Phytosociology today: Methodological and conceptual evolution

Abstract

A concise methodological and conceptual overview of the present state of phytosociology, 100 years after its foundation, is presented. The fullness of phytosociology as a synecological science is highlighted. This scientific approach, which was inherent in phytosociology from the very beginning, has made great strides forward thanks to the detailed analysis of the conditions of vegetation populations, from the community level to that of dynamic successions found in landscape contexts. This has led to the creation and development of several integrated areas of analysis that have helped to produce highly predictive models based on the distribution of environmental gradients, which thus act as valid bio-indicators that can be used in environmental and planning management. The development of phytosociology has led over time to the need to reconsider the basic concept of association. In this article, we propose a new definition of association, updating the one drawn up by Braun-Blanquet in 1928, so that it reflects the conceptual evolution of the discipline more closely. In this new definition, the concept of “characteristic species” is replaced by the concept of “preferential species” in statistical and structural terms, even in territorial terms. Taken together, these species constitute the “characteristic composition of species”, which expresses the “particular and autonomous ecology” of the association referred to in Braun-Blanquet's definition. The new definition also considers the greater knowledge we have gained of dynamic processes, which are no longer regarded as marginal aspects in the study of communities but are considered to be of fundamental importance in the transformation of plant landscape. The introduction of the concept of ecological value in the definition expresses, in quantitative terms, the response and the field of existence of an association according to the change in an environmental factor. As regards dynamic phytosociology, which is related to the concept of vegetation series (sigmetum), we suggest replacing the concept of climax, which is used to define the more mature stage of the serial trial and expresses the vegetation potential within the area of the series (tesela), with that of “current potential vegetation”, by which we mean the vegetation that is identified at present and that is interpreted according to the historical study of successions. We also present the phytosociological approach to plant landscape, which leads to the definition of the landscape unit named geosigmetum, made up of an integrated system of vegetation series that is repeated in an area with the same edaphic, bioclimatic and biogeographic conditions. Nowadays such models express the distribution of vegetation according to environmental gradients; they allow the ecological meaning of different communities and serial successions to be assessed thoroughly, providing qualitative and quantitative values of the cenocline model that the geosynphytosociological analysis represents at the plant landscape level for every bioclimatic belt. Modern technologies in a GIS environment have led to huge progress being made in the cartographic representation of vegetation (vegetation map), of vegetation series (syndynamic vegetation map) and of the representation of plant landscape (plant landscape map). Lastly, some implementation issues are addressed within the context of the objectives of the Habitats Directive (92/43/EEC), concerning the recognition of habitats and the definition of management plans. Furthermore, phytosociology has numerous applications in the agricultural sector thanks to the identification of High Nature Value (HNV) farmland areas and, more generally, to the new European Community Agricultural Policy (CAP), which is due to be implemented in 2013 and represents a radical reform of agricultural politics in favour of quality production and the environment.