Microscopic evidence in soil reveals forest garden's past

Through an innovative study published in Quaternary International, Indigenous Studies assistant professor Chelsey Geralda Armstrong and her research team examined soil phytoliths to understand the distant past of Lhemqwó:tel, a forest garden in Sts’ailes territory on the Harrison River. A collaborative effort among Sts'ailes community members and university researchers, Armstrong and her graduate student, SFU alumnus Levi Cormier (MSc, 2024), led the project.

Phytoliths are microscopic silica structures found in plants. After plants decompose, these structures are preserved in the soil. As some phytoliths have unique shapes (morphotypes), researchers can analyze phytoliths found in soil samples to identify the plants that once grew in an area.

Armstrong’s team established that phytoliths are well-preserved in forest soils in Lhemqwó:tel, challenging long-held assumptions that phytoliths don’t preserve in the Pacific Northwest. The researchers were also able to identify phytolith morphotypes for plants found in the region, demonstrating how phytoliths can be used as a reliable research tool.

By analyzing phytolith qualities in soil samples taken from deeper depths, the scientists found that Lhemqwó:tel was larger 1,400 years ago than it is today.

“Changes in specific phytolith types across soil layers suggest that open, managed forest-garden, and open meadow conditions once extended beyond the current boundaries,” explains Armstrong. “Today’s dense conifer forest appears to be a relatively recent regrowth following the imposition of reserve systems and other colonial land-use policies.”

The study shows how soil phytoliths can provide scientists with insight into an area’s past, even when archaeological features are not apparent on the surface. Soil phytoliths can help scientists understand how the land was stewarded by people in the past and to trace how land-use has changed over the course of time.