Initial lignin content as an indicator for predicting leaf litter decomposition and the mixed effects of two perennial gramineous plants in a desert steppe: A 5-year long-term study

Leaf is the main component of litter that often exists in mixed forms in nature. However, the mixed effects of leaf litter decomposition in desert ecosystems remain unclear. To reveal the mixed effects and the influence of litter quality on leaf litter decomposition in desert ecosystems, a 5-year long-term study was conducted to compare the observed and expected leaf litter mass loss in single-species and mixed (equal proportions and natural proportions) litters of two typical perennial gramineous plants (Stipa klemenzii and Achnatherum splendens) in a desert steppe in Northern China. The relationship between litter mass loss and litter qualities was also analysed. The results showed that (a) after 5 years of decomposition, the mass losses of mixed litter in natural proportions and S. klemenzii litter were significantly higher than those of mixed litter in equal proportions and A. splendens litter; (b) the mixed effects of two litters in different ratios varied with time, and the synergistic effect only appeared in the second year when an easily decomposed litter (S. klemenzii) was mixed with a slowly decomposing litter (A. splendens); and (c) litter mass loss was not correlated with the initial carbon or nitrogen content but was negatively correlated with the initial lignin content, and the initial lignin content also had a significant effect on litter mixed effects of these two perennial gramineous plant litters. These results can suggest that the initial lignin content is an indicator of predicting decomposition and mixed effects of litter with low nitrogen content.