Impacts of Chromolaena odorata on native trees' regeneration in the Lama secondary forests in Benin, West Africa

Invasive Alien Species (IAS) could have negative impacts on forest regeneration. This study aimed to assess the impacts of Chromolaena odorata on tree regeneration in secondary forests and means of controlling it at low cost. Data were collected in 77 rectangular 0.5 ha plots in secondary forests of the Lama forest reserve (Benin, West Africa). In each plot, we measured the dbh of trees (of dbh >= 10 cm) and saplings with diameter tape, counted the number of seedlings and measured the canopy cover using a densiometer. The cover of C. odorata, the target IAS, was estimated on a scale from 0 (absence) to 100% (entire canopy). The seedlings and saplings were categorised into three light-requirement groups (pioneer, non-pioneer light-demanding, shade-tolerant). C. odorata and canopy cover, tree density, basal area, mean diameter and mean canopy cover were computed and used as variables. Bilateral coefficients of correlation between the variables were computed. Regression analysis, using generalized-linear models in R software to correlate the variables to the number of seedlings/ saplings per category, showed that C. odorata was precluding the development of both seedlings and saplings of all species, whatever their light requirement category. However, canopy closure was negatively correlated with grass cover and could be a biological mean to control IAS in secondary and degraded forests.