The giraffe and its food resource in the Serengeti. I. Composition, biomass and production of available browse*

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Abstract
Summary: The quantification of the browse resource available to giraffe was undertaken as the first stage in the study of the relationship of the giraffe population and its food supply in the Serengeti woodlands. Techniques are described for estimating the seasonal standing crop biomass of available browse and its quarterly rate of production. The conversion of the mature Acacia woodland to a more open regeneration–grassland phase as a result of the combined effects of elephants and fire protection, has substantially increased the biomass of browse available to giraffe. The browse component of the wooded savanna ecosystem contributes significantly to the total ecosystem production of edible forage, and in certain cases may even exceed the production of the grasslands. Because the browse production is sustained throughout the dry‐season in the valley‐bottom woodland type, a considerable biomass of young forage is available to giraffe throughout the year. Clipping to simulate the browsing action of giraffe sustains the high rate of forage production already stimulated by browsing, but the production rate steadily declines if the browsing stimulus is removed. The effect of browsing at current giraffe densities is to increase the rate of browse production.Résumé: La quantification des ressources en pâturage disponible à la girafe fut entreprise comme première étape d'une étude des relations des populations de girafe et de leur nourriture dans les savanes boisées du Serengeti. On décrit les techniques d'estimation de la biomasse végétale saisonnière disponible et son taux de production trimestriel. La transformation d'une forêt à Acacia mature en une phase de savane ouverte à régénération par l'effet combiné des éléphants et des feux, a augmenté substantiellement la biomasse de pâturage disponible à la girafe. La composante de broutage de l'écosystème savane boisée contribue significativement à la production de l'écosystème entier en fourrage, et dans certains cas peut