Global overview of plot-based vegetation classification approaches

While classification of vegetation can be conducted in many ways, international homogenization of procedures and typologies is desirable for human societies that are highly connected in terms of sharing biodiversity information. This Special Issue of 'Phytocoenologia' includes 12 papers that document several of the plot-based classification approaches currently used throughout the world. The issue includes approaches from five continents, but noticeable gaps are South America, middle-eastern countries, northern Africa and southeastern Asia. We include in this editorial a brief synthesis of the papers included in the Special Issue, with respect to (1) the amount of vegetation-plot data and characteristics of the classification systems developed in different areas and (2) the concepts and procedures of classification approaches. One of the most important common attributes among the classification approaches is the need to define vegetation units at a low level of abstraction. 'Association' (and perhaps 'alliance' too) may be a classification level for which international homogenization of procedures would be most easy to achieve, perhaps establishing different consistent classification sections depending on ecological conditions. Several papers in this issue demonstrate that multiple approaches may coexist for higher levels, as long as they abstract vegetation from the same low level units by focusing on a specific set of concepts and defined from the perspective of applications.