Fiyalkovskyy, Oleksandr (Tetiiv Institute of Agroecology and Biotechnology, 15, Stepovoy Street, Kashperivka, Tetiiv area, Kyiv region, 09812, Ukraine; Phone: +380 4460 26370; Fax: +380 4460 26370; Email: fiyalko_agro@ukr.net)

Balance of Carbon in Natural and Anthropogenic Ecosystems of Forest-Steppe Zone of Ukraine

O. Fiyalkovskyy *

СО₂ balance in ecosystem and entrance of this greenhouse gas in atmosphere is defined by correlation of velocities of two global processes – СО₂ emission as a result of respiration of soil heterotrophic microorganisms and animals, decomposing a fall, and СО₂ flow in the form of pure initial production of plants. In the natural ecosystems flow of the carbon predominates, or value of СО₂ balance is close to zero. Agrocenosises are traditionally considered as one of the main sources of СО₂ and the other greenhouse gases in the atmosphere owing to violations of carbon rotation in ecosystem leading to intensification of mineralisation of soil organic substance. In order to correct global СО₂ emission from arable soils of Ukraine it is necessary to estimate an influence of the most frequently used farming methods in agriculture on carbon balance in agrocenosises. Taking into consideration the necessity of reduction of greenhouse gases concentration in atmosphere and binding them together in stable forms of organic substance, farming methods, providing the carbon balance with no deficit, should be revealed. Purpose of the present research was to study the carbon balance in ecosystem and in the soil under the cultivation of crops and also carbon accumulation under plowland grassing and forest overgrowing of arable soils. The researches were conducted on the grey forest soils 10 km west of village Volodarka. Carbon balance in crops of maize, spring barley and winter wheat were calculated on field experiment plots, differing by crop rotation type, fertilizer doses and type of soil cultivation during period from 1999 to 2003. Influence of artificial plowland grassing was studied in 2003 - 2004. Compound of meadow fescue (Festuca pratensis), timothy (Phleum pratense) and meadow clover (Trifolium pratense) was sowed on the old-arable eroded grey forest soils in 1991. Influence of natural forest restoration grey forest soil was studied on the plot of secondary mixed forest measuring 10 x 10 m from 2000 to 2004. Average age of the trees 35-45 years. Contribution of root respiration into СО₂ emission from soil was studied. It was calculated carbon balance in natural and agroecosystems. Estimation of carbon balance in agroecosystems on grey forest soils revealed that even under low level of the agrotechnics without fertilizer use negative carbon balance in agrocenosis and in soil is observed only in black fallow under spring barley cultivation. In all the rest of agrocenosises (winter wheat, maize, buckwheat) carbon balance was with no deficit. In the 13 years of plowland grassing the content of organic carbon in the 0 – 0,25 m soil layer increased by 22 –25%, and the reserves of microbial carbon increased by two times. Thus, farming method, allowing to change carbon balance in the soil radically toward its increase, without completely excluding the soil from agricultural rotation, is artificial grassing of soil. Plowland grassing of arable soils can be one of the prospective methods of reducing СО₂ concentration in the atmosphere and carbon accumulation in the soil, particularly in natural zones, where steppe associations are natural vegetation. In the time of resumption of natural forest vegetation on the old-arable eroded grey forest soils doubling of organic carbon reserves can be expected.