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A stepwise Selection Technique Of The Most Discriminant Parameters of Two Groups Applied to Isoberlinia Stands in Benin

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... Dans le but de conserver et d'exploiter de façon durable les espèces végétales vulnérables (Neuenschwander et al., 2011), il est nécessaire d'avoir des informations sur l'effet des activités humaines et sur l'écologie des populations cibles (Dalle et al., 2002). Plusieurs études ont évalué les impacts écologiques de l'exploitation des PFNL par l'étude de la structure des populations en calculant les densités (Hall et Bawa, 1993 ;Ndangalasi et al., 2007) et en établissant les distributions de classes de diamètre (Glèlè kakaï et al., 2006 ;Navarro et al., 2011 ;Mensah et al., 2014). Selon Ngo Bieng (2007), la densité est le moyen le plus simple de mesurer la distance moyenne entre les arbres. ...
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The present study examined the influence of human activities on the structural characteristics of the populations of P. butyracea, a vulnerable multipurpose woody species. A total of 116 plots of 500 m² were randomly installed, 68 in the sudanian region and 48 in the sudano-guinean region, for dendrometric and floristic inventories. The populations of P. butyracea were categorized according to human pressures they are exposed to, using a Factorial Analysis of Correspondences. Three groups were discriminated : Group 1 (populations of Penessoulou and Kandi), characterized by a pressure from wild vegetation fires and agricultural activities ; Group 2 (populations of Manigri and Ségbana), characterized by illegal selective logging, abusive barking of P. butyracea, animal grazing ; and Group 3 (populations of Natitingou, Toucountouna and Tchaourou), characterized by excessive seeds collection and sand removal from the stream by humans. The diameter distribution structures were of left or right dissymmetry according to pressures types to which the discriminated groups are subjected. For a conservation of remnant populations of P. butyracea, the most degraded gallery forest stands should be reforested while protecting the least degraded ones.
... The three classification rules are established on data related to the average tree-height and the average tree-diameter of the plots of a woody species Isoberlinia doka in treesavannah and woodland, by using data from Glèlè Kakaï et al. (2005). The results are presented in Figure 1. ...
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A simulation study was performed to evaluate, in discriminant analysis, the relative performance of the linear, quadratic and logistic rules, on 48,000 sample couples, characterized by the distribution and the overlap of the populations, the number of the variables, the samples size and the theoretical heteroscedasticity degree of the populations, defined in the study. For each sample couple, the relative error of the actual error rate of each classification rule is computed as well as the estimated heteroscedasticity degree and the multinormality test’s statistic of Rao and Ali (1998). The results obtained helps to notice that the linear rule can be advised when the multinomality hypothesis is accepted and the logistic rule in the other cases. The quadratic rule gives the lowest performance in most of the considered cases. Another method is based on the estimated heteroscedasticity and normality degrees of the considered sample couple
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