The microbiome of various type of abandoned fallow soils of south taiga (Novgorod region, Russian North-West)

After the collapse of the Soviet Union, huge areas of soils were in fallow state, more than 30 years have passed, and the study of the microbiological status of fallow soils is an extremely urgent task, because fallow soils represent the "hidden" food basket of Eurasia. In this context, the influence of land use type (pasture, vegetable garden, hayfield, secondary afforestation) on key agrochemical parameters and parameters of soil microbial biodiversity were studied. All anthropogenically transformed soils studied showed increased humus content and pH shift to a more neutral side compared to the mature soil, the same seemed to be the case for all nutrient elements. It was es-tablished that the key factor regulating soil microbiome composition shift is the duration and degree of irreversibility of an agrogenic impact. The key phylas of soil microorganisms were: Pseudomonadota, Acidobacteriota, Verrucomicrobiota, Bacteroidota, and Actinobacteriota. The proportion of other phyla were quite variative in soils of different land use. At the same time, all the 30-years old abandoned soils were similar to each other than to mature reference soil and 130-years old soils of monoculture vegetable garden. Thus, the first factor, regulating soil mi-crobiome composition is continuation of soil agrogenic transformation The second factor is type of land use if the soil age was equal for fallow territory in case on one initial Podzol soil and one type of landscape. Thus, 30-year-old abandoned soils are intermediate in terms of microbial biodi-versity between pristine natural Podzols and Plaggic podzol. It could be suggested, that in case of secondary involvement of soils to agriculture, the composition of microbiome may turn to mature soil or to Plaggic soil under intensive amelioration.