利用MODIS数据评估冷冻灾害对广东植被的损害

2008年初我国南方地区发生的极端冷冻灾害对植被造成了极大破坏。以广东为例,利用MODIS数据,对比分析了受损植被与正常植被的NDVI变化;利用ISODATA非监督分类方法提取受损植被分布信息,借助90m SRTM DEM数据研究受损植被与地形因子的关系,发现广东植被受损严重,受损植被总面积达19 011.06 km²。受损植被受海拔高程、坡度、坡向等地形因子影响较大;受损植被主要集中于海拔大于400 m,坡度小于15°的阴坡区域;通过MODIS土地覆盖图与受损植被的复合分析,研究了该地区受损植被的类型,发现受损植被以常绿阔叶林、混交林、落叶阔叶林、灌丛、落叶针叶林及常绿针叶林为主。     

神农架龙门河地区的植被制图及植被现状分析

依据龙门河地区所处位置的植被地理分布规律性 ,绘制了该地区 1∶50 0 0 0的植被复原图。并在野外调查、资料搜集的基础上 ,辅以全球定位系统 (GPS)、GIS软件及TM影像数据 ,绘制了该地区 1∶50 0 0 0的植被类型图。结果表明 :1 )植被海拔分布由低至高依次为常绿阔叶林 (海拔 90 0m以下 ) ,硬叶常绿阔叶林 (海拔 90 0～ 1 30 0m)、常绿落叶阔叶混交林 (海拔 1 30 0～ 1 60 0m)以及落叶阔叶林 (海拔 1 60 0～ 2 2 0 0m)。 2 )龙门河地区林地面积 441 9.2hm2 ,占该地区总面积的 93 .71 % ,共计 8个植被型 65个群系。其中常绿落叶阔叶混交林面积最大 ,为 1 674.0 9hm2 ,占林地面积的 37.88%。另外 ,果园 (3种类型 )和农田两种农业用地面积 2 2 8.1 2hm2 ,占总面积的 4 .84%。 3)由植被复原图与现状植被类型图叠加分析可知 ,干扰后增加了针叶林、针阔混交林、灌丛、草地 4种植被类型 ,占龙门河地区总面积的 34 .6 %。其中针阔混交林所占面积最大 ,996 .79hm2 。     

2000～2008年长白山地区植被覆盖变化特征

利用2000～2008年250 m分辨率MODIS/NDVI数据,结合谐波分析、影像处理和多种统计方法分析长白山地区的植被覆盖年内和年际变化特征,并结合区划图和植被类型图对不同区域和不同植被类型的植被覆盖变化进行分析.结果显示:近9年长白山地区覆盖总体呈上升趋势,其中春季植被覆盖略有下降,夏季植被覆盖变化不大,而秋季植被覆盖显著上升;和龙林业局、露水河林业局和长白山自然保护区的植被覆盖较好,而朝鲜一侧、泉阳林业局和长白林业局的植被覆盖较差;针叶林、阔叶林和针阔混交林的植被覆盖要高于荒草地、沼泽地、高山岳桦林和高山苔原,但后几种植被类型的植被覆盖增长趋势明显.     

Management oriented forest map of South India: thematic derivations

The principles and methods of the vegetation mapping undertaken at the French Institute, Pondicherry, are dealt with herein. Particularly, the characterisation of the different types of vegetation and especially the originality of the method: the dynamic interpretation of the vegetation and the depiction of the bioclimatic conditions. The programme of the forest map of South India at scale 1:250 000, undertaken in collaboration with the forest departments of the concerned states, is then described with special attention given to the source and the collection of data. This map has been conceived to serve as a basic document for the sustainable management of the forests. Three examples of its application are given. They concern the detection of anomalies between the existing forest cover and the prevalent climatic environment; the detection of areas for which protection is urgently needed; the selection of regions showing a particular interest in the field of nature conservation or as gene pool reserve. Finally, an example of a thematic map of sensibility of the forests is given, using the vegetation map as a basis.     

Vegetation structure and greenness in Central Africa from Modis multi-temporal data

African forests within the Congo Basin are generally mapped at a regional scale as broad-leaved evergreen forests, with the main distinction being between terra-firme and swamp forest types. At the same time, commercial forest inventories, as well as national maps, have highlighted a strong spatial heterogeneity of forest types. A detailed vegetation map generated using consistent methods is needed to inform decision makers about spatial forest organization and their relationships with environmental drivers in the context of global change. We propose a multi-temporal remotely sensed data approach to characterize vegetation types using vegetation index annual profiles. The classifications identified 22 vegetation types (six savannas, two swamp forests, 14 forest types) improving existing vegetation maps. Among forest types, we showed strong variations in stand structure and deciduousness, identifying (i) two blocks of dense evergreen forests located in the western part of the study area and in the central part on sandy soils; (ii) semi-deciduous forests are located in the Sangha River interval which has experienced past fragmentation and human activities. For all vegetation types enhanced vegetation index profiles were highly seasonal and strongly correlated to rainfall and to a lesser extent, to light regimes. These results are of importance to predict spatial variations of carbon stocks and fluxes, because evergreen/deciduous forests (i) have contrasted annual dynamics of photosynthetic activity and foliar water content and (ii) differ in community dynamics and ecosystem processes.     

西双版纳勐养自然保护区植被的分布与生态特征

对西双版纳勐养自然保护区植被的类型进行了划分 ,包括人工和自然群落 ,共有7个大类、1 5个群系、2 4个群落类型分布 .对每个类型的主要组成种类、生态特征和分布现状进行了初步研究 .利用地理信息系统软件制取植被图并获得了各种植被类型的分布面积和分布格局特征 ,这一地区亚热带季风常绿阔叶林的分布面积和所占比例最大 ,达总面积的 41 .2 6 % ;而热带雨林面积不超过总面积的 1 0 % .依据地形、海拔、气候和现状植被分布的规律 ,在获得景观类型图的基础上 ,得到了可以反映这一地区在完全自然条件下植被可能分布的状况的还原植被图 ,为保护区的发展和植被的恢复提供了理论依据。     

Messinian vegetation maps of the Mediterranean region using models and interpolated pollen data

This study proposes to compare the outputs from the CARAIB vegetation model forced by results from the LMD General Circulation Model with interpolated pollen data (Kriging method) from the Mediterranean region during the Messinian. The vegetation maps that have been obtained represent distinct phases of the salinity crisis: before the crisis and during the marginal evaporitic phase (interpolated map), and during the complete desiccation phase (simulated map). However, they are comparable in terms of vegetation density and agree on a strong contrast between the Northern (forest vegetation) and Southern (open vegetation) Mediterranean regions. Main differences concern the type of forests in the northern Mediterranean region, which are explained by discrepancies between precipitation amount predicted by the model and that calculated by a transfer function using pollen records. The interpolation method has been successfully tested in France using interpolated current pollen records by comparison with the present-day potential vegetation map. The resulting Messinian map is useful to validate or improve model simulation which does not take into account the depth of the Mediterranean Basin when it dried up. The Southern Mediterranean landscapes were open, with a steppe-like vegetation to the West and a savannah-like vegetation to the East. Forests prevailed to the North, organized in a mosaic system mainly controlled by relief. Such a contrast provides some explanation of the large number of deep fluvial canyons cut on the Northern margin at opposed to the South during the Mediterranean desiccation.     

片口自然保护区植被的遥感分类

采用样方法对四川片口自然保护区的植被进行本底调查,利用野外普查数据和卫星照片解译相结合的技术,分析其植被现状。结果表明：片口自然保护区的植被类型比较丰富,且保存较完整,共有6种植被类型和15种群系。     

The TRM Model of Potential Natural Vegetation in Mountain Forests

Due to advances in spatial modeling and improved availability of digital geodata, traditional mapping of potential natural vegetation (PNV) can be replaced by ecological modeling approaches. We developed a new model to map forest types representing the potential natural forest vegetation in the Bavarian Alps. The TRM model is founded on a three-dimensional system of the ecological gradients temperature (T), soil reaction (R), and soil moisture (M). Within such a “site cube” forest types are defined as homogenous site units that give rise to forest communities with comparable species composition, structure, production and protective functions. The three gradients were modeled using regression algorithms with area-wide, high resolution geodata on climate, relief and soil as predictors and average Ellenberg indicator values for temperature, acidity and moisture of vegetation plots as dependent variables summarizing plant responses to ecological gradients. The resulting predictor-response relationships allowed us to predict gradient positions of each raster cell in the region from geodata layers. The three-dimensional system of gradients was partitioned into 26 forest types, which can be mapped for the whole region. TRM-based units are supplemented by 22 forest types of special sites defined by other ecological factors such as geomorphology, for which individual GIS rules were developed. The application of our model results in an intermediate-scale map of potential natural forest vegetation, which is based on an explicit function of temperature, reaction and moisture and is therefore consistent and repeatable in contrast to traditional PNV maps.     

不同植被类型森林火灾及雷击火自组织临界性

利用黑龙江省大兴安岭林区呼中区 196 5～ 2 0 0 2年的雷击火数据、黑龙江省 1981～ 2 0 0 0年森林火灾数据及森林资源数据 ,对雷击造成的森林火灾的自组织临界性及不同植被类型条件下的自组织临界性作了研究 ,比较了在不同尺度和植被类型条件下火干扰的自组织临界性、自相似性 ,并与传统的森林火灾元胞自动机模型模拟的结果进行比较。结果表明 :中国黑龙江省不同森林类型的火干扰具有自组织临界行为 ,森林可燃物已经达到临界状态 ,其临界值在 1.8～ 2 .86之间 ,具有自相似性 ;当森林的面积过小时 ,森林火灾的“面积 -频率”分布曲线上会出现频率峰 ,表现出“有限面积效应”现象。     

A vegetation map of tropical continental Asia at scale 1:5 million

Abstract. A vegetation map at scale 1:5 million is presented. * * Attached on the inside of this issue's back cover.
It covers Bangladesh, Burma (Myanmar), India, Cambodia, Laos, Thailand, Vietnam and Sri Lanka and fills a conspicuous gap in the cartography of tropical vegetation, following the publication of vegetation maps of South America, Africa and Malaysia. For conformity, it is presented as one sheet at a scale of 1:5 million. It uses the basic map of the American Geographical Society (1942; bipolar oblique conformal projection) which forms the base for FAO's Soil map of the world. Basic information was obtained from many published maps, unpublished observations and satellite data. The limits of the main vegetation types have been updated with a complete set of Landsat MSS images (369 scenes) with a mosaic of Landsat TM data for 1991 and with recent forest maps from Asia. Nine main vegetation units, which are groups of forest formations, have been identified and mapped, including woodlands, thickets and wooded savannas. Agricultural land has been shown in a uniform pale green colour in order to clearly express the extent of human impacts on woody vegetation. In spite of the necessary oversimplification of the ground data, this map is probably the most explicit expression of the remaining forest stands and of the regression of natural vegetation in the region. It can be considered as a benchmark for future monitoring of tropical vegetation.     

Modelling riparian forest distribution and composition to entire river networks

Aim: Developing a methodology to map the distribution of riparian forests to entire river networks and determining the main environmental factors controlling their spatial patterns. Location: Cantabrian region, northern Spain. Methods: We mapped the riparian forests at a physiognomic and phytosociological level by delimiting riparian zones and generating vegetation distribution models based on remote sensing data (Landsat 8 OLI and LiDAR PNOA). We built virtual watersheds to define a spatial framework where the catchment environmental information can be specified for each river reach, in combination with the vegetation map. In order to determine the drivers that play a significant role in the observed spatial patterns in riparian forests, based on our data sets we modelled interactions between environmental information and riparian vegetation by using the Random Forest algorithm. Results: The modelling results obtained reliably reproduced the variation of riparian forest structure and composition across Cantabrian watersheds. The produced maps were highly accurate, with a more than 70% overall accuracy for forest occurrence. A clear differentiation between Eurosiberian (habitats 91E0 and 9160) and Mediterranean (92E0) riparian forests was shown on both sides of the mountain range. Topography and land use were the main drivers defining the distribution of riparian forest as a physiognomic unit. In turn, altitude, climate and percentage of pasture were the most relevant factors determining their composition (phytosociological approach). Conclusions: Our study confirms that anthropic control ultimately defines the distribution of vegetation in the riparian area at a regional to local scale. Human disturbances constrain the extension of forest patches across their potential distribution defined by topoclimatic boundaries, which establish a clear limit between Mediterranean and Eurosiberian biogeographical regions.     

A simulated map of the potential natural forest vegetation of Switzerland

Using empirical data (ca. 7500 phytosociological releves), a simple, probabilistic ‘vegetation-site’ model was developed, to simulate geographical distribution of 71 forest community types, representing the potential natural vegetation (PNV) of Switzerland. The model was interfaced to a geographic information system (GIS) and used to generate a numerical vegetation map, on the basis of digital maps of 12 environmental variables including climatic conditions (temperature and precipitation), topography (elevation, slope, aspect), and soil parameters (soil pH and physical soil parameters). The predicted distribution of forest communities was compared with several vegetation maps, prepared for some subregions of Switzerland by means of traditional field methods. Similarity ranged from 50 to 80 %, depending on the community type, level of vegetational hierarchy and the geographical region. The current resolution and accuracy of the simulated vegetation map allows us to study the vegetational patterns on the level of the entire country or its major geographical and climatic regions. The simulated vegetation map is potentially an important tool in ecological risk assessment studies concerning the possible impacts of climate change on the ecological potential of forest sites and biological diversity of forest communities.     

Tree line identification from pollen data: beyond the limit?

Aim The boreal tree line is a prominent biogeographic feature, the position of which reflects climatic conditions. Pollen is the key sensor used to reconstruct past tree line patterns. Our aims in this study were to investigate pollen–vegetation relationships at the boreal tree line and to assess the success of a modified version of the biomization method that incorporates pollen productivity and dispersal in distinguishing the tree line. Location Northern Canada (307 sites) and Alaska (316 sites). Methods The REVEALS method for estimating regional vegetation composition from pollen data was simplified to provide correction factors to account for differential production and dispersal of pollen among taxa. The REVEALS‐based correction factors were used to adapt the biomization method and applied as a set of experiments to pollen data from lake sediments and moss polsters from the boreal tree line. Proportions of forest and tundra predicted from modern pollen samples along two longitudinal transects were compared with those derived from a vegetation map by: (1) a tally of ‘correct’ versus ‘incorrect’ assignments using vegetation in the relevant map pixels, and (2) a comparison of the shape and position of north–south forest‐cover curves generated from all transect pixels and from pollen data. Possible causes of bias in the misclassifications were assessed. Results Correcting for pollen productivity alone gave fewest misclassifications and the closest estimate of the modern mapped tree line position (Canada, + 300 km; Alaska, + 10 km). In Canada success rates were c. 40–70% and all experiments over‐predicted forest cover. Most corrections improved results over uncorrected biomization; using only lakes improved success rates to c. 80%. In Alaska success rates were 70–80% and classification errors were more evenly distributed; there was little improvement over uncorrected biomization. Main conclusions Corrected biomization should improve broad‐scale reconstructions of spatial patterns in forest/non‐forest vegetation mosaics and across climate‐sensitive ecotones. The Canadian example shows this is particularly the case in regions affected by taxa with extremely high pollen productivity (such as Pinus). Improved representation of actual vegetation distribution is most likely if pollen data from lake sediments are used because the REVEALS algorithm is based on the pollen dynamics of lake‐based systems.     

Present-day and mid-Holocene biomes reconstructed from pollen and plant macrofossil data from the former Soviet Union and Mongolia

Fossil pollen data supplemented by tree macrofossil records were used to reconstruct the vegetation of the Former Soviet Union and Mongolia at 6000 years. Pollen spectra were assigned to biomes using the plant-functional-type method developed by Prentice et al . (1996). Surface pollen data and a modern vegetation map provided a test of the method. This is the first time such a broad-scale vegetation reconstruction for the greater part of northern Eurasia has been attempted with objective techniques. The new results confirm previous regional palaeoenvironmental studies of the mid-Holocene while providing a comprehensive synopsis and firmer conclusions. West of the Ural Mountains temperate deciduous forest extended both northward and southward from its modern range. The northern limits of cool mixed and cool conifer forests were also further north than present. Taiga was reduced in European Russia, but was extended into Yakutia where now there is cold deciduous forest. The northern limit of taiga was extended (as shown by increased Picea pollen percentages, and by tree macrofossil records north of the present-day forest limit) but tundra was still present in north-eastern Siberia. The boundary between forest and steppe in the continental interior did not shift substantially, and dry conditions similar to present existed in western Mongolia and north of the Aral Sea.     

祁连山南坡植被景观格局及其破碎化

以扎麻什营林区的林相图和调查资料为基础,运用GIS手段,选取合适的景观格局指数,分析了祁连山南坡植被景观格局基本特征,并进行了破碎化评价.结果表明:研究区植被以草地和灌丛为主,景观基质已退化为裸地,各植被类型斑块密度远大于裸地,平均分维数较低,景观整体破碎化水平较高;草地和灌丛边界密度和破碎化指数均高于其他植被类型,反映出该区自然植被景观主要受放牧活动的影响;森林多以小面积零散分布,其中青海云杉林景观结构破坏较为严重,异质性较低,斑块形状趋于单一,显示出较高水平的破碎化,其他林种多以小面积集中分布于某些小的生境,受人类活动干扰较少,破碎化程度较低.

Abstract：

Based on the forest form map and investigation data of Zhamashi forest area, and by using GIS, appropriate landscape pattern indices were chosen to study the basic characteristics of vegetation landscape pattern on the southern slope of Qilian Mountain, with the landscape frag-mentation evaluated. In the study area, grass and shrub were the main vegetation types, and the landscape matrix had degraded to bare land. The patch densities of all vegetation types were far larger than that of bare land, and their mean fractal dimension was lower than that of bear land. All of these characters emphasized the highly fragmented condition of the vegetation landscape in this area. The total edge densities and fragment indices of grassland and shrub land were higher than those of other vegetation types, reflecting that the natural vegetation was mainly affected by grazing. The forests were more dispersed in small areas, and the landscape structure of Picea crassifollia forest was heavily destroyed, being induced that the heterogeneity became lower and the patch shape tended to single, suggesting a high fragmentation degree. Other forest types were centralized in a certain habitat and less disturbed by human activities, suggesting a lower frag-mentation degree.     

Assessment of biodiversity in Central Federal District using satellite-based maps of terrestrial ecosystems

A research study of the ecosystem biodiversity of the Central Federal District (CFD) has been carried out at the regional level with the use of the map of vegetation in the terrestrial ecosystems, which was created on the basis of the high spatial resolution (30 m) data obtained from the Landsat satellite series. Numerical characteristics such as the areas of the forest and other terrestral ecosystems; the number of forest plots; their average areas in a federal region; the disturbed forest land areas over the past 5 years; the proportions of the coniferous, deciduous, and mixed forests; and the total number of ecosystem types found in the federal region are calculated for each federal region in the Russian Federation within the CFD. The dominant landscape type is defined using a regular grid whose cell size matches the size of the average basal area of the forest plot on the vegetation map. The areas of the forest, agricultural, grassland, and agro-forest landscapes within each grid cell are estimated. The dominant landscape areas are assessed for each federal region; the analysis reveals that, on average, a quarter of all land areas in the district are occupied by agroforest landscapes. A logical sequence of research activities has been presented to assess the indicators of biodiversity in the forest and other terrestrial ecosystems and their functions and services.     

A study on the relationship between vegetation pattern and environment in the upstream of Minjiang River,China

The vegetation pattern in the upstream of Minjiang River,and its relationship with environment factors,such as landscape position(elevation,slope,aspect),precipitation and temperature and soil are analyzed in this paper.The data used in this Paper were based on the landscape map derived from 1994 TM imagery.The results were as follows:1)dominant landscape types were forest,shrub land and grassland,which were very similar in terms of area ratio(32.87%,31.85% and 28.44%,respectively);2)the patch shape of conifer forest and mixed forest was complicated while that of broad-leaved forest and cultivated land was simple;3)the fragmentation of conifer forest and mixed forest was serious in contrast with low fragmentation of broad-leaved forest and cultivated land;and 4)closed scrub and grassland had a high contagion and good connectivity while mixed forest had a lower contagion and bad connectivity.In addition,the vegetation distribution pattern of upstream of Minjiang River Was closely related with elevation and temperature,but the relationship between vegetation and precipitation was not statistically significant.     

The impacts and implications of an intensifying fire regime on Alaskan boreal forest composition and albedo

Climate warming and drying are modifying the fire dynamics of many boreal forests, moving them towards a regime with a higher frequency of extreme fire years characterized by large burns of high severity. Plot‐scale studies indicate that increased burn severity favors the recruitment of deciduous trees in the initial years following fire. Consequently, a set of biophysical effects of burn severity on postfire boreal successional trajectories at decadal timescales have been hypothesized. Prominent among these are a greater cover of deciduous tree species in intermediately aged stands after more severe burning, with associated implications for carbon and energy balances. Here we investigate whether the current vegetation composition of interior Alaska supports this hypothesis. A chronosequence of six decades of vegetation regrowth following fire was created using a database of burn scars, an existing forest biomass map, and maps of albedo and the deciduous fraction of vegetation that we derived from Moderate Resolution Imaging Spectroradiometer (MODIS) satellite imagery. The deciduous fraction map depicted the proportion of aboveground biomass in deciduous vegetation, derived using a RandomForest algorithm trained with field data sets (n=69, 71% variance explained). Analysis of the difference Normalized Burn Ratio, a remotely sensed index commonly used as an indicator of burn severity, indicated that burn size and ignition date can provide a proxy of burn severity for historical fires. LIDAR remote sensing and a bioclimatic model of evergreen forest distribution were used to further refine the stratification of the current landscape by burn severity. Our results show that since the 1950s, more severely burned areas in interior Alaska have produced a vegetation cohort that is characterized by greater deciduous biomass. We discuss the importance of this shift in vegetation composition due to climate‐induced changes in fire severity for carbon sequestration in forest biomass and surface reflectance (albedo), among other feedbacks to climate.     

Mapping land cover and forest density in Zagros forests of Khuzestan province in Iran: A study based on Sentinel-2, Google Earth and field data

Zagros forests in western Iran have widely been destroyed because of various reasons. This study was performed to provide the land cover and forest density maps in Zagros forests of Khuzestan province using Sentinel-2, Google Earth and field data. The forest boundary in Khuzestan province was digitized in Google Earth. Sentinel-2 satellite images were provided for the study area. One 1:25000 index sheet of Iranian Mapping Organization (IMO) was selected as pilot area in the province. Sentinel-2 image of the pilot area was classified using different supervised classification algorithms to select the best algorithm for land cover mapping in Khuzestan province. In addition, to evaluate the accuracy of Google Earth data, field sampling was performed using random plots in different land covers. Field data of forest plots were applied to investigate tree canopy cover percent (forest density), as well. Classification of Sentinel-2 image in Zagros area of Khuzestan province was done using the best algorithm and the land cover was obtained. The forest density map was also obtained using a linear regression model between tree canopy cover percent (obtained from field plots) and normalized difference vegetation index (NDVI) (obtained from NDVI map). Finally, the accuracy of land cover map was assessed by some square plots on Google Earth. Results demonstrated that support vector machine (SVM) algorithm had the highest accuracy for land cover mapping. Results also showed that Google Earth images had a good accuracy in the Zagros forests of Khuzestan province. Results demonstrated that NDVI has been a good predicator to estimate tree canopy cover in the study area. Based on results, an area of 443,091.22 ha is covered by Zagros forests in Khuzestan province. Results of accuracy assessment of the land cover map showed the good accuracy of this map in Khuzestan province (overall accuracy: 91% and kappa index: 0.83). For optimum management of Zagros forests, it is suggested that the land cover and forest density mapping will be performed using SVM algorithm, NDVI, and Sentinel-2 satellite images in Zagros forests of Khuzestan province in the certain periods.