Ecosystem dynamics after forest fire. Blideen Atlas case

Human disturbances affect the majority of terrestrial ecosystems. The radical changes in the behaviour of ecological systems, partial or total destruction of plant biomass, often with the death of fundamental entities. Of these disturbances, fires affect many terrestrial ecosystems, particularly forests, by changing their floristic composition, their structure and their functioning; the global average annual forest area burned is estimated at 65 million ha. The Mediterranean basin, a hotspot, annually loses between 0.5 and 1 million hectares of forest. In Algeria, the annual average of areas destroyed by fire is between 45,000 and 50,000 ha. Our work set out to study the changes in the plant coverage of the land one year after the passage of fire. We studied the effects at the floristic, ecological and dynamic level in a forest ecosystem located in the north of Algeria (Atlas Blideen). The phytoecological inventory of vegetation (74 surveys, 162 species) was carried out from subjective sampling. To highlight the different groupings in the study area, classical statistical treatments (factorial analysis of correspondences) were applied to the floristic and ecological data. The results of computer processing made it possible to individualize and classify four plant groups according to the degree of the fire. The qualitative and quantitative analysis of these groups shows a therophytization of the flora, due to the regression of the forest cover (disappearance of the phanerophytes) caused by the passage of fire, with a floral procession represented mainly by Asteraceae, Poaceae and Fabaceae and an index disturbance which greatly exceeds 50%. However, some tree and shrub taxa such as cork oak, holm oak and Pistacia lentiscus tree have the capacity to reappear by rejecting the calcined stumps.