Effect of road construction on plant communities: a case of selected roads in the Albertine rift, western Uganda

Abstract

The discovery of oil and gas in Uganda has increased road infrastructural development within the Albertine Rift. This development is known to cause changes in plant species composition, structure and diversity of the adjacent vegetation and flora. However, the magnitude of this impact in the Albertine Rift is not well known. This study investigated the variation in species composition and structure of vegetation and also species diversity of flora from the road edge of selected roads in the Albertine Rift. Three oil roads, namely: Hoima-Kaiso (traversing Bugoma CFR), Kaseeta-Lwera (traversing Kabwoya Wildlife Reserve) and Lwera-Buhuka (traversing an escarpment) were selected for this study. From the three oil roads, three road segments, two traversing a savanna ecosystem (in Kabwoya Wildlife Reserve and on the escarpment) and one in a forest ecosystem (Bugoma CFR) were selected for plant sampling. Sampling locations, at intervals of 1 km, were established along each of the road segments. This sample location interval was reduced to 0.5 km along the escarpment segment because of its short length. At each sampling location, two transects perpendicular to the road, one on each side of the road, were established. Along each transect, a nested plot was established from the road edge for sampling of trees, shrubs, seedlings and herbaceous plants. A similar plot design was employed at 30 m, 60 m, 90 m and 120 m from the edge of the road along each transect. Correlation/regression analysis and one-way analysis of variance (ANOVA) were both used to analyze the effect of distance from road edge on species composition, structure and diversity using SPSS v25.0 software package. Results show that the proportion of weedy species on Lwera-Buhuka road (F=3.305, p=0.018) was significantly higher in areas adjacent the road edge than those far from the road edge. DBH of woody growth forms on Hoima-Kaiso road (F=3.785, p=0.009) and Lwera-Buhuka road (F=2.653, p=0.034) was significantly higher in areas far from the road edge than those adjacent to the road edge. Also, height of woody growth forms on Hoima-Kaiso road (F=2.516, p=0.047) was significantly higher in areas far from the road edge than those adjacent to the road edge. However, species richness and diversity did not vary significantly with distance from the road edge in all the three study roads. It is therefore recommended that road constructions should as much as possible avoid traversing natural plant communities. In case this is not possible, they should adopt a design that minimizes impact on the adjacent vegetation.