Root Production in Annual and Perennial Agroecosystems: Implications for Carbon Storage

Agriculture has a tremendous ‘ecological footprint’ as it is a leading contributor to carbon dioxide emissions, and other potent greenhouse gases. At the same time, innovative agricultural practices have the potential to mitigate climate change, by sequestering carbon. A transformative approach to a more sustainable agriculture has been proposed through developing perennial grain cropping systems, which produce edible grain without the need to till and replant every year. Very little is known about the growth of roots in perennial grains and how they contribute to different ecosystem services. This study took place at the Kellogg Biological Station, located in Southwest Michigan. Root biomass was quantified along a species and management gradient, comparing annual winter wheat ((Triticum aestivum var. Caledonia)) to perennial intermediate wheatgrass (Thinopyrum intermedium) under conventional and organic management practices. In June of 2011 and 2012, soil cores were taken to a depth of 100cm, where roots were recovered at different depth intervals and separated into coarse and fine roots. Minirhizotron images were also taken to assess root turnover. The perennial intermediate wheatgrass coarse root biomass was five times greater than the annual wheat root biomass, while fine root biomass was almost three times greater in perennial intermediate wheatgrass than annual wheat. A trend was observed towards management influencing coarse root biomass, and in the topsoil, coarse and fine roots were significantly different under organic and conventional management. Root turnover occurred once per season and in general, roots began to decompose 6-8 weeks following harvest. Overall, the perennial cropping systems had substantially higher root biomass than annual crops, which has important implications for building soil organic matter, reducing soil erosion, and enhancing carbon sequestration within agriculture. Continuous monitoring of belowground C dynamics overtime will occur in order to determine whether perennial species contribute to long-term carbon storage.