AN EXPERIMENTAL-STUDY OF REGENERATION ON LANDSLIDES IN MONTANE RAIN-FOREST IN JAMAICA

1 Tree seedlings of Alchornea latifolia (Euphorbiaceae), Clethra occid entalis (Clethraceae), and Vaccinium meridionale (Ericaceae), were tra nsplanted into five recent 'debris flow' landslides, and five adjacent understorey areas, in montane forest between 1450 m and 1770 m in the Blue Mountains, Jamaica. Organic fertilizer and protective barriers w ere applied in a 2 x 2 factorial design. 2 Mortality (all species) in the 15 months following transplanting was 30% on landslides, and 46% i n the understorey. Mortality was significantly higher in the understor ey than on landslides for Alchornea and Vaccinium, but was not differe nt for Clethra. In the understorey there was a peak of mortality for A lchornea and Vaccinium in the dry season, but no associated peak on la ndslides. There was no effect of fertilizer or barrier treatment on se edling survival.3 Height growth of unfertilized Clethra and Vaccinium (but not Alchornea) seedlings was greater on landslides than in the un derstorey. On landslides fertilization increased biomass (but had no e ffect on height) for all species. There were no significant effects of fertilizer in the understorey. 4 Soil nutrient concentrations were mu ch higher in understorey soils than landslide soils, pH values were si milar. 5 Foliar nitrogen concentrations for transplanted seedlings wer e lower on landslides than in the understorey, while foliar phosphorus concentrations were not different. Fertilization did not change folia r nitrogen concentrations on either landslides or the understoreys, wh ereas there was a significant increase in phosphorus concentration in fertilized seedlings on landslides. 6 Soil water content varied less o n landslides than in understoreys; soils from three of the landslides were judged to be near field capacity throughout the year. In the unde rstoreys there were significant shortages of water in the dry season w hich correlated with increased mortality in the transplanted seedlings . 7 Thus we have shown that growth of seedlings on landslides is limit ed by nutrient supply; water supply and soil movement do not limit gro wth of established seedlings. In the understoreys seedling growth is l imited by photosynthetically active radiation, nutrient supplies may l imit seedling growth due to root competition, and seasonal drought is correlated with increased mortality.