Recovery uncertain in vast swaths of piñon pine forests
By Bob Berwyn
SUMMIT COUNTY — Recent research suggests that most beetle-hit lodgepole pine forests are recovering about as expected. But other Colorado forest types have been also suffered the effects of drought and insect infestation — and the outlook for recovery is not as clear.
Across much of the West Slope and especially in the Four Corners region, the tiny ips beetle struck after piñon-juniper woodlands were left dessicated by the early 2000s drought. Within just a couple of years, by 2004, up to 80 percent of the mature piñons in the hardest hit areas were dead, and U.S. Forest Service researchers say some of those areas show little signs of regrowth.
“In lower elevation places with less moisture, there’s not much regeneration because the forest lost a lot of seed stock,” said Tom Mask, a Gunnison-based Forest Service entomologist who studied the ips beetle outbreak.
It’s unclear when — or if — piñons will make a comeback in those drier lowlands, Mask said, adding that agency’s budget hasn’t enabled researchers to closely monitor the recovery of the Southwest’s iconic forests.
Regeneration depends on several factors, as birds move the seeds around, creating caches that can sprout into new stands, given enough moisture. And it partly depends on what kind of seed source was there to begin with, Mask said.
Independently, University of Colorado researcher Miranda Redmond reached similar conclusions as she investigated the impacts of climate change on piñon pines. In that context, Redmond said she found that regeneration depended on site-specific factors.
“In area with really high mortality, there’s not much regeneration. In areas with low mortality, we saw more … especially where there is good shrub cover, with a shading effect,” Redmond said. Those areas may have more organic matter in the soil, which holds moisture better than the dry mineral dust of most desert soils.
“To regenerate pinon, all the stars have to line up, they sprout if they have enough moisture … it’s kind of an involved process to get regeneration,” said Tom Eager, another Gunnison-based Forest Service researcher who worked with Mask on studying the ips beetle invasion.
And Redmond’s research indicated that warming temperatures at higher elevations may be inhibiting seed formation, which is spurred, she believes, by the onset of cool weather in the late summer. As the climate regime in the Southwest changes, those cold snaps are becoming less frequent, resulting in less piñon regeneration.
In the lower elevations, piñon forests are also affected by the continuing practice of clearing trees for livestock grazing.
The intense and extensive ips beetle outbreak sparked concerns at the time. But the bark beetle epidemic in lodgepoles was also starting to peak, affecting more densely populated regions, as well as critical watersheds and areas with high-value recreation developments, so the vast reaches of piñon-jumiper became Colorado’s forgotten forest.
The mountain pine beetle outbreak was tracked and mapped acre by acre; politicians banged their drums to demand funding for forest treatments, and the Forest Service established a high-level task force to tackle the outbreak. By contrast, it’s hard to get a good sense of the total acreage affected by ips beetles — even though piñon-juniper is the largest forest type (about 5.5 million acres) in Colorado.
The most recent information provided by the Forest Service dates back to the mid-2000s and indicates that ips beetles killed slightly more than 2 million acres of piñon-juniper in Colorado alone, with additional acreage affected in New Mexico, Utah, Arizona and even as far west as Nevada.
CSU professor Bill Jacobi estimated a similar mortality after doing some research in the area. Overall, ips beetles may have killed 30 percent of all the piñon pines in the Four Corners region, he said.
“We have good data from pre-ips beetle era … from 20 years ago, so we can go back and compare, but it’s important to remember that we’re in whole different precipitation and temperature mode. The past 10 years much hotter and drier,” he said. “We don’t know what really should be normal in terms of regrowth.
“In a lot of these areas, juniper become dominant. whether that’s good or bad depends on whether you use pinon or juniper as an animal,” he added.Related articles
- Study: Colorado forests not doomed (summitcountyvoice.com)
- Study: Global warming reduces piñon pine seed formation (summitcountyvoice.com)
- Climate: NASA satellites see thinning forest cover (summitcountyvoice.com)
- Colorado: Pine beetle epidemic wanes (summitcountyvoice.com)
- Pointing the way to pine beetle control, but at what cost? (summitcountyvoice.com)
- The beetle beat goes on in the Black Hills, with 11,000 new acres hit (rapidcityjournal.com)