Vegetation survey: a new focus for Applied Vegetation Science

Abstract

Vegetation survey is an important research agenda in vegetation science. It defines vegetation types and helps understand differences among them, which is essential for both basic ecological research and applications in biodiversity conservation and environmental monitoring. In this editorial, we reflect on the historical development and current state of vegetation survey worldwide and introduce the Special Feature ‘Vegetation Survey’, as well as the new section of the same name in Applied Vegetation Science. The current Special Feature contains eight vegetation survey studies from North America, New Zealand, Europe and Asia. Most of these studies describe diversity of important vegetation types across large areas and some are also innovative from the methodological viewpoint. They illustrate current trends in vegetation survey in different parts of the world and also represent some examples of the type of studies that we wish to publish in the ‘Vegetation Survey’ section in future issues of Applied Vegetation Science.

Surveying the enormous diversity of the world's vegetation is one of the basic tasks of vegetation science. In recent decades the demand for vegetation survey data has been steadily increasing particularly in applied fields such as biodiversity conservation and environmental monitoring. However, vegetation survey and classification are also very important in basic ecological and biodiversity research. Interpretations of biodiversity patterns and their underlying mechanisms strongly depend on the definitions and delimitations of the studied systems (Whittaker 2010; Schwabe & Kratochwil 2011): in this context, survey and classification provide essential tools for defining vegetation or ecosystem types and a framework for understanding differences among them.

Quantitative investigation of plant communities based on sampling species composition and abundance in vegetation plots started more than a century ago (Schröter & Kirchner 1886–1902; Warming 1895; Clements 1905). Perhaps the most frequent aim of sampling was defining vegetation units by grouping plots with similar species composition and arranging these units into a hierarchical system. The association was defined as a plant community type of definite floristic composition, uniform habitat conditions and uniform physiognomy (Flahault & Schröter 1910). Various regional approaches that used species composition to classify and survey vegetation developed during the 20th century (Whittaker 1973). Perhaps the most influential was the Braun-Blanquet approach that originated in Central and Southwestern Europe (Braun-Blanquet 1928; Westhoff & van der Maarel 1973). Activities of Braun-Blanquet's private institute in Montpellier strongly influenced European vegetation ecologists and by the 1930s the Braun-Blanquet approach had been accepted as a standard method of vegetation survey in many European countries. It further developed and strengthened in the 1950s–1970s, especially through exchange of ideas at annual symposia of the International Association for Vegetation Science (IAVS). At that time, the Braun-Blanquet approach also spread outside Europe, most notably to Japan (Miyawaki 1981–1989), South Africa (Werger 1973; Mucina & Rutherford 2006), and since the 1980s to Russia (Mirkin 1987; Korotkov et al. 1991). In addition, European researchers actively surveyed vegetation in other areas of the world. The main benefit of the broad dissemination of the Braun-Blanquet approach was that much of the world's vegetation had been surveyed using a relatively uniform sampling protocol and classified into a single hierarchical framework. At the same time, however, some other remarkable approaches to vegetation survey and classification developed that received a broad regional acceptance, e.g. Daubenmire's approach in the western USA (Daubenmire 1952, 1968). Also, first attempts at formalized (‘objective’) vegetation classification based on statistical criteria appeared (Goodall 1953; Williams & Lambert 1959), which opened the way to a broad application of numerical methods to vegetation classification in the following decades (Mucina & van der Maarel 1989).

There were important methodological debates that greatly contributed to the theory and methods of vegetation survey. Perhaps most notably, followers of the Gleasonian community concept argued that vegetation classification is only consistent with the Clementsian view of communities as integrated entities, while it would have no meaning if species behaved individualistically (Moravec 1989). Gleasonian ideas inspired the development of the theory of gradient analysis (Whittaker 1956, 1967) and ordination as a tool to analyze vegetation-survey data in an alternative way to classification (Goodall 1954; Bray & Curtis 1957; Hill 1973). There were times when many ecologists understood classification and ordination as antagonistic methods of description of vegetation patterns, but these old debates seem to be resolved now: both methods are understood and used as complementary.

Since the 1990s, the field of vegetation survey and classification has received new stimuli. First, there has been an increased demand from institutions in the field of nature conservation for comprehensive systems of vegetation/habitat/biotope classifications to serve as a tool for informed conservation planning and decision making. An example at the European level is the Natura 2000 network (http://www.natura.org), which aims at safeguarding threatened habitats and species across the European Union; it has resulted in a strong demand for ecological and spatially explicit vegetation data. Second, there have been great technological advances in the setting up and management of electronic databases, which made it possible to amass huge amounts of vegetation plots sampled during several previous decades into formats easily accessible for analyses (Schaminée et al. 2009; Dengler et al. 2011). Another aspect of this new field of research, called ecoinformatics, is the development of computer information systems to make use of these databases, by integrating different levels of information and incorporating geographical information systems (e.g. Schaminée et al. 2007). Third, availability of remote sensing data and geographical information systems (GIS) offer entirely new opportunities for survey and vegetation mapping of large or remote areas, so long as they are combined with detailed ground-based vegetation survey, as demonstrated in extensive projects such as the Circumpolar Arctic vegetation map (Walker et al. 2005) or Vegetation of South Africa, Lesotho and Swaziland (Mucina & Rutherford 2006). Vegetation survey and classification methods have greatly benefited from recent methodological developments, partly borrowed from other fields, but still there remains large space for further improvements towards rigorous, repeatable and exhaustive vegetation surveys.

Parallel but largely independent developments occurred in Europe and North America during the past two decades. European researchers, centered mainly around the IAVS working group of European Vegetation Survey (Rodwell et al. 1995), were basically following the tradition of the Braun-Blanquet approach, but at the same time they were developing new methods and tools for vegetation survey, most prominently the database management software TURBOVEG (Hennekens & Schaminée 2001) and the analytical software JUICE (Tichý 2002). New approaches and tools were introduced especially in the national or regional vegetation survey projects of Great Britain (Rodwell 1991–2000), the Netherlands (Schaminée et al. 1995–1999), Mecklenburg-Vorpommern (Berg et al. 2001–2004) and the Czech Republic (Chytrý 2007 et seq.). In North America, there has been a much larger variety of approaches to vegetation classification than in Europe. Therefore, Ecological Society of America's Vegetation Classification Panel developed the US National Vegetation Classification standards with a hierarchy of vegetation units that combines a floristic approach on the lower levels and a physiognomic approach on the higher levels (Jennings et al. 2009). Simultaneously, an online database of vegetation plots (http://www.vegbank.org) was launched and procedures for review and evaluation of additions and revisions of vegetation types were set up. US vegetation scientists are now working with partners from other countries within the Americas in an attempt to extend the US National Vegetation Classification standards to other countries with a vision of developing an International Vegetation Classification (Faber-Langendoen et al. 2009).

Although these developments are challenging, they seem to be poorly reflected in the international scientific literature. This may be partly because of the persisting prejudices of editors of some journals towards vegetation survey and classification studies, which are preconceived as uninteresting or lacking a sound scientific basis. Some journals became reluctant to accept such studies and some authors, pushed by their institutions to publish their results in high-profile journals, even decided to change the focus of their research to areas in which the results are easier to publish in international peer-reviewed journals. Submissions of vegetation survey and classification studies that would be of international interest were very few even to the IAVS journals (Journal of Vegetation Science and Applied Vegetation Science), although they were very welcome to both. Therefore, in 2009 the Council of IAVS and the journals' Chief Editors decided to establish a specialized section in Applied Vegetation Science, entitled Vegetation Survey (Chiarucci et al. 2010; Chytrý et al. 2011).

Of course, the journal space is limited and likewise the number and extent of the papers we can accept in the Vegetation Survey section will be limited. Therefore, we need to be highly selective and accept only those papers that are of high international interest. Priority will be given to the papers summarizing major trends in diversity of important vegetation types over large areas (especially across national boundaries), presenting vegetation classification in a particularly interesting ecological context, contributing to international standardization of vegetation classification schemes and approaches, demonstrating new survey or classification methods, approaches and initiatives, or showing new ways in which vegetation survey and classification can serve nature conservation. Authors will need to conduct their studies and present their results clearly describing and justifying their field sampling strategies, and to quantitatively describe classification processes used or differential criteria between vegetation units. Adherence to these guidelines should create vegetation classification schemes that are repeatable and/or accompanied by unequivocally described rules for assignment of individual vegetation stands to classification units. These efforts should stimulate wider application of formal and quantitative methods in the field of vegetation classification, which is still dominated by the widespread use of rather vague expert knowledge. Of course, expert knowledge and personal field experience is extremely valuable in vegetation science, but it is a real challenge for vegetation scientists to express it in formal and quantitative terms. We hope that in this way the Vegetation Survey section will become the main platform for exchange of ideas and information on major achievements in vegetation survey and classification over the world. We believe that featuring top vegetation survey and classification studies in Applied Vegetation Science will provide new impetus to the development of local vegetation survey initiatives, especially in those countries that currently lack a systematic survey.

To start the Vegetation Survey section, we solicited papers from leading researchers from all continents where we knew of important and interesting vegetation survey projects. Eight papers that were submitted in response to our call are included in this Special Feature. They nicely illustrate the current status of vegetation survey in different parts of the world. Three studies are from North America, representing different approaches to vegetation survey on this continent. Walker et al. (2011) describe vegetation across a long transect through the North American Arctic zone and relate vegetation to climate and cryogenic processes in Arctic soils. This study significantly improves our knowledge of the relationships between floristic structure of higher plant and cryptogam communities and cryogenic processes. Additionally it provides an important framework and reference units for global change studies. The authors use the Braun-Blanquet approach, which they successfully applied in the previous project of the Circumpolar Arctic vegetation map (Walker et al. 2005). Another application of the Braun-Blanquet approach to North American vegetation is represented by the paper of Peinado et al. (2011), who collected an extensive data set on vegetation of the Pacific coast from Alaska to Baja California and proposed a comprehensive classification scheme for this vegetation. The approach of the US National Vegetation Classification is demonstrated by Matthews et al. (2011) in a study focused on alluvial forests of North Carolina. This study is interesting also because of the application of the random forest classifier, which has been so far rarely used in vegetation classification. The fourth contribution (Wiser et al. 2011) highlights that there is a strong tradition of vegetation-plot sampling in New Zealand. Their data set is based on a country-wide sample of systematically located plots, and their classification scheme follows the conventions of the US National Vegetation Classification. Studies from Europe, the traditional area of vegetation classification, are under-represented in this Special Feature, although European authors prevail. This reflects the fact that European vegetation is considered as better studied than that on other continents. Indeed the main current focus of European phytosociologists is on the revision and unification of previous schemes of vegetation classification. This type of work is exemplified here by the study of boreal pine forests (Ermakov & Morozova 2011), which covers Northern Europe and extends to Western Siberia. It contributes to another current major initiative of vegetation survey that is currently realized within IAVS: the Circumboreal Vegetation Map (Talbot 2009). Having an established system of vegetation classification, European researchers increasingly apply phytosociologically defined vegetation types for identification of habitats of conservation interest and for landscape survey. A prominent example of such application is the Hungarian national survey project MÉTA (Bölöni et al. 2011). Besides their activities on their home continent, European researchers nowadays significantly contribute to vegetation survey in those parts of the world where vegetation is still poorly known and survey activities of local researchers are limited, if any. Dry areas of central Asia are a typical example of such region, and the last two papers of this Special Feature are devoted to them (Miehe et al. 2011; Wesche & von Wehrden 2011). The former paper is an example of a survey study of an important vegetation type which extends across large areas, but its diversity has been hardly described so far. The latter paper builds upon the previously published survey studies of the same authors. It asks the recurrent and so far unresolved methodological question in vegetation classification (De Cáceres et al. 2009; Schmidtlein et al. 2010; Tichý et al. 2010): which method of numerical classification is most suitable to describe vegetation diversity observed in the field?

The papers published in this Special Feature represent some types of the target papers on vegetation survey we want to publish in future issues of Applied Vegetation Science. In the future, however, we would like to see also other types of vegetation survey papers, e.g. those demonstrating new ways of application of vegetation survey studies in nature conservation and environmental management, or those that make use of combination of remote sensing techniques with ground-based vegetation survey.

In addition to the eight papers published here, there are other papers in various stages of the editorial process which, for various reasons, did not meet the deadline for this Special Feature. After their editorial processing and eventual acceptance, these papers will be published in the regular section Vegetation Survey in future issues of Applied Vegetation Science. We invite all vegetation scientists to submit to this section their best papers on vegetation survey and classification that may be of interest to our international readership. Our ambition is to highlight first-class vegetation survey research worldwide.