Initial leaf litter traits affect soil microbial CO2 production: A laboratory experiment using the leaf litter of 41 temperate deciduous tree species

Abstract

Considering the important role of litter quality in soil processes, litter species diversity may be a key determinant of many ecosystem functions, including carbon (C) sequestration. The traits of litter that affect soil microbial CO2 production can be studied under laboratory incubation to identify specific factors through the homogenization of other conditions. However, laboratory incubation studies are often conducted using fewer plant species than in field incubation studies that involve litter bags. Thus, to test whether initial leaf litter traits were associated with soil microbial CO2 production rates, we conducted a 100-day laboratory incubation in homogenized soil using the leaf litter of 41 deciduous tree species collected in a temperate deciduous forest in Japan. Our results showed that litter effects on soil CO2 production differed over time among plant species. Leaf litter with lower C and lignin concentrations, lower lignin:nitrogen (N) and lignin:C ratios, and a lower leaf mass per area increased soil CO2 production in the early stage of the incubation (0–28 days) whereas litter with higher initial C:N and lignin:N ratios increased soil CO2 production in the later stage (43–70 days). Differences in species-specific litter effects on soil CO2 production were greatest during the early stage and declined over the course of the incubation. Cumulative CO2 production during the 100-day incubation was significantly correlated with initial leaf N content per area, leaf mass per area, C and lignin concentrations, and lignin:N and lignin:C ratios. Those parameters have been reported to be included in leaf economics spectrum. Our results indicate slower soil CO2 production by tree species at the conservative end of the spectrum. They also highlight the importance of using trait-based approaches and diverse plant species to investigate biosphere-atmosphere carbon fluxes.