Presentation on theme: "References Hawthorne WD. 1995. Ecological profiles of Ghanaian forest trees. Tropical Forestry Paper 29, Oxford Forestry Institute, Oxford, UK. 345p. IUCN."— Presentation transcript:
References Hawthorne WD Ecological profiles of Ghanaian forest trees. Tropical Forestry Paper 29, Oxford Forestry Institute, Oxford, UK. 345p. IUCN IUCN Red List of Threatened Species. Version Downloaded on 13 May 2011.www.iucnredlist.org Kouadio LY Mesures sylvicoles en vue d’améliorer la gestion des populations d’essences forestières commerciales de l’Est du Cameroun [Ph.D. dissertation]. Gembloux (Belgium): University of Liege-GxABT. 278p. Morgan D, Sanz C Best Practice Guidelines for Reducing the Impact of Commercial Logging on Great Apes in Western Equatorial Africa. Gland, Switzerland: IUCN SSC Primate Specialist Group (PSG). 32p. Todd AF, Kuehl HS, Cipoletta C, Walsh PD Using dung to estimate gorilla density: modeling dung production rate. International Journal of Primatology 29: Role of western lowland gorilla (Gorilla gorilla gorilla) to dispersal and regeneration of commercial trees in southeast Cameroon Tropical ecosystems are strongly influenced by animals through seed dispersal; Many dispersers including the western lowland gorilla (WLG) are declining in population size : WLG is listed as critically endangered (IUCN, 2011); Logging concessions encompass more than the half of WLG range; Indirect effects of timber exploitation are amongst the main drivers of WLG population decline (Morgan & Sanz, 2007). Widespread wildlife/ape-friendly logging practices represent the major challenge for their long term survival Determining the role of WLG to dispersal and regeneration of commercial trees would encourage forest managers to strengthen WLG conservation in their concessions Study site: northern periphery of Dja Biosphere Reserve; 32.4 km²; 1.18 weaned gorilla/km² Sampling period: 24 month (October 2009 to September 2011) Sample size: 446 dung piles; 391 deposition sites; 23 daily path lengths; 1211 retention time markers Deposition site characterization: canopy openness estimates by hemispherical photography; Basal area Theoretical dispersal distances and seed shadow: Retention time: captive gorillas fed with wild fruits; Dung collection twice a day (9 am & 5 pm) Daily path length: trail follow between consecutive nest sites Gut passage effect on germinability: gut passed seeds sown in a field nursery; Semi-controlled experiment (gut passed seeds vs seeds discarded from fruit pulp) Retention time: 54.3 h ± 28.9 [<8-192]. The gut passage rate of seeds depends on seed size, with small seeds being retained for longer periods than larger one (ANOVA, F = 51,373, df = 2, p < 0.05; Tukey post-hoc test, p < 0.05; Fig. 3). Daily path length: 1923m ± [ m] Ingested seeds could then potentially be dispersed far away from the parent tree, along a path as long as 23 km (2.9 km x 8 days). Dispersal of commercial tree species: Dispersal of six tree species exploited by logging companies (Tab. 3). The Tali (E. suaveolens) was previously thought to be an autochorous species (e.g.: Kouadio, 2009). The large seed size of Longhi abam (C. lacourtianum) and Ozanbili k (A. klaineanum) restrict the number of potential dispersers to large capacity gut size species Gut passage effect: Viability of seeds after gut passage ranges from 8.7 to 93.1%, nonetheless about half of all species tested retain viabilities higher than 75% (Tab. 5). Germination trials reveal that germination success is not affected by gut passage for any of the 8 species tested; in contrary it enhances the success for half of them (Fig. 3) including C. lacourtianum (Longhi abam). This study reveals that WLG are important dispersers as they disperse seeds of many species at large spatial scale, in large quantities, and with unaffected or enhanced germination success. These seeds have a high probability of being dispersed in sites with high light intensity which would be very suitable for the six commercial tree species dispersed by WLG since they are are light demanders at the seedling stage. In addition to deposition site suitability, WLG should contribute significantly to the dynamics of E. suaveolens (Tali), C. lacourtianum (Longhi abam) and A. klaineanum (Ozanbili K) due to the very limited set of potential dispersers. Conservation of WLG is therefore highly relevant to ensure ecological and commercial function of the concerned forest ecosystems, and for natural forest regeneration, a consideration which should encourage logging companies to strengthen wildlife/ape management in their concessions. Corresponding author: Charles-Albert Petre - 2 Passage des Déportés, 5030 Gembloux, Belgium - Figure 1. Canopy openness of the different habitat types Figure 2. Cumulative percentage of seed deposited in faeces after one feeding event Results Conclusion IntroductionMethodology Global seed dispersal: 55 species identified : tree (41), shrub (1), liana (6), herb (7) + ≈ 40 undidentified morphotypes Dispersal of 20.7% of the tree community (41/199 spp) 93.1% of dung piles contained intact seeds Capacity gut size of up to 9 cm 3 (Anonidium mannii, Annonaceae) Seed deposition sites: Bimodal dung production rate (Todd et al., 2008): 50% during daily displacements & 50% at nest sites During daily displacements faeces are produced mainly in closed canopy secondary forest (54.4%) and open canopy young secondary forest (35.7%) (Tab. 2) Almost all nest sites are found in light gaps and young secondary forest (50.3 & 39.7% respectively; Tab. 2) Canopy openness above individual nests is significantly higher than any other sites (pair-wise comparisons, U Mann-Whitney, p < 0.05; Fig. 1). Most of the seeds are dispersed in sites where light is not a limiting factor Charles-Albert Petre 1,2,3, Roseline Beudels 2, Nikki Tagg 3, Jean-Louis Doucet 1 1 Laboratory of Tropical and Subtropical Forestry, Unit of Forest and Nature Management, Gembloux Agro-Bio Tech, University of Liege, 2 Passage des Déportés, 5030 Gembloux, Belgium 2 Royal Belgian Institute of Natural Sciences, Conservation Biology Section, 29 rue Vautier, 1000 Brussels, Belgium 3 Projet Grands Singes (PGS) of the Center for Research and Conservation (CRC) of the Royal Zoological Society of Antwerp (RZSA), Koningin Astridplein 26, 2018 Antwerp, Belgium Figure 3. Germination success of seeds passed through the gut compared to control seeds removed from fruit pulp. (* significant differences at 5% level; chi 2 test).