Contribution of Tree Windbreaks to Soil Organic Matter Content in the U.S. Great Plains.

Tree windbreaks (or shelterbelts) have been planted extensively in the U.S. Great Plains since the Dust Bowl of the 1930’s. Until recently, the purposes of the shelterbelts introduced in the region were to control wind erosion and to alleviate drought conditions. Windbreaks are now receiving attention regarding sequestering carbon in soil and biomass, modifying the local microclimate, enhanced soil water status, and improving soil quality. The objective of this study was to evaluate changes in soil properties and to quantify carbon stored in soil and biomass within and adjacent to shelterbelts in four Great Plains states (ND, SD, NE, and KS). Two sampling sites were selected in each state that provided representative tree species, soils, previous land use, and climate of the region. Soil samples were collected to ~1.25 m depth within shelterbelts and neighboring fields. All soil samples were collected within a single soil map unit from a soil pit and two auger holes. Soil samples were analyzed for soil organic carbon (SOC), inorganic carbon (SIC), total nitrogen (TN), bulk density, particulate organic matter (POM), pH, particle size, hydraulic conductivity, and water stable aggregates. SOC stocks were on average 2.9 kg m^-2 greater under the shelterbelt than in the adjacent fields. A series of environmental benefits and soil property changes followed the changes in organic matter; lower bulk density in surface layers and increased macroaggregates stability were observed for soils beneath windbreaks. Windbreak plantings hold considerable potential to improve soil quality of degraded lands, improve crop yield, and diversify on-farm income.