Browsing by Author "Adamescu, Gabriela S."

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    Annual Cycles are the Most Common Reproductive Strategy in African Tropical Tree Communities
    (Biotropica, 2018) Adamescu, Gabriela S.; Plumptre, Andrew J.; Ndangalasi, Henry J.; Mugerwa, Badru; Gilagiza, Baraka; Bitariho, Robert
    We present the first cross-continental comparison of the flowering and fruiting phenology of tropical forests across Africa. Flowering events of 5446 trees from 196 species across 12 sites and fruiting events of 4595 trees from 191 species across 11 sites were monitored over periods of 6 to 29 years and analyzed to describe phenology at the continental level. To study phenology, we used Fourier analysis to identify the dominant cycles of flowering and fruiting for each individual tree and we identified the time of year African trees bloom and bear fruit and their relationship to local seasonality. Reproductive strategies were diverse, and no single regular cycle was found in >50% of individuals across all 12 sites. Additionally, we found annual flowering and fruiting cycles to be the most common. Sub-annual cycles were the next most common for flowering, whereas supra-annual patterns were the next most common for fruiting. We also identify variation in different subsets of species, with species exhibiting mainly annual cycles most common in West and West Central African tropical forests, while more species at sites in East Central and East African forests showed cycles ranging from sub-annual to supra-annual. Despite many trees showing strong seasonality, at most sites some flowering and fruiting occurred all year round. Environmental factors with annual cycles are likely to be important drivers of seasonal periodicity in trees across Africa, but proximate triggers are unlikely to be constant across the continent.
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    The ecology of tree reproduction in an African medium altitude rainforest
    (PloSone, 2009) Babweteera, Fred; Plumptre, Andrew J.; Adamescu, Gabriela S.; Shoo, Luke P.; Beale, Colin M.; Reynolds, Vernon; Nyeko, Philip; Muhanguzi, Geoffrey
    The occurrence of flowering and fruiting in tropical trees will be affected by a variety of factors, linked to availability of resources and suitable climatic triggers, that may be affected by increasing global temperatures. Community-wide flowering and fruiting of 2,526 trees in 206 plots were monitored over 24 years in the Budongo Forest Reserve (BFR), Uganda. Factors that were assessed included: the size of the tree, access to light, the impacts of liana load, effects of tree growth and variation between guilds of trees. Most flowering occurs at the end of the long dry season from February to April. Trees that had access to more light flowered and fruited more frequently. Pioneer and non-pioneer light demanding species tended to reproduce more frequently than shade-bearing species. Trees that grew faster between 1993-2011 also fruited more frequently. When examining all factors, growth rate, tree size, and crown position were all important for fruiting, while liana load but not growth rate was important in reducing flowering. Trees in BFR show a large decline in fruiting over 24 years, particularly in non-pioneer light demanders, shade-bearers, and species that produce fleshy fruits eaten by primates. The decline in fruit production is of concern and is having impacts on primate diets and potential recruitment of mahogany trees. Whether climate change is responsible is unclear but flowering of the guilds/dispersal types which show declines is correlated with months with the coolest maximum temperatures and we show temperature has been increasing in BFR since the early 1990s.