The Roots of Energy: Exploring Sustainable Bioenergy Crop Production Practices by Understanding Rooting Characteristics of Candidate Crops.

The spatial and temporal development of plant roots directly contributes to aboveground biomass production by supplying essential quantities of water, nutrients and plant growth regulators to the entire plant.  Although root carbon constitutes up to 50% of total plant biomass, maximum aboveground plant biomass production, during stress, is attenuated primarily by highly functional rooting traits. Plant root development, function, exudates and turnover contribute to soil carbon sequestration, soil evolution of greenhouse gases and additional ecosystem contributions to soil quality. However, very little is known about the root characteristics of current candidate perennials and annual bioenergy crops.  Once root morphologic characteristics, e.g., depth, branching, length, and surface area, are known then additional understanding of the physiology of root systems can be developed to better identify appropriate root traits for selection or management. Not only should this encompass considerations of the function of roots in the capture of water and nutrients but also responses to these and additional long and short term environmental stresses.

We used plastic minirhizotron tubes, (2” diameter and 5 ft long) to monitor rooting characteristics of 10 different bioenergy crops and cropping systems at the Great Lakes Bioenergy Research Center’s (GLBRC) sustainability research site at the Kellogg Biological Station in southwestern Michigan, U.S.A. Crops ranged from high-diversity perennial grass and forb mixtures to hybrid poplar to conventionally farmed annual monocultures of corn, soybean, canola. Root intersections are observed and recorded at 10-15 day intervals by inserting a small video camera into the tubes. Video recordings of root intersections were quantified by image processing algorithms. Initial results indicated significant differences in the root length density and fine root turnover in the different bioenergy crops. We also analyzed the rooting characteristics in relation to root zone water availability and other canopy responses.