Subaerial endolithic systems of the current extreme environments on Earth provide exclusive insight into emergence and development of soils in the Precambrian when due to various stresses on the surfaces of hard rocks the cryptic niches inside them were much more plausible habitats for organisms than epilithic ones. Using an actualistic approach we demonstrate that transformation of silicate rocks by endolithic organisms is one of the possible pathways for the beginning of soils on Earth. This process led to the formation of soil-like bodies on rocks in situ and contributed to the raise of complexity in subaerial geosystems. Endolithic systems of East Antarctica lack the noise from vascular plants and are among the best available natural models to explore organo-mineral interactions of a very old “phylogenetic age” (cyanobacteria-to-mineral, fungi-to-mineral, lichen-to-mineral). On the basis of our case study from East Antarctica we demonstrate that relatively simple endolithic systems of microbial and/or cryptogamic origin that exist and replicate on Earth over geological time scales employ the principles of organic matter stabilization strikingly similar to those known for modern full-scale soils of various climates.

No abstract

Mountain semi-natural grasslands of intermontane basins of Central Caucasus, North Ossetia-Alania and the history of its land use were studied. It was found that post-forest, meadow-steppe and partially subalpine grasslands in the study area had been used as croplands for centuries and have been transformed into grazing lands about 60 years ago. In the last 20 years, the grasslands have been underused. It was revealed that current spatial distribution of grasslands is different from the classic scheme of natural climate-induced vegetation distribution. Species composition of meadow steppes is similar in different locations and does not reflect climatic differences of "dry" leeward and "wet" windward slopes of the intermontane basins. Present-day soils reflect parent material differences and erosion degree, but not topography-induced local climate specificity. However, discovered buried soils showed contrasting soil diversity on the southern and northern slopes. It is assumed that the present convergence of soil cover and vegetation is a result of long homogenising human impact and relatively short grassland development. IzvlečekOpisali smo gorske polnaravne travnike v gorskih kotlinah srednjega Kavkaza, Republika Severna Osetija-Alanija, in zgodovino spremembe rabe tal. Ugotovili smo, da so nekdanje gozdne površine, stepske travnike in delno tudi subalpinske travnike, stoletja uporabljali kot obdelovalne površine in jih nato pred šestedestimi leti spremenili v pašnike. V zadnjih dvajsetih letih pa s travniki niso gospodarili ali pa so opuščeni. Ugotovili smo, da je trenutna prostorska razporeditev stepskih travnikov drugačna od klasične sheme razširjenosti vegetacije, ki so pod klimatskimi vplivi. Vrstna sestava stepskih travišč je podobna na različnih lokacijah in ne odraža klimatskih razlik med "suhimi" zavetrnimi in "vlažnimi" privetrnimi pobočji. Talne razmere odražajo razliko v matični podlagi in stopnji erozije, ne pa tudi posebnosti v klimi zaradi topografije. Vendar odkrita pokopana tla nakazujejo raznolikost tal na južnih in severnih pobočjih. Predvidevamo, da je današnja podobnost tal in vegetacije rezultat dolgotrajnega homogenzirajočega človekovega vpliva in relativno kratkotrajnega razvoja travišč.

No 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.