2019 Update: Region-Wide Juniper Mortality in Southeastern Utah
Michael Stapleton, USU Forestry Extension Volunteer
In mid-2018, reports began to surface that juniper trees were dying in large numbers across southeastern Utah. Characterized by a pronounced yellowing of their needles, this colorful phenomenon proved to be quite a mystery. Why were juniper trees, a notoriously hardy species, suddenly dying?
Perhaps most vocal about this disturbance was Dr. Kay Shumway, a retired professor who began to notice the yellowing junipers in May of 2018. An avid nature photographer, Shumway collected drone footage of the die-off within San Juan County and posted it on social media. Alarmed by what he was seeing, Shumway also contacted land agencies across the region with first hand reports of the disturbance.
Dana Witwicki, Vegetation Ecologist with the National Park Service, was one such representative who picked up on Shumway’s message. Concerned with what was happening to woodlands within park boundaries and across the state, she requested formal assistance from the Forest Service’s Forest Health Protection team. This team of specialists provides technical assistance to other agencies across the region to, "...prevent, suppress and control outbreaks threatening forest resources.”
On November 28, 2018, the Forest Health Protection team embarked on a field trip to assess several affected sites northeast of Blanding and in the Cedar Mesa area. Accompanying them were roughly 20 resource specialists from state and federal land agencies, researchers from Utah State University, media representatives, Shumway, and several members of the public. Under the direction of Liz Hebertson, Lead Forest Health Protection Specialist, this coalition collected tissue samples from affected junipers, soil samples from below the junipers, and insect specimens from affected trees. On-site observations combined with reports from across the region, paints a picture of this disturbance:
Current juniper mortality occurs in patches across the region; yet there is no survey of the total area affected
- Pinyon mortality has also been observed
- Affected trees are characterized by yellow needles which turn brown and eventually fall off, however lower branches and roots seem less affected
- All ages seem to be impacted
- Tree mortality is limited at high elevations and within sparse woodlands at low elevations
- Not all impacted trees die; there is evidence of regrowth in some affected areas
- Secondary pests (such as round and flat-headed borers) are present in affected trees
- Similar disturbances have occurred - notably last year in southwestern Colorado
The specific cause of this disturbance is difficult to determine. Lisa Bryant, the Bureau of Land Management’s (BLM) Canyon Country District spokesperson, is cautious against drawing conclusions at this early stage as researchers “…we are still in the initial stages of observation.” Before any answers can be reached, soil samples must be analyzed and tissue and insect specimens must be tested for diseases. The BLM has also requested aerial imagery of the affected sites to accurately determine the range of the disturbance. The Forest Health Protection team will produce a final report in 2019 that will encompass results and conclusions from the field trip and lab tests. In the meantime, Colleen Keyes, Forest Health Coordinator for the Utah Division of Forestry, Fire and State Lands, expects that drought and secondary insects may be to blame for the disturbance. San Juan County is currently in the midst of a drought and 2018 was the hottest and driest year on record. In the 1980s and early 2000s, the region experienced similar disturbances following extensive dry periods. Certain characteristics of the stressed trees and the fact that multiple species of all ages are affected stands as further evidence of possible drought-induced mortality.
If the current disturbance is drought-induced, there may be some hope though, as Bryant explains, “…we’re better positioned moisture-wise this year.” A wet spring may help stressed woodlands rebound, as evidenced by a similar case in southwestern Colorado last year (https://the-journal.com/articles/111161). Despite this, the BLM emphasizes the importance of remaining vigilant during the upcoming season because a wet season can produce a surge of cheatgrass production which, when coupled with the increase in dead trees, may heighten the potential for wildfires. “We’re asking people to be fire-wise,” explains Bryant.
The Utah Forest News will keep you posted once the official Forest Health Protection report is published and will provide updates on changes in land management or treatment