Adriana Maria Zanforlin Martini

Repeated disturbances and canopy disturbance regime in a tropical semi-deciduous forest

The canopy disturbance regime and the influence of gap methods on the interpretation of forest structure anddynamicswereevaluatedinatropicalsemi-deciduousforestinsouth-easternBrazil.Weencounteredagapdensity of 11.2 gaps ha −1 and an average size which varied from 121 to 333 m 2 depending on the gap delimitation method considered (minimum gap size was 10 m 2 ). Although average size was slightly higher, the median value obtained (78 m 2 ) was comparable to other tropical forest sites and the gap size-class distribution found supported the pattern described for such forest sites. Among 297 gap makers, snapping and uprooting were the most common modes of disturbance.Thenumberandbasalareaofgapmakersweregoodpredictorsofgapsize.Almost25%ofallgapssuffered fromrepeateddisturbanceeventsthatbroughtaboutlargergapsizes.Suchprocesses,alongwithdelimitationmethods, strongly influenced the estimation of turnover rate and therefore the interpretation of forest dynamics. These results demonstrated the importance of further studies on repeated disturbances, which is often neglected in forest studies.

Structure, diversity, and spatial patterns in a permanent plot of a high Restinga forest in Southeastern Brazil

(Structure, composition, and diversity of a high Restinga forest in the Southern Atlantic Forest) We assessed the structure, diversity and distribution of tree species in a 10.24-ha permanent plot of high Restinga forest (HRF) in southeastern Brazil. We sampled 15,040 individuals belonging to 45 families, 87 genera and 116 species (density= 1,468 trees ha -1 , and basal area= 28.0 m 2 ha -1 ). Mean richness was lower than other types of tropical forests and other HRFs that have been less intensively sampled, which is probably due to the younger age and hydromorphy of the soils in the study site. Tree density, basal area, species composition, and diversity all varied considerably depending on the size class considered. The studied plot had a density similar to other tropical forests but with a smaller basal area (fewer individuals > 60 cm in diameter), and higher density of smaller trees. Multi-stemmed individuals were not frequent (11% of the trees), though they were widespread among species (74% of the species). Spatial distribution was predominantly clumped, a pattern common to other types of tropical forests. Besides growing over white-sand soils, the PEIC plot and other white-sand forests of the world also had very similar patterns of community structure, richness and diversity. Therefore, we consider the HRF as a recognizable subtype of white-sand forest.

Population structure of Euterpe edulis Mart. in the Southern Bahia, Brazil

The objective of this study was to better understand the populational structure of jucara palm (Euterpe edulis Mart.) in the Southern Bahia Atlantic Forest, in the Ecoparque de Una, Una, BA, Brazil. The plants in the population were classified into one of six size classes: Seedlings, Juvenile I, Juvenile II, Immature I, Immature II, and Adult. For each size class, the following data were gathered: density and distributions of frequency class of height at leaf insertion, number of leaves, diameter at breast height (DAP), and diameter at soil level (DAS). Comparisons were made among these values through Pearson correlation. The population revealed a demographic structure similar to that found in studies of E. edulis in South and Southeast Brazil, except seedlings density, with a large number of immature individuals and few individuals in the largest size classes. The population density was found to be relatively low, leaving open the possibility that these populations should be treated as an ecotype different from other already studied. The variables showed positive correlations with the exception of number of leaves and DAS in the adult size class.

Community structure of vascular plants in treefall gaps and fire-disturbed habitats in the Atlantic rainforest, southern Bahia, Brazil

Os efeitos das perturbacoes sobre parâmetros da estrutura de comunidade de plantas em florestas tropicais tem sido frequentemente analisados. Porem, a maioria dos estudos realizados ate o momento tem considerado somente plantas lenhosas, principalmente arvores, e o efeito de perturbacoes sobre toda a comunidade de plantas vasculares ainda nao havia sido avaliado. No presente estudo, todas as plantas vasculares menores que 5 metros de altura foram amostradas em clareiras naturais, em uma area de floresta queimada em um incendio acidental e em areas de sub-bosque adjacentes. A area queimada diferiu das outras areas em relacao a composicao de especies, porem a riqueza de especies e a densidade de individuos nao foi diferente entre a area queimada e as areas de sub-bosque. Estes resultados estao de acordo com os modelos sucessionais que preveem que em locais sujeitos a perturbacoes de intensidade moderada ocorre uma rapida recuperacao da riqueza de especies, porem com uma composicao de especies diferenciada. As clareiras naturais e as areas de sub-bosque nao diferiram quanto ao numero de individuos e de especies, nem em relacao a composicao de especies. A ausencia de diferencas entre a vegetacao em clareiras e no sub-bosque sugere que as especies encontradas em clareiras estao diretamente relacionadas as especies presentes antes da formacao das clareiras. Foram observadas apenas pequenas diferencas entre os resultados das analises que consideraram somente as especies arboreas e as analises considerando todos os habitos de crescimento, sugerindo que os mesmos processos que atuam sobre as especies arboreas estao tambem atuando sobre toda a comunidade de plantas vasculares nestas florestas.