Mixing effects of three Eurasian plants on root decomposition in the existence of living plant community in a meadow steppe

In grasslands, roots of different plant species decay in combination in the presence of living plants, besides, most root decomposition studies are conducted on how roots of plants decomposed alone or in artificial compositions in the absence of living plants. Therefore, we evaluated how roots of different perennial plants induced effects on decomposition process under living plants and their associated mechanisms. By using litter bag technique, we determined the root decomposition process of three perennial plants, Leymus chinensis, Phragmites australis, and Kalimeris integrifolia grown in monocultures, bi- and tri-species mixtures, after 12 months of incubation under living plants and bare soil communities. We found both additive and non-additive effects on decomposition dynamics indicating that root mass losses of compositions cannot be calculated from decaying rates of individual species. The rich-nutrient roots of K. integrifolia in monocultures and in mixtures with other plant species decayed faster. Compared with bare soil, microbial activities were enhanced under living plant communities and hence stimulated decomposition rates. Our results indicated that microbial activities are important but secondary factors to root physico-chemical properties impacting root decomposition rates. In conclusion, the empirical relationships developed here are helpful to better understand the effects of root properties and microbial activities on decay rates.