Shrub facilitation of Quercus humilis regeneration in succession on calcareous grasslands
Article first published online: 24 FEB 2009
1999 IAVS - the International Association of Vegetation Science
Journal of Vegetation Science
Volume 10, Issue 4, pages 493–502, August 1999
How to Cite
Rousset, O. and Lepart, J. (1999), Shrub facilitation of Quercus humilis regeneration in succession on calcareous grasslands. Journal of Vegetation Science, 10: 493–502. doi: 10.2307/3237184
- Issue published online: 24 FEB 2009
- Article first published online: 24 FEB 2009
- Received 5 June 1998; Revision received 22 December 1998; Accepted 5 January 1999.
- Buxus sempervirens;
- Juniperus communis;
- Secondary succession
- Kerguélen (1993)
Abstract. In southern France, the natural invasion by Quercus humilis of calcareous grassland takes place in a mosaic of herbaceous and scrubby patches. We hypothesized that the presence of the shrubs Buxus sempervirens and Juniperus communis alter the rate and the pathway of the succession by facilitating the regeneration of Q. humilis. To infer the process of facilitation at a large scale, the spatial distribution of Q. humilis was studied in relation to acorn sources and the type of plant cover in grazed and ungrazed sites.
Abundant recruitment up to 80 m from the wood margins and from isolated oak trees in grassland shows that acorns are dispersed effectively. At the three study sites, the density of Q. humilis individuals was higher under shrubs than in grassland, suggesting that facilitation may occur. This density difference was much higher in the grazed sites than in the ungrazed site. Moreover, before grazing by livestock, the distribution of first-year seedlings is independent of vegetation cover. Thus, shrubs improve Q. humilis regeneration by protecting individuals from grazing. The high density of individuals at the northern edge of shrubs suggests that a second facilitation mechanism may exist, probably related to improved germination conditions. Facilitation by shrubs appears to be very important for Q. humilis dynamics.