Ignacio Santa-Regina

Aboveground Biomass and Nutrient Pools in Two Evergreen Oak Stands of the Middle Moroccan Atlas Area

The aboveground tree biomass and nutrient pools, litterfall, and weight loss of litter due to decomposition have been measured in two permanent plots of evergreen oak forest (Quercus ilex L.) of the Middle Moroccan Atlas area (Tafachna and Reggada). The aboveground biomass was estimated by cutting and weighing twenty trees from each site according to diameter classes. In order to establish biomass regression equations the best fit was obtained by applying the allometric method: Y (biomass) = aX (X = (D2H)b, D and H are respectively the diameter at 1.30 m and tree height. The aboveground biomass of the two studied stands was: 96.0 and 86.4 t ha−1, respectively, for Tafachna and Reggada of which the woody part accounts for approximately 96%. The average productions of litter are, respectively, 3030 and 3560 kg ha−1 yr−1 for Tafachna and Reggada. The leaves account for approximately 70% of the total litterfall, restored to the soil 38.3 kg ha−1 yr−1 for Tafachana and 44.6 kg ha−1 an−1 for Reggada (approximately 74% of the total nutrient amount of the litterfall). The decomposition pattern of the leaves litter follows a negative exponential equation of form RF = A +B exp (−kt). The nitrogen was the bioelement that contributed the greatest amount to the biogeochemical cycling between vegetation and soil. At the level of internal exchange to the trees, translocation, and transfer, the nitrogen was followed by phosphorus and potassium.