Effect of Mixed Proportions on Leaf Resource Acquisition Capability in Mixed Plantations of Eucalyptus and Native Trees

Abstract:

Mixed-species plantations composed of Eucalyptus and native tree species have great potential in improving stand productivity and ecosystem functions. In this study, we investigated leaf physiological, structural and chemical traits of three dominant native tree species (Machilus chinensis, Cinnamomum burmannii and Manglietia glauca) and Eucalyptus urophylla in Eucalyptus monocultures (EM) and four mixtures of Eucalyptus (EU) and native trees species (NS) with different mixed proportions (EU:NS=5:5, 6:4, 7:3, 8:2, respectively) in south China. The results showed that there was substantial interspecific variation in leaf traits among four dominant tree species. On average, M. glauca had the highest SLA, PPUE, A_mass, T_mass, N_mass and P_mass, indicating that M. glauca adopts resource acquisition strategies. E. urophylla had the lowest SLA, PPUE, A_mass, T_mass, N_mass, P_mass but the highest PNUE, indicating that E. urophylla occupies characteristics typical of fast-growing and nutrient-conserving in order to adapt nutrient-poor environments. There was nearly no overlap between M. glauca and E. urophylla in leaf traits, such as SLA, N:P, A_mass, T_mass, PPUE and N_mass, indicating that M. glauca and E. urophylla were highly complementary in the leaf resource use. Manglietia glauca may be an ideal candidate tree species for establishing mixed plantations of Eucalyptus and native tree species. At the species level, N_mass of M. glauca, P_mass of M. chinensis, A_mass and PPUE of C. burmannii in dry season increased with the mixed proportion of native species, but leaf traits of four dominant tree species were generally not affected by the mixed proportion as a whole. At the stand level, SLA, PPUE, A_mass, T_mass and N:P in mixtures of Eucalyptus and native species were significantly higher than those in Eucalyptus monocultures. Thus, plantations established with Eucalyptus and high diversity native tree species can improve the light capture and photosynthetic capability from the stand level, but also aggravate the phosphorus limitation of plant growth. Overall, it was suggested that native species with complementary resource use to Eucalyptus and capability of optimizing phosphorus biogeochemical cycle of mixed plantations should be prioritized in designing and improving the Eucalyptus plantations in south China.