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The Science Behind 4FRI: Forest Restoration In Arizona

forest trees
Andrew Bernier/KJZZ
file | staff
A test plot studying forest thinning and its ecological effects in northern Arizona in 2015.

While held up by politics and economics, the nation’s largest forest thinning project is founded on partnerships and sound science. Even though it is well behind schedule, restoration of southwestern forests may be one of the region's smartest investments.

Northwest of Flagstaff, Tayloe Dubay of Northern Arizona University’s Ecological Restoration Institute (ERI), is at a test plot studying forest thinning and its ecological effects. Surrounded by a control area of small trees, towering ponderosas stand alone in open grasses.

“I think the oldest dated tree here goes back to 1555," said Dubay. "About 350 is the average. We’re able to measure an increase in resin production. Which helps them protect against bark beetle invasion.”

The trees are oozing with sap. There's no evidence of bark beetles that has marred other parts of the neighboring forest. Dubay continues with more benefits found from the testing.

“Fire helps with soil regeneration and the positive effects of nitrates," Dubay said. "If you look here at the amount of lupin and other wildflowers, this is the burned and thinned.”

 The cut and burned plots showcase  a great diversity of flowers, supporting more insects and pollinators in contrast to the control area where small trees rob sunlight and water. At ERI, Wally Covington describes what forests in Arizona used to look like.

“What you see is open park-like stands, dominated by old growth trees with a lush understory of grasses, wildflowers and shrubs that were maintained in that condition by natural, frequently occurring, low surface fires,” said Covington.

Diane Vosick, also with ERI, describes what changed. “When Smokey Bear took fire out of the system, we lost our biggest predator in terms of dealing with small trees, which was fire,” said Vosick.

Vosick is also co-chair of the Four Forest Restoration Initiative (4FRI), which is attempting to thin 2.4 million acres of Arizona forests that have grown 10 to 30 times their normal density. Covington said when the small trees are removed, the difference is immediate.

“The canopies just look healthier. And immediately post burn you see increases in ammonium and nitrate, increases in phosphorus availability, potassium availability, and water availability,” said Covington.

Those increased elements lead to more nutrition. Grass after burning has near 14 percent protein content, whereas before is only 6 percent, making a more nutritious landscape for diverse wildlife. But mega-fires scorch soil, diminishing quality. Vosick says adding water after a major burn leads to erosion, so watershed management is just as critical as cutting and burning.

“It’s not just about trees. It has a focus on the restoration of springs, and seeps, and riparian areas. There will be roads ripped as a result of it,” said Vosick.

Those forest roads reroute water flow, altering not just the limited rainfall in the region, but displacing soil, making it even more difficult for trees to regrow.

“The worst outcome ecologically is when you lose the soil base," said Covington. "Soils build up over ten thousands of years. Houses can be rebuilt in years. So when you look at it from a social-ecological perspective, save human lives, save infrastructure, save critical wildlife habitat but pay attention to the watersheds.”

While fires directly impact the lives of those who live in these forests, Dick Fleishman with the U.S. Forest Service points out it also directly impacts people in the Phoenix area.

“Almost all the water for the city of Phoenix is produced up here. So, having a healthy forest and a healthy watershed directly affects the people in the valley,” Fleishman said.

For the first time, firefighting is now over half the Forest Service’s budget. Last month, it shifted a quarter billion dollars from regular activities to help replenish their $1 billion fire budget. This forces 4FRI to become dependent on private contractors for thinning. But now, removing small trees and not large ones, Fleishman said the timber industry will have to get creative to make a profit.

“They can’t just make board out of it, they got to do a whole bunch of different products, soil amendments, pellets, energy," said Fleishman. "The needles, the limbs, everything, the bark, decorative bark actually has value.”

The selective cutting of small trees to recreate landscape patterns is time consuming, but mixing canopy densities with meadows increases fire resistance and species habitat. And with strategic placement of treatments, it may be 35 years until Arizona returns to manageable wildfires and restore what healthy Southwest forests should look like.

Andrew Bernier was a senior field correspondent at KJZZ from 2014 to 2016.