Impact des feux de brousse sur les maquis ligno-herbacés des roches ultramafiques de Nouvelle-Calédonie

The effect of fire on two types of woody-herbaceous maquis on soils derived form ultramafic rocks was examined for over ten years using the line transect method. During the course of the study, the initial floristic composition was almost completely restored. Most of the woody species resprout, whereas five fire sensitive species reestablish slowly on burnt areas from seed. The most important change was structural, taking place in the herbaceous layer. Tussock Cyperaceae, entirely eliminated by the fire, regrew very slowly from seed. Open areas were largely occupied by a single rhizomatous species (Lepidosperma perteres) which, unlike the Cyperaceae present before burning, is resistant to the spread of fire. The formation of a new plant cover after burning thus represents ìautosuccessionî, enabling the maquis to return to its initial characteristics provided that no additional fires occur. This process of vegetation recovery can however be interrupted by premature burning, which brings about a proliferation of Pteridium esculentum, a highly flammable species that facilitates the spread of fire. Repeated burning can thus result in the establishment of a permanent fern cover.