[Effects of topographic factors on leaf traits of apricot in the Loess Plateau, Northwest China].

As important topographic factors, slope aspect and gradient affect plant growth and leaf functional traits by regulating the combination of water and heat. Exploring the response of leaf functional traits to topographic factors is helpful for understanding plant adaptation strategies. We investigated the effects of sunny slope (including half sunny slope) and shady slope (including half shady slope) and three slope gradient (15°-20°, 21°-25°, and 26°-30°) on the leaf functional traits of apricot (Prunus armeniaca L.), the main afforestation tree species on the Loess Plateau. The results showed that: 1) Slope aspect and gradient exerted significant effects on all functional traits. Except leaf water content (LWC), other leaf functional traits were not affected by the interaction of slope aspect and gradient. 2) The leaf area (LA) under the sunny slope was equivalent to that under the shady slope. Leaf dry matter content (LDMC) and LWC (0.27 g·g ^-1 and 67.0%, respectively) were significantly higher under the shady slope than under the sunny slope (0.24 g·g ^-1 and 59.6%, respectively), while specific leaf area (SLA) (163.05 cm ² ·g ^-1 ) was significantly lower under the former than under the latter (183.72 cm ² ·g ^-1 ). 3) At different slope gradients, SLA and LA reached a maximum value at 15°-20° (184.04 cm ² ·g ^-1 ) and 26°-30° (21.14 cm ² ), respectively. 4) Except no difference in soil water content (Θ) between 15°-20° and 26°-30°, it differed significantly between two slope aspects and among other slope gradients. The Θ was one of the main factors causing the differences in functional traits, especially in the 0-10 cm soil layer. 5) SLA was negatively correlated with LWC and LDW and positively correlated with LA. LDW was positively correlated with LWC and negatively correlated with LA. Θ was positively correlated with LWC but not with other leaf functional traits.