Exeter in the Amazon
The PAST team presented research from across the Amazon at the EIAA IV in Trinidad Bolivia.
Iriarte, Hilbert, De Souza, Alves, Gonda, and Robinson showcased recent discoveries, analysis, and interpretations.
Abstracts are available through the conference website http://www.4eiaa.com.
Terrestrial soil profiles provide local, fine-scale resolution evidence of vegetation and fire history as well as evidence for human modification. In each of the study areas we open test units to collect samples for phytolith, charcoal and soil organic matter analysis, and for the analysis of carbon isotopes and soil geochemistry. We use the column sampling method to collect samples at 5 cm intervals from the soil profiles.
Because of the lack of nearby lakes in many ‘terra firme’ settings, such as the geoglyphs region, these soil profiles often provide the only evidence of human disturbance outside of the archaeological sites. When lakes are present, however, the higher temporal resolution of lake sediments, with their more regional signature, can be used to complement the local data from the test units.
To characterise and quantify the extent of pre-Columbian human-modified forests we use multi-scale remote sensing information from a number of sources. We work closely with the INPE (National Institute for Space Research of Brazil). We fly a drone mounted with a high resolution multi-spectral and Light Detection and Ranging (LIDAR) sensors over our study areas; we also analyse high spatial resolution Landsat data (30m spatial resolution), as well as high temporal resolution Moderate Resolution Imaging Spectroradiameter (MODIS) data (250-500m spatial resolution).
These remote sensing data, applied for the first time in Amazonia, will provide unique, very high resolution information which will be crucial for understanding the extent of anthropogenic disturbance. At the same time, we have the opportunity to test the LIDAR technology itself and its efficacy in discovering archaeological earthworks below the tropical canopy. Although ground verification will continue to be necessary, the vegetation-removal algorithms of the LIDAR sensors can replace traditional, slow and difficult settlement mapping in tropical rainforest environments. LIDAR technology thus has the capacity to revolutionise Amazonian archaeology.
Palaeoecology from lake sediments
In order to compare archaeological and palaeoecological data, we collect samples from small and large lake basins close to the archaeological sites. In this way we investigate the impacts on the ecosystem of these different cultures, for example through deforestation or burning, as well as their land use activities such as agriculture. We apply a multiproxy analysis using pollen, phytoliths, charcoal, macrofossils and XRF scanning techniques to obtain a high-resolution, radiocarbon-dated record of environmental change and land use across the selected study regions, at a local, regional, and landscape scale.
Modern forest inventories combined with remote sensing data allow us to reconstruct the vegetation and fire histories of our study areas. In this way we can assess the long-term impacts of pre-Columbian land-use and determine whether modern forest structure and composition correlates with the palaeoecological evidence for historical disturbance. In each vegetation plot we measure and identify all plant species with a diameter greater than 10 cm at breast height (DBH), paying special attention to plants of economic importance based on previous ethnobotanical works and inventories of anthropogenic forest. Extant floristic inventories for the selected archaeological regions (eg RAINFOR-Amazon Forest Inventory Network, INPA-PPBio) will also be incorporated into the study.
Archaeobotanical remains help us to reconstruct past vegetation and the ways in which humans interacted with their environment. We analyse phytolith, starch-grain and macrobotanical samples from selected archaeological contexts, including: i) archaeological features, for example habitation floors, midden refuse areas and funerary urns; ii) column samples from exposed excavation profiles; iii) residues extracted from plant-processing tools and containers recovered during excavations, such as plant grinding stones, stone grater teeth, ceramic containers and colanders. The archaeobotanical assemblages will be checked against the University of Exeter’s reference collection, which consists of over 500 modern plant specimens and is the largest Neotropical collection in Europe.