Soil evaporation and organic matter turnover in the Sub-Taiga and Forest-Steppe of southwest Siberia

Southwest Siberia encompasses the forest-steppe and sub-taiga climatic zones and has historically been utilized for agriculture. Coinciding with predicted changes in climate for the region is the pressure of agricultural development; however, a characterization of the soil water and carbon dynamics is lacking. We assessed current soil water properties and soil organic carbon turnover in forests and grasslands for two sites that span the forest steppe and sub-taiga bioclimatic zones. Soil evaporation was 0.62 +/- 0.17 mm d(-1) (mean +/- standard error) in grasslands and 0.45 +/- 0.08 mm d(-1) in the forests of the forest-steppe site. Evaporation at the sub-taiga site was 1.80 +/- 1.70 mm d(-1) in grasslands and 0.96 +/- 0.05 mm d(-1) in forest plots. Evaporation was significantly greater at the sub-taiga site than the forest-steppe site. The density of fine roots explained the soil water isotopic patterns between vegetation types and sites. We found soil organic matter turnover to be three times faster in the sub-taiga site than in the forest-steppe site. Our results show that while climate factors, in particular snow levels, between the two sites are drivers for water and carbon cycles, site level hydrology, soil characteristics, and vegetation directly interact to influence the water and carbon dynamics.