© 2004 Heron Publishing—Victoria, Canada
Morphological and physiological responses of beech (Fagus sylvatica) seedlings to grass-induced belowground competition
Lluis Coll (1, 2), Philippe Balandier (1) and Catherine Picon-Cochard (3)
1. CEMAGREF - U.R. DFCF, Applied Ecology of Woodlands Research Team, 24, av. des Landais, BP 50085, 63172 Aubière cedex, France / 2. Author to whom correspondence should be addressed (lluis.coll@clermont.cemagref.fr) / 3. INRA - U.R. Agronomie, 234 av. du Brezet, 63039 Clermont-Ferrand, France / Received April 24, 2003; accepted June 14, 2003; published online December 1, 2003
Summary
We examined morphological and physiological responses of beech (Fagus sylvatica L.) seedlings to grass-induced belowground competition in full-light conditions. Two-year-old beech seedlings were grown
during two growing seasons in 160-l containers in bare soil or with a mixture of five grass species widely represented in
semi-natural meadows of central France. At the end of the second growing season, beech seedlings in the presence of grass
showed significant reductions in diameter and height growth, annual shoot elongation, and stem, root and leaf biomass, but
an increase in root to shoot biomass ratio. Grasses greatly reduced soil water availability, which was positively correlated
with daily seedling diameter increment. Beech seedlings seemed to respond to water deficit by anticipating stomatal closure.
There was evidence of competition for nitrogen (N) by grasses, but its effect on seedling development could not be separated
from that of competition for water. By labeling the plants with 15N, we showed that beech seedlings absorbed little N when grasses were present, whereas grasses took up more than 97% of the
total N absorbed in the container. We conclude that, even if beech seedlings display morphological and physiological adaptation
to belowground competition, their development in full-light conditions may be strongly restricted by competition from grass
species.
Keywords:
leaf gas exchange, 15N, seedling architecture, soil water content.
