Abstract: Different vein levels of plant have different functions, and the allometric growth pattern of the vein density and leaf size has important implications for understanding plant phenotypic plasticity. In this study, ArcGIS was used to construct the digital elevation model (DEM) for the study sites. We aimed to study the allometrical growth relationship between the 1° and 2° veins densities and leaf size of Robinia pseudoacacia at different slope aspects on the northern mountains of Lanzhou with the method of standardized major axis estimation (SMA). The results showed that with the change of slope aspect from north to east, south and west, the crown density, height and the soil moisture of the plant community decreased first and then increased, the individual leaf size and specific leaf area and the leaf eccentricity of R. pseudoacacia displayed a pattern of decreaseincrease, and the 1° and 2° veins densities displayed a pattern of increasedecrease. There was a negative allometric correlation between the 1° vein density and the leaf size on different slope aspects (P<0.05), and a significant negative allometric correlation between the 2° vein density and the leaf size on different slope aspects (P<0.01), with the slopes being greater than -1. The sloperelated variations in the tradeoff between leaf size and different levels of vein density of R. pseudoacacia are the result of plant’s adaptation to habitat heterogeneity.

Key words: shrub, diameter, biomass, estimation model, length