European yew (Taxus baccata) is a rare and endangered species in many European countries. Observations of high levels of T. baccata seedling mortality under the canopy of mature trees suggest that mortality due to low irradiance may contribute to the decreasing population size of this species. The primary goal of my work was to determine if light and nitrogen fertilization influence the growth and survival of T. baccata seedlings. In 2002 and 2003, we carried out a field experiment with a range of light availabilities (reducing artificial light and obtained 2, 8, 30 and 100% RPPFD-Relative Photosynthetic Photon Flux Density) and a nitrogen fertilization treatment (with and without NH4NO3 fertilizer). In 2002 and 2003, the mortality of one-yearold seedlings was very high after the first winter, especially within extreme light conditions (2 and 100% RPPFD). Biomass of seedlings was highest in 30%, intermediate in 100% and lowest in 8% and 2% RPPFD. High levels of seedling mortality during the winter suggest that low temperatures were the primary determinant of T. baccata seedling survival. Nitrogen fertilization only had a positive effect on growth in higher RPPFD values (8, 30 and 100%). Both total needle mass and needle mass allocation were higher in the nitrogen fertilization treatment Interaction of low temperature and light availability is probably the direct reason of high mortality of T. baccata seedlings located near the species range limit.
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