Impact of tree leaf phenology on growth rates and reproduction in the spring flowering species Trillium erectum (Liliaceae)

We investigated the impact of overstory tree leaf phenology on growth rates, carbon allocation pattern, and fruit characteristics in the spring flowering species, Trillium erectum (Liliaceae). Air temperature, overstory canopy closure, and T erectum phenology were monitored at three locations following a latitudinal gradient in Quebec, Canada. Northern sugar maple trees leaf out at cooler temperatures than more southern populations, while Trillum development was initiated,it the same soil temperature irrespective of the latitude Therefore, in northern areas, the nine between initiation of T. ere( tum leaf expansion and canopy closure was shorter than in southern areas, which left less time for northern plants to accumulate reserves before canopy closure. Differences in growth patterns were noted between T. erectum populations From a south-north gradient. investment to reproduction, total plant biomass. and annual growth rate decreased, while specific leaf area and stem height increased, indicating shade acclimation. The length of the high light period in early spring seems to be a determinant for spring flowering plants' growth and reproduction and may explain the northern distribution limit of some of these species.