Plant Chemistry and Morphological Considerations for Efficient Carbon Sequestration

Carbon sequestration to soils counteracts increasing CO2 levels in the atmosphere, and increases soil fertility. Efforts to increase soil carbon storage have produced mixed results, due to the multifactorial nature of this process, and the lack of knowledge of molecular details on the interplay of plants, microbes, and soil physiochemical properties. This review discusses the carbon flow from the atmosphere into soils, and factors resulting in elevated or decreased carbon sequestration. Carbon partitioning within plants defines how much fixed carbon is allocated belowground, and plant and microbial respiration accounts for a significant amount of carbon lost. Carbon enters the soil in form of soluble and polymeric rhizodeposits, and as shoot and root litter. These different carbon sources are immobilized in soils with varying efficiency as mineral-bound or particulate organic matter. Plant-derived carbon is further turned over by microbes in different soil layers. Microbial activity and substrate use is influenced by the molecular weight and chemical class of the plant-derived carbon. Further, soil carbon formation is altered by root depth, plant growth strategy (perennial versus annual), and C/N ratio of rhizodeposits. Current gaps of knowledge and future directions are highlighted.