People, Plants, and Pastures: A Multi-Proxy Approach to Understanding Human-Environment Relationships in Holocene South Arabia
Pastoralism is a social and economic activity that has shaped the landscape in South Arabia for thousands of years. Pastoralists adapt to environmental change through opportunism, evident in strategies of shifting their herd compositions and mobility both spatially and topographically, which in turn drives further landscape change. Throughout the Holocene, the climate in South Arabia has varied from cool and moist, to subtropical, to arid desert, a result of modulation of the Intertropical Convergence Zone (ITCZ) tied to a major source of precipitation, the Indian Ocean Monsoon. In order to reconstruct pastoral activity, this study focuses on a set of microfossils; phytoliths, spherulites, and diatoms, derived from bulk soil sediments. I expected that pastoral activities have a significant relationship with soil health, and therefore, used diatoms as a proxy metric for the impact of pastoralism on soils. I measured diatom diversity and density with respect to time, context, and site, to examine the relationship between diatoms and environmental change. We also derived spherulite width and density from dung mat samples and analyzed the results by time and site. None of these aforementioned variables displayed any significant relationships in quantitative analyses (univariate - Kruskal-Wallis tests), suggesting that some untested factor may be the most important control on soil health in these sites. Additionally, there was no significant relationship between the percent grasses in phytolith assemblages (an indicator of grazers) and density of aerophilous diatoms (an indicator of soil health), suggesting other studies of cattle corral residues are not comparable to those in South Arabia. This study supports the presence of a pastoral microclimate emergent with social processes.
Simpson, Neel, "People, Plants, and Pastures: A Multi-Proxy Approach to Understanding Human-Environment Relationships in Holocene South Arabia" (2022). Geology Senior Theses. William & Mary. Paper 37.