Influence of age and cropping system on tree population structure in South West Ghana

Abstract

Timber tree recruitment and retention was assessed within cocoa farms and mixed perennial farms of varying age classes in south western Ghana. The rationale was to be able to understand the pattern of change in timber tree populations within farms, as well as identify the extent to which farm management activities explain these changes. Each farm was sub-categorized according to farm age into Phase I (farm age < 5 years), Phase II (farm age > 5 years) and Phase III (abandoned farms). Density and species richness of mature trees, that is with diameter at breast height (DBH) above 5 cm and regeneration (DBH of 5 cm and below) were determined while height, DBH and crown area were measured for only mature trees. About 96 farmers were also selected from 16 communities in the study area and interviewed. Results show that regeneration was most vigorous during the phase III (abandoned farms) compared to active cropping stages. Mixed perennial farms retained much less of recruits and if efforts are made to retain much of the recruits, timber supply could be largely augmented from this system. Within cocoa based cropping system, it was also observed that mature tree populations do not reflect the vigour of regeneration during the early stages (Phase I) of farm growth and this was attributed to the influences of farm management activities. Sustainable production of timber tree species from farming areas must take into account variations in tree densities and species richness among cropping systems as well as overtime (age classes) within a cropping system.