Analysis of the relationship between photosynthetic photon flux density and natural Taxus baccata seedlings occurrence

• Published in: Acta oecologica (Montrouge) 2006, Vol.29 (1), p.78-84
• Main Authors: ISZKULO, Grzegorz, BORATYNSKI, Adam
• Format: Article
• Language: English
• Subjects: Animal and plant ecology; Animal, plant and microbial ecology; Autoecology; Biological and medical sciences; European yew; Fundamental and applied biological sciences. Psychology; Light demands; Light optimum; PAR; Plants and fungi; PPFD; Taxus baccata
• ISSN: 1146-609X; 1873-6238
• DOI: 10.1016/j.actao.2005.08.001

The aim of the present work was to analyse the relationship of seedlings and saplings of Taxus baccata to the photosynthetic photon flux density (PPFD) reaching the forest floor under natural conditions. Two permanent plots, subdivided into 1 × 1 m square plots, were established in a naturally regenerating population of T. baccata formed during last decades in the Kórnik Arboretum, Poland. All seedlings in every 1 × 1 m plots were counted. Relative PPFD was measured for every plot at the canopy height of the yew seedlings. The dependence of seedling density upon PPFD was examined. We found, that the frequency of the smallest seedlings (to 6.0 cm tall) was highest in the most shaded plots and decreased in plots with increasing PPFD. Thus, the youngest yew seedlings can germinate and grow in very shady conditions. However, the older seedlings (6.1–25.0 and 25.1–100.0 classes) were observed most frequently in 2–7% PPFD. The small numbers of older, taller seedlings in deep shade likely indicate a higher mortality rate of seedlings less than 6 cm in height without promotion to the next height class. Probably the low value of PPFD under the canopy of the stand significantly reduces the competition of other plants with the youngest yew seedlings. At higher light levels they may not be able to compete with more light-demanding plants, such as herbs and seedlings of broad-leaved trees. The seedlings of the second (6.1–25.0 cm) and third (25.1–100.0 cm) height classes were observed most frequently in the plots with 2–7% PPFD ( Fig. 1b and c).