Frost heave as a driver of plant diversity on permafrost: insights from fine-root depth distribution and mechanical strength

International Arctic Research Center, University of Alaska, Fairbanks, US

FY2025-2027 Grant-in-Aid for Scientific Research (KAKENHI)

AMADA, Gaku (Department of Forest Soils)

Rapid warming is accelerating permafrost thaw, potentially increasing carbon release from permafrost-forest soils. In permafrost regions, chemical constraints on vegetation carbon assimilation, such as nitrogen availability, have been extensively investigated. However, physical constraints have received far less attention, particularly the effects of frost heave—a phenomenon in which soil is uplifted by the formation of ice lenses during freezing, resulting in substantial soil expansion. In this study, we aim to elucidate a novel plant response mechanism to frost heave and contribute to improving predictions of vegetation dynamics under future climate warming.

This study aims to test the novel hypothesis that associations between the mechanical stress by frost heave and the mechanical strength of fine roots influence the vertical distribution of fine roots in permafrost vegetation and thereby determines plant diversity in permafrost forests of interior Alaska.

Vertical root distributions will be examined across study sites that differ in the extent of frost heave in a permafrost forest in interior Alaska. Soil expansion stress associated with frost heave will be monitored during the winter season. The mechanical strength of fine roots will also be measured to determine whether the fine roots of each plant species can withstand the soil expansion stress. In addition, frost-heave experiments will be conducted to evaluate the extent to which soil expansion stress damages the fine roots of different plant species.