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A Study of a Vegetation Catena in Guinea Savanna at Mole Game Reserve (Ghana)

G. W. Lawson, J. Jenik and K. O. Armstrong-Mensah
Journal of Ecology
Vol. 56, No. 2 (Jul., 1968), pp. 505-522
DOI: 10.2307/2258248
Stable URL: http://www.jstor.org/stable/2258248
Page Count: 20
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A Study of a Vegetation Catena in Guinea Savanna at Mole Game Reserve (Ghana)
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Abstract

At Mole Game Reserve, Northern Ghana, observations on vegetation, soil and micro-climate were made at the end of the dry season at three sites on a catena. Upper-slope savanna and riverain woodland differed markedly in structure and species composition from the prevailing savanna type on gentle middle-slopes. Four sample plots in the middle-slope savanna showed a similarity in tree numbers, species composition, density and basal area of trees, suggesting an equilibrium of vegetation and environment. In an analysis of nearest-neighbour relationships the only positive associations detected were those between trees of the same species. On a cloudless April day the diurnal range of air temperatures at 10, 35 and 150 cm above ground approached 20⚬ C, and the soil temperatures at 5 and 20 cm under ground achieved maxima of 47 and 38.9⚬ C respectively. In the early afternoon at 10 cm above ground a relative humidity figure of 28% was recorded. The two dominant trees showed different transpiration curves; Burkea africana reached its maximum transpiration rate in the morning, transpiration of Terminalia avicennioides followed physical evaporation. Marked concentration of tree roots was observed at a depth of 20-30 cm, i.e. beneath the zone of maximum grass root distribution. In a sample of fourteen species of trees whose roots were excavated, all were found sprouting, after fire damage, from enlarged underground stumps, but only Daniellia oliveri, Detarium microcarpum and Parinari curatellifolia were reproducing vegetatively by suckering.

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