Assessing land use/land cover change impacts on the hydrology of Nyong River Basin,Cameroon

Uncontrolled land use land cover change(LULCC) is impacting watershed hydrology,particularly in tropical watersheds in developing countries. We assessed the extent of LULCC in the southern portion of the Nyong River basin through analysis of three land use maps in 1987, 2000 and2014. LULCC impact on hydrological variables of the Mbalmayo, Olama, Pont So'o, Messam, and Nsimi sub-watersheds of the southern portion of the Nyong River basin were evaluated by using the linear regression modeling and the Mann-Kendall test. This study reveals that dense forest cover decreased by16%, young secondary forest increased by 18%,agricultural/cropland increased by 10%, and built-up area/bare soil increased by 3% from 1987 to 2014.The decrease in dense forest cover at 0.6% per year on average was driven by indiscriminate expansion of subsistence agricultural/cropland through shifting and fallow cultivation farming systems. Nonsignificant trends in total discharge, high flows, and low flows were observed in the large sub-watersheds of Mbalmayo and Olama from 1998 to 2013 with LULCC within the watershed. In contrast, significant decreasing trends in stream discharge(up to-5.1%and-5.9%), and significant increasing trends in high flows(up to 2.1% and 6.3%), respectively, were observed in the small sub-watersheds of Pont So'o and Messam from 1998 to 2013, particularly with increase in agricultural/cropland cover and decrease in dense forest cover. However, we found nonsignificant trends in mean annual discharge and low flows for all and whole watershed with LULCC. The results reveal spatially varying trends of stream discharge, low flows and high flows among the subwatersheds with LULCC within the study watershed.The results suggest that the impacts of LULCC on watershed hydrology are easily detected in small subwatersheds than in large sub-watersheds. Therefore,the magnitude of dense forest cover loss must be significantly greater than 16% to cause significant changes and common trends in the hydrology of the sub-watersheds of the southern portion of the Nyong River basin. The Mann-Kendall and Regression approaches show appreciable potential for modelling the impacts of LULCC on the hydrology of the southern portion of the Nyong River basin and for informing forest management.     

Land use and land cover change within the Koshi River Basin of the central Himalayas since 1990

Land change is a cause and consequence of global environmental change.Land use and land cover have changed considerably due to increasing human activities and climate change,which has become the core issue of major international research projects.This study interprets land use and land cover status and the changes within the Koshi River Basin(KRB)using Landsat remote sensing(RS)image data,and employs logistic regression model to analyze the influence of natural and socioeconomic driving forces on major land cover changes.The results showed that the areas of built-up land,bare land and forest in KRB increased from 1990 to 2015,including the largest increases in forest and the highest growth rate in construction land.Areas of glacier,grassland,sparse vegetation,shrub land,cropland,and wetland all decreased over the study period.From the perspective of driving analysis,the role of human activities in land use and land cover change is significant than climate factors.Cropland expansion is the reclamation of cropland by farmers,mainly from early deforestation.However,labor force separation,geological disasters and drought are the main factors of cropland shrinkage.The increase of forest area in India and Nepal was attributed to the government’s forest protection policies,such as Nepal’s community forestry has achieved remarkable results.The expansion and contraction of grassland were both dominated by climatic factors.The probability of grassland expansion increases with temperature and precipitation,while the probability of grassland contraction decreases with temperature and precipitation.     

Analyzing land-use change in farming-pastoral transitional region using autologistic model and household survey approach

Land change science （LCS） strives to understand and model land-use change, which will further advance the understanding of multiple issues in the socio-ecological systems. Based on GIS/RS techniques, autologistic model, and household survey method, this study investigated major land use changes and their causes from 1978 to 2008 in Uxin Banner （county-level）, Inner Mongolia in China and then developed an understanding of the relationships between household livelihood and land-use pattern. Results showed that cultivated land increased from 1988 to 2000, and leveled offafter 2000. Built-up land increased stably for the period 1978 2008. The change of grassland and bare land differed among the three periods. From 1978 to 1988, grassland increased by 23.3%, and bare land decreased by 20.48%. From 1988 to 2000, bare land expanded by 1.7%, but grassland declined by 1.3%. From 2000 to 2008, an increase in grassland area by 1.8% was observed, but a decrease in bare land area by 9.0% was witnessed. The autologistic models performed better than logistic models as indicated by lower Akaike Information Criterion （AIC） values. Factors associated with human activities significantly correlated with the change of cultivated land, forest land, grassland, and built-up land. The produce prices and extensive cultivated land use are major issues in the farming area. This study suggests that completing land circulation systems and maintaining the stability of price are effective solutions. By contrast, reclamation and overgrazing are major concerns in the pastoral areas. Implementing environmental policies effectively, transferring population out of rural pastoral areas, and developing modem animal husbandry are effective ways to address these issues.     

Land use intensity dynamics in the Andhikhola watershed,middle hill of Nepal

Land use intensity is a valuable concept to understand integrated land use system, which is unlike the traditional approach of analysis that often examines one or a few aspects of land use disregarding multidimensionality of the intensification process in the complex land system. Land use intensity is based on an integrative conceptual framework focusing on both inputs to and outputs from the land. Geographers' non-stationary data-analysis technique is very suitable for most of the spatial data analysis. Our study was carried out in the northeast part of the Andhikhola watershed lying in the Middle Hills of Nepal, where over the last two decades, heavy loss of labor due to outmigration of rural farmers and increasing urbanization in the relatively easy accessible lowland areas has caused agricultural land abandonment. Our intention in this study was to ascertain factors of spatial pattern of intensity dynamism between human and nature relationships in the integrated traditional agricultural system. High resolution aerial photo and multispectral satellite image were used to derive data on land use and land cover. In addition, field verification, information collected from the field and census report were other data sources. Explanatory variables were derived from those digital and analogue data. Ordinary Least Square(OLS) technique was used for filtering of the variables. Geographically Weighted Regression(GWR) model was used to identify major determining factors of land use intensity dynamics. Moran's I technique was used for model validation. GWR model was executed to identify the strength of explanatory variables explaining change of land use intensity. Accordingly, 10 variables were identified having the greatest strength to explain land use intensity change in the study area, of which physical variables such as slope gradient, temperature and solar radiation revealed the highest strength followed by variables of accessibility and natural resource. Depopulation in recent decades has been a major driver of land use intensity change but spatial variability of land use intensity was highly controlled by physical suitability, accessibility and availability of natural resources.     

Shrinking greenery: Land use and land cover changes in Kurram Agency,Kohi Safid Mountains of north-western Pakistan

Deforestation and other Land Use and Land Cover (LULC) changes, driven by variety of physical and anthropogenic factors, have altered the mountainous environment. Mountains around the world including northern and north western belts of Pakistan are highly sensitive to deforestation and other LULC changes, which have profound impacts on various sectors of bio-physical and socio-economic systems. Assessment of LULC changes has high significance for protection, conservation and monitoring mountainous environment. The present study is an attempt to assess the landscape changes with particular reference to forest cover depletion in Kurram Agency located in the north western mountain belt of Pakistan. For detailed comparative analysis the study area has been divided into three sections, which coincide with the present administrative divisions of the Agency, i.e., Upper, Lower and Central Kurram. Temporal span of this study covers four decades. In this study, land use map of 1970 and land sat satellite imageries of 1987, 2000 and 2014 were used as spatial data sets. The images were processed and classified into six LULC classes through geospatial packages and change detection maps were prepared for each division and time period. Findings of the study reveal two trends in the four major LULC categories. Forest and rangeland have shrunk, on average, by 15% and 7.5% respectively while, bare soil and rocks outcrops have expanded by 89% and agriculture land by 7.2% in Kurram agency. The water bodies and snow cover have minor fluctuation in its land area. Major causes of shrinking greenery is attributed to high influx of Afghan refugees and high energy demand of growing population. However, with outflow of the refugees from Kurram agency the general trend in forest cover has reverted and deforestation rate has slowed down.     

近32年来南京城市扩展与土地利用演变研究

基于1980-2012年6个时相的遥感影像分类成果,运用扩展强度的等扇分析和土地利用转移矩阵对南京市城市扩展区由城市扩展引起的土地利用布局、结构演化进行了长周期、多时段的研究。结果表明：32年间5个阶段城市扩展的方向极不均匀,城市经历了东北-东南-西南的扩展演化过程,2000年之后的扩展强度显著扩大;在总变化量的构成中,耕地净变化量和交换变化量所占的比重较为接近,在面积净减少的同时,空间位置的转移也较为突出;城市建设用地、城市绿地、采矿用地与裸地以净变化为主,水面、村镇建设用地以交换变化为主;2000年后,各时段耕地和城市建设用地年均总变化量远高于2000年之前,以2004-2008年的值最高,2008-2012年有所回落;32年间各单项类型动态度均较高,城市绿地、村镇建设用地和城市建设用地均达90%以上;综合动态度的结果揭示32年来南京城市的扩展历经了加速演变-变化趋缓-剧烈演变-整合重构4个主要阶段。     

The effect of land use changes on soil conditions in arid region

Biography:CHEN Fu(1974－ ), male,a native of Sheyang County, Jiangsu Province, doctoral candidate.His research interests include land use management.1 INTRODUCTION Land use change may influence a variety of natural and ecological processes, including soil nutrient, soil moisture, soil erosion, land productivity (FU et al., 1999), biodiversity, cycle of biographical geochemistry, and so on (VITOUSEK, 1994). So, it is very important that the studies of land use changes understand re…     

典型农牧交错区LUCC及农牧交替演化过程分析——以内蒙古赤峰市为例

以内蒙古赤峰市为例,利用TM影像解译得到的三期土地利用数据(1988、1995、2000年)研究20世纪80年代以来,典型农牧交错区的LUCC演化过程,主要采用土地利用开发度、耗减度、信息熵、空间转移矩阵等方法分析了不同阶段农牧交替演化的时空特征。结果表明:(1)草地、耕地、林地为研究区主要的土地利用方式,整个研究时段内,耕地开垦和草地减少是主导LUCC过程。耕地开垦面积达2424.12km²,草地减少1959.65km²。从前后两个时期来看,前期(1988-1995年)耕地和草地变化更为剧烈,耕地以增为主,草地以减为主;后期(1995-2000年)草地转出速度放缓,但耕地开垦速度仍相对较快,林地转出速度加快;(2)土地流转过程以农牧交替演化为主,前期草地与耕地的交替转化剧烈,草地开垦面积达到2 040.50km²,耕地撂荒还草634.75km²,耕地开垦主要集中在敖汉旗的北部;后期LUCC过程放缓,草地转耕地面积为828.50km²,主要发生在敖汉旗以及林西县北部地区等区域,伴随着一定程度的弃耕;(3)三个时期土地利用结构信息熵分别为1.290、1.301、1.304,赤峰市土地利用系统有序程度在降低。农牧交错演化过程的分析,为研究该地区人类-环境耦合系统的变化和机制提供了重要依据。     

武汉城市圈土地利用时空变化及政策驱动因素分析

武汉城市圈是全国首批“两型社会”改革试验区之一,而且是中部崛起战略和长江经济带发展战略的重点区域。为了正确认识武汉城市圈土地利用时空变化特征,以及政策因素对土地利用变化的影响,本文基于2000、2005、2010和2015年4期武汉城市圈土地利用现状数据,结合GIS空间分析、数理统计、单一土地利用动态度、土地利用转移矩阵和综合土地利用动态度方法,对武汉城市圈2000-2015年以及3个5年期土地利用变化的总体特征、转化方向和区域差异特征进行研究,并分析政策因素对土地利用变化的驱动作用。结果表明：① 总体特征上,2000-2015年耕地、草地、林地和未利用地面积持续减少,建设用地和水域面积不断增多。② 变化方向上,2000-2015年以耕地、林地转化为建设用地和水域为主要特征,2000-2005年以耕地向水域和建设用地转化为主,2005-2010年以耕地向建设用地、水域,林地向建设用地转化为主,2010-2015年以耕地、林地和水域向建设用地转化为主。③ 区域时空差异上,综合土地利用动态度最大的区域集中在武汉城市圈的中部;从单一土地利用动态度看,耕地主要分布在武汉城市圈周边地区;建设用地主要集中在武汉城市圈中部;水域集中在武汉城市圈的仙桃市;林地主要在潜江市、云梦县;草地主要为英山县。④ 政策驱动因素分析上,中部崛起、两型社会、长江经济带发展战略等政策对土地利用变化具有重要影响。     

焦家断裂带上朱郭李家矿区地质环境现状与趋势分析

位于焦家断裂成矿带上的朱郭李家矿山建设规模为大型,矿区地质环境条件较为复杂,矿山开采对矿山地质环境的影响主要是对土地、植被资源以及地下含水层的破坏。借鉴周边同类生产矿山对成矿带区域地质环境的影响,对朱郭李家矿区地质环境现状和发展趋势进行了分析研究,为投产后的朱郭李家矿区,乃至焦家断裂成矿带区域地质环境地质保护与治理提供依据。     

江苏省近30年来的土地利用变化的区域差异分析

本文利用4个时相(1985年、1995、2000年和2005年)的遥感数据,提取了江苏省三大区域(苏南、苏中、苏北)的土地利用变化转换矩阵表,分析了江苏省的土地利用区域差异,并进行人口、城市化、农业结构调整因子、政策对土地利用差异的驱动机制分析。通过土地利用变化转换矩阵表统计得到:耕地的流出面积、城镇用地面积和农村用地面积的扩大面积从南到北呈梯度递减,且随着时间的推移,区域性差异越来越显著。在驱动力分析中发现:苏南地区大量耕地存在浪费利用与超前非农化的问题在社会经济没有进入高度发达的时期之前,经济社会越是发达,人口的增长越落后于耕地的减少在城市化过程中,城市越发达,城镇人口密度的增长对耕地向城镇用地的流入的影响越小"苏南模式"是致使土地利用区域差异的重要因素。     

Remote sensing classification of western Sierra Leone using landsat TM and ETM +

The study examines the changes of land cover/use resources for the period under investigation.An unsupervised vegetation classification is being performed that provides five distinctive classes and thus assesses these changes in five broad land cover classes-high/moist forests,forest regrowth,mixed savanna,bare land/ grass and water.The remote sensing images used in this work are both images of TM and ETM+in different time periods(1986 to 2001)to determine land cover/use changes.A fairly accuracy report is recorded after performing the unsupervised classification,which shows vegetation has been depleted for over the years.Changes created are mostly human and to a lesser extent environment.Human activities are mainly encroachment thus altering the landscape through activities such as population growth,agriculture,settlements,etc.and environment due to some perceive climatic changes.This vegetation classification highlights the importance to acquire and publish information about the country’s partial vegetation cover and vegetation change including vegetation maps and other basic vegetation influencing factors,leading to an understanding of its evolution for a period.     

基于马尔可夫链和最大后验准则的模拟静止气象卫星数据地表组分温度反演

地表组分温度比像元混合温度具有更强的物理意义和实用价值,是定量遥感反演的一个重要研究方向。本文以马尔可夫链和最大后验准则地表温度尺度转换方法,结合静止气象卫星数据高时间分辨率的特点,通过模拟静止气象卫星数据地表组分温度反演进行分析和验证。在研究过程中,地面被简化为由植被和土壤两组分组成,同时假设邻近像元的植被和土壤组分温度相同。鉴此,本文通过模拟构建20×20像元大小的静止气象卫星混合像元图像,并对各像元各时刻温度添加均值为0标准差为2K的随机误差,最终应用所提算法估算各像元各时刻的植被和土壤组分温度大小。精度分析结果表明,该算法能够较为精确地反演植被和土壤组分温度,且误差基本控制在2K以内。此外,本文还进一步讨论了算法的适用性及其对混合像元温度误差、植被覆盖度误差,以及邻近像元植被覆盖度变化范围的敏感度。分析结果再次证明,该方法对混合像元温度误差和植被覆盖度误差都具有较低的敏感性,在最大温度误差条件(均值为1.8K,标准差为5K)和最大植被覆盖度误差(均值为0.18,标准差为0.2)的条件下,各组分温度的估算精度分别能控制在3K和2K以内,满足精度要求。但是,由于组分温度初值的确定方法,对所计算窗口内植被覆盖度变化范围有较强的敏感性,反演结果与植被覆盖度变化范围相关,要求窗口内植被覆盖度变化范围足够大才能满足初值估算的精度要求。     

“一带一路”区域水电站工程生态环境影响遥感监测

为实现“一带一路”区域可持续发展,我国倡导绿色、低碳、循环、可持续的生产生活方式,建设绿色“一带一路”。遥感技术在生态环境监测与评价方面具有重要作用。本文以“一带一路”区域中国援建的水电站工程为研究对象,基于陆地系列卫星(Landsat)、哨兵2号（Sentinel-2）等遥感对地观测数据,利用决策树与缓冲区分析等方法,从水电站库区概况、水电站对植被生长状况与生态资源影响等方面,开展“一带一路”区域水电站项目建设对当地经济发展和生态环境影响的遥感监测及分析。本文首先根据遥感影像与DEM确定库区及库容,结合最小外接正方形面积比及平均宽度等指标确定各水电站缓冲区类型和范围。利用NDWI及NDVI构建决策树模型,提取各缓冲区土地利用类型,分为水体、林地、草地、耕地和其它5类;结合区域植被覆盖度,估算库区生态占用并对水电站建成前后的土地利用类型和植被变化进行分析。研究结果表明：① “一带一路”沿线10座水电站造成的生态损失与库区面积呈正相关,不同工程间,在水体、林地、草地、耕地和其它方面的损失面积大小存在较大差异;② 土地利用类型与植被覆盖度年均变化幅度约为0.35%、1.27%,水电站修建对周边生态资源与植被生长状况影响较小,同时在植被覆盖度较低的地区水电站的修建会明显改善周边环境;③ 各水电站周边的植被覆盖度差异较大,大部分水电站周边植被生长状况良好;④ 水电站建设始终坚持工程建设与环境保护并重,从施工设计到水电站后期维护期间,积极采取环保措施,减少占用,保护生物多样性,生态风险防范得当;⑤ 水电站提供了优质的清洁能源,促进了当地经济和社会发展。     

东营市破解土地制约发展瓶颈探析

土地作为开发建设的载体,在保证农产品供给,提供经济发展支撑,增加政府财政收入中不可替代。随着经济社会的快速发展,土地的"瓶颈"效应日益显现。东营市国土资源局通过外延扩展,内涵挖潜,提高土地利用效率等,探索了一条破解制约经济社会发展用地瓶颈的新路子。     

基于Brovey融合与HSV锐化的ASTER影像绿地信息提取分析

为了突出图像的边缘、线状目标或某些亮度变化率大的部分,生成边缘图像,运用Brovey融合和HSV锐化方法,对广州市部分地区的ASTER遥感影像进行处理,然后,对两种方法分别处理后的图像,采用平行六面体法监督分类,提取城市用地信息,并对分类后的图像进行对比试验,着重对城市绿地信息的提取进行分析,探究ASTER遥感数据的两种影像处理方法对城市绿地信息的提取效果,及其空间分布为城市生态评价和景观生态建设提供必要的基础数据。通过对比试验,结果显示:Brovey方法较好地显示城市绿地的分布状况,可作为城市绿地动态监测的判别方法之一;融合后的影像能够清晰地显示研究区城市绿地的分布结构及毗邻关系;通过采用区域放大、勾画不同地类边缘轮廓、配合人工解译等工作,能够增加城市绿地与其他用地类型的差异,突显城市绿地的分布、结构、生态学特征。     

威海市土地节约集约利用实践

威海市人多地少,土地资源不足,补充开垦耕地难度大,随着经济的快速发展,对土地的需求日益迫切。近年来,威海市重点从农村增减挂钩、城市盘活存量、投资严控标准三方面入手,提高土地利用效率,挖掘土地潜力,用最少的土地催化最大的发展动力。     

Wind and sand control by an oasis protective system: a case from the southeastern edge of the Tengger Desert,China

Wind and sand control are important factors in combating desertification and protecting oases. An oasis protective system can provide these benefits, but quantitative research on protection effects has been lacking to date. This researchdescribes an oasis protective system in the southeastern border of the Tengger Desert. The system consists of a sand barrier belt, a shrub and herbaceous plant belt, and a farmland shelter belt.The system was compared to a bare dunes area as the control zone. The study investigated windproof effect,sediment transport, and erosion through fieldobservations. Results showed that the roughness of the shrub and herbaceous plant belt, farmland shelter belt, and sand barrier belt were increased compared with bare dunes. The shrub and herbaceous plant belt provided the highest windproof effect values for the same wind velocity measurement height, and the windproof effect values for different protective belts were as follows: shrub and herbaceous plant belt farmland shelter belt sand barrier belt. The sand barrier belt provided effective wind and sand control at heights from 0 to 50 cm above the ground. The total sediment transport for each protective belt is as follows: bare dunes sand barrier belt shrub and herbaceous plant belt farmland shelter belt. The sediment transport decreased exponentially as the height increased. In the bare dunes and protective systems, the sediment transport is mainly within 30 cm of the ground surface. The wind erosion intensity for this protective system was as follows: bare dunes sand barrier belt shrub and herbaceous plant belt farmland shelter belt. This research offers quantitative evidence for how oasis protective systems can effectively intercept sand and prevent erosion in oases. The results of this study can be applied in similar regions.     

延河流域生态环境动态监测系统与应用

以遥感 (RS)、地理信息系统 (GIS)、全球定位系统 (GPS)为核心技术 ,采用 ETM/ TM卫星数据、航空机载对地观测数据 ,结合地面测试和综合调查方法 ,完成了延河流域面积 10 0 15 .797km₂的生态环境本底调查 ,建立了 1990～2 0 0 0年的生态环境动态监测系统。查明了区内主要物种和植被分布 ,土地利用 /土地覆盖现状及其动态变化 ,划分出 5个生态区 ,2 5个生态系统 ,提出了延河流域生态建设.     

基于卷积神经网络的ICESat-2光子点云去噪分类

ICESat-2（Ice, Cloud, and land Elevation Satellite-2）是美国NASA（National Aeronautics and Space Administration）在2018年发射的激光测高卫星,其上搭载的激光测高系统ATLAS（Advanced Topographic Laser Altimeter System）采用微脉冲多波束光子计数激光雷达系统,因其低能耗、高探测灵敏度、高重复频率的特性极大改善了沿轨采样密度,但也使获取的数据中包含大量的噪声,如何有效实现光子点云去噪分类成为后续应用的关键,也是当前研究的热点和难点,为此本文提出一种基于卷积神经网络的光子点云去噪和分类算法。首先将光子点云按照沿轨和高程方向划分格网,去除明显的噪声光子,并将每个粗信号光子点栅格化为影像;然后基于少量样本构建的卷积神经网络分类模型实现光子点云精去噪和分类;最后利用机载激光雷达数据进行验证,并与ATL08产品的去噪分类结果进行对比。结果表明,对于裸地和森林区域,卷积神经网络算法均能有效去除噪声光子,特别对于森林区域,可同时实现去噪和分类;其中,裸地区域地表计算的R²和RMSE分别为1.0和0.72 m,森林区域地表和树冠计算的R²分别为1.0和0.70, RMSE分别为1.11 m和4.99 m。本文利用深度学习算法实现光子点云去噪分类,在裸地和森林区域均取得了较好的结果,为后续光子点云数据处理提供了参考。