Prediction of Osyris lanceolata (Hochst. Steud.) site suitability using indicator plant species and edaphic factors in humid highland and dry lowland forests in Kenya

摘要

Osyris lanceolata (African Sandalwood) belongs to the family Santalaceae that hosts some of the most valuable species for perfumery oil extraction. In India and Australia, Santalum album and Santalum spicatum are well developed for perfumery oil extraction through establishment of commercial plantations. In Africa, O. lanceolata has attracted significant attention as potential perfumery oils extraction species. However, African Sandalwood exploitation is through unsustainable smuggling from natural forests and woodlands. Since sustainable production of O. lanceolata oils is only feasible through establishment of commercial plantations, there is need to understand ecological requirements of the species before the remaining natural stands disappear. The aim of this study was to determine plant species and edaphic factors that can predict African Sandalwood site suitability for domestication programs. Sample plots with and without O. lanceolata were selected from natural stands in a humid highland forest and a dry lowland forest, vegetation sampled using nested-intensity plots and soils sampled in the plots simultaneously. Vegetation data was recorded according to species abundance. Soil samples were analyzed for nutrients, texture and moisture retention. Canonical Correspondence Analysis using CANOCO software was used to determine species association and relationship between species to soil variables. In the highland forest, O. lanceolata clustered with Rhus natalensis and six other species, and was correlated to soil nitrogen, moisture and clay. In lowland forest, O. lanceolata clustered with R. natalensis and Hypoestes forskahlii but did not correlate with any of the soil variables. The clustering of African Sandalwood with R. natalensis in both forest types suggests strong predictive capacity of R. natalensis for O. lanceolata site suitability in humid and dry areas. Inconsistence of O. lanceolata relationship with soil variables in the two study sites provides opportunity for further studies in different soil types.