Leaf and root inputs additively contribute to soil organic carbon formation in various forest types

Purpose In forests, soil organic carbon (SOC) formation largely originates from above- and below-ground plant inputs with different substrate qualities. However, to what extent litter and root inputs contribute to SOC accumulation across different forest types at the global scale is not fully understood. Methods We compiled 539 paired observation that was made after exclusion or double addition (additional 100% input relative to the control plots) of leaf litter, living roots, and wood inputs from forests worldwide to assess the changes in SOC concentrations under plant input manipulation. Results We found that the SOC concentration decreased by 15.1% after exclusion of plant input but increased by 10.3% with double plant input. Overall, leaf litter (- 13.4%) or living roots (-12.7%) exclusion had a similar but additive (-23.9%) impact on SOC concentration. The effects of both plant exclusion and addition on SOC did not differ among forest types (i.e., broadleaved vs. coniferous forests, deciduous vs. evergreen forests, and primary forests vs. plantations), suggesting that plant input had a similar contribution to SOC accumulation across forest types. However, for broadleaved forest, leaf litter exclusion (-14.9%) had a greater impact on SOC concentration than did living roots (-9.5%), implying that leaf litter input contributed more to stable soil carbon accumulation than living roots in broadleaved forests. The effect of plant input manipulation (both exclusion and addition) on SOC concentration increased over the experimental period. Conclusion Our results quantitatively assessed the sources, pathways, and contributions of litter- and root-derived SOC from the perspective of plant input manipulations, and the contributions of different litter types should be separated to evaluate the formation of soil organic carbon in different forest types.

Automated summary

This study quantitatively assessed the contributions of litter and roots to soil organic carbon (SOC) through plant input manipulations in different forest types. The results showed that plant inputs had similar contributions to SOC accumulation across forest types, with litter having a greater impact on SOC concentration than roots in broadleaved forests.