Intraspecific variation in leaf life span for the semi-evergreen liana Akebia trifoliata is caused by both seasonal and aseasonal factors in a temperate forest
Koyama K; Kikuzawa K
Journal of Ecology and Field Biology
We investigated the leaf demography of a temperate woody liana Akebia trifoliata in a temperate forest in Japan Akebia is semi-evergreen: some leaves are shed before winter while others remain through the winter. Previous studies of semi-evergreen species found that variation in leaf life span was caused by variation in the timing of leaf emergence Leaves that appeared just before winter over-wintered while leaves appearing earlier were shed However it is unclear whether leaves of the same cohort (i.e. leaves that appear at the same time within a single site) show variation in life span under the effect of strong seasonality. To separate variation in life span among the leaves in each cohort from variation among cohorts we propose a new method - the single leaf diagram which shows the emergence and death of each leaf. Using single leaf diagrams our study revealed that Akebia leaves within a cohort showed substantial variation in life span with some over-wintering and some not. In addition leaves on small ramets in the understory showed great variation in life span while leaves on large ramets which typically reach higher positions in the forest canopy have shorter lives As a result small ramets were semi-evergreen whereas large ramets were deciduous The longer lives of leaves on small ramets can be interpreted as a shade-adaptive strategy in understory plants.