REPRODUCTIVE EFFORT AND PHENOLOGY OF SEED PRODUCTION OF SAVANNA GRASSES WITH DIFFERENT GROWTH FORM AND LIFE-HISTORY

The phenology of seed production in natural savanna grasslands was stu died in the grass species Aristida congesta, Cymbopogon plurinodis, Cy nodon dactylon, Digitaria eriantha ssp. pentzii, Eragrostis rigidior, Eragrostis superba, Panicum coloratum, Schmidtia pappophoroides, Tragu s berteronianus and Urochloa panicoides. Maximum seed production varie d according to life history strategy and growth form from 0.03 mg seed g(-1) shoot dry weight in the perennial. D. eriantha ssp. pentzii whi ch produces long stolons and 14.8 mg seed g(-1) shoot in E rigidior, w hich produces short geniculate stolons, to 169.1 mg g(-1) in the annua l T. berteronianus. Seed production was in most species divided over s everal peaks during the season. Peaks of seed production were observed 3 to 7 months after the onset of the growth season depending on the s tart of the rains and the life history strategy and growth form of the species. Seed production varied from maxima of 180 seeds m(-2) in D. eriantha ssp. pentzii to 47000 seeds m(-2) in annual stands of T berte ronianus. Except for annual grasslands with U. panicoides, seedling em ergence data reported are smaller by at least a factor of 10 than the observed seed production. Among other factors, a low quality of produc ed seeds, predation by birds and insects and previous grazing by lives tock may have contributed to this difference.