Structure and dynamics of a tropical dry forest in Ghana

Abstract

Forest under low rainfall (averaging 745 mm yr-1) on the Shai Hills in S.E. Ghana has redeveloped following cessation of farming in the 1890s. Forest stature is low, with a canopy at about 11 m, principally of three species, Diospyros abyssinica, D. mespiliformis and Millettia thonningii. Drypetes parvifolia and Vepris heterophylla are common understorey trees. Twelve species of woody liane were recorded. Species of thicket vegetation in the area were also present at low density. Most species are evergreen.Tree mortality averaged 2.3~o yr ~ and exceeded recruitment (1.5~ yr-1). Differences between species in mortality and recruitment were pronounced: canopy species showed a small decline in density; understorey species increased markedly and the thicket species declined. Seed production was very variable, but seedling establishment was very poor for all species. Seedling mortality was high (11 ~o yr -1 ) especially for small seedlings. These population trends probably represent the latter stages of succession of forest regrowth after farming about 100 years ago.Compared with tropical rain forest, Shai Hills forest has similar relative tree diameter growth (1-3.5 ~o yr-1), mortality and recruitment rates, and small-litter fall (5.52 t ha-1 yr-1).Shai Hills forest differs from rain forest by its short stature, relatively few (evergreen) tree species, poor regeneration from seed, high soil nutrient status and low rainfall. Similar forests have been reported in east Africa and in parts of New Guinea.Abbreviations: dbh = diameter at breast height (1.3 m), gbh = girth at breast height.

Litter accumulation and its effect on seedling recruitment in a Southeast Brazilian Tropical Forest

“…Similar to Swaine et al (1990) in Ghana, Morellato (1992) in Serra do Japi in São Paulo and Haase & Hirooka (1998) in Mato Grosso, increases in litter accumulation were observed in dry season, but in this study increases of litter were also observed in the rainy season.…”

“…Mortality can also be due to very low radiance under the canopy, where small seed with low reserves cannot survive even without water stress (Swaine et al 1990).…”

Dinâmica da comunidade arbórea em uma floresta estacional semidecidual sob queimadas recorrentes

“…Estudos de longo prazo acompanham as mudanças que ocorrem continuamente na comunidade florestal e auxiliam no entendimento dos processos ecológicos relacionados ao crescimento, recrutamento e mortalidade (Swaine et al 1990;Braga & Rezende 2007;Silva & Araújo 2009). Embora difíceis de serem mantidos, esses monitoramentos são essenciais para o desenvolvimento e testes de hipóteses sobre os processos e as taxas de recuperação após perturbações, tanto antrópicas como naturais (Taylor et al 2008).…”

“…Muitos estudos abordam a dinâmica das florestas tropicais (Lang & Knight 1983;Lieberman et al 1985;Denslow 1987;Swaine et al 1990;Korning & Balslev 1994;Sheil & May 1996;Laurance et al 1998;Holl 1999;DeWalt et al 2003; Lewis et al 2004;Saiter et al 2011). Especificamente no Brasil, florestas semidecíduas, têm sido estudadas com relativa frequência (Oliveira-Filho et al 1997; Nascimento et al 1999;Chagas et al 2001;Guilherme et al 2004;Appolinário et al 2005;Oliveira-Filho et al 2007;Paiva et al 2007;Higuchi et al 2008;Silva & Araujo 2009).…”

Abiotic factors influencing tropical dry forests regeneration

“…Unlike tropical rain forests, there is no theory for gap dynamics in TDF and their role in species regeneration (Mooney et al, 1995), largely due to the structural characteristics of the vegetation, such as lower height, thickness and smaller size of trunks and branches, reduced stratification, high density of individuals, etc. (Murphy and Lugo, 1986;Terborgh, 1992, Swaine et al 1990. Drastic changes in TDF may occur regarding the availability of resources generated by causes other than the formation of gaps, for example, their marked seasonal rainfall pattern (Bullock, 1986).…”