Comparisons of litterfall, litter decomposition and nutrient return in a monoculture Cunninghamia lanceolata and a mixed stand in southern China

Litter production, leaf litter decomposition and nutrient return were compared in a monoculture Cunninghamia lanceolata and a mixed stand in southern China. The mean annual litter production was significantly higher 24% in the mixed stand than the monoculture C. lanceolata stand. Within the mixed stand, about 38% of the total litterfall was from broadleaved tree Michelia macclurei. The litterfall was concentrated during the cool and dry period (November–March) and about 65% of total litterfall occurred during this period. The mass loss of leaf litter was positively correlated with N and P content and negatively correlated with C/N ratio. The decomposition rate of leaf litter in the pure stand was increased in the order: C. lanceolata < mixture of C. lanceolata and M. macclurei < M. macclurei. Soil conditions also affected litter decomposition. The decomposition rate of mixed litter was slightly, but not significantly, faster in the mixed stand than the pure stand. N concentration in all leaf litters increased over time during decomposition, whereas the remaining amount of N decreased. The returns of N, P and K via leaf litter were significantly higher in mixed stand than pure stand, but the returns of C, Ca and Mg between both stands did not differ significantly. The percent contribution of M. macclurei leaf litter to total nutrient return varied from 23% to 79% in the mixed stand. Our results indicated that introduction of broadleaved tree into monoculture coniferous stand could increase litter production, nutrient return and thus it had advantages in degraded soil restoration and sustainable land management.