Remote sensing-based dynamic monitoring and environmental change of wetlands in southern Mongolian Plateau in 2000‒2018

The environmental change in the wetlands in the southern Mongolian Plateau has important impacts on the environment of North China and even the entire Northeast Asia,from which the global climate change can be understood on a large scale,especially the climate change in the Mongolian Plateau.This study extracted the information on the wetlands from three stages of remote sensing images(also referred to as RS images)of the study area,including Enhanced Thematic Mapper Plus(ETM+)images of 2000,TM images of 2010,and Landsat 8 Operational Land Imager(OLI)images of 2018.As indicated by the extraction results,the area of wetlands decreased from 796.90 km^(2) of 2000 to 666.24 km^(2) of 2018 at a rate of 7.26 km^(2)/a.The reduced area is 130.66 km^(2),which is about 16.4%reduction.And the patch number of wetlands decreased from 731 of 2000 to 316 of 2018 in the study area,approximately 56.8%reduction(415 patches),and the decrease in the area of the wetlands mainly occurred in the northwest endorheic region.In terms of wetland types,the change of the wetlands was dominated by the decrease of lacustrine wetlands,of which the area and patch number decreased by 106.2 km^(2) and 242,respectively.Furthermore,the area of the lacustrine wetlands decreased at the highest rate of 8.70 km^(2)/a in 2010‒2018.From the perspective of spatial distribution,the wetlands in the western part shrunk more notably than those in the eastern part as a whole in the study area.According to local meteorological data,the precipitation gently decreased and the temperature increased(about 1.7℃)from 1975-2018.Overall,the decrease in the area of the wetlands and the temperature rises in the study area were mainly driven by the Mongolian monsoon climate,reduction in precipitation,and human activities.

THE DYNAMIC MONITORING OF HORQIN SAND LAND USING REMOTE SENSING

Horqin Sand Land is regarded as the typical region for studying the problemof desertification. The integration of 3S(GIS, GPS and RS) techniques offer a roost helpful methodto study and monitor the dynamics of desertification. Based on the data derived from 3 periods'multitemporal Landsat TM imagery of the 1990s, the regional land use and dynamics of desertificationin Horqin Sand Land were studied. The main results revealed that: 1) as long as the general changetendency was concerned, the desertification of Horqin Sand Land would continue to spread; 2) therewas a gradual decrease in the area of both moving sand dunes and semi-stabilized ones, which meantthat fruitful progress had been made to control the desertification during the 1990s; 3) as a resultof unreasonable cultivation, the total area of stabilized sand dunes and grassland in the middleand western region decreased obviously. It suggested that the increasing damage caused by human wasleading to the hazard of further desertification. So in the future, it is necessary to take moreeffective measures to control the spread of desertification and restore the degraded ecosystems forthe purpose of optimizing the global eco-environment in Horqin Sand Land.

Urban Expansion in China Based on Remote Sensing Technology：A Review

Urban areas and its evolution are important anthropogenic indicators and human ecological footprints, and play decisive roles in environmental change analysis, global geo-conditional monitoring, and sustainable development. China has the highest rate of urban expansion and has emerged as an urban expansion hotspot worldwide. In this paper, the progress of studies on Chinese urban expansion based on remote sensing technology are summarized and analyzed from the aspects of urban area definition, remotely sensed imagery applied in urban expansion, monitoring methods of urban expansion, and urban expansion applications. Existing issues and future directions of Chinese urban expansion are discussed and proposed. Results indicate that: 1) The fusion of multi-source remotely sensed imagery is imperative to meet the needs of urban expansion with various monitoring terms and frequencies on different scales and dimensions. 2) To guarantee the classification accuracy and efficiency and describe urban expansion and its influences on local land use simultaneously, the combination of visual interpretation and automatic classification is the tendency of future monitoring methods of urban areas. 3) Urban expansion data have become the prerequisite for recognizing the urban development process, excavating its driving forces, simulating and predicting the future development directions, and also is conducive to revealing and explaining urban ecological and environmental issues. 4) In the past decades, Chinese scholars have promoted the application of remote sensing technology in the urban expansion field, with data construction, methods and models developing from the quotation stage to improvement and innovation stage; however, an independent and consistent urban expansion data on the national scale with long-term and high-frequency(such as annual monitoring) monitoring is still lacking.

Monitoring of Land-Cover Dynamic Change in Lancangjiang River Cascaded Hydropower Area

The analysis of the 3 stages＇ （1988,1996,2000） variation of land-cover is performed according to Thematic Mapper （TM） and Enhancement Thematic Mapper（ETM） satellite image by combining ground GIS database with GPS field collected data in the area of Xiaowan-Dachaoshan Reservoirs of Lancangjiang River cascaded Hydropower Area. Consequently, the land-cover is divided into five subclasses, namely water, paddy field and wetland, bare dryland and sparse shrub, secondary forest and density forest. The result showed that the areas of bare land, upland and secondary forest decreased in 1988-1996, whereas from 1996 to 2000, water body and density forest keep invariability while the areas of paddy field and wetland, bare dryland and sparse scrub increasing and the area of secondary forest decrease; Features of reciprocal transformation between density forest and other type of land-cover had two points, i.e. secondary forest, bare dryland and sparse shrub converted to density forest; and density forest converted to secondary forest and paddy field and wetland. It reflects the dynamic variation of density forest; the area which slope less than 8° and greater than 15° shows bigger variation, however, less change in 8°-15°.

RESEARCH ON AUTOMATIC FOG IDENTIFICATION TECHNOLOGY BY METEOROLOGICAL SATELLITE REMOTE SENSING

There is an urgent need for the development of a method that can undertake rapid, effective, and accurate monitoring and identification of fog by satellite remote sensing, since heavy fog can cause enormous disasters to China’s national economy and people's lives and property in the urban and coastal areas. In this paper, the correlative relationship between the reflectivity of land surface and clouds in different time phases is found, based on the analysis of the radiative and satellite-based spectral characteristics of fog. Through calculation and analyses of the relative variability of the reflectivity in the images, the threshold to identify quasi-fog areas is generated automatically. Furthermore, using the technique of quick image run-length encoding, and in combination with such practical methods as analyzing texture and shape fractures, smoothness, and template characteristics, the automatic identification of fog and fog-cloud separation using meteorological satellite remote sensing images are studied, with good results in application.

A RESEARCH ON THE DYNAMIC MONITORING SYSTEM FOR FORAGE-LIVESTOCK BALANCE IN THE TEMPERATE CRASSLAND OF CHINA

Some principles and methods for the dynamic monitoring of forage-livestock bal-ance in the grazing system on the temperate grassland of China were discussed in thispaper. To prepare a dynamic monitoring system or the forage livestock balance of grazingrangeland system, the following theoretical bases will be observed in this work.

Overview of Land Use/Cover Change Dynamic Monitoring Methods

With the emergence of global environmental change issues,Land Use/Cover Change(LUCC)issues have received increasing attention.Therefore,the dynamic monitoring of LUCC has also become very important.In this paper,preliminary exploration was made to the research progress on the dynamic monitoring technologies for LUCC as well as their advantages and disadvantages,and prediction was made to the development trend of future monitoring technology.

基于Landsat影像的城市土地利用动态监测

土地是自然界不可或缺的资源,土地利用反映了人地关系。随着人口数量的持续增加和社会工业化、城市化的持续推进,如何科学地开发利用宝贵的土地资源越来越受到人们的重视。本文通过2013年和2023年的Landsat影像数据,结合遥感与GIS,对10年间合肥市土地资源进行监测与分析,结果表明,经过10年的城市发展,合肥市耕地面积减少了65707.92 hm 2,建设用地增长了39181.05 hm 2,林地减少了1728.27 hm 2,水域增加了28255.14 hm 2。

盐城自然保护区盐沼植被分布动态监测及驱动力分析

为探究江苏盐城湿地珍禽国家级自然保护区盐沼植被时空演变规律,采用物候特征合成方法反演了1984—2021年保护区核心区4种盐沼植被(互花米草、芦苇、碱蓬和茅草)面积,分析其时空演变规律和驱动机制。结果表明:核心区盐沼植被总面积从11113.2 hm^(2)增长至16528.14 hm^(2),年均复合增长率为1.11%,主要得益于互花米草的保滩促淤能力;互花米草和芦苇通过占领大量碱蓬滩、茅草滩和光滩,面积分别增加了4968.62 hm^(2)和8806.95 hm^(2),年均复合增长率分别为26.67%和6.88%;受生态位竞争等自然因素和水产养殖基地等人工干扰的叠加影响,碱蓬和茅草面积分别减少了3494.25 hm^(2)和4867.38 hm^(2),年均复合增长率分别为-3.14%和-8.11%,适宜生境破碎化严重。

基于连续变化检测和分类算法的动态遥感生态指数构建

沿海地区经济社会高速发展,是生态环境变化的焦点区域。然而,沿海地区云雨天气频发,遥感信息获取能力受限,导致遥感生态质量指数(RSEI)评价结果受成像日期变化而波动,可比性较差。针对以上问题,研究利用连续变化检测和分类(CCDC)算法构建时间序列模型,通过合成任意时刻影像、重构遥感生态指数以及改进指数归一化方式,研发了一种动态遥感生态指数(DRSEI),细化了RSEI在区域生态质量监测的时间尺度,并应用于沿海城市宁波生态质量时空变化监测。结果表明:(1)RSEI对时间差异较为敏感,当影像年内成像时间相差逾1个月,RSEI差异可达0.147,这种差异会对长期生态质量动态监测的稳定性和准确性造成影响。(2)基于合成影像的DRSEI平均绝对偏差为0.097,接近成像时间相差半个月的RSEI差异(0.072),误差相对较小,一定程度上减小了真实影像时相差异引起的误差。(3)DRSEI能够表征任意时刻生态质量,通过年际(1986—2019年)和半月际(2019年)DRSEI分析揭示了宁波市生态质量总体下降趋势和时空异质性加剧过程。具体地,1986—2019年宁波市南部和西部森林区域的DRSEI持续上升,而近郊农田快速转化为建成区导致DRSEI不断下降。研究提出的DRSEI能够精确描述区域生态质量变化趋势,准确定位生态质量变化转折点,有望服务海岸带地区的生态质量定期监测与评估工作,支持沿海城市高质量发展与生态环境保护。

基于改进遥感生态指数的金寨县生态环境质量评价

为定量评价区域生态环境质量,客观反映生态环境的变化过程,为区域生态环境保护、治理及发展规划提供科学依据,该研究基于2014、2016、2018和2020年4个时期的Landsat 8卫星影像,引入归一化山地植被指数,集成绿度、湿度、热度和干度4个指标构建改进型遥感生态指数(MRSEI),进行生态环境质量时空分布制图与动态变化分析,探究金寨县周期生态环境状况及变化原因.结果表明:(1)MRSEI具有一定的科学性,能较全面地反映研究区生态环境质量情况及时空分异特征;(2)研究周期内,金寨县全域生态环境质量较高,生态质量“优”和“良”区域占比持续上升,东北部的经济开发区及其周边生态质量较差;(3)研究区MRSEI从2014年的0.668持续提升到2020年的0.869,生态环境质量持续提高.

基于时序遥感数据的城市国土空间动态监测方法研究

随着航空航天技术的发展,对地观测变得便捷、高效,使得建立时序遥感数据集开展连续的国土空间变化监测逐渐成为一种有效手段。本文通过固定的卫星平台、采用1个季度为间隔,获取连续的遥感数据,近地采取无人机摄影的方式进行补充,建立连续、完整的时序遥感数据,并进行人机交互式的解译、识别和分析,对研究城市区域开展4个季度时相的不间断获取和识别,并连续国土空间变化监测,对比分析新城区域和市中心区域的街镇变化图斑数量及组成占比,总结浦东新区建设用地变化图斑的周期性规律和趋势特点,为“上海2035”总规专题评估提供有效支撑。

基于Sentinel-1和Sentinel-2数据融合的森林林龄反演和动态监测

【目的】在Google Earth Engine(GEE)云平台上借助其强大的计算和数据存储能力,融合多源遥感数据对森林林龄进行遥感反演和动态监测。【方法】融合2017—2023年间Sentinel-1、Sentinel-2及高程数据,通过随机森林(Random forest,RF)分类获取土地覆盖信息,并进一步提取森林的分布和面积,同时构建时间序列植被指数来准确提取森林变化区域。基于森林资源清查数据和融合的多源遥感数据,在GEE上构建RF回归、分类回归树(Cart)以及梯度提升回归树(Gradient tree boost,GTB)3种回归模型,用于杉木组、马尾松组、毛竹林、硬阔叶树组以及其他类树种组的2018年林龄遥感反演,并估算出2017年和2023年的林龄信息,以揭示林龄和龄组在2017—2023年的动态变化情况。【结果】1)2017—2023年,研究区森林面积的整体变化总计113.93 km^(2),此间森林的减少和更新并存,其空间分布特征呈现出明显的区域差异。具体而言,森林面积变化多发生于靠近城区和低海拔地区,且靠近城区的森林面积减少往往不再恢复至森林;2)在5种不同树种组构建的3种模型中,RF回归模型的林龄反演结果最佳,平均R^(2)为0.845,平均RMSE为5.32 a,其中毛竹林反演精度最高,R^(2)为0.863,RMSE为2.411 a;3)2017—2023年,研究区林龄在40 a以下的森林由54.59%减少至51.06%,其中龄组变化最显著为杉木组成熟林,面积增加了38.88%。【结论】在GEE上融合多源遥感数据进行林龄反演和动态监测具有重要的应用潜力,本研究结果可为使用云平台及哨兵系列卫星数据对森林资源长时间序列的林龄反演和动态监测的应用提供参考和借鉴。

江苏省河湖动态遥感监测探索与实践

经过多年实践,卫星遥感监测技术已成为江苏省河湖监管的重要手段。2023年起,江苏省以“两河两湖”为试点开展每日动态遥感监测,利用高分卫星和无人机智能巡检技术,对存量问题进行全面清查建库,对增量问题建立“即时发现、前置处置、动态清零”的河湖违法占用动态监测处置体系,实现了河湖违法行为“早发现、早制止、早处置”,有效遏制了大型河湖违法事件的发生,为河湖管理和执法提供了即时解决方案,对其他河湖空间管控具有参考意义。

基于无人机倾斜摄影遥感技术的水土保持动态监测方法研究

为了能够充分了解土壤侵蚀分布,及时掌握水土流失变化趋势,提出基于无人机倾斜摄影遥感技术的水土保持动态监测方法。利用无人机从多个角度采集监测区域影像数据,并实施辐射定标和大气校正预处理,基于遥感影像数据提取土壤可蚀性因子、土地利用因子、植被覆盖监测因子、坡度因子,通过计算获取水土保持系数并划分等级。监测结果表明:区域1水土保持系数呈现“V字形”,区域2水土保持系数整体呈现“一字型”,区域3水土保持系数整体呈现逐渐上升状态。

基于遥感技术的东北黑土区水土流失动态监测研究

东北黑土区是我国重要的商品粮基地,近年来面临水土流失严重、面积减小、土壤质量下降等问题,已成为目前土壤保护工作中亟待解决的重要问题。以东北黑土区2018年和2022年两期遥感影像与水土保持措施的实地调查数据作为数据源,利用目视识别法开展影像解译,并通过中国土壤流失方程CSLE进行土壤侵蚀模数的计算,对东北黑土区的水土流失变化情况及原因进行分析,结果表明:耕地、草地、建设用地、其他土地面积减少,园地、林地、交通运输用地、水域及水利设施用地面积增加,造林、种草、封育、地埂、水平阶/反坡梯田等面积共增加0.84万km^(2);对比2018—2022年东北黑土区的水土流失情况,整体呈向好趋势,土壤侵蚀面积共减少约1.01万km^(2);从侵蚀强度来看,除轻度侵蚀面积增加约0.45万km^(2)外,中度、强烈、极强烈、剧烈侵蚀面积分别减少约0.43万、0.24万、0.28万、0.51万km^(2);从不同省份侵蚀面积变化情况分析,内蒙古自治区东四盟的侵蚀面积减少最多,共减少约0.37万km^(2),辽宁省侵蚀面积变化最小,共减少约0.06万km^(2);耕地、建设用地等土地利用类型面积的减少,以及林地、交通运输用地等土地利用类型面积的增加,均可大幅减少土壤侵蚀面积,同时水土保持措施面积的增加也可有效阻止土壤侵蚀的发生。总体来看,东北黑土区水土流失治理效果显著,生态环境得到改善,持续进行东北黑土区水土流失治理对环境保护具有重要意义。

基于1990—2020年综合土地利用动态变化的巩义市城市边缘区空间研究

以郑州市下辖且接壤的巩义市为研究对象,以1990年和2020年两期TM/OLI影像和统计年鉴数据为依据,使用1 km×1 km网格划分样区并提取各样区的综合土地利用动态度数值,借助数学模型分析确定城市边缘区范围,分析巩义市近30年来城市边缘区用地变化特征及扩展机制。结果表明,自然条件是用地扩张的基础因素,政策与经济是边缘区外扩的核心驱动力,交通对扩张具有指向性作用;边缘区内的土地变化主要表现为建设用地急剧增加、农业用地锐减,同时受距离和开发时序影响,用地类型交错复杂,破碎化特征明显。

基于RSEI和地理探测器的西昌市生态环境质量时空演变特征及其驱动力分析

生态环境保护对于推动社会经济可持续发展非常重要,对生态环境质量进行及时有效的监测可为城市发展规划提供依据。本文选取西昌市2001-2020年5期Landsat TM/ETM+/OLI时间序列影像为研究数据,耦合绿度、湿度、干度、热度构建遥感生态指数RSEI,并结合研究区气候、降水量、人口密度等驱动因素探究西昌市生态环境质量变化规律。结果表明:20年间,西昌市生态环境质量得到了有效改善;生态环境质量恶化区域主要位于中部流域耕作区、主城区周边及西部山脉,改善区域主要分布在海拔稍低的山区;由单因子探测分析可知,土地利用、年平均气温、年平均降水量对RSEI影响较大;由多因子探测分析可知,各因子交互作用对RSEI均有增强效果,其中年平均气温在土地利用交互作用下表现出了更强的解释力。

基于无人机遥感影像分析的基本农田土地环境质量监测方法

研究提出了一种基于无人机遥感影像分析的基本农田土地环境质量监测方法,即利用无人机技术采集基本农田土地图像,并建立土壤、植被、气候等因素的遥感反演模型。通过综合考虑多种指标,计算基本农田土地环境综合质量指数,实现对土地环境质量的动态监测。实验证明:此种方法具有较高的监测精度,能够准确评价土地环境质量并控制评价结果误差;为农田管理者提供了可靠的数据支持,促进农田可持续发展和环境保护。

水土保持遥感应用成效与展望

卫星遥感具有全面、准确、快速的特点,在水土保持领域得到广泛应用。近年来,水利部利用多源遥感数据开展了水土流失动态监测、水土保持遥感监管、东北黑土区侵蚀沟调查等工作,全面系统掌握了全国各级行政区的年度水土流失状况及动态变化情况,摸清了人为水土流失监管的薄弱环节并查处了大量违法违规行为,掌握了东北黑土区侵蚀沟数量、分布及变化情况等。随着遥感技术的发展,高光谱遥感、激光雷达、立体测绘卫星等新技术在水土保持遥感监测方面具有良好的应用前景。遥感技术在水土保持领域的创新应用和未来发展前景,必将催生水土保持新质生产力。