Wind erosion rates in the Arctic as recorded the roots of tundra shrubs  – a new dendrochronological approach

Abstract

Arctic and sub-Arctic terrestrial environments often have bare surfaces, thin and poorly developed soils, large amounts of loose sediment, and low and sparse vegetation. The sensitivity of these sites to modern climate change is reflected, among other things, in an increase in the activity of erosion processes mainly via deflation. Despite the development of modern research tools and monitoring methods, the temporal and spatial changes in the intensity of soil degradation by aeolian processes in high latitude environments is still poorly understood. In this study, we sought to determine soil erosion rates, using anatomical features of Arctic shrubs and dwarf shrubs in northeastern Iceland, central Spitsbergen, and southern Greenland. The main research question we posed was: can the dendrochronological information contained in the anatomy of shrub roots be used to reconstruct soil degradation and erosion histories? We applied dendrochronological techniques to the exposed roots of dwarf willow (Salix herbacea L.), net-leaved willow (Salix reticulata L.), and common juniper (Juniperus communis L.), and estimated surficial erosion based on abrupt changes in cell size and width of annual growth increments in the roots. The accuracy of the dating of erosion processes was checked by comparison with dendrochronological reference scales from specimens collected from undisturbed site. We observed, that after exposure of shrub roots, cell size decreases by at least 50%, with the maximum changes in individual plants exceeding 150-200%. Based on this relationship, we estimated surficial erosion rates for Iceland (1970’s-present), as well as for Spitsbergen and Greenland (1980’s-present). We observed a rapid increase in erosion rates in the latter half of the 1990’s, approaching 5.4 – 6.1 cm/year. Our results confirmed the efficiency of the dendrochronological method we employed, for determining soil erosion rates, even in unforested areas. The method is particularly applicable to low-growing, Arctic dwarf shrubs, which develop measurable growth rings and cells, making them a reliable proxy in soil degradation studies. The research was founded by a Polish National Science Centre project no. UMO-2021/41/B/ST10/03381 and project no. UMO-2019/35/D/ST10/03137.