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Abstract Spatial patterns of the variation in the composition of stable carbon isotopes (δ13C) in soil organic matter (SOM) across different types of geosystems in southern Eastern Siberia are examined. Statistical processing of isotope geochemical analysis data for 87 samples of surface humus horizons together with their physicochemical parameters and reanalysis data allows us to identify the main factors influencing δ13C variability and to model its spatial distribution. We observe a consistent enrichment of SOM with 13C from humid mountain taiga (from –29.5‰) to steppe (up to –23.0‰). The soils of mountain tundra are enriched with 13C to a similar extent as the steppe soils. The spatial variation of δ13C in the studied area is best described by the Gaussian process regression with the following input parameters: absolute altitude of the terrain, soil acidity, average air temperature, total precipitation, and evaporation over the growing season. The correlation between the empirical and model predicted δ13C values is r2 = 0.71. The largest error in δ13C values (up to 1.3‰) is observable in steppe soils, presumably, because of the microclimatic effects of intermountain basins and the smallest error values, in the mountain taiga soils on windward ridge slopes. Comparison of our results to those of similar studies indicates that climatic factors (heat to moisture ratio) are the primary driver of δ13C spatial patterns in SOM; however, the set of controlling factors is unique to each region and is largely shaped by the diversity of physiographic conditions. These results can be applied to analyze soil carbon dynamics and to reconstruct paleoclimatic conditions in the studied region.
Vanteeva et al. (Mon,) studied this question.