Phytolith evidence for large-scale climatic change in small-scale hunter-gatherer sites of the middle archaic period, eastern USA

The capacity of phytoliths to identify grasses in the fossil record has resulted in greater advances and applications than that occurring in areas where non-grass taxa are important. The eastern temperate forest region of the United States provides an example. Reference taxonomies are few and far from comprehensive. Phytolith studies in regional paleoecology and archaeology were likewise rare until recently. Interest in phytolith analysis has increased in response to the need for a durable and reliable source of evidence in this region where preserved pollen and macroremains are rarely preserved in archaeological sites. Recently requests for phytolith analysis of two archaeological sites exposed a paradoxical result. Grass phytoliths, a small percent of the assemblages in areas of forest dominance, marked microecological disturbances caused by the presence of small hunter-gatherer campsites which provided insights into aspects of the regional macroecology. Local patterns of change in grass subfamily represented by small grass phytolith populations appear to have exposed a period of widespread regional warming which is not necessarily found in regional pollen data. Explanations for why pollen and phytoliths arrived at "different" climatic data involve differences in scale, taxonomy and taphonomy in the two systems, not problems of error or bias in either system. Reconciliation of the data demonstrates the importance of (1.) developing a comprehensive phytolith taxonomy for the region to further enhance the study of ecological history, and (2.) using both pollen and phytolith analysis as powerful, complementary partners in paleoecological investigations.