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

摘要

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 % relative pho-tosynthetic photon flux density,RPPFD). There was no mortality attributable to shading even under the 3 % RPPFD treatment. Increasing shade was positively associated with specific leaf area, leaf length, leaf width and total chlorophyll content, but negatively associated with plant height, stem diameter, total dry weight and root to leaf and shoot ratio. Discoloration of the foliage occurred in plants grown in 100 % RPPFD conditions (resulting in reduced growth rates) and those transferred to 100 % RPPFD conditions after being shade-acclimated for 2 years. Evidence suggests that T. baccata has the ability to regenerate beneath a lighter canopy but beneath denser canopies gap dynamics will play an important role in facilitating successful regeneration and this needs to be reflected in management of natural populations of this declining species.