Palaeo Environmental Reconstruction of Holocene Vegetation in East Turkana, Kenya

Abstract

This study demonstrates the importance of phytolith proxy in reconstructing vegetation history and understanding human and climate impact on vegetation changes. Phytoliths are plant silica that preserves for a long period of time, even if plants are dead. The study was conducted in two regions, Ileret and Karari in East Turkana. The main objective of this study was to understand how vegetation cover changes and the key drivers contributing to these changes. The study specifically aimed to understand the correlation between phytolith assemblages and the above- ground vegetation cover and to explain the impact of humans and climate on vegetation cover changes. The study was guided by two theories, cultural ecology and climate variability theory. Plant species from inside and outside (transects) abandoned bomas were identified, tallied and recorded to understand the plant diversity and abundance. Soil samples were collected from recently abandoned bomas and from different unoccupied habitats (riverine, grasslands, bushlands, and shrublands). Also, dung (donkeys, sheep, goat, and cattle) was collected from inside the boma to determine their biased phytolith input against outside boma. In addition, sediment samples were collected from Early and Mid-Holocene sites to compare and reconstruct the vegetation history between the modern landscape and the Holocene period. Little is known about how human and climate variability influenced the vegetation cover in the region. The vegetation was classified as woody, grasslands, or mixed. Phytoliths were categorised as grass short-cell phytoliths, herbaceous phytoliths, and woody dicot phytoliths. This classification was based on the International Code of Nomenclature and available literature. The phytoliths data were plotted in R-script for vegetation data, and modern phytoliths from dung and soil. Fossil phytoliths were plotted in TILIA diagrams to understand the vegetation change between the Early and Mid-Holocene period. This study results indicate that phytoliths from current soil samples correlate with the above-ground vegetation composition. In reconstructing palaeoenvironment through phytolith analysis indicated that vegetation cover is dominated by herbs and grasses. Phytolith indices like the Aridity index indicate arid conditions in modern and Holocene landscapes while Dicotyledon versus Poaceae suggests herbaceous grassland mixed with woody. The modern and fossil phytoliths can accurately predict past vegetation cover, especially in classifying different habitats such as grasslands, wooded grasslands, and wooded vegetation.