Urbanization is recently a very important and the most rapid land-use change trend. Land conversion to urban results in considerable and usually irreversible changes in vegetation, soil cover, stocks and fluxes of energy and matter. Green house gases’ (GHG) emission has the main impact on the global processes and mainly on climate change, thus knowledge of GHG fluxes in different biomes is relevant. So far, most of our understanding of GHG fluxes and factors behind their spatial-temporal variability comes from investigation of natural and agricultural ecosystems, whereas much less in known about urban ones.
Globally urban areas occupy less than 3%; however, their contribution to biogeochemical cycles and GHG emissions can be considerable. Urban soils can store considerable amount of carbon and nitrogen resulted from adding of organic composts, wastes, intensive growth of root biomass and “cultural layers” formed in result of historical residential activity. At the same time, urban topsoil has high potential to emit CO2, CH4 and N2Othrough intensive mineralization of turf-based soil mixtures widely used in greenery, but rather non-stable in urban conditions.
Urban areas are represented by combinations of contrast functional zones, sealed and impervious territories. As a result, urban soils are very heterogeneous thus GHG emissions are likely variable in time and space. Spatial variability of GHG fluxes in urban areas can be influenced by both conventional (climatic, vegetation) and urban-specific (soil sealing functional zoning, soil pollution and physical disturbance). It is critical to understand driving factors influencing GHG fluxes in urban soils under various bioclimatic and management conditions to analyze contribution of urban soils to regional and global GHG balance.
Central European Russia (CER) is rather variable in bioclimatic conditions, including boreal, sub-boreal and steppe conditions. Besides CER is the most populated territories in Russia with as percentage occupied by urban areas up to 7-10% in some regions. The aim of the study was to analyze driving factors behind spatial variability urban soils’ carbon stocks and fluxes under different bioclimatic conditions in CER.
We analyzed two cities, contrast in bioclimatic conditions: Moscow (south-taiga zone, reference soddy-podzolic soils) and Kursk (forest-steppe zone, reference grey forest soils and chernozems). In each city three functional zones (industrial, residential and recreational) were observed. For each plot, we measured soil GHGemission in situ (Li-820, May-November, 15 replicas, 10 days’ time step), soil temperature and moisture.
In both regions, we found average CO2 outflow higher than in referenced natural sites. Moreover, CO2 emission was increasing in a row recreational residential recreational industrial aeas, following intensificatin of anthropogenic pressure. Methane emission was typical for athropogenic changed ecosystems, whereas CH4 uptake was more likely natural biomes. The highest spatial variability in CO2 emission (CV up to 60%), and in carbon stocks (CV up to 40%) was found for the industrial areas, whereas the lowest – for residential and recreational.