Barcelona Field Studies Centre

Garraf Natural Park: effects of fire on vegetation diversity and dynamics

Two main types of vegetation are widespread in the Park. Of these the maquis is undoubtedly a type of sclerophyllous (evergreen, leathery and spiny leaves) vegetation. It is dominated by shrubs and, although these vary very much in height and species from place to place, they are predominantly of the same life-form: although some are near-leafless, spiny plants, the great majority are evergreens with leathery, drought-resistant foliage. Species like the wild olive (Olea europaea), the carob (Ceratonia siliqua), the lentisk (Pistacia lenti.scus), the Kermes oak (Quercus coccfera), the cistus (Cistus spp.) and the arbutus (Arbutus unedo) are typically sclerophyllous, but they are often mixed with heathers (Erica spp.), gorse (Ulex spp.) and broom (Genista spp.) which are of different life-forms. Many types of maquis have been recognised, often within the same general area, each being named after its dominant species .

Garrigue also covers large areas in the Park, particularly on more pervious outcrops such as limestone. Although some species of typical maquis reappear in garrigue along with a number of really low-growing, prickly shrubs, typical garrigue communities are characterised by aromatic, herbaceous plants and should not therefore be classed as true sclerophyllous vegetation. Species of the deadnettle family (Labiatae) and thyme (Thymus spp.) are characteristic in many places.

Though there is no doubt that much of this present-day maquis and garrigue occupies the territory of former forests, it is also certain that, over limited areas, these scrub communities are true climatic climax. This is probably true of areas where very pervious rocks and wind exposure give exceptionally dry habitats.

Study Questions

1. Which species respond most successfully to fire damage and why?

2. How does fire affect the relavative abundance of species?

3. Does competition from neighbours affect resprouting?

4. Does slope angle affect the degree of resprouting or reseeding?

5. Does aspect affect the degree of resprouting or reseeding?

6. Does fire intensity affect the degree of resprouting or seeding?

7. How does fire affect soil nutrient content and structure?

8. Does fire damage favour certain species, and can these species encourage further fires?

9. Does fire disturbance result in higher species diversity?