Annual Carbon Budget of Biogenic Greenhouse Gases under Mixed Land Use: Lgov District as a Model Object of the Central Chernozem Zone, Russia

Abstract

A comprehensive study of the net carbon balance of Lgov administrative district (Kursk oblast) in the Chernozem zone of the European part of Russia is carried out. The data sources included field estimates of carbon dioxide and methane exchange between soil and atmosphere, above- and below-ground phytomass stocks, simulation models parameterized on these data, official statistical and meteorological information, and published scientific data. Watered filtration fields of waste disposal sites of sugar industry are responsible for 26% of CH4 emissions from the territory of the district, although they occupy only 0.04% of its area. The maximum of CO2 emission is found at volumetric soil moisture of 30%, whereas, with exceeding this value, methane emission begins to rise linearly, reaching a maximum on the open surface of water reservoirs, and among them – on watered filtration fields. Another significant local source of methane is compost storages (22%). However, water reservoirs and ponds are the largest source of CH4 (43%). Amongst the net sources of CO2 the combustion of fossil fuels by transport and agriculture machinery predominates (22.3%). In contrast to methane, which emission is mainly determined by powerful point sources, the input of net fluxes of CO2 positively correlates with their area. Currently observed low rate net CO2 flux in the district area (–6.4 g C m–2 per year), is decisively overlapped by local methane sources (+95 g C (CO2-eq.) m–2 per year). The influence of the types of land use and methods of calculation on the C-balance of the territory in study, and a way of its transformation into a carbon-neutral state are discussed.