Summary 0[ Composition\ growth and turnover of trees in two species!rich tropical gallery forests were examined to evaluate what community reorganization may be needed to transform recently created tropical forest fragments into stable refugia for regional forest biotas[ 1[ Rates of tree growth and turnover over a 4!year interval were comparable to those recorded in continuous forests and in both communities there had been some tree species turnover in the measured stem size classes during the 4!year interval[ 2[ The more abundant tree species in both communities formed three functional groups along gradients between streams and forest edges] edge!concentrators\ core! concentrators and generalists[ 3[ Soil fertility showed no consistent increase close to streams and neither tree growth nor recruitment rates were increased in this zone[ In contrast\ forest edge zones exhibited increased rates of tree growth and recruitment indicating that growth pro! cesses in these forests are light!limited rather than soil!limited\ and that forest edge zones are generally favourable habitats for tree populations[ 4[ Both communities showed signs of past _re incursions\ and the tendency of a subset of tree species to concentrate in the more growth!limited core habitats is attributed to their _re sensitivity[ 5[ Rapid development of an edge zone of _re!insensitive tree species is considered to be essential to the survival of forest community fragments in the _re!prone landscapes of the tropics\ and the edges of gallery forests are recommended as potential sources of species with which to fashion these protective ecotones[ 6[ Preservation of a diverse forest biota in the _re!protected interiors of fragments will require natural or arti_cially enhanced immigration rates that are su.cient to o}set local extinctions[ Key!words] ecotone\ fragmentation\ riparian habitat\ savanna _re[ Journal of Applied Ecology "0887# 24\ 084Ð195

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A new technique for estimation of tree species richness in tropical forests was developed and tested in this study. The missing species extrapolation technique is based on the assumption that the rate of accumulation of new species with increasing area is the same within sampled and unsampled areas of similar habitat within a region. This new technique was tested on four 1-ha sites of subtropical moist forest in Rio Bravo, Belize for which complete species counts of trees ≥10cm dbh are available. Estimates given by the technique are 115, 98, 93 and 106% of the actual species counts within the four sites. The accuracy of these estimates was found to be equal to or better than most others obtained by using existing methods of extrapolation. The missing species extrapolation technique was also applied to a 21-ha riparian forest patch in the Mountain Pine Ridge, Belize, where it was used to obtain an estimate of the number of tree species ≥10cm dbh in the entire patch.

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