Plant communities in gradients

Abstract

The work deals with the confrontation of two approaches in vegetation science, which already had their origins at the beginning of the past century: gradient analysis and classification of communities. We tested whether samples are arranged along gradients according to the individualistic or the integrative concept. We studied gradients in several case studies – successional, altitudinal, gradient of human impact, phenological, macroecological, (phyto)geographical – and tried to detect the main gradient (by direct or indirect ordination methods) and arrange the plant assemblages along the gradient. We then applied different classification methods to test whether it is possible to detect discrete plant communities. We analyzed the secondary succession of birch forests in Slovenia, the process of autosuccession of Pinus brutia in Turkey, the altitudinal distribution of communities in rock crevices on silicate bedrock in Slovenia, the gradient of spruce planting in beech forest, the influence of the introduction of non-native tree species into forests, the macroecological and phenological development of weed vegetation in Europe, and the circum-Adriatic pattern of broadleaved ravine forests. The results show that, in most cases, the turnover of species composition along the gradient, according to the integrative concept, is due to species interactions. This enables us to detect and describe discrete plant communities in terms of the central European Braun-Blanquet method.