Soil Organic Carbon Dynamics Beneath Tree Windbreaks in the Russian Steppe and U.S. Great Plains.

Tree windbreaks represent an attractive multiple-benefit land use through their ability to mitigate climate change by modifying the local microclimate to improve crop growth and by sequestering carbon in the soil and tree biomass.  The objective of this project was to use detailed soil profile descriptions and spatially-distributed soil sampling to determine the soil C sequestration potential of tree planting across climatic gradients at three sites in the Central Russian Uplands and the U.S. Great Plains.  The three Russian sample locations, Streletskaya, Yamskaya, and Kamennaya spanned a gradient of mean annual temperature of 5.3°C and precipitation of 580 mm for Streletskaya to 5.8°C and 480 mm at Kamennaya.  The three U.S. locations, Reynolds, ND; Huron, SD; and Norfolk, NE; had ranges of annual temperature of 3.9°C and precipitation of 450 mm for Reynolds to 9.2°C and 690 mm at Norfolk.  Several tree species were represented at the sites and ranged in age from 19 to 70 years.  Soil samples (0-30 cm) were taken in a grid across each windbreak along with soil pit and auger samples to 1.2 m or greater in each land cover (tree, crop, and undisturbed grassland as reference).  Samples were analyzed for pH, total nitrogen, and organic (SOC), inorganic (SIC), and permanganate oxidizable (POXC) carbon as well as for stable carbon isotope signature (del 13C, natural abundance).  The results indicate that windbreaks with more cool and moist climate conditions are more favorable for humus accumulation in the surface soil layers and a significant proportion of this accumulation could be attributed to tree biomass.  The relationship between humus accumulation and climate factors as expressed by the hydrothermal coefficient of Selyaninov (1928) enables the estimation of soil carbon stocks in existing windbreaks and the prediction of potential carbon sequestration in future plantings.