SHOOT GROWTH AND MORPHOMETRIC ANALYSES OF SERENGETI GRAMINOIDS

Nine species from the Serengeti National Park, Tanzania, were studied to provide morphometric and growth rate parameters for a stimulation model of their growth (Coughenour, McNaughton and Wallace, 1984). Short grasses had a much greater capability than taller species for packing a large number of shoots with a high proportion of lamina on a given crown biomass. Absolute growth rates varied with species height group, shoot type and growth phase. The frequency distribution of growth rates indicated that maximum growth rates were similar but that model growth rates decreased with height. This may be an important trait allowing short grasses both to endure unfavourable conditions and to effectively exploit transient showers and resultant water availability. The ability of smaller-saturated species to concentrate a high number of shoots with a large proportion of blade on a given crown area is an effective mechanism for increasing productivity early in the growing season. Taller grasses could achieve the same production rates as short grasses only with greater individual growth rates of fewer shoots. These patterns may help to explain gradients of graminoid stature along rainfall and growing season gradients.