Analyzing Carbon Stocks and Fluxes to Assess Urban Soil's Functions at the Multiple Scales.

Formation and functioning of urban soils are directly and indirectly effected by humans. Historically, urbanization was mainly studied as a potential threat to soils, however, recent views highlight the capacity of urban ecosystems and soils to support specific functions. Urban soils’ forming conditions and features are principally different from natural and agricultural ones, but their functions and services remain poorly quantified. Analyzing and assessment of urban soils’ functions provide a relevant methodology to assess the environmental and social role of soils and to communicate the results of soil research to policymakers and society. Lack of relevant indicators constrains implementing this approach in urban soil’s management. Our research explores the monitoring results of carbon stocks and fluxed to assess urban soils’ functions. Considering high spatial-temporal variability, typical for urban soils’ features, different parameters, describing urban soil’s carbon stocks and fluxes at the different scales and over the different time periods were used. The following groups of parameters were selected: static (carbon stocks in soil and biomass), dynamic (ÑÎ2 emission in situ) and integral (soil microbiological activity). The selected parameters were investigated in urban soils under various bioclimatic conditions (boreal and steppe) and functional zones (residential, recreational and industrial), as well as for contrast anthropogenic pressures (contamination, acidification and salinization) and for different urban soil constructions. The investigated parameters were used to assess the key functions of urban soils (e.g. gas exchange, bioresources and fertility), whereas the parameters were chosen considering the spatial level of analysis. For example, at the local scale, the sustainability of the model urban soils constructions’ functioning was described by annual CO2 emission and biomass productivity. However, at the regional scale, soil carbon stocks and microbiological activity, averaged for topsoil and subsoil layers, tended to be more informative to analyze the effect of urbanization on the soil functions.