Population structure and regeneration of multiple-use tree species in a semi-deciduous African tropical rainforest: Implications for primate conservation
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Date
2009
Authors
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Publisher
Forest Ecology and Management
Abstract
The conservation of threatened frugivorous primates (e.g. chimpanzees) and birds in the Albertine Rift
Ecoregion rainforests requires the conservation of food tree species aided by an understanding of their
natural regeneration and population trends. However, little is known of the population structure and
regeneration patterns of a wide range of multiple-use tree species in many of these forests.
We examined the population structures and regeneration patterns of 15 tree species (including
pioneer, non-pioneer and shade-bearers) that are both timber and primate food sources in Budongo
Forest Reserve, NW Uganda, by constructing species population size-class distributions (SCDs), and
calculating SCD slopes, seedling:juvenile and juvenile:adult ratios. The SCD slopes were used as
indicators of population structure, while the slope values were used to summarise, in a single number,
the shape of the SCD for a species.
Species composition between forest communities varied significantly, suggesting the influence of
spatial environmental variations. Nine species had significant positive correlations between seedling
and adult densities. Nine species, namely Lasiodiscus mildbraedii, Celtis mildbraedii, Pouteria altissima,
Chrysophyllum albidum, Cynometra alexandri, Diospyros abyssinica, Funtumia elastica, Chrysophyllum
perpulchrum and Antiaris toxicaria had highly negative SCD slopes spanning 2.47 to 1.1, and
juvenile:adult ratios spanning from 5.34 to 1.62. Hence, clearly exhibiting ‘inverse J’ type curves, and
suggesting a successful or healthy regeneration pattern. In contrast, both Alstonia boonei and Cordia
millenii had weakly negative SCD slopes of 0.25, and juvenile:adult ratios <1; hence a pulsed or
discontinuous regeneration pattern and low recruitment. The SCD slopes and juvenile:adult ratios varied
between forest communities and historical management practices (HMPs). Most species recruit
successfully and continuously over time, and hence have a more stable population structure. However, a
discontinuous regeneration pattern for some, reflects unsustainable harvesting, that potentially
eliminates seed sources for future generations. Hence, management of the Budongo Forest Reserve
requires plans/practices that will enhance and facilitate the recruitment of both the vigorously and
poorly regenerating species to ensure sustainable forest development. Preserving some fruiting trees in
logged areas will benefit both long-term sustainable timber production and wildlife conservation, by
providing food for frugivorous animals that will disperse the seeds.
Description
Keywords
Chimpanzee conservation, Discontinuous regeneration, Natural regeneration, Logging, Primate food trees, Size-class distributions (SCDs)
Citation
Mwavu, EN, & Witkowski, ET (2009). Population structure and regeneration of multiple-use tree species in a semi-deciduous African tropical rainforest: Implications for primate conservation. Forest Ecology and Management , 258 (5), 840-849. doi:10.1016/j.foreco.2009.03.019