First and second sets of shoots in five evergreen woody species from Tiantong National Forest Park of Zhejiang, China

Abstract

Aims Some woody species of subtropical evergreen broad-leaved forests in Eastern China form a second set of shoots in late summer or autumn after a first set in spring. Our objective is to elucidate features of this second set of shoots, including their adaptive significance. Methods We investigated differences between the first and second sets of shoots for five evergreen woody species (Symplocos lancifolia, Loropetalum chinense, Eurya rubiginosa var. attenuata, Myrica rubra, and Castanopsis fargesii) from an evergreen broad-leaved forest in Tiantong National Forest Park of Zhejiang, China. Herbivore damage of leaves was estimated, leaf emergence rate, leaf expansion rate and duration were calculated, and twig investment (leaf number and individual leaf area within twigs, twig stem length and diameter) was measured for both sets of shoots. Important findings Leaves of M. rubra and C. fargesii suffered greater herbivore damage to the second shoots compared with the first, and no significant difference was found in damage between the two sets of shoots for S. lancifolia, L. chinense and E. rubiginosa var. attenuata. The first and second sets of shoots shared the same leaf emergence pattern. Symplocos lancifolia, L. chinense, E. rubiginosa var. attenuata, and M. rubra showed a succeeding type of leaf emergence, and C. fargesii showed a flushing type of leaf emergence. However, duration of leaf emergence was much shorter in the second set of shoots for S. lancifolia, E. rubiginosa var. attenuata and M. rubra than in the first but not for the other two species. Leaf expansion rate was significantly higher for the second set of shoots for S. lancifolia, L. chinense and E. rubiginosa var. attenuata and was indistinguishable for M. rubra, C. fargesii leafed out late in the first set of shoots. Moreover, leaf number (except for L. chinense), individual leaf area, twig stem length (except for L. chinense) and diameter were significantly smaller in the second than in the first set of shoots for four species, indicating lower twig investment in the second shoots for all the sampled species. In general, leaf herbivory damage, rates of leaf emergence and expansion were not smaller (sometimes significantly greater), but the total investment on twigs was significantly lower in the second shoots compared to the first. We speculate that these differences might result from the selective force of heavy herbivory pressure and adverse climate conditions of coming winter for the leaves produced during the second set of shoots.