Future shifts in soil cover type and abundance may alter soil functions in the vulnerable and fast changing Antarctic ecosystems. Characterizing the specific influences of different soil cover types for subjacent soils might enable us to better understand the implications of these future changes.
The overarching research question of our study was to compare how mosses and biocrusts on Deception Island influence the structure and activity of subjacent microbial communities, as well as the chemical composition of soil organic matter. We additionally explored the possibility for species-specific effects of two common moss species, since in comparison to the widely acknowledged species-dependent connections with belowground functioning for vascular plants, the role of moss identity keeps being underrecognized.
Map of Deception Island, South Shetland Islands, maritime Antarctica (adapted from Wikipedia, https://upload.wikimedia.org/wikipedia/commons/8/8d/
Deception_Island_Map.svg).
Antarctic mosses and biocrusts - initiators of soil formation and guardians of soil microbial hotspots
The beneficial impacts of mosses and biocrusts for soil functioning are widely acknowledged in literature and have been investigated in a variety of different ecosystems, yet with a focus on non-polar deserts or mediterranean drylands. Besides their profound impacts for soil stabilization by preventing (wind-) erosion, biological soil covers also modulate the soil microclimate, govern crucial carbon and nutrient inputs, and provide overall favorable habitats for a variety of soil organisms in the barren landscape, which consequentially also leads to the establishment of activity hotspots for soil microbial communities. While mosses and biocrusts are the two major biological soil cover types in maritime Antarctica, dominating the prevailing flora, their effects are rarely studied due to the remoteness of the ecosystem. Nonetheless, by representing the main primary producers in the barely vegetated ecosystem, their effects on soil microbial communities and organic matter buildup might be even stronger, than in other ecosystems with e.g., more complex vegetation patterns and more developed soils. To understand how different soil cover types shape the subjacent soils is of particular importance in the context of ongoing rapid climate change on the Antarctic Peninsula, as future shifts in the distribution and abundance of soil cover may substantially impact multiple soil processes in this vulnerable ecosystem.
“Our study highlights the strong interconnectedness between soil cover and soil biogeochemistry, a crucial link for deepening our understanding of belowground functioning in Antarctic soils.”
Example of a soil sample that was derived under the cover of Polytrichastrum alpinum at Fumarole Bay. Foto credits: A. Richter & C.M. Müller.
State-of-the-art-techniques under Antarctic conditions
To compare the effects of mosses versus biocrusts on subjacent soil microbial communities and soil organic matter properties, we used sterile equipment to sample soils (0 – 2 cm) below biocrusts, which consisted of lichen, algae, fungal and bacterial biomass, together with senescent moss biomass. We correspondingly also sampled soil under adjacent vital cover of the two most common moss species found on Deception Island: Polytrichastrum alpinum (a haircap moss) and Sanionia unicinata (a feathermoss). These two investigated moss species do not only belong to different families, but are also biologically quite distinct, differing in e.g., their habitat preferences, growth habits, or specific water- and nutrient-uptake mechanisms.
To our best knowledge, APRI member Andreas Richter was first to determine (relative) soil microbial growth-rates under mosses and biocrusts at ambient conditions in Antarctica during his stay at the spanish Gabriel de Castilla Base. For this, he used a (completely safe) state-of-the-art-stable-isotopes-method, where water with heavy oxygen atom is applied to the soils. Back in the labs of the University of Vienna, we assessed a wide range of standard soil parameters, and complemented the dataset with a thorough qualitative and quantitative characterization of the soil organic matter pool and microbial community composition.
Vital cover of Polytrichastrum alpinum at Fumarole Bay (A) and the biological soil crust at the respective site (B). Foto credits: A. Richter & C.M. Müller.
Important links between soil cover identity and soil properties
We found that mosses and biocrusts affect subjacent soils differently. Soils under biocrusts showed lower microbial activity and more microbial biomass, while key soil organic matter groups were less abundant under mosses. Additionally, we advert that moss-specific traits, such as e.g., root-like structures in P. alpinum (only occuring in specific moss groups) or the association of S. unicinata with atmospheric nitrogen-fixing cyanobacteria (beneficial in N-scarce, pristine environments) do seem to matter. With our study, we want to highlight the importance of linking soil cover identity to soil properties and functions in the Antarctic ecosystem, and the need to not consider these vegetation forms with cryptic lifestyles being a uniform group.
Media information
Written by Victoria Martin.
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Header image credits: British Antarctic Survey 2017.
https://phys.org/news/2017-07-moss-migration-globe.html
About the scientific authors
Victoria Martin is a PhD student in the Research Group Richter.
Original Publikation
Martin, Victoria; Schmidt, Hannes; Canarini, Alberto; Koranda, Marianne; Hausmann, Bela; Müller, Carsten W.; Richter, Andreas (2024): Soil cover shapes organic matter pools and microbial communities in soils of maritime Antarctica. In Geoderma 446, p. 116894. DOI: 10.1016/j.geoderma.2024.116894
Samples were collected with sampling permission (number II 2.8 – 94033/106) under the Protocol on Environmental Protection to the Antarctic Treaty issued by the German Federal Environmental Agency.
