Influence of forest floor and moisture conditions on seed germination and establishment of seedlings of Brachylaena huillensis

Abstract

Investigations were carried out in Karura and Muguga forests with the objective of finding out the influence of forest floor and moisture conditions on the low regeneration of Brachylaena huillensis in the forests. - The investigations focused on aspects of field seed germination, seedling establishment conditions and available moisture. The ecological implications of the study results on the regeneration of the tree were also considered. Germination and seedling survival were influenced by the amount and distribution of moisture. Litter reduced germination rates, and survival of germinated seedlings, but only when moisture was limiting. When moisture was limiting, litter on the forest floor dried faster than the mineral soil and germination was poor for seed that fell on litter. No major problem of a litter barrier was expected, but where litter was suspected of deterring germination and survival, simple scarification of the forest floor, tripled germination capacity. Results of the studies of seedling establishment and survival in the forest over four dispersal seasons indicated clearly that several seasons of seed dispersal result in no established seedlings. Once in a while, in a year of good rain (in amount and distribution) useful regeneration of B. huillensis results. This is clearly reflected by the commonly observed well defined height size classes within a group of regenerating seedling/sapling mosaic of the species in natural conditions.