T. C. Whitmore

Species diversity, susceptibility to disturbance and tree population dynamics in tropical rain forest

. In 1964 a census of all trees > 9.7 cm diameter at breast height (DBH) was conducted on 22 plots totalling 13.2 ha in lowland tropical evergreen rain forest on Kolombangara, Solomon Islands. Over the following 30 yr (1964–1994), populations of all individuals > 4.85 cm DBH of the 12 most common tree species and amounts of disturbance have been monitored on a declining number of these plots (in 1994, nine plots totalling 5.4 ha were still being recorded). Between November 1967 and April 1970, Kolombangara was struck by four cyclones, although only two of these caused substantial amounts of damage to the canopy structure. Multivariate analysis has identified six forest types on Kolombangara (Greig-Smith et al. 1967). The species richness and diversity of trees in the 1964 census, turnover rates of the populations monitored over 1964–1975, and the amount of disturbance sustained during a cyclone in 1970, were all positively correlated across five of the forest types. The sixth forest type was a consistent outlier in these analyses and is believed to have been seriously disturbed by humans about a century ago. The floristics, turnover and disturbance data support Connells intermediate disturbance hypothesis. The most species-rich forest types contained a higher proportion of fast-growing individuals and species that are early-successional and which have low density timber. Properties of these species rendered them more susceptible to damage when struck by the 1970 cyclone. They showed higher turnover rates because disturbance-dependent species are also characterised by higher mortality and recruitment rates. Thus, periodic cyclones appear to favour the maintenance of differences in species diversity and composition between forest types.

A framework for the worldwide comparison of tropical woody vegetation types

Abstract A simple, flexible, pantropical forest classification framework is proposed to provide a common platform for foresters, vegetation mappers, climatic modellers, biogeographers and plant ecologists. The framework is provided by bioclimatic types, defined on annual rainfall, seasonality and mean temperature of the coldest month. Within each bioclimatic type a series of forest formations occurs, defined on forest structure and physiognomy. The formations are pantropical. The main schemes of forest classification published for continental Asia, the Malay Archipelago, America and Africa are given in Table 1 , Table 2 , Table 3 , Table 4 , set against this bioclimatic framework. Different authors have used different names for forest formations and is unlikely to ever be general agreement on nomenclature. Floristic composition varies across continents and regions. For some purposes it is useful to divide bioclimatic types into ecofloristic zones. The correspondences given in this paper are between bioclimates and forest formations in the absence of anthropic impacts.