东洞庭湿地植被格局变化及其影响因素

东洞庭湖(也称东洞庭)湿地植被格局的变化特征及其影响因素的分析是该地区湿地植被保护与恢复策略制定的基础。基于美国陆地资源卫星Landsat TM/ETM+数据,应用决策树分类法分别提取东洞庭湖1999年、2002年、2006年三个时期湿地景观信息,通过转移矩阵法和质心迁移法对植被的时空演变分析。结果表明:(1)1993～2002年东洞庭湖芦苇、林地、苔草滩地面积均有所增加,芦苇增长速度最快,年均增长面积为28.93km²;2002～2006年林地面积迅速增加,年均增长面积为29.655km²,苔草面积有所减少,芦苇面积保持基本稳定;(2)东洞庭湖湿地植被质心呈现从林地—芦苇—苔草逐层靠近湖心的分布特点,1993～2006年三种植被类型的质心均不断向湖心迁移,其中以林地与芦苇的变迁更为显著。     

Exploring the potential of perennial crops in reducing soil erosion: A GIS-based scenario analysis in southern Tuscany,Italy

Preserving soils is a major challenge in ensuring sustainable agriculture for the future. Soil erosion by water is a critical issue in the Mediterranean regions and usually occurs when high-erosive precipitation is in temporal association with poor vegetation cover and density. Modelling soil erosion risks over large spatial scales suffers from the scarcity of accurate information on land cover, rainfall erosivity and their intra-annual dynamics. We estimated the soil erosion risk on arable land in a Mediterranean area (Grosseto Province, southern Tuscany, Italy) and investigated its potential reduction as a response to the change in intra-annual distribution of land cover due to the increase of perennial forage crops. A GIS-based (R)USLE model was employed and a scenario analysis was performed by setting criteria for raising the performance of perennial forage crops. Statistical data on agricultural crops provided an insight into current intra-annual land cover dynamics. Rainfall erosivity was computed on the basis of 22-year hourly precipitation data. The model was used to: i) quantify the potential soil losses of arable land in the study area, ii) identify those areas highly affected by erosion risks iii) explore the potential for soil conservation of perennial crops, thereby enabling appropriate preventive measures to be identified. The erosion rates, averaged over an area of about 140’000 ha, are estimated to 33.42 Mg ha⁻¹ y⁻¹. More than 59% of the study area was subjected to soil losses higher than 11 Mg ha⁻¹ y⁻¹ (from moderate to severe erosion) and the highest rates are estimated for steep inland areas. Arable land with severe soil erosion rates (higher than 33 Mg ha⁻¹ y⁻¹) represent about 35% of the whole study area. The risk of soil loss by water erosion in the study area is estimated to be reduced on average by 36% if perennial crops are increased in terms of 35% of the total arable land. The soil erosion data produced compared well with the published local and regional data. This study thus provides useful preliminary information for landscape planning authorities and can be used as a decision support tool in quantifying the implications of management policies.     

Biophysical and Spectral Characteristics of Cool- and Warm-Season Grasslands under Three Land Management Practices in Eastern Kansas

Grasslands are the largest of the Earth's four major vegetation types and are among the most agriculturally productive lands. Grassland management practices alter biophysical factors, such as plant species composition, soil structure and chemistry, and primary productivity. Large-scale changes in land management practices can have significant impacts on available natural resources, therefore impacting a regional socioeconomics. For these reasons, an improved understanding of the geographic distribution of changing land management practices and how these changes affect grassland biophysical characteristics of an area is critical to improve land use planning and practices. This study investigated the spectral characteristics, as measured using satellite remotelysensed data, of three land management practices [grazing, haying, and management under Conservation Reserve Program (CRP)] on areas dominated by cool- and warm-season grasslands. The satellite imagery was acquired in May, July, and September in 1997 over Douglas County, Kansas. Biomass, vegetation cover, and species richness data were collected around the satellite overflight periods. Our results indicate that the biophysical characteristics and spectral reflectances are significantly different among the three management practices over cool- and warm-season grasslands. Interestingly, sites grazed by livestock had the highest species richness and the highest forb cover, although the total cover is almost the same as the other practices, and they have the highest near-infrared reflectance throughout the growing season.     

基于地表覆盖物光谱特征的土地覆被分类系统--以鄱阳湖流域为例

土地覆被主要表现为陆地表面的形态特性和动态变化特征,土地利用是其动态变化的外在驱动力,植被是土地覆被的“主要”而非唯一的组成部分,土地覆被也包含着它的功能特性。地表覆被物的光谱特征及其季节性变化规律是土地覆被的本质特征,也是土地覆被分类的基本依据之一;利用遥感资料所表达的地表覆被物特征值 (如以NDVI为指标的绿度值、始绿期、终绿期、波形、峰值、谷值等) 可以方便地对土地覆被分类标准进行量化处理;对于一些复杂的复合单元,应着重于它的组合 (包括组成成分和结构) 特性及其对地面过程的影响来赋予更确切的内涵。据此,构建了包含7个一级类别和20个二级类别的开放式 (open-end) 的鄱阳湖流域土地覆被分类系统,并且应用SPOT4-VEGETATION 的时序NDVI数据,对各类别的面积比重进行了分析,结果显示鄱阳湖流域的现状覆被主要由常绿覆被和作物-树-草混合覆被以及人工栽培植被 (作物) 等构成。     

基于遥感时序特征的地表覆被信息提取

地表覆被作为自然过程和人类活动共同作用的重要地表景观特征,对全球或局地气候、水热循环、物质传输及陆面生态系统多样性等影响深远。利用年内时序遥感影像自动提取不同地表覆被类型的方法,以新疆阜康地区为研究目标,组织2016年植被全生长季的Landsat 8 OLI地表反射时序影像,研究不同物候期植被冠层的纹理响应信息,考察研究区典型地表覆被类型在3—11月多波段波谱、归一化植被指数(NDVI)及增强型植被指数(EVI)的时序特征,构建提取地表覆被类型的策略规则,形成时序特征匹配方法,将其应用于2018年研究区地表覆被填图的提取。最后,基于高分辨率卫星影像和野外实地调查对随机选取的2500个样点进行对比验证。结果表明:提取结果和验证数据一致性较好,总体精度为97.2%,Kappa系数为0.9655,且实地考查结果显示本方法在复播作物识别和有效降低单一时相中“异物同谱”现象上展示潜在优势。     

华北平原“杨上粮下”现象的驱动机制——以河北省文安县为例

以Landsat5TM遥感影像、农户调查数据和统计数据为基础数据,运用3S技术提取了案例区河北省文安县1995～2007年土地利用变化信息,分析了杨树扩张的时空格局;并从农户杨树种植决策行为视角,运用数理统计、投入产出法分析了杨树扩张占地的驱动因素。结论如下:(1)杨树林地扩张幅度大、速率快。(2)杨树扩张所用土地92.14%来源于耕地,"杨上粮下"现象突出。(3)杨树扩张速率的空间差异显著。杨树扩张受生产要素、土地产品市场及政策因素的综合驱动,其中劳动力因素和经济因素起主要作用。(4)非农从业人员比率和农民年人均收入越高,杨树扩张速度越快。在劳动力由富余转为相对稀缺的情况下,农户为提高经济收益,倾向选择耗工少,劳动生产率较大的杨树,是杨树扩张占地的根本原因。     

应用线性光谱分离技术研究喀斯特地区土地覆被变化——以贵州省关岭县为例

喀斯特地区土地覆被主要类型除了和非喀斯特地区一样的植被和裸露土壤外,还存在一个广泛分布的裸露基岩,一般遥感处理方法不具备直接定量提取这三类土地覆被参数的能力。基于地物光谱线性混合模型的线性光谱分离技术,可以在亚象元的尺度上直接获取植被覆盖、裸露土壤和裸露基岩等在各象元区域内的比例,非常适合用于喀斯特地区的土地覆被变化的研究。本文利用1987年2月17日和1999年12月27日LandsatTM各6波段遥感影像,使用ENVI软件,分离出植被、裸露土壤、裸露岩石和阴影等土地覆被丰度和RMS的空间分布。对比结果表明,研究区1987～1999年,植被覆盖率上升593%,裸露土壤面积下降1215%,裸露基岩面积上升408%。表明研究区尽管植被在恢复、水土流失总量在减少,但石漠化面积在明显上升,生态形势依旧严峻。     

The role of fire as a long-term landscape modifier: Evidence from long-term fire observations (1922–2000) in Greece

The objective of this paper is to document the role of fire in shaping the landscape by identifying links between historical fire records and the current landscape indicating that fire favors certain land use/land cover (LULC) types. We geo-referenced fire records taken from 1922 to 2000 in Aitoloakarnania, the largest prefecture -in terms of surface area- of Greece and compared the past LULC classes where fires burned to the present landscape. The outputs indicated a shift of the historic fire ignition points from natural to agricultural-related LULC classes since a significant proportion of fire incidents that, according to the fire records, burnt natural vegetation units is currently located in agricultural landscape units. Additionally, a significant proportion of the fire-affected land cover classes retain their character thus supporting the argument that these classes, especially fire-prone or fire-resistant, have developed mechanisms to cope with fire. In such ecosystems the role of fire is to maintain rather than transform land cover classes.The findings of this research lead us to conclude that fire can be perceived as a long-term landscape modifier in the Mediterranean, although its effects may vary from region to region because of differences in regeneration patterns among the main land cover types, topographic constraints and local fire histories. Historical fire records extending back to the early 20th century proved to provide valuable information that can reveal interesting patterns of fire burning history and explain present land cover and use patterns. This knowledge, documented from historical records, can be used to develop fire management and land cover/land use management planning.     

黑河中游不同土地覆被土壤水文环境及植被特征

 以黑河中游6种典型土地覆被类型（百年灌溉农田、新垦灌溉农田、人工杨树林、人工樟子松林、人工梭梭灌木林和天然荒漠草地）为研究对象,对其部分土壤生态水文和植被因子进行了测定。结果显示,6种土地覆被类型不仅在地表生态水文环境特征、土壤结构特征、土壤化学和微生物群落特征等方面存在显著差异,而且在植被的盖度、密度和生物量方面也存在显著差异。不同土地覆被类型的植物生物量与田间持水量、土壤黏粉粒含量、土壤全氮、土壤有机碳和土壤碳氮比等因子具有密切的关系。该研究为如何通过改变土地覆被方式而有效地保护和利用绿洲荒漠系统提供了一定的思路,也为进一步解析气候变化和人类活动影响下荒漠绿洲生态系统水、土、气、生的相互作用过程及其机制提供了一定的科学依据。     

1974-2011年白洋淀土地覆盖时空变化特征

在野外调查的基础上,运用遥感和地理信息系统技术对1974年、1979年、1984年、1987年、1989年、1991年、1996年、2001年、2006年和2011年10期遥感影像进行解译和分析,揭示了白洋淀近37年土地覆盖动态变化。结果表明:近37年白洋淀土地覆盖类型变化极为复杂,主要表现为水体、芦苇地、耕地3种土地覆盖类型相互转化。1974-2011年,水体面积从58.01 km2上升到80.07 km2,芦苇地面积从104.94 km2下降到72.95 km2,水生植被从14.02 km2下降到4.27 km2。1974-2011年,耕地、水体、芦苇地、居民点转化为其它类型的比例相对较小,分别为39.25%、34.46%、53.74%和18.15%。水体面积增加主要分布在地势较低的东部和北部地区,水体面积减少主要分布在地势较高的西南地区。水位变化、入淀径流量变化、淀区气候变化、人类活动及管理政策是白洋淀土地覆盖变化的驱动因子。研究揭示了白洋淀土地覆盖与人类活动的相互作用关系,对白洋淀土地管理和生态系统服务可持续供给具有重要意义。     

准格尔丘陵沟壑区五分地沟流域土地覆盖分析(英文)

以准格尔丘陵沟壑区五分地沟流域为研究区,应用彩红外航片和IKONOS卫星影像,绘制了1987、2002年土地覆盖/植被类型图,并数字化基于地面土地利用调查绘制的1979年土地利用图.利用景观格局指数,评价了研究区土地覆盖/植被空间格局现状及土地覆盖类型动态变化;并以ETM 数据为信息源,绘制了2002年土地覆盖/植被类型图.研究表明:2002年研究区土地覆盖/植被呈现出一个耕地、草地、人工乔木林和人工灌木林以及种植稀疏灌木的草地高度镶嵌的景观格局特征;20年内土地覆盖类型发生了显著的变化,景观异质性增强.基于研究区景观的高度破碎化,绘制小流域精细尺度土地覆盖图,高空间分辨率遥感数据十分必要.     

准格尔丘陵沟壑区五分地沟流域土地覆盖分析

以准格尔丘陵沟壑区五分地沟流域为研究区,应用彩红外航片和IKONOS卫星影像,绘制了1987、2002年土地覆盖/植被类型图,并数字化基于地面土地利用调查绘制的1979年土地利用图.利用景观格局指数,评价了研究区土地覆盖/植被空间格局现状及土地覆盖类型动态变化;并以ETM 数据为信息源,绘制了2002年土地覆盖/植被类型图.研究表明:2002年研究区土地覆盖/植被呈现出一个耕地、草地、人工乔木林和人工灌木林以及种植稀疏灌木的草地高度镶嵌的景观格局特征;20年内土地覆盖类型发生了显著的变化,景观异质性增强.基于研究区景观的高度破碎化,绘制小流域精细尺度土地覆盖图,高空间分辨率遥感数据十分必要.     

Land Cover Status in the Koshi River Basin,Central Himalayas

The Koshi River Basin is in the middle of the Himalayas, a tributary of the Ganges River and a very important cross-border watershed. Across the basin there are large changes in altitude, habitat complexity, ecosystem integrity, land cover diversity and regional difference and this area is sensitive to global climate change. Based on Landsat TM images, vegetation mapping, field investigations and 3S technology, we compiled high-precision land cover data for the Koshi River Basin and analyzed current land cover characteristics. We found that from source to downstream, land cover in the Koshi River Basin in 2010 was composed of water body (glacier), bare land, sparse vegetation, grassland, wetland, shrubland, forest, cropland, water body (river or lake) and built-up areas. Among them, grassland, forest, bare land and cropland are the main types, accounting for 25.83%, 21.19%, 19.31% and 15.09% of the basin’s area respectively. The composition and structure of the Koshi River Basin land cover types are different between southern and northern slopes. The north slope is dominated by grassland, bare land and glacier; forest, bare land and glacier are mainly found on northern slopes. Northern slopes contain nearly seven times more grassland than southern slopes; while 97.13% of forest is located on southern slopes. Grassland area on northern slope is 6.67 times than on southern slope. The vertical distribution of major land cover types has obvious zonal characteristics. Land cover types from low to high altitudes are cropland, forest, Shrubland and mixed cropland, grassland, sparse vegetation, bare land and water bodies. These results provide a scientific basis for the study of land use and cover change in a critical region and will inform ecosystem protection, sustainability and management in this and other alpine transboundary basins.     

三江平原别拉洪河流域湿地农田化过程研究

自20世纪50年代以来,三江平原的别拉洪河流域在经历了3次大规模开荒后,大面积的湿地被农田所替代,耕地面积迅速增加,湿地农田化过程干扰和破坏了原有的湿地环境。在遥感和地理信息系统技术支持下,应用景观生态学方法,利用1954年、1976年、1986年、2000年和2005年的土地利用数据,分析了研究区近50 a来的湿地农田化过程。结果显示,湿地农田化过程中大面积的湿地斑块被农田斑块所取代,破碎化的小耕地斑块又逐渐合并为大的耕地斑块,并导致斑块形状复杂度指数逐渐增大,景观均匀度指数呈现波动变化;耕地面积在1954~1986年期间增长幅度较大,特别是在20世纪70年代末和80年代初的改革开放初期,研究区景观动态度为0.201,远高于其它时期;目前,农田景观已成为主要景观类型,农田面积占研究区总面积的63.69%,湿地面积占研究区总面积的比例由1954年的64.83%减小到2005年的19.44%。质心模型的分析结果显示,近50 a来研究区耕地景观质心平移幅度明显大于湿地景观,湿地景观质心不断地向东北方向移动,偏移了约20.5 km,而农田景观质心逐渐向东平移,平移了约44.7 km。农业开垦是研究区湿地大面积消退的主要原因。     

Improving the factual knowledge of landscapes: Following up the European Landscape Convention with a comparative historical analysis of forces of landscape change in the Sjodalen and St⊘lsheimen mountain areas,Norway

A focus of implementing the European Landscape Convention (ELC) in Norway is on improving the factual knowledge of landscapes, which implies analysing the forces transforming them. The article aims to identify important forces of change and to elucidate its complexity by a comparative historical study of land cover and land use in two mountain areas in Western and Eastern Norway. The land covers and uses in focus are transport infrastructure, seasonal farming, vegetation, tourism and outdoor recreation, and nature and landscape protection. Based on an understanding of forces as something being exerted, a framework including pressure, attraction, friction, repulsion, and working force is developed. A comprehensive literature analysis shows how differences in intensity and extent of land use and development of land cover result from a complex interaction of common extrinsic forces with locally different intrinsic forces. To control landscape change and to maintain diversity among landscapes as a Europe-wide resource, the national implementation of the ELC will require a strong focus on the local level. Moreover, understanding the ELC as an origin of forces is recommended, because it allows more appropriate individual responses to landscape change.     

2003—2017年植被变化对全球陆面蒸散发的影响

蒸散发是陆面水循环的关键环节和过程,是研究水循环对人类活动和气候变化响应的关键要素。过去十几年,全球下垫面的植被变化剧烈,但如何影响全球陆面蒸散发仍未得到清晰的揭示。本文采用500 m分辨率MODIS数据驱动PML-V2模型,定量解析了2003—2017年植被变化对全球陆面蒸散发的影响。结果显示：在全球尺度上,植被变绿使得全球蒸散发呈现显著的增加趋势,使陆地水循环加快;区域尺度上,植被变化对蒸散发的影响则存在明显的地带性和非地带性特征,如在北美洲中北部、欧洲、中国东部、非洲南部和澳大利亚东北部等地区,蒸散发总量的增加主要是由植被蒸腾增加而引起的。分析不同植被功能类型区的贡献显示,下垫面变化对灌木和耕地影响尤为明显,并在2012年以后呈现增强趋势;这2个植被类型区的全球年总蒸散发累积增加量为0.41×10³ km³ a^-1,约为黄河流域多年平均径流量的8倍。该研究结果有助于进一步加强关于下垫面变化对陆地水循环的影响及其可能带来的局部气候变化的认识。     

Forest landscape patterns dynamics of Yihe-Luohe river basin

Based on the information from forest resources distribution maps of Luoning County of 1983 and 1999, six indices were used to analyze spatial patterns and dynamics of forest landscapes of the typical region in the middle of the Yihe-Luohe river basin. These indices include patch number, mean patch area, fragment index, patch extension index, etc. The results showed that: (1) There was a rapid increase in the number of patch and total area from 1983 to 1999 in the study area. The fragment degree became very high. (2) The area of all the forest patch types had witnessed great changes. The fractal degree of each forest patch type became big from 1983 to 1999. The mean extension index of Robinia pseudoacacia forest, non-forest, shrub forest, sparse forest, and Quercus species forest increased rapidly, but that of economic forest became zero. The fractal dimension each showed that forest coverage has been promoted. (3) The changes of landscape patterns were different in different geomorphic regions. From 1983 to 1999 the vegetation cover area, the gross number and the density of patch, diversity and evenness of landscape were all reduced greatly in gullies and ravines, but the maximum area and the mean area of patch types were increased. In hilly region, both the forest cover area and the number of patch increased from 1983 to 1999, but the mean area of patch was reduced greatly. In mountain region, even though the area under forest canopy reduced from 1983 to 1999, the patch number was increased greatly, the mean area of all patch types was reduced, the extension index, diversity index and evenness index of landscape were all increased. Furthermore, because of different types of land use, human activity and terrain, the vegetation changes on northern and southern mountain slopes were different. According to these analyses, the main driving forces, such as the policies of management, market economy, influence of human activities etc. are brought out.     

Land Cover Changes on Ambergris Caye,Belize: A Case Study of Unregulated Tourism Development

Measuring land-use, land-cover change in biodiverse, tropical countries is critical for conservation management and sustainable planning because it provides quantifiable data regarding broad environmental changes. This project uses Landsat satellite imagery to document vegetation cover change on Ambergris Caye, Belize, from 2000 to 2017. The close proximity of the Belize Barrier Reef Reserve System has made Ambergris Caye the most popular tourist destination and economic hub in Belize. As a result, the region has undergone intense commercial and residential development coupled with rapid population growth over the past two decades. Understanding general trends in landscape dynamics is critical for the natural resource–based tourism industry of Belize to continue to thrive. Unsupervised classification methods and a per pixel postclassification comparison were used with Landsat imagery to estimate loss in vegetation cover and increases in urban and barren land. The results indicate a 10.85 percent decrease in vegetation and a 39 percent increase in urban and barren land during the seventeen-year study period with an annual forest loss rate of 0.67 percent per year using a compound interest rate formula. The results of this analysis represent a baseline study of vegetation change on Ambergris Caye to inform management and conservation efforts.