Investigating plant-soil-water relationships in western juniper (Juniperus occidentalis) woodlands
The connections between upland water sources, groundwater, and downstream valleys influence the amount of water available to multiple ecohydrologic processes that drive many ecosystem services (e.g., forage and water provisioning, water quality, wildlife habitat, recreation, etc.).
Our long-term ongoing research study in central Oregon has provided critical information regarding vegetation and hydrology interactions in western juniper dominated landscapes.
Project objectives are:
1) Characterize water-plant-soil interactions occurring in previously treated (juniper removed) and untreated watersheds,
2) Determine hydrologic connectivity between upland watersheds and downstream valleys, and;
3) Determine juniper reestablishment effects on ecological and hydrological function ten years after treatment.
Various instrumentation including weather stations, flumes, groundwater wells, soil moisture, and tree transpiration sensors are being used to collect hydrological data.
- Nearly half (46%) of total annual precipitation is intercepted by juniper canopy cover.
- Greater streamflow and spring flow levels observed in the treated watershed.
- Seasonal soil moisture and aquifer recharge in response to winter precipitation and snowmelt runoff inputs.
- Greater grass (perennial and annual) and shrub cover observed in the treated watershed.
- Greater grass cover is positively correlated with changes in soil moisture, whereas juniper cover shows a negative correlation with soil moisture.
- Strong hydrologic connections between upland watersheds and the valley during the winter/spring season.
Peer-reviewed publications related to this project:
Ecology and Hydrology of Western Juniper - OSU Range Field Day 2016
The OSU Range Field day featured this 23-year research project being conducted in the heart of juniper country in central Oregon. The event that took place on 28 June 2016 at Brothers, OR included morning presentations on project research findings, followed by a tour to the paired-watershed study site.
This range field special report, which includes contributions from OSU and USDA-ARS researchers, illustrates some of the ecological and hydrological relationships found in western juniper woodlands of eastern Oregon.