Abstract: Leaf expansion in plants is a process determined by both genetic and environmental factors and is considered to reflect life history strategies at the population level and to be a mechanism for maintaining species diversity at the community level. The evolution of leaf phenology has been suggested to maximize plant carbon gain and minimize leaf losses due to the herbivory. In temperate broad-leaved forests, because low light levels often limit the photosynthetic capacity of understory woody species, understory species are expected to leaf out earlier in the spring than canopy species so as to obtain long leaf life span and positive carbon balance. Leaf traits, including leaf length, area, and leaf dry mass per unit area (LMA), together with leaf phenology, including timing of leaf emergence, duration of emergence, expansion, and leaf expansion rate, were investigated from the beginning of March to early June of 2001 and 2002, for the dominant shrub and tree species in three deciduous broad-leaved oak forests in the Nanjing area, East China. The leaf traits and leaf phenological parameters were compared among canopy and understory species, and the relationship between leaf traits and leaf phenology was examined by correlation and regression analyses. The canopy species were characterized by larger leaf areas and higher LMA than the understory species. The understory species leafed out earlier, but not significantly earlier, than the canopy species. This is in contrast to the hypothesis, possibly because individuals experienced different environmental conditions due to habitat heterogeneity that affected leaf phenology. Leaf expansion rate of canopy species was greater than that of shrub species: the larger the final leaf area of the species, the greater the expansion rate. This is assumed to be a strategy for large-leaved canopy species to decrease defoliator damage during leaf expansion. Small-leaved species were found to leaf out earlier than species with large leaves. This suggests a possible approach for small-leaved species to avoid leaf loss since herbivory pressure is often low in early spring. Inter-specific correlation analysis indicated that species with high LMA leafed out earlier than their counterparts. This is consistent with results of previous studies on leaf life span, including mathematic models and empirical investigations, in which species with high LMA were found to need more time to gain positive carbon balance. In general, dynamics of leaf emergence and expansion of the woody species in the study forests indicate that the timing of leaf emergence is of significance for a species' carbon gain, survival and reproduction.