Effect of Exotic Tree Plantations and Site Management on Plant Diversity

Background

In this study of species richness, species behavior and stand parameters were analyzed under fast growing exotic tree plantations and compared with the characteristics of nearby secondary forest patches in Pointe-Noire and Loudima in Congo. The plantations were established in a grass-dominated vegetation of native savanna. The planted species investigated were mainly eucalypts hybrid (PF1), and secondarily Acacia auriculiformis and Pinus caribaea.

Research Goals & Methods

The plots investigated were disturbed plots with similar age and history planted in 1983-1984 and logged in 1991, experimental unexploited plantations, selected commercial plots coppiced with trees from 5-6.5 years old. Heights and dbh of woody plants if relevant were measured, whereas the presence and cover percentages of herbaceous species, mainly Poaceae and Cyperaceae, were estimated. Planted tree characteristics, density, height and dbh, were also measured.

Conclusions & Takeaways

The results show that exotic timber plantations facilitated an important floristic change from the grass-dominated vegetation of native savanna toward undergrowth characterized by important woody plants. The total number of undergrowth species was relatively low under the exotic tree plantations compared to the secondary forests. In the individual plantations, the relatively high species richness in the undergrowth of eucalypt plantation at Loudima was attributed to the older age (26 years) and site conditions particularly soil. Forest proximity also increased the number of species, 50 species located in the closest (10m-50m).