Effect of incubation time, litter diversity and species richness on decomposition dynamics of tree species from western Himalayas

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Biodiversity loss may seriously impact some of the major ecological functions like primary productivity, nutrient cycling and decomposition. Decomposition is a fundamental ecosystem process regulating nutrient mineralization, microbial community composition and structure, carbon sequestration in the soil. Therefore it is important to find out the link between biodiversity and decomposition dynamic which is of key interest recently among ecologists, hence we took up eleven combinations of leaf litter mixtures of four multipurpose tree species commonly occurring together in western Himalayas to find out the direction, magnitude and drivers of litter mixing effect. We found positive non significant effect of litter diversity for all mixtures except two which showed antagonistic effects after three months of decomposition. But we found positive non additive effects (NAE)/interaction effects for all litter mixtures at later stage of decomposition i.e. after nine months. The strength of litter mixing effect varied from 5.45% to 14.75% among litter mixtures. The interaction effects are observed to be greater for those litter mixtures which are more heterogeneous with respect to initial nitrogen, and phosphorus content. However the effect of chemical diversity is more marked on interaction effect/ NAE than variation in single trait(N or P content) as revealed by R2 value (coefficient of determination). Interaction effect values increased with increase in percent of fast decomposing species in the litter mixture but rate of increase decreased when the mixtures move towards homogeneity. Interaction effect also increased with increase in species richness significantly up to three species, thereafter the increase is non significant. Our results indicate that tree diversity alters decomposition dynamics of component species in the mixture. Chemical diversity is more important factor in determining non additive effect rather than taxonomic diversity of a mixture.