Abstract
The soils of East Antarctica have no rhizosphere with the bulk of organo-mineral interactions confined to the thin microbial and cryptogamic crusts that occur in open or cryptic niches and are collectively known as biological soil crust (BSC). Here we demonstrate that cryptic hypolithic varieties of BSC in the Larsemann Hills of East Antarctica contribute to the buildup of soil organic matter and produce several types of continuous organogenous horizons within the topsoil with documented clusters of at least 100 m2. Such hypolithic horizons accumulate 0.06–4.69% of organic carbon (TOC) with isotopic signatures (δ13Corg) within the range of −30.2 – −24.0‰, and contain from 0 to 0.38% total nitrogen (TN). The properties of hypolithic organic matter alternate between cyanobacteria- and moss-dominated horizons, which are linked to the meso- and microtopography patterns and moisture gradients. The major part of TOC that is stored in hypolithic horizons has modern or centenary 14C age, while the minor part is stabilized on a millennial timescale through shallow burial and association with minerals. Our findings suggest that hypolithic communities create a “gateway” for organic carbon to enter depauperate soils of the Larsemann Hills and contribute to the carbon reservoir of the topsoil at a landscape level.
Highlights
The ice-free landscapes of East Antarctica provide a very limited number of pathways for soil formation with only small amounts of organic matter accumulated in pedogenic environments[1,2,3,4,5,6,7,8,9]
We www.nature.com/scientificreports observed transitional series of hypolithic horizon, that were represented by both cyanobacteria- and moss-dominated morphotypes with the latter one proliferating into epiedaphic environment between unevenly distributed pavement components
We recognized dark colored horizons with filamentous biofilms on sandy particles that were buried in the microtopography traps immediately below contemporary hypolithic horizons dominated by cyanobacteria (Fig. 3)
Summary
The ice-free landscapes of East Antarctica provide a very limited number of pathways for soil formation with only small amounts of organic matter accumulated in pedogenic environments[1,2,3,4,5,6,7,8,9]. According to a global estimate[15] the cryptogamic covers located both on terrestrial mineral surfaces and plants are responsible for nearly 7% of the net primary production by terrestrial vegetation and half of the biological nitrogen fixation on land Their contribution to carbon and nitrogen cycles and to the buildup of soil organic matter could differ significantly between biomes and still needs to be assessed at various scales. Hypolithic organisms often produce the only organogenous horizon that is recognized in a soil profile, their influence on soil development in the ice-free landscapes of East Antarctica is barely documented at a detailed scale
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