Diversity, Properties and Geochemical Features of the Soil Cover in the Ecosystems of the Floodplain-Delta Part of the Transboundary Uldza River (Daursky Biosphere Reserve)

The diversity of ecosystems and soil cover in the floodplain-delta part of the Uldza River were studied for the first time. Marshy, meadow-marshy, meadow and steppe-meadow ecosystems are the most common. The small area of the territory under study is characterized by a variety of soils - from poorly developed stratified alluvial to highly-humified alluvial dark-humus and dark-humus (quasi) gley soils. They are supplemented by highly waterlogged and subaqueous soils of swamps and swampy depressions, where alluvial processes proper are less pronounced, and accumulation of humus, peat, formation of gley or quasi-gley horizons prevail. The main and additional (cryo-, eolian- and halogenesis) soil-forming factors for different types of soils are characterized. In the area of detailed soil survey, alluvial dark-humus (meadow) and light-humus (turf) carbonate soils prevailed, which are loamy in the upper horizons and sandy-sandy loam in the underlying ones. They are characterized by strongly alkaline pH values and carbonate saturation, insignificant humus content, except for the organogenic horizon (AU) of the alluvial dark humus (meadow) soil. The absorption capacity is at an average level of provision, but significantly decreases in sandy-sandy loam sediments. The exchangeable cations are dominated by Ca2+ and Mg2+, but the proportion of Na+ increases with depth. Alluvial soils are slightly saline, and the salinity chemistry is predominantly magnesium-sodium according to the cation ratio, and chloride-soda, taking into account anions. Geochemical features of the soils were established to be the accumulation of Ca, Sr, As and dispersion of iron group elements. A weak degree of chemical weathering (CIA), low biological activity, high heterogeneity of sediments (HM) were revealed according to geochemical coefficients. Soils under the study should be preserved as protected natural objects, as the basis for the diversity and functioning of original protected ecosystems. The obtained materials will be necessary for monitoring of possible functional and dynamic changes in the ecological status of floodplain-delta landscapes both under global and cyclic climate changes.