Anatomical changes in dwarf shrub roots provide insight into aeolian erosion rates in northeastern Iceland

Abstract

Iceland is known for having strong aeolian erosion events, as evidenced by erosional escarpments on the soil surface; these are known locally as rofabards. The aim of the study was to estimate aeolian erosion rates at two research plots affected by severe erosion, using anatomic features of the roots of Arctic, woody, dwarf shrubs. Ours is the first study to utilize dendrochronological analyses of exposed roots of dwarf willows (Salix herbacea L.) as an indicator of aeolian erosion. When dwarf shrub roots are exposed to the atmosphere by erosion, cell sizes are reduced by >50 %, with maximum changes in individual plants exceeding 150–200 %. We detected the erosion signal by analyzing changes in cell-size and width of growth rings in the roots. Using this relationship, were able to estimate erosion rates (the retreat of escarpments) since the 1970s for the study area. During the 1970s and 1980s, erosion rates were fairly constant, with retreat ranging from 1.0 to 2.5 cm yr−1. Rapid increases in erosion rates were observed after the late 1990s, occasionally as much as 4.4–5.4 cm yr−1. Increased aeolian erosion rates may be linked to continuous heavy grazing by sheep and climate change, as this period coincides with increased numbers of hot and warm, and dusty days. Our results indicate that dendrochronological methods can be highly useful in determining past geomorphic activity, due to modern environmental changes observed in the Arctic. The methods employed here can be applied even in treeless areas.