Identifying Human and Climatic Influences on Ancient Plant Communities in Dhofar, Oman

Abstract

Through identifying changes in plant community changes over time, we can better understand how natural and anthropogenic processes affect vegetation. As climate changes, the natural environment and available resources for anthropogenic use are altered. Human responses to a changing environment include social changes like new settlement patterns or changing family sizes. Consequently, human resource use strategies adapt to these changes, which can have feedback effects on the natural environment. Anthropogenic influences and human presence in a landscape are identifiable through the variations of plants present, which we can measure using vegetation proxies. Our research uses plant fragments found within fossilized midden deposits of desert rock hyraxes (Procavia capensis) to study anthropogenic vegetation changes in Dhofar of Oman over the past 3,500 years BP. The hyrax is a small herbivore that grazes in close proximity to its den, so that hyrax middens reflect localized vegetation. From 45 middens samples, we extracted identifiable macrofossils. We used incident light microscopy and a digital camera to compare specimens with modern reference material. We relied on radiocarbon ages from 33 of the 45 middens to understand the temporal shifts of vegetation patterns. To grasp what past vegetation was present in the landscape, identified fragmented macrobotanicals were weighed and analyzed for the presence of 5 particular "indicator" species of anthropogenic activity. The "Indicatory Species Approach" identifies particular plant communities present indicative of human's presence in a landscape. Through statistical analysis, we recognized many distinct types and categories of species that provided quantifiable proxies of desert vegetation while we also analyzed the ability of the middens to capture anthropogenic activity. We conducted a canonical correspondence analysis (CCA) and detrended correspondence analysis (DCA) for 89 identifiable fossilized botanical species specimens in 45 different locations. The results from the DCA suggested that the vegetation developed as an adaptation to more arid climates. For the CCA, the variables, which are a) distance to human monuments and b) distance to freshwater, explained 26% of the species variation. This result suggested that plant assemblages are influenced by human pressures.