The effect of grubbing and heavy winter rainfall on mycorrhizal mycelium production

Mycorrhizal fungi play a crucial role for both plant nitrogen uptake and ecosystem carbon dynamics and storage. Most of the stored carbon in Arctic soils could be derived from mycorrhizal mycelium rather than from plant litter. As the Arctic carbon storage is suspected to be a crucial factor for climate change, our knowledge about below-ground processes and how they could be impacted by climate change is of paramount importance. In the High Arctic, changes are rapid, with increased temperatures combined with increases in winter precipitation, i.e. rain-on-snow events (ROS) creating ice layers. At the same time, goose populations and subsequent herbivory (grubbing) are increasing, leading to changes in both soil carbon stock and sink capabilities. During this fieldwork we will gather new information on how climatic factors like climate warming, rain-on-snow (ROS) events during winter and goose grubbing affect mycorrhizal mycelium production. We will test the hypothesis that grubbing and ROS decrease soil carbon sequestration by hampering the production of extraradical mycorrhizal mycelium. Production of extraradical mycelium will be measured using ingrowth cores. We expect both grubbing and ROS to decrease below-ground carbon storage by reducing mycorrhizal mycelium. This is expected to happen due to the physical soil disturbance and root damage caused by grubbing, and the severe frost damage to plants during the winter due to ROS events.