Floristic composition patterns of Mediterranean annual non-nitrophilous grasslands in Eastern Portugal

Abstract

Helianthemetea guttati communities are pioneer spring and early summer ephemeral grasslands, dominated by non-nitrophilous therophytes. In Continental Portugal, these communities have not yet been fully investigated, and thus the objectives of the present study are: (1) to identify community types in therophytic grasslands; (2) to recognize those communities that configure the European priority habitat 6220* (pseudo-steppe with grasses and annuals); (3) to establish environmental gradients underlying their spatial variation; (4) to assess how floristic composition is affected by land use factors. Vegetation sampling using phytosociological methodology was carried out on 80 grasslands. Modified Twinspan classification and canonical correspondence analysis (CCA) was applied for the classification and ordination of relevés whereas partial CCA (pCCA) and variation partitioning were used to assess the relative influence of individual land use factors. Some 270 species were identified across 11 community types whose floristic patterns were mainly explained by environmental gradients related to altitude and soil type while land use variables could only explain a small part of the floristic variation. Based on biogeography and the determination of diagnostic species, four phytosociological new associations and a new subassociation are proposed: Holco-Brachypodietum distachyi, Holco-Micropyretum tenellae, Micropyro-Anthoxanthetum aristati and Leontodonto-Vulpietum bromoidis vulpietosum membranaceae.

Keywords:

• Community types
• environmental factors
• land use factors
• therophytic grasslands
• variation partitioning

Acknowledgements

The authors wish to acknowledge Rui Ribeiro and Carla Figueiredo for their collaboration in the fieldwork, Tiago Monteiro-Henriques for his contribution to bioclimatic indices, Carla Cruz, Francisca Aguiar and José Carlos Costa for their important comments, Luisa Mendonça and Bruce Richardson for proof-reading the English version and the production editor for they important improvements. This study was supported by the Foundation for Science and Technology (FCT) through the Ph.D. project SFRH/BD/29515/2006.