Long-term post-fire evolution of understorey biomass in Pinus halepensis Mill. forests of Central Greece

The long-term post-fire development of evergreen sclerophyllous shrub biomass was studied along a chronosequence of Pinus halepensis stands. These shrubs are regarded as the most important component of the understorey vegetation concerning the Mediterranean coniferous forests in question. Eighteen (18) forest stands of different post-fire age were selected for sampling in the Attica region (Central Greece) and the neighbouring island of Evia. Most of the forest stands were re-sampled for two to four consecutive years, depending on their post-fire age, since younger stands change more rapidly, and on the time available for this task. In every stand, the total cover and maximum height of evergreen sclerophyllous shrubs were recorded. Measurements were carried out within three 10x1 m randomly established plots. Each plot was divided into ten (10) 1x1 m quadrats. Thus, there were 30 quadrats per forest stand. Using two published regression equations, with the product of shrub height with the square of cover as the independent variable, the total understorey fuel load (TLOAD) and the “active” fuel load (ALOAD) for fire modelling purposes were calculated. It was shown graphically and through regression analysis that, at least in Central Greece, there are two distinct types of Pinus halepensis forest stands in regard to the understorey vegetation. The first (type 1) is characterized by the dominance of evergreen sclerophyllous shrubs in the understorey, with a shrub cover of 50-80%. In the other (type 2), the cover of such shrubs is much lower, usually