Invasive Species Compendium

Detailed coverage of invasive species threatening livelihoods and the environment worldwide

Abstract

Spinescent East African savannah acacias also have thick bark, suggesting they evolved under both an intense fire and herbivory regime.

Abstract

This study was conducted to determine whether woodland Kenyan Acacia species have (i) relatively thin bark compared to local co-occurring thicket species and other African Acacia species; and (ii) a relatively strong degree of spinescence as would be predicted by resource trade-offs and the local dominance of either herbivory or fire. The study was conducted at Segera Ranch which is located in Laikipia-Sambura, Central Kenya. This savannah is dominated mainly by A. drepanolobium, especially on the black soil areas. The mean RBT of the five woodland acacia species (14%) is almost double that of thicket species (7%). The two non-woodland species, A. brevispica (thicket species) and A. mellifera (arid savannah), have low RBT (7%). There is a non-significant positive relationship between RBT and spinescence (r2 = 0.14). In conclusion, it is suggested that many of these East African Acacia species evolved in both a high fire and herbivory landscape. Possibly, this is due to favourable rainfall and nutrient conditions. It is further suggested that thicket encroachment is occurring due to a relative absence of intense fires which is facilitating the expansion of thinbarked broadleaved species.