Search

Abstract: The recent inclusion of communities of planktonic algae and microbial crusts into the system of European vegetation types is critically discussed. It is argued that formal vegetation classification should be limited to plant taxa represented by macroscopic individuals within a plot, including all vascular plants, bryophytes, lichens, charophyta and macrophytic chlorophyta, rhodophyta or phaeophyta. In the interest of comparability and methodological stringency, all microscopic algae and all prokaryotes, including cyanobacteria, and the habitats dominated by such microorganisms (e.g. plankton, biofilms and crusts), should be excluded from vegetation classification. [ABSTRACT FROM AUTHOR]

Aim Multivariate mixture models offer the ability to streamline the typically multi-stage process of vegetation classification and mapping into a single, simultaneous analytical step. Our aim is to demonstrate the model's utility over large and diverse areas, with comparison to existing classification and mapping conventions. Location New South Wales, Australia. Methods We demonstrate a statistical model that uses both multivariate species data and environmental covariate data to simultaneously classify observations into groups and predict those groups out into environmental and geographical space. We used two large data sets to demonstrate the method: an ~810,000 km2 area with 4,715 sites and 488 species and a ~220,000 km2 area with 5,183 sites and 446 species. A range of topographic, terrain, climate and soil predictors were used as environmental variables, including future projected climate variables. Models can be fit with the R package ' RCPmod.' Results The method results in probabilistic memberships to vegetation assemblages, for both the classification and map. There was general agreement between our approach and existing vegetation classification conventions, but we explore some notable differences. We were able to examine the environmental gradients that define the predicted vegetation distributions, as well as make predictions about how the distribution of species assemblages might shift as a result of climate change. Main conclusions Our approach tightens the link between description of biodiversity patterns and their depiction in space, by considering both biotic and spatially explicit abiotic information simultaneously. The method allows uncertainty to be quantified objectively across a consistent set of groups for both vegetation classification and mapping, which is rarely the case in traditional multi-stage approaches. A simultaneous modelling approach increases capacity to make predictions into varying spatial, temporal and environmental dimensions, providing new ecological insights and increasing capacity for evidence-based decision making. [ABSTRACT FROM AUTHOR]

Question What are the main plant communities and vegetation zones on Socotra Island in relation to climatic, geological and topographic factors? Location Socotra Island ( Yemen). Methods A total of 318 relevés were sampled along an altitudinal gradient. Floristic and environmental (topographic, geological and climatic) data were collected and analysed using numerical classification and NDMS ordination; an analysis of the correlation between plant communities and environmental factors was also performed. Results Eight types of woody vegetation, seven of shrubs, six of herbaceous and seven of halophytic vegetation were identified. Ordination revealed the importance of altitudinal and climatic gradients, as well as of geological substrata. Conclusions Four vegetation zones were identified. The first three are located in the arid region with altitude ranging from 0 to 1000 m and the fourth in the semi-arid region from 1000 to 1500 m a.s.l. Specifically they are: (1) an arid coastal plain mainly located on an alluvial substratum between 0 and 200 m, characterized by shrubland and grassland communities; (2) a transition zone from 200 to 400 m, between the alluvial substratum and the upper limestone area; (3) an arid limestone zone between 400 and 1000 m, interspersed with hills and plateaus; and (4) a semi-arid upper zone of the Haghier Mountains from 1000 to 1500 m on a granitic substratum. [ABSTRACT FROM AUTHOR]

This article provides guidelines for the description, documentation, and review of proposals for new or revised plant associations and alliances to be recognized as units of vegetation within the U.S. National Vegetation Classification (NVC). By setting forth standards for field records, analysis, description, peer review, and archiving, the Ecological Society of America's Vegetation Classification Panel, in collaboration with the U.S. Federal Geographic Data Committee, NatureServe, and Others, seeks to advance our common understanding of vegetation and improve our capability to sustain and restore natural systems. We provide definitions for the two floristic levels of the NVC hierarchy: associations and alliances. This is followed by a description of standards for field plot records and the identification and classification of vegetation types. Procedures for review and evaluation of proposed additions and revisions of types are provided, as is a structure for data archiving and dissemination. These procedures provide a dynamic and practical way to publish new or revised descriptions of vegetation types while maintaining a current, authoritative list of types for multiple users to access and apply. [ABSTRACT FROM AUTHOR]

Question: How can we determine differential taxa in a vegetation data set? Methods: The new algorithm presented here uses an intuitive fidelity threshold based on relative constancy differences. It is tested on a simulated and a real data set. The results of the proposed algorithm are discussed in comparison with other methods used for the determination of differential taxa. Results: The new algorithm defines each taxon in each group of relevés as: (1) positively differentiating, (2) positively-negatively differentiating, (3) negatively differentiating, or (4) non-differentiating. Each taxon in a data set may be: (1) positively, positively-negatively or negatively differentiating for each group in the data set, (2) differentiating for some groups and non-differentiating for the remaining groups, or (3) non-differentiating for all groups in the data set. Conclusions: The new algorithm finds the relevé groups that are positively differentiated against other groups that are negatively differentiated. It reveals differentiating structures in the data set and thus makes quantification of the relations among and between different syntaxonomic ranks conceivable. As it distinguishes between different types of differential taxa, it might improve standards of typification in vegetation classification. [ABSTRACT FROM AUTHOR]

The impact of an exotic species in natural systems may be dependent not only on invader attributes but also on characteristics of the invaded community. We examined impacts of the invader bitou bush, Chrysanthemoides monilifera ssp. rotundata, in fore and hind dune communities of coastal New South Wales, Australia. We compared invader impacts on vegetation structure, richness of both native and exotic growth forms and community variability in fore and hind dunes. We found that impacts of bitou invasion were context specific: in fore dune shrublands, functionally distinct graminoid, herb and climber rather than shrub growth forms had significantly reduced species richness following bitou invasion. However, in forested hind dunes, the functionally similar native shrub growth form had significantly reduced species richness following bitou invasion. Density of vegetation structure increased at the shrub level in both fore and hind dune invaded communities compared with non-invaded communities. Fore dune ground-level vegetation density declined at invaded sites compared with non-invaded sites, reflecting significant reductions in herb and graminoid species richness. Hind dune canopy-level vegetation density was reduced at invaded compared with non-invaded sites. Bitou bush invasion also affected fore dune community variability with significant increases in variability of species abundances observed in invaded compared with non-invaded sites. In contrast, variability among all hind dune sites was similar. The results suggest that effects of bitou bush invasion are mediated by the vegetation community. When bitou bush becomes abundant, community structure and functioning may be compromised. [ABSTRACT FROM AUTHOR]

Questions: How similar are solutions of eight commonly used vegetation classification methods? Which classification methods are most effective according to classification validity evaluators? How do evaluators with different optimality criteria differ in their assessments of classification efficacy? In particular, do evaluators which use geometric criteria (e.g. cluster compactness) and non-geometric evaluators (which rely on diagnostic species) offer similar classification evaluations? Methods: We analysed classifications of two vegetation datasets produced by eight classification methods. Classification solutions were assessed with five geometric and four nongeometric internal evaluators. We formally introduce three new evaluators: PARTANA, an intuitive variation on evaluators which use the ratio of within/between cluster dissimilarity as the optimality criterion, an adaptation of Morisita's index of niche overlap, and ISAMIC, an algorithm which measures the degree to which species are either always present or always absent within clusters. Results and Conclusions: 1. With the exception of single linkage hierarchical clustering, classifications resulting from the eight methods were often similar. 2. Although evaluators varied in their assessment of best overall classification method, they generally favored three hierarchical agglomerative clustering strategies: flexible beta (β = - 0.25), average linkage, and Ward's linkage. 3. Among introduced evaluators PARTANA appears to be an effective geometric strategy which provides assessments similar to C-index and Gamma evaluators. Nongeometric evaluators ISAMIC and Morisita's index demonstrate a strong bias for single linkage solutions. 4. Because non-geometric criteria are of interest to phytosociologists there is a strong need for their continued development for use with vegetation classifications. [ABSTRACT FROM AUTHOR]

Question: What is the variation in species composition of Central European semi-dry grasslands? Can we apply a training-and-test validation approach for identifying phytosociological associations which are floristically well defined in a broad geographic comparison; can we separate them from earlier described Associations with only a local validity? Location: A 1200 km long transect running along a gradient of increasing continentality from central Germany via Czech Republic, Slovakia, NE Austria, Hungary to NW Romania. Methods: Relevés with > 25% cover of Brachypodium pinnatum and/or Bromus erectus were geographically selected from a larger database. They were randomly split into two data sets, TRAINING and TEST, each with 422 relevés. Cluster analysis was performed for each data set on scores from significant principal coordinates. Different partitions of the TRAINING data set were validated on the TEST data set, using a new method based on the comparison of % frequencies of species occurrence in clusters. Clusters were characterized by statistically defined groups of diagnostic species and values of climatic variables. Results: Species composition changed along the NW-SE gradient and valid clusters were geographically well separated. Optimal partition level was at 11 clusters, six being valid: two clusters Germany and the Czech Republic corresponded to the Bromion erecti; two clusters from the Czech Republic and Hungary to the Cirsio-Brachypodion, and two clusters were transitional between these two alliances. Conclusion: The training-and-test validation method used in this paper proved to be efficient for discriminating between robust clusters, which are appropriate candidates for inclusion in the national or regional syntaxonomic overviews, and weak clusters, which are specific to the particular classification of the given data set. [ABSTRACT FROM AUTHOR]

Question: The utility of beta (β-) diversity measures that incorporate information about the degree of taxonomic (dis)similarity between species plots is becoming increasingly recognized. In this framework, the question for this study is: can we define an ecologically meaningful index of β-diversity that, besides indicating simple species turnover, is able to account for taxonomic similarity amongst species in plots? Methods: First, the properties of existing measures of taxonomic similarity measures are briefly reviewed. Next, a new measure of plot-to-plot taxonomic similarity is presented that is based on the maximal common subgraph of two taxonomic trees. The proposed measure is computed from species presences and absences and include information about the degree of higher-level taxonomic similarity between species plots. The performance of the proposed measure with respect to existing coefficients of taxonomic similarity and the coefficient of Jaccard is discussed using a small data set of heath plant communities. Finally, a method to quantify β-diversity from taxonomic dissimilarities is discussed. Results: The proposed measure of taxonomic β-diversity incorporates not only species richness, but also information about the degree of higher-order taxonomic structure between species plots. In this view, it comes closer to a modern notion of biological diversity than more traditional measures of β-diversity. From regression analysis between the new coefficient and existing measures of taxonomic similarity it is shown that there is an evident nonlinearity between the coefficients. This nonlinearity demonstrates that the new coefficient measures similarity in a conceptually different way from previous indices. Also, in good agreement with the findings of previous authors, the regression between the new index and the Jaccard coefficient of similarity shows that more than 80% of the variance of the former is explained by the community structure at the species level, while only the residual variance is explained by differences in the higher-order taxonomic structure of the species plots. This means that a genuine taxonomic approach to the quantification of plot-to-plot similarity is only needed if we are interested in the residual system's variation that is related to the higher-order taxonomic structure of a pair of species plots. [ABSTRACT FROM AUTHOR]

Question: What are the effects of grazing abandonment on the vegetation composition of Estonian coastal wetlands? Location: Vormsi Island and Silma Nature Reserve in western Estonia, Europe. Methods: Local knowledge and field reconnaissance were used to identify current and historical management levels of wetland sites within the west Estonian study area. Nine study sites, with varying management histories, were selected comprising an area of 287 ha. A total of 198 quadrats were taken from 43 distinct vegetation patches in five of the sites. TWINSPAN analysis was used to identify community type, and a phytosociological key was constructed for character taxa. This vegetation classification was then applied within a GIS-based context to classify all the study sites, using a ground survey technique and 1:2000 scale air photos. Results: We identified 11 different brackish coastal wetland community types. Indicator species were defined with community characteristics for the seven main vegetation types readily recognisable in the field. Coastal wet grasslands were most extensive in grazed sites, or sites that had been more intensively grazed, while abandoned sites were largely composed of Phragmites australis stands, tall grassland, and scrub. Site variations based on vegetation composition were significantly correlated with past grazing intensity. Plant community types showed significant edaphic differences, with particularly low soil moisture and high conductivity and pH for open pioneer patches compared to other vegetation types. Conclusion: Abandonment of traditionally grazed coastal grasslands threatens their characteristic biodiversity. This study found that grazing abandonment reduced the extent of coastal wetland grasslands of particular conservation value. Nevertheless, plant species of conservation interest were found across the sequence of community types described. The study shows that grazing is an important factor influencing coastal wetland plant communities but suggests that vegetation distribution is affected by environmental variables, such as topography. [ABSTRACT FROM AUTHOR]

Question: Is it possible to mathematically classify relevés into vegetation types on the basis of their average indicator values, including the uncertainty of the classification? Location: The Netherlands. Method: A large relevé database was used to develop a method for predicting vegetation types based on indicator values. First, each relevé was classified into a phytosociological association on the basis of its species composition. Additionally, mean indicator values for moisture, nutrients and acidity were computed for each relevé. Thus, the position of each classified relevé was obtained in a three-dimensional space of indicator values. Fitting the data to so called Gaussian Mixture Models yielded densities of associations as a function of indicator values. Finally, these density functions were used to predict the Bayesian occurrence probabilities of associations for known indicator values. Validation of predictions was performed by using a randomly chosen half of the database for the calibration of densities and the other half for the validation of predicted associations. Results and Conclusions: With indicator values, most relevés were classified correctly into vegetation types at the association level. This was shown using confusion matrices that relate (1) the number of relevés classified into associations based on species composition to (2) those based on indicator values. Misclassified relevés belonged to ecologically similar associations. The method seems very suitable for predictive vegetation models. [ABSTRACT FROM AUTHOR]

There has been a great deal of interests in the estimation of grassland biophysical parameters such as percentage of vegetation cover (PVC), aboveground biomass, and leaf-area index with remote sensing data at the canopy scale. In this paper, the percentage of vegetation cover was estimated from vegetation indices using Moderate Resolution Imaging Spectroradiometer (MODIS) data and red-edge parameters through the first derivative spectrum from in situ hypserspectral reflectance data. Hyperspectral reflectance measurements were made on grasslands in Inner Mongolia, China, using an Analytical Spectral Devices spectroradiometer. Vegetation indices such as the difference, simple ratio, normalized difference, renormalized difference, soil-adjusted and modified soil-adjusted vegetation indices (DVI, RVI, NDVI, RDVI, SAVIL = 0.5 and MSAVI2) were calculated from the hyperspectral reflectance of various vegetation covers. The percentage of vegetation cover was estimated using an unsupervised spectral-contextual classifier automatically. Relationships between percentage of vegetation cover and various vegetation indices and red-edge parameters were compared using a linear and second-order polynomial regression. Our analysis indicated that MSAVI2 and RVI yielded more accurate estimations for a wide range of vegetation cover than other vegetation indices and red-edge parameters for the linear and second-order polynomial regression, respectively. [ABSTRACT FROM AUTHOR]

In order to identify appropriate plant materials for studying the gene expression and biological function of vegetative storage proteins (VSPs) in woody plants, the VSPs in the seedlings of Swietenia macrophylla King were investigated by using light microscopy, sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and Western-blotting. The seed of S. macrophylla was rich in storage proteins that accumulated in the vacuoles of cotyledon parenchyma cells in appearance of compact spherical grains. The growth and development of S. macrophylla seedlings were characterized by an obvious growth rhythm. The storage proteins in seeds disappeared during seedling growth while VSPs appeared in the stem 2 weeks after seedling leaves matured. Thereafter, the VSPs in the seedling stem almost exhausted during new shoot growth, and when the leaves of new shoot just matured, both the stem beneath the new shoot of seedlings and the stem of new shoot started to accumulate VSPs. Nitrogen application dramatically increased the level of VSPs, but had little influence on the dynamics of VSP consumption and accumulation in seedling stem. Together with these data, the fluctuation of VSPs in seedlings was very similar to that in the branches of the adult trees. In addition, seedlings are easy to be treated due to their small size. Our results suggested that S. macrophylla seedlings were suitable for investigating the biological roles of VSPs and the mechanism of nitrogen storage in trees. [ABSTRACT FROM AUTHOR]

Aim To understand the impact of glacial refugia and migration pathways on the modern genetic diversity of Pinus sylvestris. Location The study was carried out throughout Europe. Methods An extended set of data of pollen and macrofossil remains was used to locate the glacial refugia and reconstruct the migrating routes of P. sylvestris throughout Europe. A vegetation model was used to simulate the extent of the potential refugia during the last glacial period. At the same time a genetic survey was carried out on this species. Results The simulated distribution of P. sylvestris during the last glacial period is coherent with the observed fossil data, which showed a patchy distribution of the refugia between c. 40° N and 50° N. Several migrational fronts were detected within the Iberian and the Italian peninsulas, and outside the Hungarian plain and around the Alps. The modern mitochondrial DNA depicted three different haplotypes for P. sylvestris. Two distinct haplotypes were restricted to northern Spain and Italy, and the third haplotype dominated most of the present-day remaining distribution range of P. sylvestris in Europe. Main conclusions During the last glacial period P. sylvestris was constrained under severe climatic conditions to survive in scattered and restricted refugial areas. Combining palaeoenvironmental data, vegetation modelling and the genetic data, we have shown that the long-term isolation in the glacial refugia and the migrational process during the Holocene have played a major role in shaping the modern genetic diversity of P. sylvestris in Europe. [ABSTRACT FROM AUTHOR]

1. The primary effects of climatic conditions on invertebrate litter communities, and the secondary effects of different forest types, were distinguished by using the sierra palm as a control in a natural experiment along an elevational gradient in the Luquillo Mountains. These mountains have three well-defined forest types along the gradient, with the palm occurring as stands within each forest. 2. Palm litter samples were richer in nutrients, particularly phosphorus, than nonpalm litter, significantly so at higher elevations where leaching would have been expected. In nonpalm litter, mineral concentrations were significantly lower at higher elevations. 3. Animal abundance mirrored the pattern of mineral amounts and declined significantly in mid- and high-altitude forests, but did not decline with increasing elevation in palm stands. A pulse of post-hurricane litterfall was reflected in the high abundance of Coleoptera and Isoptera the following year. 4. The species richness of communities (Margalef's index) declined with increasing elevation in nonpalm forest litter, but was remarkably similar in palm litter at all elevations. 5. Palm litter communities were more similar to each other (Sørensen's index) than nonpalm communities, which became less similar with increasing elevation. 6. The differences observed from the lower slopes to the summits, in animal abundance, species richness and the uniformity of communities, are better explained by the contribution of forest composition to the chemical and physical nature of litter and forest heterogeneity, rather than to direct effects of temperature and rainfall differences. [ABSTRACT FROM AUTHOR]

This paper describes the use of supervised methods for the classification of vegetation. The difference between supervised classification and clustering is outlined, with reference to their current use in vegetation science. In the paper we describe the classification of Danish grasslands according to the Habitats Directive of the European Union, and demonstrate how a supervised classification can be used to achieve a standardized and statistical interpretation within a local flora. We thereby offer a statistical solution to the legal problem of protection of certain selected habitat types. The Habitats Directive protects three types of Danish grassland habitats, whereas two remaining types fall outside protection. A classification model is developed, using available Danish grassland data, for the discrimination of these five types based on their species composition. This new Habitats Directive classification is compared to a previously published unsupervised classification of Danish grassland vegetation. An indicator species analysis is used to find significant indicator species for the three protected habitat types in Denmark, and these are compared to the characteristic species mentioned in the interpretation manual of the Habitats Directive. Eventually, we discuss the pros and cons of supervised and unsupervised classification and conclude that supervised methods deserve more attention in vegetation science. [ABSTRACT FROM AUTHOR]

The feasibility of identifying races of Fusarium oxysporum f.sp. dianthi by tests for vegetative compatibility type was investigated. Nitrate non-utilizing nitI and NitM mutants were generated from 51 isolates of F. oxysporum (.sp. dianthi., 18 isolates of F. oxysporum from Dianthus spp. not belonging to f.sp. dianthi and, for comparison, 11 isolates of F. proliferatum from Dianthus spp. Vegetative compatibility groups (VCGs) among the isolates were identified by pairing all nitI with all NitM mutants. Vegetative compatibility was found between isolates of F. oxysporum f.sp. dianthi races I and 8 (VCG 0022), races 2, 5 and 6 (VCG 0021) and race 4 (VCG 0020), and wilt-causing isolates previously classified as F. redolens from D. caryophyllus (VCG 0023) and D. barbatus (VCG 0024). Three self-compatible wiltcausing isolates were vegetatively incompatible with all other isolates (VCGs 0025,0026 and 0027). Two VCGs were found among isolates of F. oxysporum from D. caryophyllus not belonging to f.sp. dianthi: six non-pathogenic isolates were self-compatible but vegetatively incompatible with all other isolates. The foot-rot-associated isolates of F. proliferatum from D. caryophyllus constituted a separate VCG. Virulence analyses revealed at least four new races among VCGs 0023 to 0027. New isolates could be eategorized as races as a result of VCG analysis and VCG classification correctly indicated that the race identities previously ascribed to two old isolates had been incorrect. Vegetative compatibility tests offer the prospect for rapid identification of races, although inoculation tests continue to be necessary to differentiate races that belong to a single VCG. [ABSTRACT FROM AUTHOR]

74 patients suspected of having allergic contact dermatitis to wild vegetation were patch tested with ether extracts of 13 plants of the family Compositae and 7 other weeds or trees. Anthem is cotula (dog fennel) and Xanthium strumarium (cocklebur) gave the most frequent positive results, demonstrating a change of frequency in sensitivity compared to the 1950s. when Ambrosia artemisiifolia (ragweed) was recognized as the most frequently sensitizing weed. The reasons for these changes of incidence and clinical patterns are examined. [ABSTRACT FROM AUTHOR]

The paper presents a brief and personal history of the main developments in British vascular plant taxonomy and distribution studies in a European setting since the Second World War. It assesses the importance of the 'European view', and considers recent and current work under two main heads: the factual information itself, and the presentation of the facts, especially in the form of dot distribution maps. [ABSTRACT FROM AUTHOR]

The British National Vegetation Classification (NVC) was used to describe the vegetation of a 49 000 ha upland conifer plantation in north-east England. The survey covered unplanted land, including roads, rides, rivers and larger unplanted areas, together with first-rotation conifer crops and restocked areas. Eighteen NVC communities and sub-communities were recognized, of which nine accounted for most of the unplanted land. In conifer plantation, 17% of stands had no vegetation, while in a further 40% the vegetation cover and species diversity was too low to allow fitting to recognizable NVC communities. Only five communities were recognized within planted stands. Variation in the floristic composition of vegetation assigned to a single community reflected both natural variability, related to altitude and soils, and forestry operations, including changes in land management, ploughing and planting. Species characteristic of low intensity agricultural management were frequent and often dominated the vegetation. Plant communities associated with more extreme environmental conditions, high altitudes and deep peats, were most sensitive to afforestation. In contrast, widely distributed communities composed mainly of cosmopolitan species were relatively resilient to the effects of plantations. [ABSTRACT FROM AUTHOR]

The article discusses the classification and mapping of ecological communities in Australia. Researchers in the country use the non-agglomerative, flexible unweighted pair group arithmetic averaging (UPGMA) approach to classify vegetation within a landscape context. The author explains that vegetation maps are spatial expressions of vegetation type and structural patterns. He also points out about the variation in the quality of vegetation maps. He states that the variation is caused by the quality of remote sensing images across different regions.