Plant-soil-herbivore interactions in the Arctic
Arctic ecosystems are important sinks for carbon dioxide (CO2) and hold considerable amounts of the world's total pool of soil organic carbon. Climate warming is proceeding faster in the Arctic than elsewhere on Earth. Plant-soil-herbivore interactions have potentially large consequences for a variety of ecosystem processes such as carbon sequestration, greenhouse gas production/emission and plant diversity and community composition.
We aim to elucidate 1) How grazing by muskoxen affects the carbon sequestration and allocation patterns in an Arctic wetland, 2) How grazing affects greenhouse gas production and fluxes, 3) How grazing effects the composition of vascular plant species of key importance to greenhouse gas production and emission, and 4) How grazing may modulate effects of a changing climate on carbon sequestration and greenhouse gas fluxes.
To address the aims we will use a combination of in situ field measurements and detailed analysis in the laboratories using novel isotope techniques. The field site is a fen located in the Zackenberg valley (74°30'N / 21°00'W) in Northeast Greenland, close to the Zackenberg Research Station. The project can be divided into three different sub-experiments as listed below.
In the summer 2010 five blocks where established (by Niels Martin Schmidt and Mads Forchhammer from NERI) in the Zackenberg valley. Each block consists of three 100 m2 squares, i.e. a control, a snow fence and an exclosure preventing muskoxen grazing. To determine greenhouse gas fluxes, pore-water concentrations of labile carbon compounds (e.g. organic acids) and to monitor physical parameters we established two 40x40 cm measuring plots within each square. On these plots, measurements will be carried out throughout the field seasons in years to come to determine both the direct and long-term effect of grazing on the ecosystem.
At another location in the fen (similar vegetation composition and soil properties), five smaller blocks are established. These block consist of a control and a treatment where we simulate grazing by clipping the vegetation 5 cm above ground two to three times during the growing season. The same measurements are performed as in the exclosure experiment described above.
Here monoliths (intact samples of peat and moss and sedge vegetation) are taken from the Zackenberg valley fen and transported back to the laboratory at Lund University. In the laboratory the monoliths will be grown under carefully controlled environmental conditions and subjected to detailed studies, of the link between grazing, pore-water chemistry and greenhouse gas fluxes, using novel isotope techniques.