Seed production, germination, seedling growth and domestication potential of Afrocarpus Usambarensis Var.dawei and Podocarpus Milanjianus in Sango Bay, Uganda

Abstract

Podocarpus is a genus of conifers consisting of about 100 species and distributed in tropical and sub-tropical areas of the southern hemisphere. Afrocarpus was, until recently, also part of Podocarpus in terms of the genus. These species are rarely planted in Uganda due to the long rotation period.

The aim of the study was to investigate the seed production, germination potential, on-farm seedling growth rates and potential for on-farm planting of Afrocarpus usambarensis var.dawei and Podocarpus milanjianus in Sango Bay area.

Data were collected on seed production, seed germination, seedling growth rates and willingness of the local community to plant the species. Growth rates of P. milanjianus and A. usambarensis seedlings on-farm were examined in a participatory study involving farmers around the Sango Bay forests. Seeds were collected using seed traps (polythene sheets) and germination tests were undertaken in a nursery setting. Descriptive and inferential statistics were employed to analyse the data.

It was found that A. usambarensis produces more seed with a mean seed yield of 32 seeds per tree per year than P. milanjianus that had a mean of 9 seeds per tree per year. A. usambarensis seeds germinate better with a mean germination of 22% than P. milanjianus at only 10% under the same conditions. Watering enhances germination of the seeds. Generally, A. usambarensis seeds take longer to germinate; a priod of 35-55 days to emerge than P.milanjinanus seeds that take between 30-48 days.

When planted out, A. usambarensis has better survival with a mean survival of 63% across the three sites than P. milanjianus with a mean survival of 48% in Sango Bay. Lack of information on the tree growth, non availability of seed and seedlings as well as inadequate awareness about seed production, seed germination and growth potential hinder on-farm planting of A. usambarensis and P. milanjianus.

A long term study of 10-15 years would be necessary to ascertain any cyclic nature of seed production by these two species. Further, a study should be undertaken to monitor the growth rates of the two species for a relatively longer period of time exceeding five years. Research should also be undertaken to establish if A. usambarensis can be grown on a commercial scale in other areas of the country. A. usambarensis rather than P. milanjianus should be promoted for on-farm growing by the local communities to relieve pressure off the natural populations in Sango Bay forests.