Fig. 5

Interactions between the two species at stand level (crosses) and effects of the mixture on each species (circles for poplar, diamonds for black locust) over time in terms of biomass production per hectare, aboveground net primary production, leaf area index, and tree nitrogen per hectare (means ± standard errors, n = 2). The effects of date (D), species (S), and their interaction are indicated for *P ≤ 0.05, **P ≤ 0.01, and ***P ≤ 0.001; ns for non-significant. Different letters indicate significant differences among dates