Abstract: . . .  obtenus sur les arbres mesurés. Cette méthode ne saurait donner qu’une estimation de la biomasse d’un peuplement. fines a été déterminée dans l’horizon 0-10 cm par 12 prélèvements au cylindre dans chacune des parcelles 83.12 et 83.13. O Mesure de la composition minérale Pour chaque composante de la biomasse, un échantillon a été fait à partir du matériel rapporté au laboratoire afin de déterminer la composition en azote, phosphore, potassium, calcium et magnésium. O Mesure de la biomasse souterraine Pour un arbre de chaque espèce, on a déterré les racines orthotropes jusqu’à 1,5 in de profondeur . . .
. . .  species were selected for their representativity, and cut down ; For each tree, the different parts (trunk, branches above 7 cm diameter, branches between 2 and 7 cm diameter, and twigs under 2 cm diameter) were weighed separately in the field, and samples were taken to the laboratory for dry weight determination. A regression coefficient between tree girth and tree weight allowed to calculate the aerial biomass of tree stands. Root weight was measured for one tree of each species and root biomass of the stand was estimated according to the root shot ratio of this tree. In savanna soil the nutrient amount . . .
. . .  espèces de plusieurs racines verticales, de racines horizontales de surface vers 10-20 cm de profondeur et de racines horizontales ou obliques vers 40-50 cm de profondeur. Les racines représentent une faible part de la biomasse totale : 13,2 % chez A. auriculiformis et 15,9 % chez A. niangium. MINÉRALOMASSE Les teneurs en éléments minéraux des différentes parties de l’arbre sont données dans le tableau VIII. Le bois est caractérisé par des teneurs extrêmement faibles en minéraux, particulièrement en phosphore, potassium et magnésium. Pour ces demiers Cléments, les teneurs se situent à la limite . . .
. . .  stands and leaf fall did not increase in older stands. Twig and fruit litter fall appeared to increase with age stand. More fruit and less leaves were collected under A. ailriculiformis compared to A. mangium. Mean annual wood production was calculated and added to annual litterfall to estimate annual productivity, which ranged about 25 tlhalyear for the two species. With the wood density given by Nat. Res. Council (1983) and by Nat. Acad. (arenoso1 feralic, classification). The climate was subequatorial, although the dry season lasted 4-5 months. The mean annual rainfall was 1 250 mm. sandy soils . . .
. . .  (1980), the wood production of the studied stands ranged from 21 to 27 m3/ hdyear. Compared to other data in the tropical world, these values are low and must be related to the low nutrient soil content and to the long dry season. The measured biomass was comparable to that of the industrial Eucalyptus plantations on the same soil (Loumeto, 1986). Litter production of Acacia was very high, and accounted for almost 50 % of the annual production in A. mangiunz. Accumulation of nutrients in the biomass of Acacia was low but nitrogen accumulated much more than in E Z J C ~ lyptus. Nutrient cycling by litter . . .
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