Natural regeneration and bark production in Prunus Africana (Hook.F.) Kalkman (Rosaceae) and its sustainable utilization and conservation in Kenya

Abstract

Studies on natural regeneration and bark production in Prunus africana were
carried out in Kenya to provide basic information required to develop
guidelines for sustainable utilization and conservation of the species. The
objectives were: to analyse patterns of population structure; to develop an
understanding of the effect of herbivory and disease infection on natural
regeneration; and to assess available quantities of ecological sustainable bark
yield per tree and characteristics that could influence it.
The results showed that the population density is relatively low and a high
proportion of trees are greater than 20 cm diameter. Prunus africana was most
abundant along forest edges and on forest patches. The average density of trees
was 6 trees/ha. The spatial pattern was clumped, and linked to gap creation.
Size structure suggests that Prunus africana's recruitment is episodic and is
dependent on canopy openings. Disease infection and herbivore damage was
higher closer to parent trees where seedling density was high, and decreased
with increasing distance away from the parent trees. Mortality of seedlings in
Prunus africana is very high; the number of seedlings present at each stage
decreases as the seedlings develop from one stage to another. This evidence is
consistent with the Janzen-Connell model describing the spacing out of
recruitment (away from parent trees) through the action of density- or distance
responsive herbivores or pathogens. However, the hypothesis is too simple to
determine the final recruitment pattern in Prunus africana.
Populations of Prunus africana growing in open habitats have thicker bark
compared to those in closed canopy forests. The mean bark yield per tree was
75.81 kg in closed canopy forest and 73.38 kg in open farmland. Tree diameter
and bark thickness are the best estimators of bark yield. However, variability in
tree form between different habitats may require separate equations for
accurate predictions. The ability of Prunus africana to withstand bark damage
offers the potential for sustainable harvesting.
It is recommended that a full-scale inventory and resource assessment of
Prunus africana be done in Kenya and harvesting regulations and quotas should
be developed and enforced to achieve sustainability. To promote the recovery
of Prunus africana populations in harvested area, interventions should include
opening the canopy around, and clearing the undergrowth beneath seed
bearing trees. More research work is necessary to assess the correlation
between bark production and bark quality; the influence of tree-fall gaps on
spatial patterns of recruitment; the best sustainable bark harvesting techniques;
minimum exploitable diameter and intervals for sustainable bark harvesting in
Kenya.

Date of Award	2003
Original language	English
Awarding Institution	Bangor University
Supervisor	John Hall (Supervisor)