Productivity, carbon sequestration and species diversity in virgin and secondary meadow steppes of the Bashkir Cis-Urals

Steppes are of great importance for the global biogeochemical cycle and are characterized by high economic value. Carbon stocks in the soil of flat steppe landscapes are about one-fourth of the total carbon deposited in global soils. However, improper methods of pasture management, especially overgrazing, have a serious negative impact on the structure and functioning of steppes. The aim of this study is to analyze carbon accumulation in virgin and secondary meadow steppes in the Bashkir Cis-Urals (Russia) depending on various methods of agricultural use. The data were collected on 10 sample plots laid on cropland, as well as in secondary and virgin meadow steppes. It was found that secondary meadow steppes on fallow lands abandoned for about 20-45 years are close to virgin steppes in terms of the dominant species composition but differ by low floristic diversity, a different proportion of steppe specialist species and lower root phytomass (60-100% lower than in the virgin steppe). The phytomass of all fractions of plant matter was the highest in virgin steppe. Under moderate agricultural use (occasional and moderate haymaking or grazing), the succession goes towards the restoration of steppe community structure and soil organic carbon content. Intensive grazing slows down the restorative succession and reduces the organic carbon content in the soil. Compared with the meadow steppes located at the foot and the lower part of the hill, the steppes of upper and middle parts of the same slope have a high stock of above-ground phytomass but contain less carbon in the soil due to water erosion.