了对比分析。在此基础上,探讨了两类不同尺度上分类方法的优点、缺点及适用范围。     

扎龙湿地景观的遥感信息提取

文章以扎龙自然保护区为研究区域,利用2014年与2020年扎龙湿地遥感影像作为数据源,对遥感影像进行处理,获取研究区内各种不同地表类型的训练样点,提取训练样本,得到各自的训练数据,利用神经网络分类方法对整个扎龙湿地地表覆盖类型进行分类,得到扎龙湿地景观类型分类图。通过2014年与2020年2a的影像对比,得出6a来扎龙湿地的各部分面积变化,分析6a间各部分景观面积变化的影响因素,为湿地生态系统的研究及保护工作提供数据基础。结果表明：神经网络分类结果较为精确,2014—2020年6a间,扎龙自然保护区内草地面积增加明显;明水、有水湿地面积略有增加;而农田、盐碱地、以及无水湿地面积减少,其中无水湿地面积减退较多,湿地整体情况稳中向好。     

2013～2018年东洞庭湖水域面积变化遥感监测与分析

为研究新形势下洞庭湖的江湖格局变化情况,基于2013～2018年Landsat 8-OLI卫星9个时相的遥感数据,提取近期东洞庭湖水域面积时程变化特征,并利用已有的水位观测资料,建立了水域面积与城陵矶站水位之间的相关关系。结果表明：（1） 2013～2018年东洞庭湖水域面积呈现动态变化,介于229.55～996.32 km²,平均502.00 km²;（2）年内汛期6～7月份水域面积最大,枯季水域面积则最小,空间分布上东洞庭湖沿湘江深水河槽以及湖区西北部较深的分叉型水槽为常年水体,其面积占比不足湖区总面积的20%;（3）东洞庭湖水域面积与城陵矶站水位呈显著正相关,相关系数可达0.96。水位变化是湖区水域面积变化的主控因素,研究成果进一步验证了洞庭湖涨丰枯退水情下的江湖格局。     

黑河和白河流域湿地变化及其归因分析EI北大核心CSCD

通过构建决策树模型对黑河、白河流域沼泽化草甸湿地、沼泽湿地、湖泊等主要湿地类型进行划分,选取3种景观格局指标分析湿地类型的变化特征,采用主成分分析方法对湿地变化的驱动因素进行分析。结果表明:2000年以来,黑河、白河流域湿地总面积呈增加趋势,沼泽湿地变化趋势与草甸湿地相反,存在此消彼长的特征;两河流域湿地变化的地域分异显著,黑河流域草甸湿地面积呈扩大态势,破碎化程度降低,沼泽湿地有所减少,但斑块密度降低,存在局部连片情形;白河流域沼泽湿地面积增加,适宜地形和水文条件下,草甸湿地和周边草甸可转为沼泽湿地;两河流域湿地变化具有“社会经济+农牧业因素+气候变化”交互作用的特征,社会经济类因素对年代际尺度湿地变化起主导作用。     

基于时序特征的黄河三角洲土地覆盖动态及驱动力分析

综合不同土地利用类型的Landsat影像时序特征和面向对象分割方法,分析1985-2018年现代黄河三角洲土地覆盖时空特征,探讨土地覆盖变化的驱动机制。结果表明:1985-2018年间研究区天然湿地面积大幅减少,共减少9.9847×104 hm²,其中沼泽和草甸湿地面积减少尤为明显,而人工湿地面积则逐年增加,年平均增加率达54.66%,主要是盐田养殖场和水稻种植面积的增大;社会经济因素对研究区土地覆盖的影响程度高于水文因素;输沙量是影响研究区土地覆盖变化的主要水文因素,实测径流量的减少进一步导致天然湿地向旱地类型转化;人口和GDP变化对人工湿地面积增加的正相关作用比较显著,而天然湿地面积的减少则与该两个指标的负相关关系比较明显。     

基于遥感和GIS的江苏滨海地区湿地信息提取及动态变化分析

掌握湿地分布及动态变化特征能够为更好地保护湿地提供科学依据。以江苏省滨海湿地为研究对象,对研究区1992年、2002年、2012年3个时期的遥感数据进行处理,利用最大似然法分类提取湿地信息,研究滨海地区的湿地信息、动态变化并对驱动因子进行分析。结果表明江苏滨海湿地总面积呈减少趋势,其中人工湿地所占比重增加了22.43%,自然湿地所占比重则相应减少,此外自然湿地呈现以獐茅、盐蒿群落大幅度减少以及米草先大范围扩散后相对稳定的趋势;在转移过程中,转入面积最高的是人工养殖塘,而转出率由光滩变成了浅海水域;滨海湿地变化驱动因素主要是人类活动影响。     

近10年来洞庭湖区水面面积变化遥感监测分析

以Terra/MODIS 8d合成的250m地表反射率数据产品MOD09Q1(MODIS Terra Surface Reflectance 8-Day L3 Global 250m)为主要数据源,采用多源信息水面提取的方法对2000年3月—2008年12月间洞庭湖区水面面积的变化特征和趋势进行了监测分析。分析结果显示:(1)洞庭湖区水面变化的季节性特征显著,其中枯水期11月—次年4月份间的湖区水面相对较小,基本在500km2左右,而洪水期5—10月份的水面则相对较大,尤其每年的7—9月份最大,维持在2000km2左右,两者几乎相差了4倍;(2)受气候变化与三峡工程初期运行等因素的共同影响,洞庭湖区水域面积总体上呈现出一定程度的下降趋势;(3)通过流域年降水量变化分析和三峡水库蓄水运行前后松滋、太平和藕池三口年径流量变化对比,发现流域内降水带来的入湖水量偏少是近年来洞庭湖区水面面积减小的主要驱动因子;(4)近年来9、10月份洞庭湖流域降水减少与三峡水库汛末蓄水同期,将共同造就最终入湖水量锐减,加重湖区夏秋连旱程度,进而诱发系列生态安全问题。     

洞庭湖湿地生态保护现状及对策

洞庭湖湿地是国际重要湿地,具有调蓄长江洪水、维系水域生态平衡、保护珍稀候鸟、繁衍生物多样性等功能,是长江流域重要的经济区。详细介绍了近5年来洞庭湖湿地生态保护所取得的成绩,指出了存在的问题,提出了进一步做好生态保护工作的对策。     

阿穆尔河流域水环境变化条件下的生态环境分析

阿穆尔河流域水环境变化条件下,运用GIS和RS技术,对阿穆尔河流域的2期NOAA影像数据和1期MO-DIS影像数据进行解译判读,获取不同时期阿穆尔河流域湿地与生态要素数据,为研究区的生态地质环境治理提供数据依据。通过动态度模型和转移矩阵模型,对研究区1992年-2010年间的湿地与生态的动态变化情况进行了量化的分析。结果表明:1992年-2010年18a间,沙化土地的动态度最大,为15.25,属于急剧变化型,沼泽和湿地面积大面积减少,林草混杂地面积减少,沼泽、湿地、林草和混杂地快速转化为林地和耕地,在近10a间,沙化土地面积又有增加趋势,主要转入类型为林地和草地混杂地。     

洞庭湖区土地覆被对长江水位变化的响应分析

为了研究长江水位的变化对洞庭湖区土地覆被的影响,基于洞庭湖区近26 a土地覆被遥感影像的解译成果,分别构建了东洞庭湖区和西+南洞庭湖区水域、泥滩、草洲、芦苇地、裸地和防护林面积与对应时段城陵矶水位之间的回归方程。分析结果显示：东洞庭湖区水域、泥滩、草洲面积和西+南洞庭湖区水域面积与城陵矶水位之间具有极显著的相关关系,而芦苇地、裸地和防护林等面积与城陵矶水位之间的关系并不显著;城陵矶水位变化对东洞庭湖区土地覆被的影响明显高于对西+南洞庭湖区土地覆被的影响。此外,依据所构建回归方程,预测长江上游大型梯级电站运行将导致洞庭湖区呈现泥滩和草洲挤占水域的态势。     

生态文明视野下长江中下游湿地生态承载力评价

在生态文明视野下,提出了区域生态承载力新内涵,创建了人地系统耦合协调模型及状态空间模型,从生态支撑力、资源能源消耗压力以及环境污染排放压力3个方面构建生态文明视野下长江中下游湿地区域生态承载力评价体系,并选取2010年数据进行定量评价。研究表明：（1）研究区德安县、湖口县、南县以及永修县4个县市为超载失调区,新建县等10县市为可载失调区,进贤县及武汉等10个县市为可载较协调区,安庆县等15个县市为微超载较协调区;（2）生态承载力超载失调区域全部位于洞庭湖湿地区与鄱阳湖湿地区,而可载失调区域则比较分散,基本位于长江干流湿地区以及鄱阳湖湿地区东部;（3）利用SEPI模型分析,洞庭湖、鄱阳湖湿地区、江汉湖群湿地区以及长江下游干流湿地区县市经济社会压力的特点都是偏重环境污染。综合以上分析结果,提出了发展建议。     

Impacts and Implications of Major Changes Caused by the Three Gorges Dam in the Middle Reaches of the Yangtze River, China

The impoundment of the Three Gorges Dam (TGD) has disturbed the hydrological regime downstream and has directly affected the relationship between the Yangtze River and Dongting Lake. To trace the realistic and potential impacts, this paper examined the changes of the channel morphology and sedimentology caused by the TGD through a field survey on the channel cross-sections and then analyzed the impact on lake water level through BP neural networks. The possible impacts on inundation patterns in lake wetlands were studied based on the lake basin DEM. The results indicate that drastic sediment decline and severe channel erosion are putting considerable pressure on the river and lake. Changing river channels are evident in some monitoring cross-sections. Dongting Lake, for the first time, changed from trapping to supplying net sediment to the Yangtze River. During the water storage periods of the TGD, the water level decreased 2.03?m in 2006 and 2.11?m in 2009 at the outlet of the lake, with extreme decreases up to 3.30?m and 3.02?m, respectively. These changes have inevitably induced alterations in the inundation patterns of the lake wetlands, which in turn have disturbed the ecological function of lake wetlands as habitats for both migratory birds and aquatic fish. The serious droughts in Dongting Lake recent years were largely connected with the above changes. Therefore, proper attention should be paid to this occurrence.     

Changes in Marsh Area Along the Canadian Shore of Lake Ontario

Baseline marsh area is approximated for the Canadian shoreline of Lake Ontario west of the Bay of Quinte using maps dated from 1789 to 1962. The measured difference between that and the area of marsh indicated on topographical maps dated from 1977 to 1979 reveals a net loss of about 4,000 acres or 57% of the baseline area for 38 marshes. Using extrapolation for another 24 marshes, the net loss for 62 marshes is estimated at approximately 4,745 acres or 43% of the baseline area. Losses were particularly high for marshes west of and including Toronto. Estimated net loss was lower in absolute terms, but similar in proportion to that from a previous study which was based on waterfowl production habitat. Relative losses of marsh area along the Canadian shoreline of Lake Ontario are consistently higher than previous estimates for inland wetlands in counties fronting the same shoreline. This and other studies suggest that heavily settled Great Lakes environments have generally lost up to 75% of their baseline wetland area and almost 100% in a few cases. The use of historic maps provides an early baseline estimate of wetland area, in some cases the only estimate possible, but it is less subject to standardization, probably reflects emergent vegetation, and is somewhat cumbersome.     

Edge effects on abiotic conditions,zooplankton, macroinvertebrates,and larval fishes in Great Lakes fringing marshes

Fragmentation and edge creation is common in many freshwater coastal wetlands, though relatively little is known about edge effects on abiotic conditions and faunal communities within these habitats. We investigated edge effects associated with anthropogenic fragmentation in 16 fringing coastal marshes of Lake Michigan and Lake Huron. Environmental data, zooplankton, macroinvertebrates, and larval fish were collected along transects extending into each marsh from reference (i.e., where the wetland naturally interfaced with open water) and anthropogenic edges (i.e., where the wetland interfaced with open water habitats created by vegetation removal). Physical and chemical gradients were apparent from marsh edges toward marsh interiors regardless of edge type. Faunal communities appeared to respond to these gradients. Zooplankton biomass, macroinvertebrate richness and macroinvertebrate Shannon diversity were depressed at edges and increased toward marsh interiors. Larval fish catch per unit effort, taxon richness, and Shannon diversity increased from reference edges toward marsh interiors. Larvae of individual fish species displayed varying patterns across edges. Our results suggest that because of edge effects, fragmentation of coastal marshes causes impacts that exceed the area of marsh habitat that is actually lost. For example, as a marsh's protected inner core area is reduced, the marsh fragment may cease to function as a viable refuge from hydrologic energy and open water predators. Therefore, fragmentation should be viewed as a significant impact to freshwater coastal marsh ecosystems similar to how it is regarded in terrestrial ecosystem management.     

Environmental Monitoring of Spatio-temporal Changes Using Remote Sensing and GIS in a Mediterranean Wetland of Northern Greece

Loss and degradation of terrestrial and aquatic habitats and degraded water quality are major environmental concerns worldwide. Especially wetlands are sensitive ecosystems that are subject to stress from human activities. Remote sensing techniques have been primarily used to generate information on land cover/use changes. Geographical Information Systems (GIS) and remote sensing can be used to provide a rapid or a large-scale understanding of lake change and in developing lake management strategies. The principal objectives of this study are to monitor and assess the spatial and temporal changes in land cover/use by using GIS, and to determine the main environmental factors affecting these changes. This paper presents a case study for the application of integrated remote sensing and GIS data for the classification and monitoring of the spatial and temporal changes in land use types. The study was conducted in a small natural wetland of Lake Cheimaditida, located in the East Mediterranean region of Northern Greece. Data analysis was conducted using GIS software. During the past several decades Lake Cheimaditida wetland has been influenced by many anthropogenic activities. The variables chosen for the assessment included condition of wetland and lake areas, present extent of wetlands relative to historic area, cover of natural habitat, wetland disturbances, etc. These variables address catchments properties that are important for maintaining and improving wetland habitats and water quality and assessment of trends useful for environmental monitoring. Land cover/land use patterns were assessed and compared using aerial photographs taken in 1945, 1969, 1982, and 1996. Over this period, reed beds enormously increased by 1,655.19%, while open-water areas and peat lands decreased by 74.05 and 99.5%, respectively. The significance of the changes in land cover distribution within the Lake Cheimaditida wetland are discussed in relation to the historical pattern of reed beds colonization, the importance of Phragmites australis in the process and the implications for strategic management of freshwater wetland resources.