Archeobotanical study of traditional agroecosystems based on SEM-EDX analysis of buried phytoliths

Abstract

The FP7 Project "MEditerranean MOntainous LAndscapes: an historical approach to cultural heritage based on traditional agrosystems (MEMOLA)" (http://www.memolaproject.eu/it) is studying past landscapes using ancient soil horizons as archaeological records. The project aims at evaluating the biodiversity of no longer existing environments, in order to reconstruct the past agroecosystems. One of the approach used in the study consisted in the selective sampling of buried paleo-soil horizons for the search of “testimonials” or useful pedo-archaeological "indicators" that can tell something about past environments and peculiar ecosystems no longer present. To this purpose it was decided to start extracting from soil samples and studying the phytoliths. Phytoliths are produced in and between the cells of living plants. They consist of biogenic silica, also referred to as opal, namely a hydrated amorphous form of silica (SiO2.nH2O) formed by complex inorganic polymerization processes. Once the plant dies, phytoliths are released in the environment due to the decomposition of the organic matter. In general, phytoliths are not transported over long distances because they are relatively “heavy” particles (as opposed to pollen, for instance). Phytoliths can thus have taxonomical significance and be good indicators of past vegetation cover and environmental conditions, they can give evidence of paleoenvironment or vegetation change and represent a first step to explore the biodiversity of recent and past- environments. Phytoliths were documented by means of scanning electron microscopy (SEM) also embedded in the buried and carbonized plant micro-particles that were recovered during the soil sieving procedures.