Abstract: To explore the suitable stand density of moso bamboo (Phyllostachys edulis) in the agroforestry systems of bamboo-Sophotora flavescens and bamboo-Catsia tora, we investigated the growth and biomass of two nitrogenfixing species, S. flavescensandC. tora, under three moso bamboo densities, D1 (1600±200 stems·hm^-2), D2 (2400±200 stems·hm^-2) and D3 (3200±200 stems·hm^-2) with the same site conditions and management levels. The results showed that plant height, basal diameter, tissue biomass and total biomass of both species all decreased with the increases of moso bamboo density. The decreased amplitude followed the order of D3>D2>D1. The biomass proportions of leaf and bean of S. flavescensshowed an inverted V shaped pattern, while the root biomass proportion and root/shoot ratio varied with a Vshaped pattern, and the stem biomass proportion decreased linearly with the increases of bamboo density. Except for the stem, the biomass proportions of other organs had no significant differences (P>0.05) among three bamboo densities. With the increases of moso bamboo density, stem biomass proportion, root biomass proportion and root/shoot ratio ofC. tora seedlings showed a similar trend to that of theS. flavescensseedlings. The proportions of leaf biomass and bean biomass showed an increase trend, with the values in D1 being significantly higher than that of D2 and D3 (P<0.05).Results from the principal component analysis and Rtype factor analysis showed that the comprehensive scores of growth and biomass allocation of bothS. flavescens and C. tora followed the order of D1>D2>D3. Our results indicated that the bamboo density had negative effects on the growth and biomass allocation ofS. flavescens andC. tora seedlings. D1 (1600±200 stems·hm^-2) would be the suitable bamboo density for the management of both agroforestry systems.

Key words: dry matter accumulation, rice-wheat, yield, nitrogen use efficiency, pig manure