NAU researchers are discovering carbon accounting strategies may be doing harm to the environment.

Thomas Kolb, Matthew Hurteau and Alex Finkral have been working on different projects, all developing a method for carbon accounting in forests and researching the input and output of carbon with the goal of reducing catastrophic wildfires.

Peter Fule, associate professor at the school of forestry and associate director of the Ecological Restoration Institute, said forests store carbon. 

“People originally believed that the more dense the forest, the better for carbon storage, so people would plant more trees,” Fule said. “However, in the case of our Southwest forest, which is more dense today than ever from a carbon point of view, we’re storing more carbon in the ground and the problem is the forests are vulnerable to loss of large areas of trees in the case of a fire.”

Matthew Hurteau, a research associate in NAU’s Merriam Powell Center for Environmental Research, said the increase of the stock of carbon growing in the forest becomes a problem in the dry forests in Flagstaff. 

“By having more trees in the landscape, in the forest system that used to burn, when you add more trees you get more fire and release a lot of carbon in the atmosphere,” Hurteau said. “If you include fire emissions in the release of the carbon in the atmosphere, we would be better served. It would be good to reduce the number of trees.” 

Hurteau said reducing fire severity is the message of his work. 

“We want to manage our forests with a scientific understanding and look at carbon storage and the services that forests provide,” Hurteau said.

“Nowadays, when the forest is more dense, we have bigger fires that kill more trees, and carbon is released into the atmosphere,” Fule said. “These changes in the forest are actually more vulnerable to loss and we damage the ecosystem with large fires.”

Hurteau has done research in California to find out more about thinning forests.

“My research has found that we need to manage fire-prone forests,” Hurteau said. “What we want to do is restore forest structure. When we have fewer trees, there is a lower density and we can consolidate carbon better when the forest is less dense. Carbon sequestered is more permanent in more dense areas than with a small density of trees.”

Fule said NAU has been researching the effects of thinning forests for 15 to 20 years. 

“We were first to pioneer this research,” Fule said. “We began looking at effects with forest structure and past patterns of fires. We want to thin the larger trees and reintroduce fire so it burns fuel in a safe way. We need to budget where the carbon goes to help manage the forests.”

Kolb, principal investigator for the NAU Carbon Flux Research, has been studying the amount of carbon absorbed from the atmosphere. Their research is focused on three plots of land: undisturbed forest, which has never been burned; ponderosa forest, thinned to reduce fuels; and once-thick forest, which was burned in 1996 by the Horseshoe forest and is reduced to a grassland.

“We have been measuring ecosystem levels of exchange for the last three years using complex instruments on towers built up to the treetops in the forests,” Kolb said. “We have also measured the exchange of water from land to atmosphere.”

Kolb’s studies concluded that the fire grassland is still releasing carbon.

“Twelve years after the fire, photosynthesis is lower than the respiration due to the decomposition of the trees,” Kolb said. “We found that thinning decreased the ability for the forest to take in and store carbon. We are focusing on how quickly the thin site recovers. We know that after thinning, the trees grow faster and take in more carbon. 

“We will continue to measure the sites and learn if the decrease of carbon is short term or if it will persist.”