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under climate and human pressure
Forest regeneration
Overview
The study of forest regeneration focuses on five model tree species that answer precise and relevant criteria in the socio-economic context of the study zone. The selected species are socio-economically important, provide a diversity of services and are relatively abundant in the study area. Moreover, those species produce seeds of large size whose dispersal and thus regeneration closely depend on the community of large frugivorous vertebrates. This community is itself very likely to be disturbed by anthropogenic pressures, which make large-seeded tree species diversity and its associated services particularly vulnerable. The study of seed dispersal processes is thus a crucial step in studying the regeneration capacity of the selected tree species. This activity focuses on intrinsic properties as well as habitat dependent variables likely to affect seed disperser’s ecology and plant regeneration capacity. More precisely, in the context of forest fragmentation, we are studying the effect of distance from forest edge on the intensity of fauna-flora interactions likely to have consequences on trees regeneration capacity.
Objectives
Our first goal in this activity is to estimate the quantitative capacity of seed dispersal as well as the shape of the dispersal kernels. We then aim at defining the effect of seed ingestion by a model species of large frugivore on seeds’ germination capacity, and finally, at estimating the fate of dispersed and undispersed seeds and seedlings. We will highlight variations of the dynamic of such plant-animal interactions according to the different tree species studied and their distance from forest edges.
Approaches
Fieldwork takes place south of the Landscape Lake Tumba in the Bandundu province. This region is characterized by a forest-savanna mosaic ecotone, which can be depicted by a complex structure of fragments with varying size, shape, and connectivity. Forest edges are thus strongly represented in the vegetation structure, hence the relevance of considering this variable in forest regeneration processes. Data are gathered in a forest bloc, which is adjacent to the very fragmented mosaic in the south and connected to the extensive equatorial forest in the north.
In order to study the quantitative capacity of seed dispersal we quantify the production of seeds by the trees as well as the number of seeds that are extirpated by each species of the faunal community, thus by either seed dispersers or seed predators. Such observations will be done are varying distances from forest edge. To know the distribution of dispersed seeds in space, we will compute different seed dispersal kernels according to the species-specific seed disperser assemblages. Such kernels are crucial information to feed the model and evaluate tree colonization capacity at the landscape scale. Then, in order to study the effect of seed ingestion on seed germination capacity, we will use a model species; which is known as a relatively large frugivore species in its environment and capable of ingesting large seeds: the bonobo, Pan paniscus. Feces of bonobos will be collected in the field as to gather and identify dispersed seeds and their germination capacity. After dispersal, the first step of the regeneration process is the recruitment of the plants. We thus study the fate of seeds and seedlings, which will be undispersed and experimentally dispersed. This protocol will allow reporting for density dependent predation pressure. Recruited seedlings will then be observed to study their survival and growth rate.