Providing phytolith analysis since 2008, the extraction method we prefer minimizes damage to phytoliths to maximize data recovery. Sonication and excessive treatment with strong acids / alkalis can destroy specimens and dramatically alter assemblage data. These treatments aren’t necessary for US Midwest and Great Plains soils, and while minimal treatment may produce cluttered slides, the assemblage data are more consistent.
We emphasize interpreting phytoliths as assemblages, related to ecosystems, for the purpose of understanding land management and climate. Phytoliths only occasionally indicate individual species, and are more often indirect artifacts of human activity than direct ones. For example, in a landscape (or soil profile) one is very likely to encounter a change in phytolith assemblage resulting from precontact or post contact land management, but far less likely to encounter an individual phytolith that would be the result of something a person did there. Phytoliths are always present where phytolith-producing plants grow, regardless of human activity. Human activity can cause changes in assemblages through management, can cause things to be out of place through earth-moving, or can concentrate phytoliths through use of plants as textiles or foods.
A good result depends on:
- Experimental design – a sampling plan that can answer a research question.
- Context provided to the analyst (photos of profile and landscape, maps, sketches) and communication with analyst.
- Reference samples? If your research question involves determining whether something is different than the surroundings, you need at least one off-site sample.
The interpretation of assemblages to provide a useful set of data is entirely dependent upon these three things.