Effects of shade on growth, biomass allocation and leaf morphology in European yew (Taxus baccata L.)

Abstract

The impact of shade on the growth of European yew (Taxus baccata L.) saplings was investigated over a three-year period using artificial shading to simulate four different light regimes (3%, 7%, 27% and 100% of photosynthetically active radiation, PAR). There was no mortality attributable to shading even under the 3% PAR treatment. With increasing shade, specific leaf area, leaf length, leaf width and total chlorophyll content increased, whilst plant height, stem diameter, total dry weight and root to leaf and shoot ratio decreased. Discoloration of the foliage occurred in plants grown in 100% PAR conditions and those transferred to 100% PAR conditions after being shade-acclimated for two-years, resulting in reduced growth rates. We confirm that T. baccata, a declining species in parts of Europe, is a shade tolerant plant. Evidence suggests that it has the ability to regenerate beneath a lighter canopy but that this tolerance may not be sufficient to facilitate successful regeneration beneath the denser canopy of conifers. Management of natural populations needs to reflect the shade strategy of this species.