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Continuous and Fluctuating Leaf Phenology of Adults and Seedlings of a Shade-tolerant Emergent Tree, Dipterocarpus sublamellatus, in Malaysia


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Continuous leaf phenology, with sequential production of metamers, is usually found in pioneer species, but is rare in shade-tolerant species. Because of the nature of ‘continuous’ growth, continuous phenology has seldom been related to meteorological factors. We studied the leaf demography of seedlings and tall trees of a shade-tolerant emergent species, Dipterocarpus sublamellatus (Dipterocarpaceae), in Malaysia. Although leaf phenology of D. sublamellatus was classified as continuous, the rates of leaf production and leaf fall were not constant and greatly fluctuated during the census period. Seasonal patterns of leaf production and fall were not synchronized across tall trees in most combinations or between seedlings and tall trees. Mean number of leaves produced per month and its seasonal fluctuation were greater in tall trees than in seedlings. Moreover, relationships between leaf phenology and meteorological factors (monthly rainfall, net radiation, maximum and minimum temperature, and minimum relative humidity) differed among trees. This suggests that endogenous rhythms, i.e., differences in allocation of resources to growth and storage among trees, are important to fluctuations in leaf phenology. These patterns are in contrast to patterns found in various pioneer species with continuous phenology, in which rates of leaf production and fall are generally constant. Different patterns might be caused by differences in allocation to growth and storage between pioneer and shade-tolerant species, and might be related to their regeneration strategies.