Vegetation and soil seed bank in a 23-year grazing exclusion chronosequence in a Mediterranean dry grassland

Abstract

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Fire increases the reproduction of the dominant grass Brachypodium retusum and Mediterranean steppe diversity in a combined burning and grazing experiment

“…Long‐term exclosure from grazing results in a strong biomass increase mainly due to the growth of perennial grass species (Bond & Parr, ). Abandonment of grazing also increases litter biomass and C:N ratios, and decreases soil nutrient content (Peco, Carmona, de Pablos, & Azcárate, ; Saatkamp et al., ). Thus, fire temperatures are higher and therefore fire has a stronger effect on plant species than in grazed systems with lower living and dead biomass (Hobbs, Schimel, Owensby, & Ojima, ).…”

“…The grassland is species‐rich, dominated by annual plants and the perennial grass Brachypodium retusum (Buisson & Dutoit, ; Appendix ). In long‐term grazing exclosures (since 2001), 40% of initially occurring grassland species disappeared and have been replaced by high‐growing herbaceous ruderal species (Saatkamp et al., ).…”

“…At grazed sites, the species is highly dominant. Long‐term grazing exclosure results in an increase of Brachypodium retusum height and the development of other competitive perennial grass species such as Dactylis glomerata (Saatkamp et al., ).…”

“…Similarly, grazing was found to have a positive effect on the growth of Brachypodium retusum (Coiffait‐Gombault et al., ) and on the diversity of its associated plant community (Saatkamp et al., ). However, grazing may reduce sexual reproduction due to vegetative biomass and/or inflorescence removal (Vidaller et al., ).…”

“…Similar to fire, grazing increases mineralization of organic matter and nutrient availability during the seedling recruitment period (Bond & Keeley, ). Although several studies have shown that grazing is needed to maintain the unique species composition of Mediterranean steppe communities (Briske & Noy‐Meir, ; Buisson & Dutoit, ; San Miguel, ), the consequences of short‐term and long‐term grazing abandonment are not precisely known (Saatkamp, Henry, & Dutoit, ). There is also a lack of studies analyzing the interaction of fire and grazing in Mediterranean grasslands.…”