Mohamed Boulmane

Estimation du stock de carbone organique dans la chênaie verte du Moyen Atlas marocain

Abstract The present study was carried out in Quercus ilex forest of the Middle Moroccan Central Atlas (Tafachna and Reggada). It aims at the determination of the organic carbon stock in the various layers of the soils, the litter and the various components of the tree (wood of the trunk, bark, branches, smal branches and leaves). It comes out from this study that the stock of total carbon (SCOT) in the ecosystem of the holm oak is of 145 t C/ha for Tafachna and 114 t C/ha for Reggada. The organic carbon stock of soils (SCOS) represents more than 50% of the SCT. This stock varies considerably with the density of peuplement with 80 t C/ha for Tafachna (5192 species/ha) and 56 t C/ha for Reggada (1584 species/ha). Contrary to the carbon stock in the phytomass which is equal 64 t C/ha for Tafachna and 58 t C/ha for Reggada. More than 80% of the organic carbon stock of the soils is stored in the first 30 centimeters, that is about 63 t/ha (43% of the SCOT) for Tafachna and 47 t/ha (41 % of the SCOT) for Reggada.

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.

The potential of Eucalyptus plantations to restore degraded soils in semi-arid Morocco (NW Africa)

Key messageShort-rotation forestry using eucalyptus in degraded oak forests in the semi-arid area of NW Morocco can be a useful strategy to avoid further degradation and carbon loss from this ecosystem, but it might be constrained by nutrient and water supply in the long term.ContextLand degradation and deforestation of natural forests are serious issues worldwide, potentially leading to altered land use and carbon storage capacity.AimsOur objectives were to investigate if short-rotation plantations can restore carbon pools of degraded soils, without altering soil fertility.MethodsCarbon and nutrient pools in above- and below-ground biomass and soils were assessed using stand inventories, harvested biomass values, allometric relationships and selective sampling for chemical analyses.ResultsCarbon pools in the total ecosystem were low in the degraded land and in croplands (6–13 Mg ha−1) and high in forests (66–94 in eucalyptus plantations; 86–126 in native forests). The soil nutrient status of eucalyptus stands was intermediate between degraded land and native forests and increased over time after eucalyptus introduction. All harvest scenarios for eucalyptus are likely to impoverish the soil but, for the moment, the soil nutrient status has not been affected.ConclusionAfforestation of degraded land with eucalyptus can be a useful restoration tool relative to carbon storage and soil fertility, provided that non-intensive forestry is applied.