Background/Question/Methods Plant species differ in the quantity, location (above- or belowground), and chemistry of detrital inputs, which in turn influence the quantity and turnover of soil organic matter (SOM). In three separate field experiments, I measured soil organic carbon (SOC) dynamics in conjunction with various species traits, including detrital production, both above- and belowground, and chemistry of the plant detritus, including carbon fractions, N, P, Ca, Mg, K, and Al. Two of the field studies were conducted in 10- and 15-year-old experimental plantations in the moist tropical biome. The third experiment was situated in agricultural plots of various crop rotations dominated by corn (Zea mays L.) under conventional tillage in the Midwestern U.S.
Results/Conclusions Quantity of aboveground detrital inputs was not correlated with changes in SOC, whereas fine-root growth was highly correlated (P < 0.02) in all three experiments, including the tilled agroecosystems. In all ecosystems, fine roots contributed a relatively small proportion to total detrital production, 6-22% of total corn net primary production (NPP) in the agroecosystems and 11-29% of total NPP in plantations. Nevertheless, belowground inputs played a disproportionately larger role in SOC dynamics. In younger plantations, root C:N and fine root growth accounted for most of the variability in SOC changes (partial R² = 0.70 and 0.14, respectively). In older plantations, contrary to expectations, SOC declined with increasing fine-root lignin concentrations (P < 0.01), indicating that lignin-derived C did not dominate refractory SOC pools. Fine-root Al was the only chemical trait that was highly correlated with both SOC accrual and C mineralization. Together, these correlations suggest that location of detritus plays a critical role in SOC dynamics. It is hypothesized that differences among plant species in their capacity to influence SOC sequestration are driven by fine-root growth and chemistry traits which promote soil microbial turnover and, thus, production of recalcitrant, microbial-derived C fractions.