Possibility of Using Zoning of Fallow Vegetation by Vegetation Indices to Assess Organic Matter Accumulation in Postagrogenic Soils

Abstract

Abstract Light gray forest soils (Eutric Retisols (Loamic, Cutanic, Ochric)) were studied under a 20–25-yr-old fallow at the stage of overgrowing by meadow vegetation, pine, and birch. The studied area plot was confined to one element of topography, without morphological evidences of erosion processes, and with relatively homogenous soil texture. To assess the influence of fallow vegetation on the formation of soil organic matter (SOM), the plant cover was zoned according to vegetation indices calculated on the basis of remote sensing data. The k-means algorithms and the Random Forest method were used for this purpose. It was shown that there were statistically significant differences between the types of land cover in terms of the SOM stocks in the upper layer of the old-arable horizon with the specification of three and four clusters. The specification of three classes of vegetation on the fallow—coniferous woody vegetation, deciduous woody vegetation, and herbaceous vegetation—proved to be the most expedient; the correctness of their allocation was confirmed by the geobotanical survey of the territory. The results of a pairwise comparison of sites occupied by different types of fallow vegetation indicated that they significantly differ in the SOM stocks only in the uppermost 5-cm-thick layer of the old-arable horizon and only for the pair of coniferous woody and herbaceous vegetation. Differences in the accumulated humus stocks in the layer of 0–10 cm were statistically significant for the soils under deciduous and coniferous woody vegetation and under herbaceous and coniferous woody vegetation. There was no significant difference in this indicator between the soils under deciduous woody vegetation and herbaceous vegetation.