Competition for water between beech seedlings and surrounding vegetation in different light and vegetation composition conditions

To gain a better understanding of beech growth requirements and assess the competition with the: surrounding vegetation at two successional stages after agricultural land abandonment, we introduced two-year-old beech seedlings (i) in a recently abandoned meadow (one half weeded) and (ii) in an old meadow colonised by 25-year-old natural Scots pine, with one part thinned to increase light availability at ground level. Beech seedlings presented significantly different stem diameter growth rates according to vegetation composition (grasses or dicotyledon species) and light availability for both successional stages. Grass species, which developed efficient strategies, to extract soil water, competed strongly with beech seedling compared with dicotyledon species. Water competition led to a strong reduction of beech diameter growth. For a Given vegetation composition, increasing light availability improved beech growth.