Sapling trunk height (the vertical distance from the ground to the highest apex) and trunk diameter at 1/10 height were measured. Undamaged saplings (23–193 cm tall) of each species in each canopy condition (gap and closed) were harvested in summer 2005, noting the seed or sprout origin ( Jones and Raynal, 1986) of F.
Saplings were collected in several small canopy gaps of 60–80 m 2 canopy gaps were distinguished from closed canopy by the absence of upper canopy above 10 m. This study was done on mid- to lower slopes where Acer–Fagus co-dominance is prevalent. grandifolia on drier, upper slopes ( Arii et al., 2005 Takahashi et al., 2007). saccharum tends to be more abundant than F. grandifolia are the two most frequent canopy trees throughout the reserve, but A. and Tsuga canadensis (L.) Carriére ( Maycock, 1961 Arii et al., 2005). grandifolia, the frequent canopy trees include Quercus rubra L., Fraxinus americana L., Tilia americana L., Betula alleghaniensis Britton, Acer rubrum L., Populus grandidentata Michx, Pinus strobus L.
Beaudet and Messier (1998), however, showed that the height growth of Fagus saplings was greater than that of Acer saplings at any light condition 400 years old ( Cook, 1971). Theory shows that this sort of trade-off can underpin species co-existence or co-dominance ( Chesson, 2000), and the trade-off has been shown to be important in a wide variety of forests ( Kitajima, 1994 Kobe et al., 1995 Condit et al., 1996 Poorter and Arets, 2003 Baraloto et al., 2005 Sterck et al., 2006). grandifolia in closed-canopy conditions, but that the height growth of A. Canham (1988) and Poulson and Platt (1996) reported that A. growth rate in high light conditions associated with canopy gaps is the primary mechanism accounting for the frequent co-dominance of A. The prevailing view is that a trade-off between survival rate in low light conditions typical of forest understorey vs. Many mechanisms have been proposed to account for this unusual co-dominance: reciprocal replacement of canopy trees contrasting modes of reproduction differences in edaphic affinity and differences in sapling responses to disturbance ( Fox, 1977 Woods, 1979, 1984 Runkle, 1981, 1984 Cypher and Boucher, 1982 Canham, 1988 Arii and Lechowicz, 2002). are frequently co-dominant in northern hardwood forests, and this co-dominance apparently is unique among the 125 extant Acer species ( van Gelderen et al., 1994) and 11 Fagus species ( Fang and Lechowicz, 2006) worldwide. American beech, crown architecture, crown allometry, height growth rate, net production rate, saplings, sugar maple INTRODUCTIONĪcer saccharum March.
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