Hydrological Response of Bamboo Plantations on Soil–Water Dynamics in Humid and Semi-Arid Coastal Region of Kenya

Abstract

Soils and water are major resources that drive a country’s economy, and therefore should be conserved and utilized sustainably. However, in Kenya, these two resources are facing huge depletion and degradation due to anthropogenic factors and climate change. Bamboo species, especially on large plantations, can significantly alter ecological, hydrological, and biogeochemical processes in the long term. This study aimed to evaluate the effects of different species of bamboo and tree plantations on important soil–water processes like infiltration, bulk density, runoff, and soil loss in Kenya. The research was conducted at two sites (Gede in Arabuko Sokoke forest and at Baolala, in Kilifi County) managed by the Kenya Forestry Research Institute (KEFRI). The Arabuko Sokoke forest has a hot–humid coastal climate, while Baolala is a hot semi-arid area with little precipitation. The study involved measurement of soil–water infiltration rates using infiltrometers, installing runoff plots to quantify surface runoff and sediment loss, and analyzing soil properties like bulk density for growing periods for different bamboo and tree species. At the Gede forest site, the 30-year-old Thyrsostachys siamensis and Bambusa bambos plantations recorded the highest infiltration rates. Mature bamboo plantations of T. siamensis and B. bambos recorded higher infiltration rates compared to mature plantations of E. camaldulensis and G. arborea. It was observed that the bamboo plantations manifested lower soil bulk density compared to bare land, which recorded the highest bulk density. At Boalala, infiltration rates were significantly higher in the bamboo species compared to grassland and bare land. The painted bamboo (B. vulgaris vittata) had a slightly higher water infiltration rate compared to B. vulgaris. Runoff and erosion patterns reinforced the benefits of more mature bamboo plantations as well. There was a significant correlation between amount of runoff and collected soil loss through erosion. The data showed reductions in surface runoff volumes and sediment loss as the bamboo plantations aged compared to younger species. Therefore, by enhancing infiltration and reducing runoff and erosion, well-managed bamboo plantations can protect valuable soil resources, improve water recharge, and support sustainable land use over the long term. In conclusion, this study showed the strong potential of bamboo as a soil and water conservation tool in Kenya.