Data-processing in phytosociology,retrospect and anticipation

Summary The existence of the Working Group for Data-Processing in Phytosociology spans about six years, 1969–1975. Its activities are summarized and a series of papers to appear in Vegetatio, presenting results of various numerical treatments, mainly of salt marsh vegetation, is introduced. A survey is given of seven releve selections to which treatments were applied. Five main fields of activities are discussed: systematical data-processing, rearrangement of phytosociological tables, development of classification and ordination techniques, numerical syntaxonomy, and theoretical phytosociology.The establishment of the Working Group for Theoretical Phytosociology and its first symposium on theoretical aspects is announced.Contribution from the Working Group for Data-Processing in Phytosociology, International Society for Vegetation Science.     

Trgrps — an interactive algorithm for group recogniton with an example from spartinetea

Summary TRGRPS can detect groups or signal if discrete groups cannot be found in a sample. The present paper elaborates on the concepts, describes the algorithm and provides illustrations from syntaxonomy. A computer program (TRGRPS.BAS) is available from the author upon request.Contribution from the Working Group for Data Processing in Phytosociology, International Society for Vegetation Science. For nomenclature of species see Lausi, Beeftink & Kortekaas (1975).The research project, from which this paper summarizes partial results, is supported by a National Research Council of Canada grant. Computer time was provided by the University of Western Ontario.     

Twenty years of numerical syntaxonomy

The development of numerical syntaxonomy during its first 20 yr is reviewed. The use of methods of numerical classification and ordination is the dominating feature of the development. National and local phytosociological data banks were established, large data sets handled and many important vegetation monographs were methodically based on multivariate data analysis. Particularly the development in Italy, the Netherlands, Czechoslovakia, and Sweden contributed to new theoretical elements of numerical syntaxonomy. Ordination became a common tool of searching for reticulate synsystematic relations between community types. The most popular ordination techniques have been Principal Components Analysis and Detrended Correspondence Analysis. Hierarchical agglomerative techniques of clustering still prevail in classification, although the divisive strategy of TWINSPAN has also become an effective tool for phytosociological clustering and table sorting. Extensive program packages, also for personal computers have now become standard equipment for many vegetation scientists.     

Long‐term datasets: From descriptive to predictive data using ecoinformatics

This Special Feature includes contributions on data‐processing of large ecological datasets under the heading ecoinformatics. Herewith the latter term is now al so established in the Journal of Vegetation Science. Ecoinfomatics is introduced as a rapid growing field within community ecology which is generating exciting new developments in ecology and in particular vegetation ecology. In our field, ecoinformatics deals with the understanding of patterns of species distributions at local and regional scales, and on the assemblages of species in relation to their properties, the local environment and their distribution in the region. Community ecology using ecoinformatics is related to bioinformatics, community ecology, biogeography and macroecology. We make clear how ecoinformatics in vegetation science and particularly the IAVS Working Group on Ecoinformatics has developed from the work of the old Working Group for Data Processing which was active during the 1970s and 1980s. Recent developments, including the creation of TURBOVEG and Syn Bio Sys in Europa and VEGBANK in the USA, form a direct link with these pioneer activities, both scientifically and personally. The contributions collected in this Special Feature present examples of seco‐infeveral types of the use of databases and the application of programmes and models. The main types are the study of long‐term vegetation dynamics in different cases of primary and secondary succession and the understanding of successional developments in terms of species traits. Among the future developments of great significance we mention the use of a variety of different large datasets for the study of the distribution and ecology and conservation of rare and threatened species.     

Vegetation patterns and their underlying processes: where are we now?

This Special Feature of the Journal of Vegetation Science contains ten contributions from the 56th Symposium of the International Association for Vegetation Science (IAVS), which was held in Tartu, Estonia, 26–30 Jun 2013, and focused on processes underlying vegetation patterns. These contributions give an overview of recent advances in vegetation science, with topics ranging from the introduction of new methods and ideas to comprehensive analysis of vegetation patterns on a global scale. The focus of these Special Feature contributions indicates that vegetation science is becoming more global, more complex and more interdisciplinary. It is likely that progress in methods and accumulation of data have led vegetation science into a ‘new era of discovery’.     

Modelling Environmental Responses of Plant Associations: A Review of Some Critical Concepts in Vegetation Study

The definition of vegetation types at different hierarchical levels, both to study the vegetation processes and for practical cartographic representation, is still considered a critical issue in many circles of plant ecologists. The problems are mainly related to the misleading idea that classification of the vegetation system, as developed by European phytosociologists during the last century within the discipline called syntaxonomy, would imply the assumption of the organismic concept of the plant community. After a short discussion on the role of Braun-Blanquet approach in plant ecology and in landscape ecology, the methods to detect multispecies responses along environmental gradients are briefly reviewed. In the main part of this article, we intend to stress that concepts considered critical, such as plant association and its ecological niche, are just operational tools that have nothing to do with the individualistic or organismic interpretation of plant communities in vegetation studies. Important to our views on vegetation, we believe that plant associations as well as the higher syntaxa can be regarded as fuzzy sets in an operational context for describing vegetation along ecological gradients in synthetic ways and can further the understanding of vegetation variation.     

Pre-climax epiphyte communities of bryophytes and lichens in Mediterranean forests from the Central Plateau (Spain)

The pre-climax epiphytic communities of forests from the Spanish Mediterranean region (Central Plateau) were studied by numerical and traditional floristic methods. One hundred phytosociological relevés were analyzed through a classical numerical approach based on hard partitions improved by PCoA — Principal Coordinates Analysis — ordinations. Two groups easily related to two different suballiances included in Frullanion dilatatae Lecointe 1975, Ulotenion crispae (Barkman 1958) Lecointe 1975 and Fabronienion pusillae Barkman 1958 were detected. Two new syntaxa within the ass. Ortotrichetum lyellii (Allorge 1922) Lecointe 1975 are proposed. Phytogeography, syntaxonomy and ecology of these communities are discussed.     

基于大气辐射校正的广州市植被覆盖度遥感估算

植被覆盖度是描述生态系统的基本参数,也是进行生态系统健康与安全评价的重要生态参数.基于1990、1995、2000和2005年4个时相的TM遥感数据源,以广州市为研究区域,运用减少大气辐射影响的植被指数计算模型,通过非监督分类及图像空间模型运算,修正了大气辐射校正参数,建立了植被覆盖度与校正植被指数的模型,估算了不同时期内广州市的植被覆盖度.结果显示,广州市植被覆盖度在1990—2000年的10年内持续下降,从2000年开始呈上升趋势,符合广州市的经济发展与环境建设实际.所建立的模型适合于区域植被覆盖度动态变化研究,且在植被覆盖度的动态变化特征研究方面有较大优势,其结果适于进行城市生态环境质量与动态评价.     

Vegetation structure and substrate of the northern part of the Great Dyke,Rhodesia environment and plant communities

Summary In the northern part of the Great Dyke, Rhodesia, the physiognomic and floristic differences between the vegetation types on serpentine and on non-serpentine substrates are very striking and the boundaries between these types are generally sharp. On either of the substrates there are also differences in the vegetation which correspond to differences in habitat. An outline of the Great Dyke environment is given. A number of plots, laid out in transects across the Great Dyke, were sampled according to the Braun-Blanquet approach. Six plant communities are distinguished and described in detail: one occurring on granite, two on pyroxenite and three on serpentine. The syntaxonomy of these communities is discussed. A riverine forest community which strongly differs from all these vegetation types is also described.Nomenclature is according to the present (1.1.1977) usage at the National Herbarium, Salisbury, Rhodesia.One of us (M. J. A. Werger) wishes to gratefully acknowledge the financial support for this study by the Netherlands Foundation for the Advancement of Tropical Research (WOTRO) and by the Faculty of Science, University of Nijmegen.     

A dynamical systems perspective on vegetation theory

A dynamical systems perspective is employed to develop a simple conceptual model of vegetation and environment as coupled dynamical systems. The conceptual model characterizes the influence of environment on vegetation, the effect of vegetation on the environment, and the subsequent response of vegetation to the modified environment. Vegetation and environmental dynamics are modeled as trajectories in complementary state spaces, with the trajectories jointly determined by the position of a given site in both spaces. The vegetation and environment state spaces are coupled by the physiological requirements of the component species and the modification of environment by vegetation. From a dynamical systems perspective, current vegetation theory and analyses overemphasize environmental determination of vegetation composition and neglect the effects of vegetation on environment. A dynamical systems perspective is capable of synthesizing previous concepts of vegetation; the continuum and community type concepts are possible consequences of site specific differences in vegetation metabolism and environmental plasticity.I would like to acknowledge the helpful comments and criticisms of Drs G. Cottam, J. D. Aber, T. F. H. Allen, R. P. McIntosh, C. G. Lorimer, and anonymous reviewers.I would like to thank the University of Wisconsin, Madison for a fellowship which supported this research. This paper is dedicated with great respect and gratitude to Professor G. Cottam on the occasion of his retirement from the University of Wisconsin.     

Classification of vegetation: Past,present and future

Abstract. This paper is a report on the past, status-quo and perspectives of vegetation classification, still a major occupation of many vegetation scientists. The history of vegetation classification is discussed against a background of several controversial issues such as the problem of continuum vs. discontinuum, naturalness vs. arbitrariness of the nature of plant communities, universality vs. ad hoc character of syntaxonomic schemes, as well as classical versus numerical approaches to data analysis for classification purposes. The development of the methodology of vegetation science and the present image of vegetation classification is documented by a bibliometric analysis of the publication record of four majorjournals: Journal of Vegetation Science, Vegetatio, Phytocoenologia and Tuexenia. This analysis revealed a persisting controversy between traditional and numerical approaches to vegetation classification. A series of important changes in vegetation science (foundation of new journals, change of editorial policy by the established, important meetings) punctuate a period called the ‘Innovation period’. Several trends in the development of methods of vegetation systematics are summarized under the headings formalism, pluralism, functionalism, pragmatism and indeterminism. Some new features, such as the development and improvement of numerical tools, use of large data banks and attempts to summarize the theory of vegetation classification are discussed. The new growth-form system of Barkman initiated a revival of physiognomy-based vegetation classification. Within this framework the use of the character-type concept and the development of new numerical methods for studying the hierarchical structure of character-set types seems to be a promising approach. The achievements of population biology and ecophysiology have affected vegetation science by emphasizing the functionality of species within plant communities. The use of guilds and other functional groups has experienced an increasing interest from vegetation scientists. Applied in vegetation science, fuzzy-set theory has bridged the techniques of classification and ordination of plant communities.     

黄土高原森林草原区退耕地植被自然恢复与土壤养分变化

研究了黄土高原森林草原区退耕地植被自然恢复过程与土壤养分变化.结果表明,在显域生境下,植被自然演替过程虽然趋向于该区原有植物群落类型,但经过40～0年的时间,仍未形成灌丛或稀树等群落,分布较多的仍是长芒草、铁杆蒿、白羊草、大针茅和达乌里胡枝子等群落类型.从植被恢复时间对土壤养分变化的影响来看,除全P外(P＞0.0),有机质、全N、速效氮、速效钾的变化极显著(P＜0.001),速效磷变化较显著(0.0＜P＜0.01),并随植被恢复时间的延长而呈增加趋势.除恢复时间外,养分含量变化也随土壤剖面深度而变化,其中除全P含量变化较显著外(P＜0.0),其余各养分含量变化都达极显著水平(P＜0.001).土壤养分变化具有明显的表聚性.相关分析表明,土壤有机质、全N、有效氮与速效钾相互间相关极显著(P＜0.001),而与全P与速效磷相关性不明显(P＞0.0),全P与速效磷二者相关性也不明显(P＞0.0).     

《中国植被志》的植被分类系统、植被类型划分及编排体系

植被志(vegegraphy)是基于植被调查资料, 全面记叙植被的群落外貌、种类组成、结构和功能、生境条件, 以及地理分布等特征, 并对同类植被进行归纳和总结的志书。“植被志”的英文译为“vegegraphy”, 是本文的新造词, 它是由“vegetation”的词头“vege-”和英文后缀“-graphy” (记叙之意)组成的合成词。《中国植被志》的研编是一项时间紧迫、内容复杂、工作量浩繁的重大科学工程。它的完成将极大提升中国植被科学和生态学的研究水平, 并为中国植被资源的合理利用、生物多样性保护及生态环境治理等提供不可或缺的基础资料。本文首先简述了植被的基本特征(主要包括外貌特征、种类组成、群落结构以及动态变化等)和国内外植被调查的进展情况, 简要回顾了中国植被分类系统的研究历史, 并对以往的分类系统进行了若干修订。在此基础上, 着重讨论并提出了《中国植被志》卷册编排体系和用于《中国植被志》研编的植被类型划分方案。在对植被分类系统的修订方面, 主要对高级分类单位及相对应的英文名称进行了讨论和修订。按照本文修订的分类系统, 中国植被的分类单位及其对应的英文名称分别是: 植被型组(Vegetation Formation Group)、植被型(Vegetation Formation)和植被亚型(Vegetation Subformation)、群系组(Alliance Group)、群系(Alliance)和亚群系(Suballiance)、群丛组(Association Group)以及群丛(Association)。在植被型组中, 划分为9类: 森林、灌丛、草本植被、荒漠、高山冻原与稀疏植被、沼泽与水生植被、农业植被、城市植被及无植被地段。关于《中国植被志》的卷册编排和“植被类型”划分, 首先按高级分类单位——植被型划分相应的“卷”; 在此框架下, 模糊“植被亚型”、“群系组”和“群系”的概念, 确定“植被类型” (Vegetation type), 并将其作为植被志各卷中的“册”。这样处理不仅保证了研编工作的可操作性, 也保持了同一卷册中特定植被类型的完整性。《中国植被志》编排体系中的“植被类型”的划分很重要, 它是指具有相同建群种及相同优势类群(如种、属)的植被组合, 但它不是严格意义上的植被分类单位。“植被类型”的划分遵循“优势类群及生活型的同一性, 生境条件的相对重要性, 植被特征及用途的差异性, 以及突出植被志的应用性”等原则。按该编排体系, 《中国植被志》将由48卷约110册组成。     

我国植被数量分析方法的研究概况和发展趋势

植被数量分析是现代植被研究的重要手段,数量分类和排序是现代植被生态学研究最重要的,也是应用最广泛的生态学技术。数量分析方法在20世纪50年代引入植被生态学研究领域,我国学者在70年代后期开始研究植被的数量分类和排序。本文主要从相关资料、应用研究、新方法研究三个方面论述了我国植被数量分析方法的发展,重点阐述了从20世纪70年代后期以来出现的并且被广泛应用的新方法及其应用研究概况,并在此基础上分析了植被数量分析方法未来的发展趋势。     

Classification and ordination in the Indian Peaks area,Colorado Rocky Mountains

Summary A mid-latitude, Northern Hemisphere alpine vegetation in the Colorado Rocky Mountains was suitable for analysis by syntaxonemie and numerical methods, which interpreted the Braun-Bianquet association data, distributed by habitat and vegetation dominance types, correspondingly. Classification and ordination yielded complementary, interpretable results, which combined were more informative than results of either technique alone. Syntaxonomic results can faeilitate the interpretation of numerical results; the syntaxonomic relationships can be clarified by the results of numerical analysis.Alliances and orders of the Braun-Blanquet hierarchy, and their diagnostic taxa groups were derived by numerical methods from an association/taxa matrix. On the basis of this matrix, numerical methods demonstrated some of the environmental gradient complexes controlling the compositional variation. The compositional distinctiveness and uniformity of orders and alliances parallel environmental distictiveness and uniformity.The following attributes of the sampled vegetation and environment were probably responsible for the successful combination of syntaxonomic and numerical results: 1. The sampled area as a geographically limited universe, characterized by relative environmental, biotic, and historical distinctiveness and uniformity, 2. The wide range, high diversity, and clear denfinition of habitat and vegetation dominance types. Because it effectively summarizes and simplifies field data, syntaxonomy can play an important role in building local vegetatio models.Most of the figures in this paper are from a book version of a University of Colorado, Department of Environmental, Population, and Organismic Biology, Ph. D. thesis which was produced at the Institute of Arctic and Alpine Research. I would like to thank Dr. P.J. Webber, the thesis advisor, for his support, for suggesting the numerical methods, and for computer programs which were written by W.F. Reid. Vicki Dow, Marilyn Joel, and Karen Sproul drafted the majority of figures. I am grateful to Gwen Archer for editorial help.     

Die Siedlungsvegetation des Böhmischen Karsts. 1. Syntaxonomie

The paper deals with the vegetation of village settlements at the territory of the Bohemian Karst. In the first part of this study, syntaxonomy of ruderal communities is presented. Deductive method of syntaxonomical classification was applied. An attempt for numerical evaluation of a species diagnostic value in phytosociology is presented. Discussion remarks on the current state of ruderal phytosociology are included.     

Impact of ecological redundancy on the performance of machine learning classifiers in vegetation mapping

Vegetation maps are models of the real vegetation patterns and are considered important tools in conservation and management planning. Maps created through traditional methods can be expensive and time‐consuming, thus, new more efficient approaches are needed. The prediction of vegetation patterns using machine learning shows promise, but many factors may impact on its performance. One important factor is the nature of the vegetation–environment relationship assessed and ecological redundancy. We used two datasets with known ecological redundancy levels (strength of the vegetation–environment relationship) to evaluate the performance of four machine learning (ML) classifiers (classification trees, random forests, support vector machines, and nearest neighbor). These models used climatic and soil variables as environmental predictors with pretreatment of the datasets (principal component analysis and feature selection) and involved three spatial scales. We show that the ML classifiers produced more reliable results in regions where the vegetation–environment relationship is stronger as opposed to regions characterized by redundant vegetation patterns. The pretreatment of datasets and reduction in prediction scale had a substantial influence on the predictive performance of the classifiers. The use of ML classifiers to create potential vegetation maps shows promise as a more efficient way of vegetation modeling. The difference in performance between areas with poorly versus well‐structured vegetation–environment relationships shows that some level of understanding of the ecology of the target region is required prior to their application. Even in areas with poorly structured vegetation–environment relationships, it is possible to improve classifier performance by either pretreating the dataset or reducing the spatial scale of the predictions.     

Climate change and vegetation response

This study, as many other current investigations in palaeoecology is focused on the long-term dynamics of vegetation and the extent to which they are controlled by climate change. Climate and classes of climate change are defined and reviewed, and examples cited of vegetation response. The concepts of vegetation, plant community and equilibrium are examined, with particular emphasis on theories on short term dynamics developed by ecologists working with temperate and boreal forests. Vegetation response to climate change can be modified by anthropogenic factors, topographic diversity and soils, life-cycle characteristics and hysteresis.I am grateful for comments on an earlier version of this paper by Keith Bennett, Les Cwynar and Glen MacDonald, and I particularly appreciate the useful remarks by Colin Prentice.I am grateful for comments on an earlier version of this paper by Keith Bennett, Les Cwynar and Glen MacDonald, and I particularly appreciate the useful remarks by Colin Prentice.