Effect of air temperature on bud burst phenology in ecodormant subtropical trees of different ages

Key message

The temperature response of bud burst timing varies according to tree age in subtropical tree species, but in part of the tree species the variation is minor.

Abstract

Temperature is a pivotal factor regulating the spring phenology of trees. Despite some emerging research on age-related phenological differences, the temperature response of the spring phenology in trees of different ages remains poorly understood. We determined the response experimentally for 5-year, 20-year, and 50-year-old trees of three subtropical tree species: pecan (Carya illinoensis), hickory (Carya cathayensis), and torreya (Torreya grandis). On the basis of the results, we formulated for each tree species and age a model for the air temperature response of the rate of ontogenetic development toward bud burst, which was then used in computer simulations predicting bud burst in Hangzhou, south-eastern China in 1958–2019. The experimental results showed minor differences between the tree ages in pecan, but in the other two species, the rate of development decreased with tree age, leading in computer simulations with hickory and torreya to bud burst taking place an average of 9 and 17 days earlier, respectively, in the 5-year-old trees than in the older ones. Across the tree species and ages, the rate of ontogenetic development during the experimental treatments correlated with the total non-structural carbon concentration of the buds measured at the start of the experiment but not with the concentrations of the plant hormones ABA and GA. Our results show that tree age needs to be taken into account in simulation studies addressing the spring phenology of trees under current and future climate conditions.