Researcher seeks juniper cores to reconstruct Crook County groundwater metal history

Danielle Cass, a visiting associate professor of chemistry at Reed College, asked Crook County landowners on June 25 for permission to take small cores from juniper trees so her team can test annual tree rings for metals and look for historical signals in local groundwater.

Cass told the Crook County Board of Commissioners that groundwater supplies everyday drinking water and that local well testing is episodic and does not give a long-term record. “What we can imagine is if we have a tree…they’re storing [metals] in little chunks, in an annual basis,” she said, describing “phyto‑monitoring,” the practice of using plants as historical environmental records.

Cass said junipers are a good candidate because they are abundant in the region and tend to take water from deeper soil horizons and groundwater. The method uses a pencil‑diameter coring tool at about waist height; researchers typically collect two cores from each tree so one core can be used for dating and the other for chemical analysis. Cass said published studies show coring does not harm trees when performed properly.

She described limited preliminary results from two short cores collected in October 2024 that extend back only to about 2015. Those small samples show differences between a valley site (Site 1) and a higher site (Site 2) for manganese and aluminum in some recent rings, including a rise around 2020–2022 and a drop in 2023–2024, but Cass emphasized the dataset is too small to draw conclusions. “I’m very, very much take this with a grain of salt…we need a lot more samples,” she said.

Cass said environmental factors such as drought or changes in groundwater level can affect uptake and ring width; the team plans to compare ring chemistry with local hydrologic records. She asked landowners with junipers or recently cut juniper logs to contact her via email, phone, or the project form; she also said the team can collect well water samples to strengthen correlations. She added she will share results with the community when analyses are available.

No formal county action was taken; the presentation was a request for voluntary participation and for staff to help notify landowners.