The dynamics of mediterranean shrubs species over 12 years following perturbations

The response of woody species to experimental burning, cutting and ploughing was studied for a period of twelve years in a shrub community in NW Spain. The treatments represent the perturbations most frequently imposed by man on these shrub communities throughout history. The response to burning is much faster than the response to cutting. The response to ploughing is slower due to the regeneration mechanism that species use: germination. In general, the dominant species, Erica australis, influences the regeneration patterns of the rest of the species, which make up the community. There is a significant increase in the cover of woody species until the fourth year, and of herbaceous species until the third year. Subsequently, Erica australis attains dominance, returning to its original spatial occupancy and cover values, removing the herbaceous species and negatively influencing the growth of woody ones like Halimium umbellatum, Halimium alyssoides and Quercus pyrenaica. Both Erica australis and Chamaespartium tridentatum regenerated by sprouting in the burnt and cut plots, and by germination in the ploughed plot. Arctostaphylos uva-ursi only recovers after burning and ploughing. Halimium alyssoides, Halimium umbellatum, Erica umbellata and Calluna vulgaris regenerate by germination in the three plots. Differences in cover values and spatial occupancy during the first years of succession tend to be eliminated twelve years after treatment and most of the species tend to recover their initial cover values. These shrubland communities have a high degree of resilience due to the strong sprouting potential of the component species.