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Summary 1We evaluate the eects of large-scale disturbance on tropical tree communities by examining the population dynamics of all individuals >4.9 cm in diameter at breast height (d.b.h.) of 12 tree species over 30 years (1964±94) in lowland tropical rain forest on Kolombangara, Solomon Islands. 2 During the study period Kolombangara was struck by four cyclones between 1967 and 1970. The last cyclone caused most damage to canopy structure. Mortality in the 6-month interval spanning the ®rst cyclone was 7.0% of all trees, while mean annual mortality for all other intervals (including those spanning other cyclones) was 1.4±2.2% year À1 . Mortality varied between species but was independent of topography and geographical location. 3 Recruitment increased from very low rates (median 0.0% year À1 ) before the ®rst cyclone to median values of 1.6±3.2% year À1 during 1971±79, i.e. following a lag period of 3.5±8 years after the ®rst cyclone. Recruitment rates were higher on plots showing greater mortality rates during this cyclone. Recruitment and mortality rates were still higher in 1994 than they had been before the 1967±70 cyclones. 4 Mean annual mortality rates were positively correlated with mean annual recruitment rates across species. This relationship re¯ects a continuum of life-history characteristics and contributes to constancy in the relative abundance of the 12 species when the same sets of plots are compared over all measurement intervals up to 30 years. 5 We conclude that cyclone impacts have only short-term eects on the relative abundance of common tree species on Kolombangara, and do not therefore prevent the establishment of an equilibrium rank abundance hierarchy or create spatial variation in tree species composition. Dierences in forest composition across Kolombangara are more likely to have been caused by dierential anthropogenic disturbance linked to settlement patterns.

Study of forest dynamics commonly requires measurement of canopy gap size. Hemispherical photographs can be analysed to provide various measures whereby gaps can be ranked in order of size. For ten artificial gaps in a Bornean tropical rain forest these measures were better correlated with gap microclimate than gap area measured physically on the ground. All these measures are however relative. For detailed (e.g. ecophysiological) studies the greater detail provided by absolute measures of photosynthetically active radiation (PAR) are required. Long term PAR values can be computed from hemiphots so long as measurements in the open nearby are available. Correction for cloudy weather is essential. Computed and measured PAR are compared for the test gaps. Both have inherent limits which means that below c. 15% canopy openness, differences in PAR between gaps cannot be assessed accurately.