Forest canopy and community dynamics in a temperate old-growth evergreen broad-leaved forest, south-western Japan: a 7-year study of a 4-ha plot

1 Forest canopy gap and community dynamics were studied in a 4-ha permanent plot of an old-growth evergreen broad-leaved forest dominated by Castanopsis cuspidata var. sieboldii and Distylium racemosum in the Tatera Forest Reserve, Tsushima Islands, south-western Japan. The forest was affected by a powerful typhoon in 1987 and was monitored from 1990 to 1997. 2 In 1990, all woody stems greater than or equal to 5 cm diameter at breast height (d.b.h.) in the plot were identified, mapped and marked, and the state of 1600 5 m x 5 m contiguous quadrats used to locate canopy gaps. Gaps occupied 17.1% of the plot, which contained 4494 tree and shrub stems (total basal area 63.48 m(2) ha(-1)). Gaps were re-censused in 1997 and both marked and newly recruited (greater than or equal to 5 cm d.b.h.) stems were recorded in 1992 and 1997. 3 Over 7 years the rates of canopy gap formation and closure were 0.72% year(-1) and 1.61% year(-1), respectively, mortality and recruitment rates were 0.97% year(-1) and 0.99% year(-1), and the rates of loss and gain in basal area were 0.95% year(-1) and 0.83% year(-1). 4 The mortality of stems was size-dependent, with those in middle size classes having the lowest rates. Mortality of stems was lower in canopy and higher in the understorey, while the proportion of stems killed by disturbances increased with height. 5 Stems that died during the 7 years were predominantly located in newly created gaps, whereas stems were recruited into both established and new gaps. Deciduous broadleaved species were largely restricted to gaps that remained open throughout the study. 6 Both composition and structure of the forest changed in response to disturbance-related effects on canopy dynamics.