Fire, climate change, and forest resilience in interior alaska1

In the boreal forests of interior Alaska, feedbacks that link forest soils, fire characteristics, and plant traits havesupported stable cycles of forest succession for the past 6000 years. This high resilience of forest stands to fire disturbanceis supported by two interrelated feedback cycles: (i) interactions among disturbance regime and plant-soil-microbial feedbacks that regulate soil organic layer thickness and the cycling of energy and materials, and (ii) interactions among soil conditions, plant regeneration traits, and plant effects on the environment that maintain stable cycles of forest community composition. Unusual fire events can disrupt these cycles and trigger a regime shift of forest stands from one stability domain to another (e.g., from conifer to deciduous forest dominance). This may lead to abrupt shifts in forest cover in response to changing climate and fire regime, particularly at sites with intermediate levels of moisture availability where stand-scale feedback cycles are only weakly constrained by environmental conditions. However, the loss of resilience in individual stands may foster resilience at the landscape scale, if changes in the landscape configuration of forest cover types feedback to stabilize regional patterns of fire behavior and climate conditions.