Arctic greening and its climate change feedback: cascading long-term effects of above- and belowground linkages
Konstantin Gavazov
Eidgenössische Forschungsanstalt für Wald, Schnee und Landschaft - WSL
Lay summary
Tundra plant communities naturally occur in areas beyond the latitudinal and elevation limits of tree growth, reaching out to alpine and polar deserts and glaciers. Due to their extreme environment, these plants are small and slow growing, yet they are responsible for the accumulation of the largest terrestrial stock of organic carbon, roughly equivalent to 70% of the present day atmospheric CO2 content. With the concerning extent of arctic warming and its anticipated feedback to climate change, ecologists and biogeochemists alike have shown vivid interest in documenting tundra plant community dynamics, such as shrub and tree expansions. Yet the inherent limitations of tedious belowground research and harsh work conditions in the Arctic have precluded us from building a mechanistic understanding of the rates and magnitude of soil processes driven by such shifts in arctic plant communities.
To address this knowledge gap, our team of early career scientists launched in 2018 the project ALTER (Abisko Long-Term Ecological Research), some 200 km north of the Arctic Circle in Sweden. In our project, we adopt a functional classification approach by grouping diverse plant species into distinct vegetation types according to their symbiotic association with characteristic soil microorganisms (mycorrhizae), which in turn regulate the accumulation and degradation of soil organic carbon belowground. By doing that, we aim to characterise the ecosystem carbon sink potential, based on the dominant vegetation type, which is readily observable aboveground and can be scaled in time and space using historical photographs, vegetation maps, drone and satellite images. To implement this in the field, we selectively remove one or another vegetation type from the plant community to assess its functional role belowground in comparison to a control treatment of random plant species removal.
With the generous support of the SPI Exploratory Grant, we aim to equip our experiment for long-term monitoring of belowground vegetation and microbial dynamics. Specifically, we aim to peek into the “black box” of arctic soils and monitor non-destructively and at high spatial and temporal resolution the dynamics of fine root and hyphae production, phenology and turnover. We are convinced that this is of primary importance as in the Arctic up to 80% of living plant biomass is found belowground and fine root and microbial turnover represent a major sink of terrestrial net primary productivity. To this end, we will install minirhizotrons as the primary tool to study root dynamics in the field, micromesh exclosures to partition root vs. hyphae contribution to soil processes, in-growth bags to quantify fungal hyphae production and composition, litterbags to quantify soil organic matter decomposition vs. stabilisation, and use genetic markers to assess soil microbial diversity.
