Influences of species mixture on biomass of Masson pine (Pinus massoniana Lamb) forests

The effect of tree diversity on productivity in subtropical forests in China is poorly understood. We investigated the biomasses of trees, understory vegetation, coarse roots, and fine roots with varying proportions of Pinus massoniana, mixed with other tree species in stands of the same age, to examine the effects of tree diversity. With an increase of P. massoniana proportion, the tree and understory biomasses increased at first, and then gradually decreased. As expected, the biomass of fine roots decreased with soil depth. Stands with 40 to 60% P. massoniana had the highest biomass, whereas stands with <20% P. massoniana had the least biomass. Stands with <20% P. massoniana had the least understory biomass, whereas those with 20 to 40% Masson pine had the least fine root biomass.