Population structure of three woody species in four ethnic domains of the sub-sahel of Burkina Faso

Abstract

In developing countries many people depend on woody resources for their livelihoods. Monitoring human impact on the populations of socio-economically important species is therefore important for the conservation of vulnerable plants. In order to assess and compare the population structure and regeneration patterns of three multipurpose species, namely Acacia seyal Del., Balanites aegyptiaca Delile and Pterocarpus lucens Lepr. in four ethnic areas of the sub-Sahel of Burkina Faso (Samo, Gourmantché, Fulani and Mossi), we used the size-class distribution method (SCD) (Condit et al., 1998). Diameter at breast height (Dbh) of adult individuals of each species were sampled on 1000m 2 (20m×50m) plots in each ethnic domain. Recorded Dbhs were distributed among eight size-classes of 5cm intervals. For each species, the slope of the regression of the SCD was considered to be an indicator of the population structure. Seedlings and saplings were recorded on five nested 25m 2 plots and fell into five height classes of 0·5m intervals. The target species had significant (p<0·001) negative SCD slopes with an inverse J-shape distribution in all ethnic areas; indicating stable populations with good regeneration. Kruskal-Wallis test for the SCDs of A. seyal, B. aegyptiaca and P. lucens did not differ significantly among the ethnic areas (p>0·1). This suggests that the dynamics of each of the three species is similar across ethnic domains and the sub-Sahel. Data from P. lucens depicted an apparent stable population structure which contrasted with our field observations, perception of local people and previous studies. © 2010 John Wiley & Sons, Ltd.