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Visiting scientist salon: Permafrost and the boreal forest

Wednesday, Sep 21, 2022 at 3:00 pm 4:00 pm

IARC is hosting a salon with visiting scientists from Forestry and Forest Products Research Institute and Shinshu University. There will be five short presentations about research related to permafrost and the boreal forest.

Attend in person in Akasofu 401 or email Amber Keith to attend virtually.

Yojiro Matsuura, Forestry and Forest Products Research Institute (FFPRI)

Title: Permafrost depth regulates black spruce stand structure along the slope position.

Abstract: Aboveground biomass (AGB) of black spruce stands varies much along a northeast-facing slope in CPCRW. Much AGB accumulation was observed in the upper part of the slope, less AGB, and sparse forest stand structure in the lower part of the slope. The depth of the active layer in early autumn and AGB along the slope showed a significant relationship. Once subsided permafrost will re-rise after forest floor vegetation recovery. The deeper root system will lose its function because of packed into frozen soil. The main goal of our new research in Poker Flat is the detection of the permafrost re-rise effect after ca.20-year black spruce stands.

Kyotaro Noguchi, FFPRI

Title: Fine root dynamics in permafrost black spruce forests.

Abstract: Fine roots (roots <2mm in diameter) have a key role in below-ground carbon flux because of their high production rates. To understand how fine roots respond to different permafrost conditions, we have examined fine root growth at a black spruce forest in Caribou Poker Creek Research Watershed, where active layer depth is shallower at the lower slope in general. Our results showed that the fine root growth rate was greater at lower slope than at upper slope and that contribution of understory plants to the fine root growth was greater at the lower slope. These results suggested that fine root responses to different permafrost conditions would vary with plant species or functional types. This year, we started a soil warming experiment at a black spruce stand in Poker Flat Research Range. We are planning to examine how soil warming affects fine root growth in this experiment.

Tomoaki Morishita, FFPRI

Title: Greenhouse gas dynamics in boreal forest ecosystems.

Abstract: Carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O) are major greenhouse gases. Generally, aerated forest soils play sources of CO2 and N2O, and sink of CH4. On the other hand, CH4 is emitted from soil and stem of trees in wetland. I have measured these gas dynamics in boreal regions. In this seminar, I will show some results of gas dynamics in related to forest fire, and increased precipitation.

Shinta Ohashi (FFPRI)

Title: How does rising permafrost table affect water use efficiency and growth of trees? – An introduction of the research plan

Abstract: The permafrost table subsided by a wildfire is expected to re-rise as the regenerated forest develops, and the rising permafrost table probably reduces root function and increases tree mortality. To test this hypothesis, it is important to understand physiological responses of trees to thinning active soil layer and increasing root damage. In this study, we are going to analyze stable carbon isotope ratios (δ13C) and widths of tree rings to determine how intrinsic water use efficiency (iWUE) and secondary growth of black spruce have changed with the rise of the permafrost table.

Koh Yasue (Shinshu University)

Title: Change over time in development of root stocks of black spruce growing on permafrost in interior Alaska.

Abstract: To understand the interactions between forest development and permafrost, the development of root stocks and soil environmental changes for black spruce (Picea mariana) forest were reconstructed for past 108 years. The research sites were the upper and lower positions of a north facing slope on permafrost of Caribou Poker Creek Research Watershed in interior Alaska. The lateral root development as well as root stock radial growth were reconstructed using dendrochronological techniques. The seasonal temperature changes were observed at different depths. The results revealed that root stock consist of tap root and main stem, and a large portion of root stock was main stem, not tap root. The abrupt radial growth reduction occurred earlier in deeper position. Newer lateral roots tend to formed in shallower layer. These two changes were observed only in lower slope. Both upward changes should attributed to increase in organic layer and decreasing temperature in deeper position. Upward shift of the position with abrupt radial growth reduction is faster compared to the upward shift of the position with new root emergence. This suggests that changes in the soil environment over time have a significant impact on tree growth changes.