Within-tree variation in wood production and wood quality in sycamore (Acerpseudoplatanus): its relation to crown characteristics

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Abstract
To quantify patterns of wood formation in sycamore (Acerpseudoplatanus L.), the seasonal progress of wood production and structure was followed systematically throughout the outer growth sheath of the main stem and major branches. These data were considered in relation to the profile of leaf dry weight down through the crown in 8- and 12-year-old trees at stages before and after canopy closure, respectively. Mature fibre production was earliest towards the tips of the branches of the midcrown, and spread basipetally along the branches. In the main stem, mature fibre production was earliest at the tip and spread down the tree, taking about 10 days to reach the base of both pre- and post-canopy closure trees. In the stem, later fibre production down the tree was offset by later cessation of fibre maturation basally. Branch data suggested that the pattern of cessation may depend on the branch position, because cessation was latest at the base of the upper branches and at the tip of the lower branches. The maximum rate of fibre production was in the upper stem, several internodes higher than the internode bearing maximum leaf dry weight. Despite this, ring width increased down the stem, presumably as a result of the increased duration of fibre production and increased cell size. Within growth rings, vessel size remained nearly constant before declining sharply towards the end of the ring. Trees with narrower growth rings tended to have more of their ring occupied by declining vessel size suggesting a slight inverse relationship between ring width and specific gravity. Specific gravity increased down the outer growth sheath of the stem, and this increase was associated with systematic trends in fibre and vessel dimensions, together with changes in the relative proportions by area of the different tissues. Although some anatomical characters appeared to vary with the profile of the crown, others appeared to be independent of crown profile.