ИСТИНА

Soils inside the rocks develop under the influence of endolithic communities occupying structural cavities in the interior of solid rocks. First scientific rationale for endolithic organisms was provided by Friedmann (1982) revealing that bacteria, algae, fungi and specific lichens find their ecological niche within few upper centimeters of the rocks, thus escaping in hot/cold deserts and high mountains the intensive UV-radiation, moisture deficit and wind abrasion. There is usually a strong autotroph component in this communities represented mainly by cyanobacteria and green algae, thus providing a biomass for consecutive heterotroph development. The most suitable rocks for endolithic colonization are sandstones, various granitoids, marbles and any others with a significant content of translucent and/or transparent mineral grains (dark basalts are more subjected to epilithic colonization). For instance, the content of quartz and feldspars in granites of East Antarctica is sufficient for the development of endolithic organogenic horizon at the depth of 0,5-1,0 cm under the rock day surface. It is a macroscopic horizon in a sense that it is clearly visible to a human eye (0,2-1 cm), however it could not be seen to the observer from the outside of the rock unless the upper weathering crust is removed. Our studies show that the system “endolithic organisms – parent rock” has all characteristic features of soils: (1) the rock (parent material) layer subjected to the action of external abiogenic factors, (2) the living organisms functioning in this rock and synthesizing/decomposing organic matter, (3) the in situ transformation of the initial rock under the impact of abiogenic and biogenic factors with accumulation and removal of the transformation products and development of the vertical heterogeneity composing the microprofile. It is very important that endolithic pedogenesis is capable to produce autochthonous fine earth. The other crucial feature related to pedogenesis is the presence of organomineral horizon – the hotspot of biota-rock interactions. Most endolithic biota is presented by biofilms. The subaerial biofilms concept (Gorbushina, 2007) could be fully applied to the endolithic ones. Endolithic biofilms react with the rock and often turn to the endolithic organo-mineral coatings. The potential to change initial mineral matrix is very high - there are examples of dissolution of the idiomorphic quartz grains by endolithic cyanobacterial biofilms (Brehm, 2005). The similar process we widely observe in Antarctica endolithic soils. Several specific features of endolithic soils on granitoids of East Antarctica can be distinguished: (1) the main focus of biomineral interactions—the endolithic organomineral horizon—is found not on the rock surface but inside the rock; (2) the soil microprofiles are developed in both directions from the organomineral horizon containing endolithic community, i.e., in the spalling plate above it and in the underlying rock; (3) the major products of the endolithic pedogenesis are the silty–sandy fine earth and abundant amorphous Fe–Al–Si–C-containing films with admixtures of K, Na, Mg, Ca, S, and Cl that are formed on the walls of the fissures inside the rocks and on the lower face of spalling plates; precipitation of these film is specified by the mechanical and oxidation geochemical barriers at the air/rock interface; (4) the development of true macro horizons is impossible because of the periodic rejuvenation of the rock surface under the impact of spalling; and (5) after the spalling, the fine earth is removed by the wind, and the exposed rock surface is only covered by the endolithicaly generated films, which are partly abraded and transformed by the external agents. Endolithic soil is the worldwide phenomena. It could be found in places where harsh environment pushes organisms to shelter inside the rock since the superficial habitats occur to be poorly suitable for sustaining life (the rock itself should be favourable for producing cavities and light transmission). Endolithic life has been reported in cold and hot deserts and high mountains from all continents. Endolithic pedogenesis in quartzite sandstones can lead to the development of inverted upside down podzol-like bodies, with an E horizon hidden inside the rock, where endolithic community develop and BHF horizon formed on the top, actually on the day rock surface. BHF is formed by the upward flow of the Fe(Al,C)-substances and its immobilization on the surface geochemical barrier. Edwards et al. (2004) provided the evidence that interaction between endolithic biota and sandstone leads to mobilization of haematite initially cementing quartz grains, its hydration and subsequent deposition on the surface of the rock in the form of goethite. Thus, there is a sugar-white E-like horizon depleted in Fe left inside the rock and Fe enriched horizon on the day surface. Further exfoliation of sandstone rock is possible along E-like horizon missing its cementing agent. The study of “endoliths-rock” interactions with the approaches of soil science needs more systematization and understanding of the place these objects occupy in the soils world. It can turn out that endolithic soils are the most spatially abundant soil bodies in extreme environment of Antarctica, some highlands and deserts. Besides such objects should be recognized as an early-Earth “protosoils”.