Sergey Fedorovich Khokhlov

Thearticlepresents the results of a comprehensivestudy of the soilcover of the islands of UrupandSimushir, which are partoftheKurilRidge. The mainfocus is on analyzing the impact of environmentalconditionssuchasclimate,vegetation,topography, andvolcanicactivityonsoilformationanddiversity.Duringthefieldwork, keysiteswithsoilsectionswerelaid,ageobotanicaldescription of plantcommunities was carried out, and samples were selected forlaboratoryanalysis. It has been establishedthat the soil-forming processesontheseislandsareintermittentand are associatedwith the periodicburial of soilhorizons with pyroclasticmaterial. Based on the morphological descriptions of the profiles of the surveyed territories, a stratotype of the soil pyroclastic cover (SPC) was compiled separately for the sites on Urup Island and Simushir Island, reflecting the history of the profile formation. A special feature of the soilsis the highcontent of organic carbon in the surfacehorizons,whichvariesfrom5.1to15.1%,reachingmaximumvaluesunderthickets of KurilbambooonUrup Island,as well as the presence of horizons with andic properties, usually associated with volcanic soils.Soilacidity(pH)rangesfrom3.7to6.4,increasingwithdepth. A CKrmarkerashhorizon with an age of ~2100years has been identified, which plays a keyroleinstratigraphy. The soils forming on Urup Island are characterized by a large accumulation of organic carbon compared to the soils of Simushir Island, where the soil cover is younger and formed on a substrate that is initially poor in organic matter, the slag from the eruption of Zavaritsky volcano (195 y. a.). The andicpropertiestestconfirmed the presence of reactivehorizonsin the lowerparts of the profiles. The density of the soilcompositionvariesfrom0.42to0.66gcm–3,which is typicalforvolcanicsoils. It is shownthatplantassociationsplay a keyrolein the processes of humus accumulationandsoilprofileformation. The dataobtained are importantforunderstanding the mechanisms of soil formation involcanicislandecosystems.