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1.
We discuss the usefulness of the concept of Potential Natural Vegetation (PNV), which describes the expected state of mature vegetation in the absence of human intervention. We argue that it is impossible to model PNV because of (i) the methodological problems associated to its definition and (ii) the issues related to the ecosystems dynamics.We conclude that the approach to characterizing PNV is unrealistic and provides scenarios with limited predictive power. In places with a long‐term human history, interpretations of PNV need to be very cautious, and explicit acknowledgement made of the limitations inherent in available data.  相似文献   

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The main goal of the Habitats Directive, a key document for European conservation, is to maintain a ‘favourable’ conservation status of selected species and habitats. In the face of near-future climatic change this goal may become difficult to achieve. Here, we evaluate the sensitivity to climate change of 84 plant species that characterise the Danish habitat types included in the Habitats Directive. A fuzzy bioclimatic envelope model, linking European and Northwest African species’ distribution data with climate, was used to predict climatically suitable areas for these species in year 2100 under two-climate change scenarios. Climate sensitivity was evaluated at both Danish and European scales to provide an explicit European perspective on the impacts predicted for Denmark. In all 69–99% of the species were predicted to become negatively affected by climate change at either scale. Application of international Red List criteria showed that 43–55% and 17–69% would become vulnerable in Denmark and Europe, respectively. Northwest African atlas data were used to improve the ecological accuracy of the future predictions. For comparison, using only European data added 0–7% to these numbers. No species were predicted to become extinct in Europe, but 4–7% could be lost from Denmark. Some species were predicted to become positively affected in Denmark, but negatively affected in Europe. In addition to nationally endangered species, this group would be an important focus for a Danish conservation strategy. A geographically differentiated Danish conservation strategy is suggested as the eastern part of Denmark was predicted to be more negatively affected than the western part. No differences in the sensitivity of the Habitats Directive habitats were found. We conclude that the conservation strategy of the Habitats Directive needs to integrate the expected shifts in species’ distributions due to climate change.  相似文献   

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As conservation planning increases in scale from specific sites to entire regions, organisations like The Nature Conservancy face a critical need for GIS-based tools to evaluate landscapes on a regional scale. An existing, field-based approach to analyse the diversity of a landscape is by delineating natural community types, which is a time-intensive process. This study evaluated the utility of using an existing, GIS-derived landscape diversity model as a predictive tool for mapping natural communities on a large (8369 ha) upland forest site in the northern Taconic region of Vermont. The GIS model incorporates four geophysical factors: elevation, bedrock type, surficial deposits, and landform. A significant level (α=0.05) of association between eight pairs of landscape diversity unit (LDU) types and natural community types was found. However, the strength of these associations is low (Cramer's V values 0.172), suggesting a poor predictive efficiency of landscape diversity units for natural community types. The results suggest that variables in the LDU model are relevant to natural community distribution, but the LDU model alone is not an effective tool to aid in mapping of natural community types of upland forests in Vermont. Until better landscape-level techniques are developed, the role of this type of model is limited to screening the landscape for areas with a particular set of geophysical characteristics, which can help an ecologist interpret the patterns on the landscape, but cannot substitute for a field-based approach to natural community mapping.  相似文献   

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Colombian vegetation, at the ecological level of the biome, is reconstructed at six sites using pollen data assigned a priori to plant functional types and biomes. The chosen sites incorporate four savanna sites (Laguna Sardinas, Laguna Angel, El Piñal and Laguna Carimagua), a site on the transition between savanna and Amazon rainforest (Loma Linda) and a site within the Amazon rainforest (Pantano de Monica). The areal extent of tropical moist forest, tropical dry forest and steppe have been subject to significant change: differential responses of the vegetation to climatic shifts are related to changes in plant available moisture, duration of dry season and edaphic controls on the vegetation. The record from El Piñal shows that the present-day savanna vegetation, dominated by steppe (Poaceae) with little occurrence of woody savanna taxa (e.g. Curatella, Byrsonima), was present since the last glacial period of the northern hemisphere. Unfortunately, El Piñal is located on an edaphic savanna and is not particularly responsive to registering change. Most records cover the early Holocene; one site records the El Abra stadial (Younger Dryas equivalent), when forest expansion reflects more humid climatic conditions and higher plant available moisture. During the early and middle Holocene, the maximum expansion of steppe and tropical dry forest occurred, indicating that dry climatic conditions continued to around 4000 14C BP. The following period, from shortly before 4000 14C BP, is characterised by an increase in forest and gallery forests, reflecting a wetter period probably with a shorter annual dry season. Anthropogenic influence on the vegetation is recorded by all the records over the last millennial, particularly characterised by a reduction in forest cover and high amplitude changes in vegetation.Biome transitions from one type to another, and the environmental controls on this shift, are investigated by applying a vegetation model (BIOME-3). The model uses climatic data from six meteorological stations that, encompass a range of environments within lowland Colombia, which are similar to the pollen data. The signals of vegetation change can be translated to the main environmental controls of temperature and moisture to indicate the degree of change needed in these parameters to record the vegetation change depicted by the pollen data. Moisture balance is the dominant control on driving vegetation change whether under seasonal or annual control. The combined reconstruction from pollen data and model output of biome-scale vegetation dynamics for lowland Colombia allows an understanding of the environmental controls to be developed.  相似文献   

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Question: Does the course of succession on a coal mine restored by hydroseeding converge with a reference community in terms of species composition and vegetation structure? What is the rate of succession on restored areas? How does the balance between local colonization and extinction rates change during succession? Which species group (native or hydroseeded) determines the successional process? Location: Large reclaimed coal mine in the north of Palencia province, northern Spain (42°50′N, 4°38′W). Methods: Between 2004 and 2009 we monitored annually vascular plant species cover in nine permanent plots (20 m2 each) at a restored mine; these plots were structured to account for site aspect (north, south and flat). Three identical permanent plots were established in the surrounding reference community and monitored in 2004 and 2009. We used detrended correspondence analysis to assess successional trends and rates of succession, generalized linear mixed models to derive patterns of vegetation structural changes and turnover through time, and Huisman–Olff–Fresco modelling to illustrate response of individual species through time. Results: The three restored mine areas exhibited a successional trend towards the reference community through time, although speed of convergence differed. However, after 6 years the restored sites had diverged considerably and this was greater than the dissimilarity reduction with respect to the reference community. Richness, diversity and native species cover increased linearly through time, whereas hydroseeded species cover decreased. Success of hydroseeded species initially differed in the three areas, and this was negatively related with native species colonization rates. Response patterns through time of ten hydroseeded and 20 most common native species are described. Conclusions: Vegetation structural parameters rapidly converged with the reference community, whereas compositional convergence needed much longer. At the same time, successional composition trajectories and rates were related to site properties (here aspect).  相似文献   

7.
Abstract. Separate logistic regression models were developed to predict the distribution and large-scale spatial patterns of dominant graminoid species and communities in alpine grasslands. The models are driven by four bioclimatic parameters: degree-days of growing season (basis 0 °C), a moisture index for July, potential direct solar radiation for March, and a continentality index. Geology and slope angle were used as a surrogate for nutrient availability and soil water capacity. The bioclimatic parameters were derived from monthly mean temperature, precipitation, cloudiness and potential direct solar radiation. The environmental parameters were interpolated using a digital elevation model with a resolution of 50 m. The vegetation data for model calibration originate from field surveys and literature. An independent test data set with samples from three different climatic zones was used to test the model. The degree of coincidence between simulated and observed patterns was similar for species and communities, but the κ-values for communities were generally higher (κ= 0.539) than for species (mean individual κ= 0.201). Information on land use was detected as a major factor that could significantly improve both the species and the community model. Nevertheless, the climatic factors used to drive the model explained a major part of the observed patterns.  相似文献   

8.
湖北植被区划(下)   总被引:14,自引:2,他引:12  
Ⅰ_2 湖北南部中亚热带常绿阔叶林地带本植被地带居湖北南半部,位于英山、罗田、新洲、黄陂、天门、荆门、远安、兴山一线以南。东部为幕阜山脉北坡,以丘陵低山地貌为主,中部为坦荡的冲积平原,大小湖泊星罗棋布,是湖北水生植物分布最广的区域;西部为武陵山系的东北麓,以山地丘陵为特点。年均温16℃以上,≥10℃年积温4800—5600℃,为本省区两个高温区域之所在,无霜期在250天以上,年降水量1100—1600毫米。长江贯穿全境,还有众多的大  相似文献   

9.
本植被地带居湖北南半部,位于英山、罗田、新洲、黄陂、天门、荆门、远安、兴山一线以南。东部为幕阜山脉北坡,以丘陵低山地貌为主,中部为坦荡的冲积平原,大小湖泊星罗棋布,是湖北水生植物分布最广的区域;西部为武陵山系的东北麓,以山地丘陵为特点。年均温16℃以上,≥10℃年积温4800—5600℃,为本省区两个高温区域之所在,无霜期在250天以上,年降水量1100—1600毫米。长江贯穿全境,还有众多的大小支流。  相似文献   

10.
Weakly-supervised learning has recently emerged in the classification context where true labels are often scarce or unreliable. However, this learning setting has not yet been extensively analyzed for regression problems, which are typical in macroecology. We further define a novel computational setting of structurally noisy and incomplete target labels, which arises, for example, when the multi-output regression task defines a distribution such that outputs must sum up to unity. We propose an algorithmic approach to reduce noise in the target labels and improve predictions. We evaluate this setting with a case study in global vegetation modelling, which involves building a model to predict the distribution of vegetation cover from climatic conditions based on global remote sensing data. We compare the performance of the proposed approach to several incomplete target baselines. The results indicate that the error in the targets can be reduced by our proposed partial-imputation algorithm. We conclude that handling structural incompleteness in the target labels instead of using only complete observations for training helps to better capture global associations between vegetation and climate.  相似文献   

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神农架龙门河地区的植被制图及植被现状分析   总被引:7,自引:1,他引:7       下载免费PDF全文
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 。  相似文献   

13.
Abstract. Empirical ecological response surfaces were derived for eight dominant tree species in the boreal forest region of Canada. Stepwise logistic regression was used to model species dominance as a response to five climatic predictor variables. The predictor variables (annual snowfall, degree-days, absolute minimum temperature, annual soil moisture deficit, and actual evapotranspiration summed over the summer months) influence the response of plants more directly than the annual or monthly measures of temperature and precipitation commonly used in response surface modeling. The response surfaces provided estimates of the probability of species dominance across the spatial extent of North America with a high degree of success. Much of the variation in the probability of dominance is apparently related to the species' individualistic response to climatic constraints within different airmass regions. A forest type classification for the Canadian boreal forest region was derived by a cluster analysis based on the probability estimates. Five major forest types were distinguished by the application of a stopping rule. The predicted forest types showed a high degree of geographic correspondence with the distribution of forest types in the actual vegetation mosaic. The distribution of the predicted types also bears a direct relationship to seasonal airmass dynamics in the boreal forest region.  相似文献   

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陕西佛坪自然保护区植被的基本特征   总被引:14,自引:2,他引:12  
对陕西佛坪自然保护区植被优势植物的区系地理特征,主要植被类型及其时空动态特征进行了讨论。本区属中国-日本森林植物区系的一部分,温带分布属占较大比例,热带分布属也占相当比重,低中山森林植被优势植物以华中、华北及华东成分为主,亚高山灌丛及草甸则主要由唐古特成分及中国-喜马拉雅成分构成,本区可被视为我国温带植物区系的典型地区。本区植被可分为3个垂直自然带;(1)落叶阔叶栎林带(2000m以下);(2)落  相似文献   

16.
九宫山自然保护区植被及其特征的初步研究   总被引:2,自引:2,他引:2  
九宫山自然保护区位于中国中亚热带向北热带过渡区,植被构成以森林植被为主。通过调查和分析,将九宫山自然保护区植被划分为5个植被型组,11个植被型,32个群系。九宫山自然保护区的种子植物区系分布中温带性质和热带性质的属分别为384和302属;植被类型中主要森林植的构成为:暖温性、温性和寒温性针叶林群系数目依次是1、1、0,常绿阔叶林、落叶常绿阔叶混交林和落叶阔叶林群系数目分别为3、7、7;森林植被中落叶常绿阔叶混交林的分布面积最大。与井冈山自然保护区、庐山、后河自然保护区、清凉峰自然保护区、神农架自然保护区以及董寨鸟类自然保护区等地植被相关特征的比较分析表明,该区植被种子植物的主要组成种类以及森林植被类型和分布等具有明显的地带性过渡特性。  相似文献   

17.
Conservation evaluation of large areas ( > 10 000 km2) in Australia requires detailed mapping of vegetation types. Predicting the original vegetation cover of extensive cleared areas in an explicit, consistent and repeatable manner necessitates the use of statistical modelling. This paper describes an integrated approach to vegetation mapping in a region of New South Wales, Australia. The approach uses separate statistical models for each tree and shrub species to predict the vegetation composition in each grid cell in a geographic information system (GIS). Allocation of these grid cells to communities allows communities that no longer exist in the remaining remnants of woodland to be defined. Examples of use of this information for management are presented. This paper addresses the practical considerations which constrain the way statistical modelling can be used for vegetation mapping in an applied project. Constraints include: (1) data availability (use of sampling to fill gaps in existing data), (2) the effects of cover abundance values, (3) availability of GIS predictors, (4) data management, (5) current generalised additive model methods and (6) prediction methods. Careful attention to the practicality of all components of a vegetation mapping study is essential if modern methods are to be applied in regional studies which must provide functional products for land managers with limited resources, skills and finances at their disposal.  相似文献   

18.
东莞大屏嶂森林公园的现状植被及林分改造对策   总被引:10,自引:0,他引:10  
杨加志  苏志尧  许月明 《生态科学》2004,23(2):144-146,153
采用改进的线路调查方法对东莞大屏障森林公园植被进行调查。结果表明大屏障森林公园植物种类多样,植物资源丰富。公园的现状植被可以划分为5个类型,8个亚型。森林可分为次生常绿阔叶林、人工马占相思林Acacia mangium、油茶林Camellia oleifera等3个亚型。此外,还有荒草坡、农田植被以及其他类型的植被。据此探讨了对大屏障森林公园植被的改造对策,为森林公园的建设提供依据。  相似文献   

19.
论滇南西双版纳的森林植被分类   总被引:3,自引:0,他引:3  
朱华 《云南植物研究》2007,29(4):377-387
本文基于多年研究成果的总结,对西双版纳森林植被的分类、主要植被类型及其特征进行了系统归纳,并讨论了它们与世界类似热带森林植被的关系。以群落的生态外貌与结构、种类组成和生境特征相结合作为植被分类的原则和依据,可以将西双版纳的热带森林植被分类为热带雨林、热带季节性湿润林、热带季雨林和热带山地常绿阔叶林四个主要的植被型,包括有至少二十个群系。热带雨林包括热带季节雨林和热带山地(低山)雨林二个植被亚型。热带季节雨林具有与赤道低地热带雨林几乎一样的群落结构和生态外貌特征,是亚洲热带雨林的一个类型,但由于发生在季风热带北缘纬度和海拔的极限条件下,受到季节性干旱和热量不足的影响,在其林冠层中有一定比例的落叶树种存在,大高位芽植物和附生植物较逊色而藤本植物和在叶级谱上的小叶型植物更丰富,这些特征又有别于赤道低地的热带雨林。热带山地雨林是热带雨林的山地亚型,是该地区热带山地较湿润生境的一种森林类型,它在植物区系组成和生态外貌特征上类似于热带亚洲的低山雨林,隶属于广义热带雨林植被型下的低山雨林亚型。热带季节性湿润林分布在石灰岩山坡中、上部,在群落外貌上类似热带山地常绿阔叶林但在植物区系组成上与后者不同,它是石灰岩山地垂直带上的一种植被类型。热带季雨林是分布在该地区开阔河谷盆地及河岸受季风影响强烈的生境的一种热带落叶森林,是介于热带雨林与萨王纳之间的植被类型。热带山地常绿阔叶林(季风常绿阔叶林)是西双版纳的主要山地植被类型,它分布在热带季节雨林带之上偏干的山地生境。它在植物区系组成上不同于该地区的热带季节雨林,在生态外貌特征上亦不同于热带山地雨林,是发育在受地区性季风气候强烈影响的热带山地的一种森林植被类型。  相似文献   

20.
The optimum vegetation indexand methods for collecting vegetation information in loess plateau area were studied and appraised. In this area, there were deciduous broadleaved forest, steppe and desert. Vegetation types were rich and diverse. However, collection of vegetation information was strongly influenced by the soil background. The modified soil-adjusted vegetation index (MSAVI) after being compared and analysed not only could enhance vegetation signal, but also could minimize greatly the soil background effects. It could also reflect the distribution of the vegetation types macroscopically in this area. At present, it has been a more or lessideal vegetation index for collection vegetation information in loess plateau area. The collection and monitering of vegetation information for the normalized difference vegetation index (NDVI), soil-adjusted vegetation index (SAVI) and perpendicular vegetation index (PVI) were used in high, medium density and rare vegetation area respectively. For a variety of vegetation indices, the images which were produced by cumulative multitemporal vegetation indices could extract vegetation information well reflecting the vegetation distribution of that particular area.  相似文献   

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