Colonization of native tree species beneath a teak plantation adjacent to Budongo forest in western Uganda

Abstract

The hypothesis that exotic tree plantations foster the regeneration of native woody species was tested through a study of tree species diversity, composition, and functional traits of native trees colonizing the Nyakafunjo teak plantation adjacent Budongo forest in Masindi district. The exotic teak plantation was compared with the natural forest for diversity, composition and functional traits of native woody species. Data were collected by laying 20 plots of 10 ×10 m for recording trees (≥ 5 cm dbh) in the teak plantation and the natural forest. All trees planted and regenerating in the established plots were measured for height and Diameter at breast height. To compare diversity and functional traits of colonizing woody species between the teak plantation and natural forest, separate generalized linear models were fitted with each diversity index and functional trait as a response and forest type as the explanatory factor. Non-metric multidimensional scaling ordination was used to assess species composition. A total of 493 trees across 61 species were recorded in the study. The family Moraceae was the most abundant with 96 individuals followed by apocynaceae (52 individuals), mimosoideae (35 individuals) and meliaceae (29 individuals). Alangianceae, flacourtiaceae, lecythidaceae, and passifloraceae all had one tree species encountered. Tree species abundance and richness were significantly higher in the natural forest than the teak plantation but tree evenness and Shannon did not show significant differences between the forest types. The species composition of colonizing native species was different between the teak plantation and natural forest. The functional traits of native tree species varied significantly between the forest types. As the dbh of the teak trees increases, the abundance of native trees regenerating in the teak plantation also increases and an increase in height of teak trees causes a decline in the abundance of regenerating native trees. These results support the concept that exotic tree plantations can foster the regeneration of native woody species, which increases their conservation value, especially when established in landscapes containing native seed sources.