Phytoliths in the Flora of Ecuador: Methodology for Paleoenvironmental Reconstruction

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With National Science Foundation support, Dr. Deborah Pearsall and her students will construct diagnostic phytolith profiles for a variety of present day Equadorian vegetation communities. `Phytoliths` are microscopic silica forms which are produced by plants and which are eventually incorporated into the soil. Although a single species produces more than one phytolith form and few forms are unique to any single species, through analysis of phytolith assemblages preserved in the ground, it is often possible to identify the plants which were present. Phytolith analysis therefore constitutes an important tool for environmental reconstruction. For many years archaeologists have worked in Equador and attempted to understand how complex societies arose in this region. The country varies ecologically from the better watered Northern to drier Southern coast. From West to East vegetation zones change from arid coastline across the Andes to tropical Amazonian rainforest. Paleoecologists know that these zones shifted significantly in response to past climate changes and archaeologists wish to understand cultural change in relation to these natural phenomena. Dr. Pearsall's research will provide data to assist in this process. She and her students will establish two transects across Equador, one running North-South, the other East-West. Through analysis of already collected specimens as well as additional fieldwork they will define phytolith assemblages which correlate with specific environments and note the most important indicator types. On this basis it will then be possible to extract phytolith assemblages from old soils and reconstruct paleoenvironments. This work is important for several reasons. It will help to establish an environmental context to understand cultural change. It will also shed new light on long term human impact on the environment. Ecologists are uncertain about how humans who functioned prehistorically at technologically simple levels affected their surroundings. To what extent were rainforest boundaries and plant communities influenced by small scale slash and burn agriculture? The data collected during this research will shed new light on this question. It will also establish a data base which will be widely used by archaeologists and natural scientists.