Showing papers by "Valerie Kapos published in 1985"

Regeneration following clearing in a Jamaican montane forest: results of a ten-year study

Abstract: Succession was monitored over ten years in a 10×10m plot in forest with mor humus at 1550 m in the Blue Mountains of Jamaica, following the removal in January 1975 of all aerial plant parts and some of the root material. In April 1977, August–January 1980/1 and August 1984, all woody recruits in the plot were tagged and numbered, identified and measured (height), and mapped on a 1 m grid. The height of coppice was recorded. Ten of the eleven tree species present before felling produced coppice shoots. Two individuals almost attained canopy height by 1984. Twenty tree species and three shrub species were recruited from seed; six of the tree species were normally absent from the forest. Species composition changed very little with time.The rate of seedling recruitment was greatest immediately after clearing. The overall den-sity of individuals changed little after 1977. Overall mortality of recruits was about 10% per annum. Mortality of the earliest recruits declined with time since establishment. Later recruits and individuals with poor growth had higher mortality than other plants. Mortality was not density-dependent. Growth rates of recruits were relatively slow. Only ten individuals exceeded 4 m by 1984.Recruitment rates, density, growth and species diversity were greatest in the parts of the plot where the mor humus had been removed or piled up during the initial clearance. Recruit-ment, growth and density were least, and mortality was greatest, at the edge. There was no relationship between any of these parameters and the presence of coppicing stumps.Tree species showed a clear spectrum from obligate gap-demanders to obligate shade-bearers. The persistence of gap-demanding species in this forest (in which gaps are normally rare) may be due to infrequent hurricanes, and also to a natural ability to produce basal sprouts. The succession conforms to an initial floristic composition model; it is slow, and we suggest that at least 50 years will elapse before the plot begins to resemble the undisturbed forest.

Water Relations of Jamaican Upper Montane Rain Forest Trees

Abstract: We studied the water relations of an upper montane rain forest at an elevation of ~ 1550 m in the Blue Mountains of Jamaica to investigate whether the growth of the forest is limited by water shortage and/or whether the characteristically hard, leathery leaves of tropical montane rain forest trees are an adaptation to water shortage. Daily courses of leaf water potential, leaf relative water content, leaf resistance, and leaf temperature were followed for nine tree species at the driest time of year. The lowest leaf water potential measured was -1.7 MPa. Leaf resistance was usually low and rarely showed increases that might be attributed to water shortage; it was significantly correlated with light levels. Leaf relative water content was always >86% and was not correlated with leaf water potential. Leaf sublethal water deficits (SLD) averaged 27% (12 species). There was no relationship between SLD and leaf structural characteristics. We conclude that water supply rarely, if ever, seriously limits the growth of these montane forests and that their xeromorphic leaves are not an adaptation to water limitation.