Changes in the vegetation of Quercus pubescens woodland after cessation of coppicing and grazing



Abstract. The cessation of coppicing and grazing in Quercus woodlands, with its subsequent changes in the structure, composition and functioning of vegetation communities, is becoming more frequent throughout the Mediterranean Basin. In southern France, we have studied successional changes in Quercus pubescens woodlands by visiting previously studied sites 18 yr later. Changes in vertical structure, species richness, floristic composition, life form and dispersal type were analysed and compared between woodlands that had previously been grazed or ungrazed.

Both successions showed a decline in vegetation cover in the 0–25 cm height class and in the height class immediately under the canopy layer, due to oak litter accumulation and tree ageing. In post-grazing succession, the abandonment of grazing and associated burning has allowed the vegetation cover to increase in the 0.25-2 m height class. In both successions, grassland species decreased in frequency and forest species increased, a trend which was stronger in undisturbed succession. Species richness decreased with time in the undisturbed succession, but remained stable in the post-grazing succession mainly because of the slow decline of plants linked to grazing. In undisturbed succession, therophytes and hemicryptophytes decreased. In contrast, therophytes and hemicryptophytes remained stable in post-grazing succession. In both successions, endozoochorous species (notably Ruscus aculeatus) increased. Plants dispersed by non-animal vectors decreased in undisturbed succession, but stability was observed in most of the dispersal types in post-grazing succession. These results showed that a time-lag existed between undisturbed succession and post-grazing succession, the latter remaining at a younger stage of successional development due to more recent impact of grazing. However, both successions have converged suggesting that most of the traces of grazing on vegetation will disappear within a few years. The vegetation of these coppices, regardless of the previous grazing regime, will become increasingly similar to the vegetation of undisturbed woodlands. However, their floristic composition will probably never be identical to that of undisturbed woodlands, mainly because of the rarity of these undisturbed woodlands and of the short-distance dispersal of many forest plant species.