"In interior Alaska black spruce forest succession and vegetation properties are tightly linked to fire disturbance, partly due to the functional properties of species. Climatically induced changes in the fire regime could negatively affect some functional groups and potentially lower the functional diversity of stands through changes in fire severity and site moisture. In addition, there is little information regarding the relationship between pre- and post-fire community composition in black spruce communities of interior Alaska. To contribute to our knowledge regarding post-fire plant community dynamics, I investigated how post-fire community properties in relation to fire severity and site moisture: 1) species composition, in which pre- and post- fire community composition was compared to determine changes in species richness and functional diversity and 2) the functional traits of species. Pre- fire species composition in black spruce forests was dominated by late successional understory species and was most similar in species composition to low severity burned sites (regardless of stand age). Site moisture did not appear to affect the change in species composition post-fire in the first two years following fire. Functional groups that showed significant changes post-fire were bryophytes, lichen and evergreen shrubs. When each species was deconstructed into a set of functional traits, I observed that these traits were tightly linked to fire severity. These results have large implications under projected climate scenarios that predict increasing fire extent and severity in the boreal forest because high severity fire changes the species composition and associated functional traits of black spruce post-fire communities in interior Alaska"--Leaf iii.

Black spruce (Picea mariana (Mill) B.S.P) is the dominant forest cover type in interior Alaska and is prone to frequent, stand-replacing wildfires. Through impacts on tree recruitment, the degree of fire consumption of soil organic layers can act as an important determinant of whether black spruce forests regenerate to a forest composition similar to the prefire forest, or to a new forest composition dominated by deciduous hardwoods. Here we present a simple, rule-based framework for predicting fire-initiated changes in forest cover within Alaska's black spruce forests. Four components are presented: (1) a key to classifying potential site moisture, (2) a summary of conditions that favor black spruce self-replacement, (3) a key to predicting postfire forest recovery in recently burned stands, and (4) an appendix of photos to be used as a visual reference tool. This report should be useful to managers in designing fire management actions and predicting the effects of recent and future fires on postfire forest cover in black spruce forests of interior Alaska.

Black spruce (Picea mariana (Mill) B.S.P) is the dominant forest cover type in interior Alaska and is prone to frequent, stand-replacing wildfires. Through impacts on tree recruitment, the degree of fire consumption of soil organic layers can act as an important determinant of whether black spruce forests regenerate to a forest composition similar to the prefire forest, or to a new forest composition dominated by deciduous hardwoods. Here we present a simple, rule-based framework for predicting fire-initiated changes in forest cover within Alaska's black spruce forests. Four components are presented: (1) a key to classifying potential site moisture, (2) a summary of conditions that favor black spruce self-replacement, (3) a key to predicting postfire forest recovery in recently burned stands, and (4) an appendix of photos to be used as a visual reference tool. This report should be useful to managers in designing fire management actions and predicting the effects of recent and future fires on postfire forest cover in black spruce forests of interior Alaska.

Global warming is altering the fire regime of interior Alaska, which may have cascading effects on the prevalence of forest types and species dominance across this region. Our objective was to investigate the relationship between vegetation composition and fire in the boreal forest of interior Alaska. We utilized data from over 700 plots sampled across the landscape designated as the Tanana region by the US Forest Service for Forest Inventory Analysis (FIA), as well as fire history records. We compared biomass and stem density of conifer and hardwood forest types, as well as individual tree species, across a gradient of landscape topography (uplands vs lowlands, aspect, slope, elevation), time since fire, and number of fires. Hardwood biomass was greater than conifer biomass and black spruce has far greater stem density than all other tree species. Conifer biomass was more affected by upland or lowland position and time since fire than elevation, slope (except at slopes >25%) or aspect. Conifer density was only affected by time since fire, increasing after 50 years. Hardwoods were more variable than conifers; biomass was only driven by time since fire and stem density was only driven by upland or lowland position. Several conifer and deciduous species (black spruce, balsam poplar, quaking aspen) showed a decline in biomass at sites that burned twice since 1940 compared to sites that burned once. White spruce and paper birch did not show a decline in biomass, and tamarack showed a decline in stem density. Certain elevation ranges, especially 1000-2050, were more favorable for high biomass levels of species such as white spruce and paper birch. Our results suggest that upland or lowland position and time since fire are more important variables than slope or aspect for determining forest type and species composition in this ecosystem, and that elevation is a variable that creates spaces on the landscape that may be favorable to a limited number of species. As fire increases in frequency and extent in Alaska, this may have important consequences for vegetation composition, thus creating lasting impacts on the landscape of Alaska for the foreseeable future.