GROWTH OF FAGUS-SYLVATICA SAPLINGS IN AN OLD-GROWTH FOREST AS AFFECTED BY SOIL AND LIGHT CONDITIONS

Studies were conducted on 41 five yr-old common beech (Fagus sylvatica ) saplings collected in an old-growth beech wood (Fontainebleau forest , biological reserve of La Tillaie, France), under varying humus and l ight conditions, following gypsy moth (Lymantria dispar) caterpillar i njuries. Aerial and subterranean parts of each sapling were described by means of 34 parameters and environmental conditions at the microsit e, where each sapling was excavated, were characterized by 23 paramete rs. The development of beech saplings is strongly affected by microsit e conditions. An increase in sapling size was associated with darkness of the A-horizon, typical of zones with poor mineralization of organi c matter. Light conditions were more important in influencing the deve lopment of the root system than that of the aerial parts. Rooting dept h was shallower and rate of mycorrhiza development by the black ascomy cete Cenococcum geophilum was lower in microsites receiving incident l ight during the morning than in those never receiving incident light d uring this period. Results are discussed in the frame of survival of y oung beech individuals in varying environmental conditions, when submi tted to competition by other vegetation and adverse climate conditions .