The effect of invasive species lantana camara on soil chemistry at Ol- Donyo Sabuk National Park, Kenya.
Wekhanya, Marystella Nango’ni
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Invasive species are a major ecological and management concern in natural ecosystems and pose a threat to many of Kenya’s protected areas. Invasive plant species compete and hybridize with native species often to the disadvantage of the native species. Invasion can lead to the phasing out of native species and loss of ecosystem services such as water filtration, soil stabilization, and pest control. They may also result in reduction of wildlife forage or death of animals when they feed on poisonous invasive plant species. Invasion of native plant habitats by invasive plants can drastically change soil chemical properties such as pH, mineral composition and mineral levels. The aim of this study was to establish whether the invasive plant Lantana camara L. alters the soil chemical properties at Ol-Donyo Sabuk National Park. The key objective was to evaluate the soil nutrient composition in areas invaded by Lantana camara L. and how these differ from areas without Lantana camara. Five study sites were selected by purposeful sampling out of the existing 10 blocks. Soil samples were collected randomly from L. camara invaded areas and similarly from adjacent areas free from L. camara. The soil samples were collected during the wet season (November-December, 2014) and during the dry season (January-March, 2015). The soil samples were analysed for the following nutrients and parameters: pH, potassium (K), calcium (Ca) magnesium (Mg), total nitrogen (N), phosphorous (P), total organic carbon, manganese (Mn), copper (Cu), iron (Fe), zinc (Zn), sodium (Na) and texture. The data obtained was analysed using Two-way ANOVA test to determine difference in nutrients composition in Lantana invaded and non-invaded areas. Three-way ANOVA test was also used to determine the interactions between wet and dry season, invaded and non-invaded areas and the study sites. A post-ANOVA test, Tukey's Honest Significant Difference was done to separate the means. The analysed results were presented in graphs and descriptive tables. Results from the study indicated Lantana invaded areas had an increase in pH value (invaded 6.88, non-invaded 6.30), P (invaded 20.76, non-invaded 18.81), N (invaded 0.36, non-invaded 0.18), Mn (invaded 1.03, non-invaded 0.84), Fe (invaded 24.97, non-invaded 17.72) and total organic carbon (invaded 1.73, non-invaded 1.72) compared to the patches with native plant species. During both wet and dry seasons Lantana invaded areas had an increase in pH value (dry-invaded 6.88, non-invaded 6.30; wet-invaded 6.48, non-invaded 6.30), P (dry-invaded 20.76, non-invaded 18.81; wet-invaded-21.11, non-invaded 18.81)) and Mn (dry-invaded 1.03, non-invaded 0.84; wet-invaded 0.94, non-invaded 0.77) compared to non-invaded areas. Most nutrient levels were found to be higher during the wet season compared to the dry season which could be attributed to high pH and accelerated Lantana biomass litter decomposition. High pH also makes P to be more available to plants that is why P was high in the L. camara invaded areas. The soil texture was almost the same in Lantana invaded and non-invaded areas. This study has revealed that Lantana camara remarkably changes the soil nutrient levels leading to changes in soil chemistry of invaded areas. This is in a bid to suit its survival to the detriment of the native plants. This study is hence vital for designing an effective eradication and preventive strategy of Lantana in Ol-Donyo Sabuk National Park and in other protected ecological habitats in Kenya.