Mixed-Species Plantation of Pinus massoniana Lamb. and Quercus variabilis Bl. and High Soil Nutrient Increase Litter Decomposition Rate

Changes in land use and forest planting have led to substantial changes in soil fertility and leaf litter input. The effects of mixed planting on the leaf litter decomposition rate in contrasting soil nutrient conditions are poorly understood. To elucidate the effects of litter composition and soil fertility on litter decomposition, we conducted a field litterbag-decomposition experiment with single (Pinus massoniana Lamb. or Quercus variabilis Bl.) and mixed (P. massoniana and Q. variabilis) litter treatments on soils of three nutrient levels (high, medium, and low). During the 3-year decomposition, at each decomposition stage and soil nutrient level, the mass-loss rate (MLR) was higher in mixed-litter than in the two single-litter treatments, with the exception of Q. variabilis, which recorded a higher MLR at 724 d in medium and high soil substrates. Between the two single-litter treatments, the MLR of Q. variabilis litter was higher than that of the P. massoniana litter; the MLR of the component litter of P. massoniana and Q. variabilis was higher than that of the corresponding two single-litter treatments. The k values over the 3-year-experiment period increased with the soil nutrient level for all litter treatments, as did microbial biomass carbon and nitrogen content. These findings suggest that mixed planting and high level of soil nutrient can accelerate litter decomposition.