 One strategy for mitigating climate change is to increase the amount of carbon stored in the soil in the form of soil organic matter, abbreviated here as SOM. Of particular interest is stable SOM, which can store carbon for centuries before it can return to the atmosphere as carbon dioxide. Stable SOM forms from decomposing plant matter, also called litter. To better understand this process, the decomposition of tall grass litter was investigated in a recent study. The findings reveal two distinct decomposition pathways, which result in SOM with different degrees of stabilization, and therefore different longevity in the soil. SOM primarily consists of decomposed plant matter, the microbes involved in its decomposition, and their waste. Plant litter consists of a slow decaying fraction, which includes many of the structural components of the plant, such as lignin, and a fast decaying water-soluble fraction, which includes many of the non-structural components, such as sugars and amino acids. It has long been assumed that stable SOM is almost exclusively formed from slow decaying plant litter components. However, mounting evidence suggests that water-soluble litter components, which can be efficiently transformed by microbes, can also form stable SOM, where the stability is provided by bonding with minerals. Isotope labeling was used to track the fate of tall grass plant litter during decomposition. The researchers fed heavy carbon and nitrogen isotopes to the plants as they grew and then added the labeled plant litter to the soil in a natural tall grass prairie. These labels allowed the researchers to follow the plant matter as it descended through the soil and became incorporated into microbes. They could then identify the litter degradation products as they formed new SOM. In the laboratory, they assessed how well this new SOM withstood further microbial attack. These laboratory and field measurements revealed that, in the early stages of litter decomposition, stable mineral-bonded SOM is formed by the water-soluble, non-structural parts of the plant litter with the help of microbial transformation. Later in the decomposition process, the slow decaying components of the litter are physically transported into the soil to form less stable, coarse, particulate SOM. This finding contradicts the previous understanding of most stable SOM being formed from lignin later in the decomposition process. Though the focus of this study was natural systems, its findings could have important implications for soil management. Current soil management practices are based on the idea that adding slow decaying plant residues is the most effective way to increase soil organic matter. However, for soils with the potential to bond additional carbon with minerals, a different strategy may work. The results of this study suggest that a superior approach may be to add fresh residues and manage the soil's microbial community in order to increase the efficiency with which the plant litter retains carbon.