Ecosystem services of soils of the Lena River Delta

Abstract

The Lena Delta is the largest Arctic delta with an area of about 29,630 km2. The large rivers deltas are a special type of ecological systems in which the formation of soil occurs under conditions that differ from the uplands. Soil formation in deltas is closely related to the interaction of stream flow and drift flowing. The Lena Delta is located in the tundra zone, cryogenic processes such as permafrost activities, cracking and solifluction occur in the soil. Thermokarst forms a spotty fine-polygonal and hillocky microrelief on watersheds and its slopes; large-polygonal and flat large hillocky microrelief - on extensive marshy plains. Soil diversity in the delta is represented by several groups: Podzols, Cryosols, Fluvisols, Umbrisol, Histosols, Gleysols. Vegetation is mainly represented by moss-lichen tundra, as well as motley-grass phytocenoses on the territories of flooding. One of the most important ecological functions of soils in this region is the regulation of the organic matter fluxes in the biosphere. The delta is a great reservoir of organic matter, presented in the form of peat. The content of organic carbon reaches 25% in the topsoils organic horizons. In conditions of global warming and coastal abrasion all the organic matter that was once part of permafrost is exposed and becomes accessible to various microorganisms that exude methane and carbon dioxide. Data were obtained on the microbiological activity of soils, the mean value of СО2 emission is about 80 mgCO2 / 100g * day-1. In our view, the CO2 emission is closely related to the microrelief and soil structure, since the highest emission value is found in flooded meadows and thermokarst lakes. Carbon stocks in the soil of the delta are estimated at 496 * 1013 kg at a depth of 1 meter. According to the molecular content of humic substances in the soil accumulates a large amount of stable aromatic compounds. Within arctic biomes such accumulation is not typical, this may indicate that soil formation occurs according to the podzolic type. A fulvate-humate type of humus mostly characterizes the soils of the Lena Delta. These data indicate that the degree of humification of organic matter rises and the biogenic substances do not drift down the profile but accumulate in the organic horizons, which is a prerequisite for a high level of fertility. The increase in temperature due to global warming will primarily affect the biodiversity of the region. In the delta today, a large number of shrubs (dwarf birch, willow), as well as trees (larch) develops. With the rise of temperature, these species will increasingly holder the territory of the delta and possibly displace the zonal ones. Thus, the soils of the Lena Delta are an important link among all of the ecosystem services in the region. In the conditions of a severe Arctic climate, they serve as a favorable place for soil microbiota, which indicates active processes of humification and transformation of organic matter in the soil.