Secondary succession after perturbations in a shrubland community

Shrubland responses to experimental burning, cutting and ploughing treatments were studied over 15 years in two shrubland communities dominated by Erica australis. The treatments represent the most frequent forms of anthropogenic disturbances experienced by these communities throughout their history. The response to burning and cutting treatments is similar, and the succession process is characterised as autosuccession. The highest values for herbaceous annuals and perennials were observed in the third and fourth years. Generally, herbaceous species remain present throughout the study period, while woody taxa ones increase their cover values over time. The quantity of herbaceous species present is in inverse proportion to the quantity of woody taxa. The woody species that appear immediately after treatments are sprouting species, namely Erica australis and Arctostaphylos uva-ursi. The response to ploughing is slower, reflecting the recovery mechanism (seedlings). However, after 15 years, there are no significant differences in regeneration between treatments. The first stages of this post-ploughing succession are dominated by annual species until the fourth or fifth years, after which woody species begin to dominate and herbaceous taxa decrease considerably. Woody species with high germination values are Halimium alyssoides and Halimium umbellatum. These shrubland communities have a very high resilience to such perturbations and start regenerating rapidly, reaching the original state in about 9 years. The appearance of the climax arboreal species of the area, Quercus pyrenaica, when it comes from germination, occurs 15 years after the perturbations. (C) 2002 Editions scientifiques et medicales Elsevier SAS. All rights reserved.