Fallow lands demutation and bioproductivity under Khakass hilly steppe conditions

The objective of the study is to carry out a comparative assessment of the rate of restoration of the vegetation cover of an 18-year-old fallow and its bioproductivity for elementary landscape positions of a gentle slope, coupled with soil fertility. At all slope positions (transeluvial – upper and middle parts and eluvial-accumulative – lower) phytocenoses on the southern chernozem have passed the initial stage of demutation and are in transitional stages. In transeluvial positions, where the potential soil fertility is low, and the effective soil fertility is low and medium, the succession processes are inhibited, they are in the rhizome stage of demutation (edificator Bromopsis inermis (Leyss) Helub – awnless rump). In the eluvial-accumulative position, in more favorable hydrothermal conditions of the landscape and soil fertility (poten-tial – medium, effective – high), recovery processes are accelerated, with a pronounced tendency to sec-ondary healing. The phytocenosis is in the third stage of demutation – rhizome-loose shrub (dominant Poa angustifolia L. – narrow-leaved bluegrass) with the introduction of sod steppe grasses: Stípa capillata L. – hair grass feather grass and Festuca valesiaca Gaudin – Walissian fescue. Fallow cenoses are unproduc-tive, the total bioproductivity varies from 10 to 13 t/ha, of which 2.3–3.4 t/ha was aboveground mass and 6.6–10.4 t/ha – underground. The stocks of mortmass, composed of rags and root residues, are 1.8–2.0 times lower than the stocks of the total living phytomass at transeluvial positions and by 1.3 times at eluvial-accumulative ones. In the latter, the enhanced mineralization of plant residues increases soil fertility and, as a consequence, increases the productivity and speed of the demutational recovery process. How-ever, most of the sources of humus are in the eroded soil of the middle part of the slope, where, with a significant deficit of moisture and nutrition, plants develop the maximum number of living roots.