Non-additive responses of litter decomposition, litter chemical traits, and soil C:N:P stoichiometry to mixing with Eucalyptus in plantation environments

Although litter decomposition is closely linked to soil biochemical processes, the non-additive effects of litter mixing on soil C:N:P stoichiometry and the factors that regulate it have been rarely studied.

In this study, an in situ foliar litter decomposition experiment examined the effects of mixtures of the foliar litter of Eucalyptus urophylla × grandis with five native tree species (Acacia crassicarpa, Castanopsis hystrix, Michelia macclurei, Magnolia sumatrana and Mytilaria laosensis) in subtropical China. We investigated the decomposition and element release dynamics of single and mixed foliar litters, their non-additive effects on soil C:N:P stoichiometry, and the potential factors regulating this non-additive effect.

Our results show that foliar litter mixing promoted mass loss and element release, with less mass remaining for one mixture. The magnitude of the non-additive effects of decomposing mixed foliar litter on mass remaining, element release, and soil C:N:P stoichiometry varied by litter type. Specifically, antagonistic effects were common for mass remaining (accounting for 10.0% of all cases), the release of N (16.7%) and N:P (10.0%) of mixed foliar litter, and soil C:N (13.3%). Synergistic effects were common for the release of C (23.3%), P (10.0%), C:N (23.3%), C:P (26.7%) of mixed foliar litter, and C (20.0%), N (16.7%), P (16.7%), C:P (13.3%), N:P (10.0%) of soil. Mixing the foliar litter of Eucalyptus with some species had significant synergistic effects on soil N and N:P, whereas mixing it with other species had significant antagonistic effects on soil C:P and N:P.

Overall, foliar litter mixtures affected soil C:N:P stoichiometry in non-additive ways, and the magnitude and direction of these effects were jointly regulated by edaphic factors, initial litter chemical traits, and the presence of an invasive species, Eucalyptus.