We are examining the growth, growth history and climate sensitivity of white and black spruce trees on the floodplains of the major rivers fed by glacial meltwater in Interior Alaska. To date we have sampled 624 trees on 41 sites distributed across 1,783 km of the Yukon River, 375 km of the Tanana River, and 370 km of the Kuskokwim River, for a total of 2,528 km of river length.

Ecosystem processes in northern systems depend heavily on inputs of biologically fixed nitrogen (N) from A. tenuifolia, which contributes the majority of N accumulated during boreal forest succession. However because of the high phosphorus (P) demands of this plant, we hypothesize that N-fixation inputs are controlled by the ability of alder to assimilate P through associations with ectomycorrhizal fungi (EMF), which produce enzymes that mobilize organic and recalcitrant P forms.

Bonanza Creek LTER focuses on the Alaskan boreal forest. The forest provides important ecosystem services that include tangible benefits for the communities that reside in Interior Alaska.  Non-timber forest products (NTFPs) such as berries, mushrooms, firewood, and birch bark are key resources that are gathered from the landscape. NTFPs are harvested for subsistence, cultural, personal, and commercial purposes.

This poster outlines molecular analyses of soil fungi within the Bonanza Creek LTER over the last six years. We examined community structure in three studies in mixed upland, black spruce, and white spruce forests. While fungal diversity is extremely high, and we were unable to saturate diversity in one quarter gram of soil with 5000 clone sequences, we were nevertheless able to saturate diversity across the 12 black spruce sites after combing over 2000 soil cores and 30,000 clone sequences.

Oviposition site preference and larval performance
of the aspen leaf miner (Phyllocnistis populiella)

Russell Dennis, Patricia Doak, and Diane Wagner

University of Alaska, Department of Biology and Wildlife, Fairbanks AK 99775 (email: ftred@uaf.edu)

Soil microbes are key drivers of ecosystem processes, yet their role in regulating landscape-scale vegetation change is not known. Comprehensive studies of treeline position have noted that ectomycorrhizal fungi may be an important factor delineating the boundary between forest and tundra. Yet, these critical plant-fungal symbioses are sensitive to wildfires. Fire is the primary landscape-scale disturbance in the boreal forest and increasingly important in tundra.

Increased summer air temperatures in interior Alaska have caused drought stress and growth suppression in several boreal tree species. The response of Alnus tenuifolia (thinleaf alder) to a warming climate could substantially impact interior Alaskan floodplains due the role alder plays as the dominant N-fixer. We studied the effects of inter-annual variation in monthly meteorological and hydrological variables on annual alder radial growth (directly related to N-fixation input), the landscape variability in alder climate sensitivity, and the long-term trends in climate and hydrology.

Permafrost plays an important role in shaping the chemistry of streams by restricting subsurface flows through catchments to soils. During the summer thaw of soil, subsurface flows migrate through deeper soil horizons presumably resulting in seasonal shifts in the inputs of carbon and nitrogen to the streams. Within streams, the extent of the hyporheic zone may also shift with seasonal thaw. Hyporheic zones have high mineralization and nitrification rates; thus expansion of the hyporheic zone throughout the season has important implications for stream chemistry.