Effects of big herbivores on the functioning of decomposers and primary producers in High Arctic tundra (GrazeAct)
by Olga Gavrichkova, National Research Council of Italy
GrazeAct is a project funded through the SIOS access programme. The fieldwork was originally planned for the summer of 2020, but due to Covid-19 it was postponed. The fieldwork was finally and successfully completed in the summer of 2021. The report from the project is presented below.
Future changes of the carbon balance in the Arctic remain one of the primary scientific uncertainties. On the local scale, herbivores impact the structure and functioning of terrestrial ecosystems, affecting the carbon and nitrogen cycles. The sign and magnitude of change in the carbon cycle depends on how grazing affects its two primary components: primary producers (vegetation, fixing of CO2), decomposers (microbial community, mineralising organic material) and their interaction. By modifying the quantity and quality of the organic matter inputs to the soil (litter and faeces) and affecting microbial efficiency, grazing can have either positive or negative effects on ecosystem functioning in terms of capacity to sequester carbon. In this project, we aim to study the effect of reindeer grazing on the functioning of the main players of the ecosystem carbon balance, vegetation and microbial community. The experiment was performed in plots excluded from grazing of the Svalbard reindeer and in the surrounded grazed areas of the village of Ny-Ålesund and involved competences in the field of plant biology, botany and soil science.
Variation of carbon balance in plots subjected to grazing and excluded from it was assessed using gas exchange measurements at the plot scale. Plant carbon uptake, carbon release from soil and a net balance between these two opposite processes are measured weekly. Functioning of microbial community is assessed through decomposition experiment of the litter bags and by analysing microbial indices related to size and efficiency of the microbial pool.
The experiment will last until the end of the growing season 2022, when all the litter bags will be extracted and analysed. Collected data will be shared in dedicated databases such as the Italian Arctic datacenter (IADC) and SIOS Data Management System and will result in a scientific paper on the role big herbivores can play in determining feedbacks of arctic ecosystems to climatic changes.
Fig.1 Experimental set-up in Kolhamma fence.
Fig.2 Gas exchange measurements with transparent and opaque chambers. Fig.3 Soil sampling and preparation of decomposition litter bags.