Leaffall Phenology And Patterns Of22Evergreen Woody Species In Subtropical Evergreen Forest In Hantong Zhejiang, China

Leaf fall penology and patterns reflect the physiological ecology adapting of leaf to environments, which are the basis for the ecosystem process and function. It is of importance to understand plant history strategies, forest dynamics and diversity of species.In the present study, leaf fall patterns are determined in22common evergreen broad-leaved species with different canopy structure and different life-forms or life history stages of Tiantong evergreen forest, Zhejiang Province. Leaf fall phenology, leaf dynamics on current-year and older branches were recorded. Simultaneously, the main function traits of mature leaves such as leaf mass and photo synthetic rate were measured in summer and autumn from within one year. The primary objective of this study is to reveal the diversity of leaf fall pattern and its possible influencing factors. The results are shown in the following:1. The total annual percentage of leaf fall ranged from7%to96%among the species in this study. On the community level, Canopy species were significant greater than understory ones (species average72%and34%respectively); In the same species, tall tree individuals were larger than sapling ones, but little difference was found between understory saplings and shrubs.2. The total annual percentage of leaf fall were related to the age structure of canopy leaf populations and the average life expectancy of leaves. the higher age class of the species owned, the smaller the percentage of total leaf fall. The total amount of perennial leaf fall was also correlated with current-year new leaf amount. When expressed as leaf numbers, the more the numbers of new leaf on a unit twig, the more leaf fall numbers of the perennial leaves on the branches attached to the same trunk.3. Leaf fall phenology of evergreen broad-leaved woody species have a seasonal dynamic characteristics of diversity, according to the peaks of leaf shedding and temporal distribution, they can be divided into seasonal feaf lall peak and successively leaf fall patterns. In the22species,5species showed a spring leaf fall peak (2canopy species and3understory ones),8species showed a summer leaf fall peak (3canopy species and5understory ones),1species showed an autumn leaf fall peak (belong to canopy species),1species showed an spring and autumn bimodal leaf fall peaks (belong to canopy species) and7species shed their leaves successively year round and without a remarkable leaf fall peak. On community level with different life forms, canopy tree species are most seasonal leaf fall patterns, while understory shrub species showed successively leaf fall patterns; Moreover, the same species in different life history stages showed a same leaf fall pattern.4. The leaf fall process was mainly affected by the leaf out process during spring in subtropical evergreen forest in Tiantong. The results showed the earlier the leafing begins or the more numbers of leaf emergence, the more numbers of leaves were dropped during spring and summer periods. During autumn, climatic conditions such as decreased precipitation also have an influence on the dynamic of leaves to some extent; however, the degree of leaf fall differed among species.