Recovery of burnt Pinus halepensis mill. forests. II. Pine reconstruction after wildfire

Abstract

The recovery of Aleppo pine ( Pinus halepensis Mill.) forests, between one year and thirty years after fire, was investigated on 51 plots in the region around Montpellier with regard to the density, age structure, area distribution and growth of the pine. Pine density was recorded on three 100-m 2 transects on all the sites. Then, on ten sites, selected at random, the age of trees was recorded on three 100-m 2 transects, and the distance of new trees from a seed-bearing tree was measured on three 60-m 2 transects. Pine density increased to a maximum during the first fifteen years after fire. It then decreased, probably because of mortality brought about by intra- and interspecific competition. A fair correlation was found between stem density in burnt sites and the number of adult pines in paired control sites. Concerning the age of pines two kinds of sites were distinguished; (a) the majority with an age structure following a model with a reverse J shape, the others (b) with an age structure which did not fit a model. In the first model, two submodels exist: the former represented by a decreasing exponential function, showing a constant mortality rate whatever the age of individuals, the other fitting a decreasing power function indicating a decrease of mortality in relation to the age of individuals. In the second case, the absence of young individuals could be due to a high mortality rate or a scant seed source. The areal distribution of young pines was uniform on all the study sites. This was apparently due to the superimposition of seed from various sources. A more particular study on the influence of seed-trees did not demonstrate any particular pattern. An excellent correlation existed between the height of Aleppo pine trees and their phytomass.