Thèse-EliseBuisson-Chapitre4

Interchapter 3-4 Seeding experiment in La Crau In the previous chapters, we described the impact of strong exogenous disturbances on Mediterranean herbaceous plant communities that have evolved with regular endogenous disturbances for centuries. We show that these communities are degraded and need to be restored. In order to plant restoration adequately, it is necessary to find out what irreversibility thresholds have been passed. We know that reference grassland seeds hardly disperse into degraded grasslands, but when they do get there, do they find appropriate environmental conditions to germinate? In other words, we need to know if grassland species can be re-introduced by sowing. In order to answer this question, we carried out some experiments on the germination potential of our two species, Thymus vulgaris and Brachypodium retusum, in the lab and on their emergence potential in the field. I now briefly discuss our experiments and results. First, we carried out standard germination tests in growth chamber (20°C, 16 hours of day light) as well as germination test with various scarification treatments (cold, heat). As the two species (Thymus vulgaris and Brachypodium retusum) germinated relatively well (>50%), we carried out emergence tests in the field. Sowing seeds to restore grasslands is a technique widely used to enhance species richness, accelerate succession or fully restore grasslands (Wells 1990; Stevenson et al. 1995; Hutchings & ...