Change in the Net Primary Production and Carbon Stock Recovery in Fallow Soils

Abstract

Abstract In Tuva, during the fallow succession on ordinary chernozem (Voronic Chernozem Pachic, WRB 2006) and chestnut soil (Haplic Kastanozem Chromic, WRB 2006), changes in the species composition of phytocenoses, total stock and structure of the phytomass, and net primary production were determined. It was found that the species composition of the zonal phytocenosis and humus stock characteristic of the virgin soils are restored first of all. The structure of belowground plant matter is restored most slowly. The first stage of the succession is characterized by the high stock of aboveground phytomass and low stock of belowground phytomass. During succession, the amount of aboveground phytomass decreases, while the amount of belowground phytomass increases. In 4–17 years, the total stock of plant matter in the ordinary chernozem and chestnut soil increases twofold and threefold, respectively, but does not reach the values typical of the reference zonal soils. In the same period, the net primary production increases by 1.5 times on the ordinary chernozem and 2.5 times on the chestnut soil. The net primary production is almost two times higher in the zonal steppes. The total net primary production (expressed in carbon) was calculated for 17 years of succession; it amounted to 67 and 49 t C/ha in the meadow steppe (chernozem) and dry steppe (chestnut soil), respectively. The total production is distributed as follows: its share spent for the accumulation of aboveground and belowground phytomass is equal in both ecosystems, whereas its share converted into humus is twice higher in the dry steppe with chestnut soil. The CO2 emission reaches 70–75% of the total production in both cases.

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