ARS | Publication request: 14c Cycling in Lignocellulose-Amended Soils: Predicting Long-Term C Fate from Short-Term Metrics

Submitted to: Biology And Fertility Of Soils
Publication Acceptance Date: September 1, 2004
Publication Date: September 13, 2004
Citation: 2004. 14c Cycling In Lignocellulose-Amended Soils: Predicting Long-Term C Fate From Short-Term Metrics. Biology And Fertility Of Soils.

Interpretive Summary: There is interest in the scientific and government communities in ways to reduce greenhouse gases in the atmosphere especially carbon dioxide (CO2). The most well known way is for plants to utilize more CO2 incorporating it into tissue and wood, thus planting more forests would decrease atmospheric CO2. However, as plants die soil organisms metabolize the plant tissue into CO2. Our research investigated how the metabolism of resistant plant tissue compounds varied among several different ecosystems. We found that decomposition was related to the amount of fungi verses bacteria in the soil. We also found that the decomposition over time was related to the amount decomposed in a short time and the sand content of the soil. Impact This data is important to scientists because we can develop management systems such as reduced tillage tailored to specific sites and soils. We can identify which agricultural or forest system has the potential for maximum soil C storage thus reducing atmospheric CO2.

Technical Abstract: The degradation of recalcitrant, abundant, naturally occurring compounds such as lignocellulose is a significant component of the global C cycle. Identifying land uses that maximize the storage of this C in soil rather than its mineralization to CO2 will aid in recommendations designed to offset greenhouse C emissions from anthropogenic sources. Furthermore, identifying simple relationships that can be used to predict which soils are most likely to store C will also aid in C storage management planning. We compared lignocellulose-14C degradation over 8 months in contrasting soils from each of five ecosystems across the United States. 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 non-fertilized). We found soils that rapidly metabolized freshly added C exploited endogenous and newly transformed C to a lesser degree over the course of the incubation resulting in greater amounts of C stored. We also pooled the data to find a strong relationship between soil 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 d) and lignocellulose-C remaining after 8 months (R= 0.94). Thus the initial rate of substrate utilization, be it pine needles or grass, may be an important factor in ecosystem C storage.