Rapid climate change over the past century has altered the interrelationships among physical, biological and social drivers to influence the regional system of interior Alaska. The boreal forest is experiencing among the fastest rates of warming on Earth, leading to significant climate feedbacks resulting from landform changes and associated atmospheric carbon(C), water and energy exchanges. These feedbacks are of global significance because the boreal forest covers 12 million km² of the Northern Hemisphere and contains a massive pool of soil C which is vulnerable to atmospheric exchange. 

Climate warming has radically changed the dynamics of and interaction among disturbance regimes, notably fire size and severity, surface hydrology and rates of permafrost thaw, and the outbreak behavior of insects and pathogens, resulting in threshold shifts in biogeochemical cycling, successional trajectories, and ecosystem and landscape function. BNZ scientists have documented an increase in fire severity brought on by climate warming that will likely shift the Alaskan boreal forest from a spruce- to a broadleaf-dominated landscape. Fire effect on soil organic layer depths is a key factor that can disrupt stable patterns of conifer dominance. Severe fires consume much of the soil organic layer, which allows deciduous tree species such as aspen and birch to establish at high densities. Because initial post-fire succession sets the stage for decades to centuries of plant succession, changes in seedbed conditions caused by a severe fire can catalyze a switch from conifer dominance to alternate plant successional trajectories dominated by deciduous trees (Fig 1.).

BNZ scientists have discovered that permafrost thaw is causing the rapid decomposition of frozen organic carbon that has accumulated over thousands of years in boreal forest soils (Fig 2.).  BNZ scientists have also discovered that the snow free season in Alaska’s boreal forest is lengthening, which will likely speed the rate of warming by increasing the amount of light energy absorbed by the land surface. Field measurements have shown positive responses of plant C uptake to climate warming may be offset by greater respiratory losses of the old soil C in previously frozen soils.  When scaled across the entire permafrost zone, it appears that potential C losses in the form of CO₂ and methane from permafrost thaw could become an important biospheric source of C from terrestrial ecosystems to the atmosphere. In addition, modeling simulations over boreal Alaska have documented changes in albedo due to changes in the duration of the snow season and changes in the amount of young forest stands on a landscape due to changes in the fire regime. The sum of these feedbacks indicates that changes in boreal Alaska have recently, and will continue to warm the atmosphere.

Changes in climate and fire regime are also affecting rural Alaskan communities where indigenous people have historically led a subsistence lifestyle as hunters, fishers, and gatherers (Fig 3.). Warming has changed the timing of freeze up and melting of rivers and reduced the thickness of river ice, reducing the safety of winter travel and access to some hunting grounds.  Lower river levels reduce opportunities for barge delivery of fuel and increase the cost of living and the dependence on subsistence harvesting. Wildfire is a risk to life and property, reduces access to the land, threatens cultural and historic resources, and reduces moose and caribou abundances for one to several decades. Sources of resilience to address these changes include local residents’ intimate knowledge of village homelands, oral traditions transmitted by community elders and traditional sharing networks that maintain community identity while sustaining food supplies to the most vulnerable households and allowing hun...

Please report errors in award information by writing to: awardsearch@nsf.gov.