Allometric models are necessary for estimating biomass in terrestrial ecosystems. Generalized allometric relationship exists for many tropical trees, but species- and region-specific models are often lacking. We developed species-specific allometric models to predict aboveground biomass for 11 native tree species of the Sudanian savannawoodlands. Diameters at the base and at breast height, with species means ranging respectively from 11 to 28 cm and 9 to 19 cm, and the height of the trees were used as predictor variables. Sampled trees spanned a wide range of sizes including the largest sizes these species can reach. As a response variable, the biomass of the trees was obtained through destructive sampling of 4 754 trees during wood harvesting. We used a stepwise multiple regression analysis with backward elimination procedure to develop models separately predicting, total biomass of the trees, stem biomass, and biomass of branches and twigs. All speciesspecific regression models relating biomass with measured tree dimensions were highly significant (p < 0.001). The biomass of branches and twigs was less predictable compared to stem biomass and total biomass, although their models required fewer predictors and predictor interactions. The best-fit equations for total above-ground biomass and stem biomass had R2 > 0.70, except for the Acacia species; for branches including twig biomass, R2-values varied from 0.749 for Anogeissus leiocarpa to 0.183 for Acacia macrostachya. The use of these equations in estimating available biomass will avoid destructive sampling, and aid in planning for sustainable use of these species. (Résumé d'auteur
Declining Wild Mushroom Recognition and Usage in Burkina Faso. Ethnomycological investigation was carried out in Burkina Faso, West Africa, using standardized interviews focused on 40 representative mushroom species assembled in a traveling herbarium (photographs plus preserved specimens). A total of 540 informants from 18 localities representing three main ethnic groups-Mòosé, Bobo, and Gouin-were interviewed, though the bulk of those interviewed were Mòosé (or Mossi) from the more populous central region of the country. Among the study species, as many as 24 were considered edible by the different ethnic groups; a few medicinal uses also were noted. The edibility of a common Chlorophyllum species is confirmed for the three ethnic groups. Mushroom nomenclature is not well developed in any of the three groups as evidenced by the fact that many mushrooms, including some common edible species, do not appear to have specific local names, but are instead simply referred to by a general term for "mushroom." Preliminary observations about inter-ethnic variation in recognition, naming, and appreciation of mushrooms are noted. Older people recognized many more mushroom species than did younger people, and women appeared to be slightly more knowledgeable about mushrooms than men. The most important finding is that the gathering and consumption of wild edible mushrooms seems to be dying out in Burkina Faso, especially in the central part of the country, apparently because of declining mushroom populations resulting from disappearing forest habitats.
The importance of mounds created by Macrotermes subhyalinus as safe site for tree regeneration was analysed in a savannah woodland of Burkina Faso. Plantlets (height \1.5 m) were sampled and followed over an year in 72 9 4 m 2 quadrats located on M. subhyalinus mounds and adjacent areas. The mechanisms of regeneration and plantlet mortality were also determined. We identified three regeneration mechanisms: seedlings regenerated by seed (abundant on mounds), sprouts (abundant on adjacent areas) and root suckers (a rare case on both sites). A total of 37 species representing 17 families and 30 genera were found on all quadrats, of which 29 species were found on termite mounds and 22 species on adjacent areas. Species richness and density of plantlets at the 4 m 2 scale were higher on mounds than in the adjacent area (P \ 0.05). Among plantlet categories, seedling density was significantly different among microhabitats (P \ 0.001) and across sampling periods (P \ 0.01) and, the majority of plantlet individuals appeared within the 0-25 cm height class. The mortality of plantlets and particularly seedling mortality differed significantly between microhabitats (P \ 0.01) and between periods (P \ 0.01), whereas more than half the variation in the death of Acacia erythrocalyx seedlings (the most abundant species) were related to the density of the live seedlings of the same species (P \ 0.001). The observed mortality rate was way below 50%; plantlet density remained higher on mound during sampling periods as compared to the adjacent area. It can thus be concluded that Macrotermes termite mounds are favourable sites for the recruitments of woody plants in savannah woodlands.
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