Abstract: The relationship among plant functional traits is a habitat adaptation strategy that can affect their ability to use space resource, reflecting pathways and mechanisms of plant adaptation. Using the method of standardized major axis (SMA) estimation, we examined the relationship between leaf dry mass and leaf area, leaf thickness of Hippophae rhamnoidesunder three natural habitat conditions in Taohe River riparian forest: full sun (I), gap (II), under canopy (III). The results showed that soil moisture gradually increased, and the photosynthetically available radiation (PAR) displayed decreasing trends with decreasing light availability. Population height, canopy closure, leaf area (LA), leaf thickness (LT), leaf dry weight (LDW), transpiration rate (T_r), and stomatal conductance (G_s) gradually increased, while specific leaf area (SLA) decreased with increasing shading. There were significant different growth relationships of leaf area, leaf thickness, and leaf dry mass of H. rhamnoides among three habitats (P<0.05). There was an allometric relationship between LDW and LT, but an isometric relationship between LDW and LA at habitat I. The increasing speed of LDW was greater than that of LT. The LDW was isometrically related to LA and LT at habitat Ⅱ. At habitat Ⅲ, there was a clear allometric relationship between LDW and LA and an isometric relationship between LDW and LT, with the growth rate of LA being greater than that of LDW. H. rhamnoides grown in the full sun habitat and under canopy habitat generally had small and thin, big and thick leaves respectively, reflecting an investment trade off among plant leaf functional traits in adapting to heterogeneous light environment.

Key words: light, leaf thickness, leaf size, allometry, Hippophae rhamnoides, riparian forest.