14C Cycling in lignocellulose-amended soils: predicting long-term C fate from short-term indicators

We compared lignocellulose (the second most abundant component of plant material) degradation over 8 months in contrasting soils from each of five sites across the United States with the aim of assessing which soils are likely to store more C. The soils were collected from a tallgrass prairie restoration (farmland, and plots restored in 1993 and 1979), the semiarid shrub-steppe (cool, moist upper slope and warm, dry lower slope soils), long-term farmland (no-till and conventional-till), and from two forest soils (loblolly pine and Douglas fir; fertilized and nonfertilized). Soils that rapidly metabolized freshly added C exploited endogenous and newly transformed C to a lesser degree over the course of the incubation (lower slope shrub-steppe, nonfertilized Douglas fir, and tallgrass prairie farmed and 1993 restorations). We also pooled the data to find a strong relationship between sand content and lignocellulose C remaining in the soil after 8 months (R=0.68) and also between short-term storage of lignocellulose C (at 7 days) and lignocellulose C remaining after 8 months (R=0.94). To predict C storage, models of C and soil properties must be modified to reflect the structure and function of microbial communities. Communities in richer soils may be more competent to use native C following fresh C additions when compared with communities in poorer soils.