Plant Phenology Patterns in Lake Manyara National Park, Tanzania

Seedling emergence of annual and sprouting of perennial grasses and the moisture content of green leaves of shrubs and grasses were studied in relation to rainfall in Lake Manyara National Park. Two strategies were described for annual grasses. Of one group seedling emergence is at the middle of the long rains after an accumulated rainfall of 400 mm, of the other group seedling emergence is already after 150 mm. Three strategies were apparent in perennial species. The first group sprouts after 50 mm, the second group a little later after 100 mm, while the third group remains green all year and does not show seasonality. Within the shrubs three groups could be distinguished. Deciduous shrubs produce new leaves after an accumulated rainfall of 150 mm, riverine evergreens show a strong seasonality, while non-riverine evergreens do not show seasonality. An irrigation experiment showed water to be a limiting factor in the seasonal grasses and shrubs. These results are discussed in relation to photosynthetic pathway and to the food quality for large herbivores.