Litter mixing effects (LME) during decomposition contribute greatly to material cycling in ecosystems, but they are strongly affected by nitrogen deposition. However, whether and how litter diversity affects the influence of nitrogen deposition on LMEs during natural vegetation succession remains unclear. We aim to clarify these issues and provide a scientific basis for maintaining nutrient cycling in ecosystems affected by nitrogen deposition. All the possible litter mixtures of Artemisia gmelinii Weber ex Stechm., Chrysanthemum indicum L., and Sophora davidii (Franch.) Skeels, three common species in an abandoned shrub-grassland in the Loess Hilly Region, were used to simulate mixed litter decomposition on the surface of soil. The influence of nitrogen deposition on the LMEs of mixtures with different species (chemical) diversity was compared. Under natural conditions, litter mixtures with low and high species (or chemical) diversity had synergistic and antagonistic effects on litter decomposition, respectively ( P < 0.05). Under nitrogen deposition, the synergistic effects were weakened, whereas the antagonistic effects were enhanced ( P < 0.05). The adverse effects of nitrogen deposition decreased as chemical diversity increased, especially for chemical dispersion ( P < 0.05). In the view of material cycling function of shrub-grassland ecosystems, maintaining high species diversity is beneficial for maintaining their long-term stability under nitrogen deposition.
Li et al. (Thu,) studied this question.