Shell Midden Archaeology and Maryland’s Plant Communities
Drawing on a variety of innovative technologies, an interdisciplinary team of archaeologists and biologists investigated how past Native American land use—documented by people’s food remains, ceramics, tools, and other materials deposited in archaeological sites—influenced soil conditions and plant communities today (Figure 1). We examined soils and plants on and off of shell middens, dense accumulations of oysters, bones, and artifacts, near the Rhode River. We excavated six shell middens, with a key part of our work using Accelerator Mass Spectrometry (AMS) radiocarbon dating to document the age of the sites. An oyster shell fragment, charred seed, or deer bone was used for AMS dating to build a site chronology, often with error rates of ~30-40 years.
Figure 1. 18AN308 is a ~3000 year old shell midden. The area harbors unique plant communities compared to adjacent off-site areas. After documenting the age and types of artifacts, shells and animal bones at the sites, we collected soils from shell middens and immediately adjacent (off-site) to the site. We focused on six archaeological sites that were AMS dated from 3000-200 years ago. Applying different technologies, we tested soil acidity, grain/particle size, and nutrients such as nitrogen and calcium. We found that midden soils, even those ~3000 years old, were greatly enriched in nitrates and calcium, with more neutral pH compared to the off-site soils. Plant communities were also significantly different, with shell midden soils supporting more plant species compared to areas immediately off-site, especially grasses and herbs. The shell middens also were more likely to host more native plants.
The use of innovative technologies like AMS radiocarbon dating and the analysis of soil chemistry/nutrients showed a correlation between Native American land use over hundreds or thousands of years and the abundance of native plants growing on a shell midden today. This knowledge is important for environmental managers seeking to understand future changes in plant and other communities in the wake of climate and other environmental change. This research also underscores the value of conserving and studying archaeological sites, the importance of using innovative technologies, and the need for interdisciplinary work integrating archaeology and biology.