ИСТИНА

The main goal of the study is to describe the influence of spatial vegetation and relief heterogeneity on turbulent CO2 fluxes between land surface and the atmosphere using a process-based two-dimensional turbulent exchange model. As a key area for this modeling study the hilly territory situated at the southern boundary of broadleaf forest community of European Russia (Tula region) was selected. The vegetation cover in the region is mainly represented by mosaic of agricultural areas, grasslands, mires and groves that makes adequate determining the local and regional CO2 fluxes using any experimental approaches very difficult. Applied two-dimensional model is based on solution of the Navier–Stokes and continuity equations using the one-and-a-half order (TKE) closure scheme in the appropriate coordinate system taking into account the shape of the surface (the structure of relief). The vegetation is modeled as a continuous permeable medium resisting the air flow. For description of plant canopy photosynthesis and respiration an aggregated approach based on model of Ball et al (1987) in Leuning modification (1990, 1995), the Beer-Lambert equation for the description of solar radiation penetration within a plant canopy (Monsi, Saeki 1953), and also an algorithm describing the response of stomatal conductance of leaves to incoming photosynthetically active radiation is used. All necessary input parameters describing the photosynthesis and respiration properties of plants and soil were obtained from the field measurements or taken from the literature. To quantify the possible effect of relief and vegetation heterogeneity on CO2 fluxes several transects crossing the study area were chosen. For each transect the CO2 fluxes were calculated for actual vegetation structure and for scenario assuming total deforestation. The modeling results showed a significant impact of both relief and vegetation heterogeneity on CO2 fluxes.