“The recent several decades of wildfires are changing the boreal forest from a weak carbon sink – that is the forest and soil are accumulating carbon and helping offset rising atmospheric carbon dioxide concentration – to a weak carbon source,” Stith Gower of the University of Wisconsin told environmentalresearchweb. “The implications are that wildfire management may help offset rising atmospheric carbon dioxide concentrations, and climate change does not appear to have a large positive effect on carbon storage.”

Gower and colleagues used the Biome-BGC process model to simulate what is happening in the Boreal Ecosystem-Atmosphere Study (BOREAS) region, which at 1000 km × 1000 km makes up 15–20% of the North American boreal forest.

“To pursue the question of quantifying the boreal forest carbon budget, we established a chronosequence – a series of stands that are presumably identical with the exception of time since last disturbance – in essence we trade space for time,” says Gower. “We quantified the major carbon pools and fluxes and then used these data to verify an ecosystem process model, which we used to simulate carbon dynamics for the entire landscape. This is a very common scaling approach in ecosystem ecology.”

Boreal forest in the area is dominated by three types of vegetation – the black spruce (Picea mariana), which is coniferous, the deciduous trembling aspen (Populus tremuloides Michx.) and bryophytes (mosses). The larger, more frequent, wildfires occurring in the late 20th century increased the abundance of deciduous trees and mosses in the forest at the expense of coniferous trees.

“My lab [will] continue to examine how future climate change and wildfire may continue to affect the boreal forest carbon balance,” said Gower. “I have a co-funded – US Department of Energy and Manitoba Hydro – experimental warming study where we are heating the soil and air inside large chambers to simulate the climate 50 years from now to better quantify the effects of climate warming on boreal forest carbon budgets. We are also pursuing additional funds to forecast the effects of climate change on wildfire dynamics, and their effects on boreal forest carbon balance.”

The researchers reported their work in Nature.