Dendrometric and orographic factors influencing the natural regeneration of Aleppo pine (Pinus halepensis Mill.) in semi-arid regions (Djelfa, Algeria)
The present study aims to show the effects of dendrometric and orographic factors on the natural regeneration of Aleppo pine (Pinus halepensis Mill.) in the Saharan Atlas, particularly the Senalba Chergui massif (Eastern Senalba mountain range) in Algeria, for its important forest area occupied by Aleppo pine in semi-aridregions. The sampling adopted is stratified and subjective; stratified sampling makes it possible to obtain representative stations for the various existing ecological situations, we divided our study area into 04 homogeneous stations according to the appearance of vegetation, the slope exposure and the type of the soil; and for every station, temporary observation plots are installed through subjective sampling, this method is used to study heterogeneous ecological environments; we installed in our study stations seventy (70) temporary plots, and the plot is a circular sampling unit that covers an area of 400 m2. In each plot, dendrometric variables were measured: diameter at breast height, total tree height, dominant height, average density per hectare, basal area per hectare, the age of stands, and cumulative surface of crown cover; and a phytoecological survey was carried out to determine the environmental parameters, such as altitude, slope, exposure and lithology. We used the principal component analysis (PCA) to identify the homogeneous sample plots (compared to the regeneration), descriptive statistics, and the Analysis of variance (ANOVA). The number of seedlings per square meter varies between 0 and 0.23, and there are several factors affecting these results,mainly: Crown cover, density, basal area, age of stands and slope exposure.