Litter mixture effects on decomposition change with forest succession and are influenced by time and soil fauna in tropical mountain Andes

In highly transformed regions, such as the tropical Andes, identifying the influence of forest succession and soil fauna on non-additive effects of litter decomposition is crucial for gaining a more realistic understanding of carbon dynamics and nutrient cycles. The objective of this paper was to analyze the changes of litter mixture effects on decomposition between different soil fauna treatments (macrofauna inclusion vs macrofauna exclusion) and successional stages (mature forests vs secondary forests) in upper Andean tropical forests along time by using a reciprocal translocation experiment of 1,344 litterbags that ran for 18 months with six common native Andean species. Thought t-tests, linear regressions, and linear mixed models, I found that litter mixture effects vary among sites and increase with time in secondary forests until the year of decomposition in litterbags with macrofauna exclusion. Mature forests exhibited strong antagonistic effects, while pronounced synergistic effects were observed in secondary forests. Although soil macrofauna did not increase significantly litter decomposition and synergistic effects in the mixtures at any of the stages of decay, it is likely that soil macrofauna may impact litter mixtures through top-down effects within soil food webs, rather than exerting a direct effect in the litter consumption as has been reported in tropical lowland ecosystems. Overall, this study supports the idea that litter mixtures exhibit significant variability across sites, can change with successional stage, and are influenced by soil fauna depending on the stage of decay in tropical Andean montane forests.