Understory Vegetation in Fast-Growing Tree Plantations on Savanna Soils in Congo

background

The study investigates the hypothesis that tree plantations established adjacent to natural forests may catalyze the regeneration of natural forest biodiversity in the Congo.

Research Goals & Methods

The researchers rely on studies of  floristic diversity and structure in fast-growing tree plantations. Eucalyptus, Pinus caribaea, and Acacia auriculiformis stands, with ages ranging from 6-20 years growing on sandy and clayey soils and the adjacent native secondary forest were selected for this study. Vegetation assessments within the stands were conducted.

Conclusions & Takeaways

The results showed that eucalypt, pine or acacia plantations did not inhibit colonization by native plant species. The plantation understory consisted of mainly woody species whose floristic composition changes over time. Factors that favored an increase of floristic diversity and development included plantation age and density and proximity to native secondary forests. It was observed that development in the plantations was slowed down by disturbance factors including fire, herbicide use and other plantation weeding practices. Increasing stand age led to an increase in both total number and proportion or number of forest species, particularly after age 10, whereas the understory of younger plantations was composed of savanna-type species. The effect of proximity to the forests seem to have had no effect beyond approximately 50m. Also, an increase in plantation density from 3.7 to 5.7 had little effect with few changes in the understory floristic. The most important forest species found especially in most Eucalypt and the other plantations were Premna lucens, Psorospermum tenuifolium and Psychotria cf. peduncularis. Alchornea cordifolia, Anthocleista nobilis, Barteria nigritiana and Bertiera cf. batesii were also important. The authors conclude that open savanna areas which are either unused or under-utilized by local people can acquire greater value through tree plantation establishment, which can provide an economic activity and contribute to restoration of the biodiversity of poor lands.