Does tree species composition affect soil CO2 emission and soil organic carbon storage in plantations?

Abstract

Mixed tree plantations are potential silvicultural systems to increase soil carbon storage through altering litter and root inputs and soil physiochemical properties. Afforestation and reforestation are major strategies for global climate change mitigation. Different tree species composition can induce diverse changes in soil CO2 emission and soil carbon sequestration in tree plantation. This study employed three plantations of monoculture and mixed Pinus yunnanensis and Eucalyptus globulus to estimate the effect of tree species composition on soil CO2 emission and soil organic carbon storage in subtropical China. We found that tree species composition had a significant effect on the soil CO2 emission and soil organic carbon storage. Soil CO2 emission was lower in the mixed plantation than in the P. yunnanensis plantation, whereas it was higher than in the E. globulus plantation. Differences in soil CO2 emission among the three plantations were determined by leaf litterfall mass, fine root biomass, soil available nitrogen, pH, soil bulk density, and soil C:N ratio. Soil organic carbon storage was 34.5 and 23.2 % higher in the mixed plantation than in the P. yunnanensis and E. globulus plantations, respectively. Higher soil organic carbon stock in the mixed plantation was attributed to lower C/N ratio of leaf litter and soil, greater fine root biomass and soil organic carbon content, and lower soil CO2 emission. We conclude that mixed tree plantation can enhance soil carbon sequestration, but can decrease or increase soil CO2 emission through altering litter and root inputs and soil physiochemical properties.