Allometry of a neotropical palm, Euterpe edulis Mart.

Abstract

RESUMO -(Alometria de uma palmeira Neotropical, Euterpe edulis Mart.). Neste trabalho foram analisadas as relações entre o diâmetro e a altura de uma palmeira Neotropical (Euterpe edulis) comum na Floresta Atlântica do SE do Brasil. As relações observadas entre a altura e o diâmetro ao longo do estipe (diâmetro ao nível do solo (DAS), e diâmetro ao nível do peito (DAP) foram comparadas a três modelos teóricos de estabilidade mecânica: similaridade elástica, similaridade de estresse e similaridade geométrica. As inclinações das regressões altura-diâmetro não se ajustaram a nenhum dos modelos de estabilidade mecânica. Diferenças significativas na alometria do estipe foram encontradas comparando-se as relações altura-DAS com altura-DAP, sugerindo maior incremento em DAP com a altura. A relação entre o fator de segurança do diâmetro contra quebra e a altura mostrou que tanto o DAS como o DAP encontram-se acima do limite teórico de quebra de McMahon para árvores, mas alguns indivíduos aproximam-se deste limite em relação ao DAP. Apesar de apresentarem padrão similar de decréscimo do fator de segurança com a altura, as diferenças encontradas para o fator de segurança ao longo do estipe -maior fator de segurança para o DAS quando comparado com o DAP -indicam que o risco de quebra em palmeiras depende do tamanho e varia ao longo do estipe. As relações alométricas distintas ao longo do estipe obtidas para Euterpe edulis podem estar refletindo possíveis diferenças na forma do estipe e nas estratégias de crescimento.Palavras-chave: fator de segurança, risco de quebra, instabilidade mecânica, floresta tropical semidecídua, Brasil ABSTRACT -(Allometry of a Neotropical palm, Euterpe edulis Mart.). The stem allometry (stem diameter vs. tree height) of a Neotropical palm (Euterpe edulis)found in rain and seasonal forest of Southeastern Brazil was examined. Observed height-diameter relationships along the stem (diameter at ground level, (dgl), and diameter at breast height (dbh) were compared to three theoretical stability mechanical models: elastic similarity, stress similarity and geometric similarity. Slopes of log-transformed height-diameter relationships did not lie near those predicted by any stability mechanical models. Significant differences in stem allometry were found when comparing dgl to dbh, suggesting greater increase in dbh with height. The relationship between stability safety factor (SSF) and palm height showed that both dgl and dbh were found to be above McMahon's theoretical buckling limit for dicotyledonous trees, but some individuals approached this limit in relation to dbh. Despite displaying a similar decreasing pattern of SSF with height, differences found in SSF along the stem -greater SSF for dgl when compared to dbh -indicate that the risk of mechanism failure in palms depends upon the size and varies along the stem. Distinct allometric relationships along the stem obtained for Euterpe edulis may be reflecting possible differences in stem design and growth strategies.

Growing straight versus growing decumbent: soil quality and allometry in Syagrus glaucescens Becc. (Arecaceae), an endemic and threatened palm of the Espinhaço Mountains, Brazil

“…Hence, linear regression coefficients values (an indication of stem height variation in response to diameter) did not match the values predicted by any of the three stability models. Our data on the allometry in S. glaucescens corroborates the study by Schatz et al (1985) for tropical palms, indicating that a direct relationship between stem height and diameter may not always exist; i.e., it can change in shape during stem growth (Alves et al 2004). This fact was observed in palm Euterpe precatoria that showed geometric similarity in individuals under one meter, whereas palms above this value did not adjust to any mechanical model (Avalos & Otárola 2010).…”

“…Cecropia species from Amazonian and from southeastern Brazil in open or disturbed habitats were all close to the geometric similarity model (Sposito & Santos 2001). For other pioneer species, the values did not fit any of the predicted mechanical stability models (Alvarez-Buylla & Martinez-Ramos 1992;Santos 2000), as it was also found for Euterpe edulis, an endemic palm of Brazilian Atlantic Forest (Alves et al 2004). For all mentioned species, strong allometric relations between stem height and diameter were found, making Syagrus glaucescens an exception to the provided models along with Metroxylon sagu (Kjaer et al 2004).…”

“…Finally, the geometric similarity model predicts that structures of different sizes retain isometric proportions, so that increases in height causes a directly proportional increase in diameter, following the relation D  H 1 (Niklas 1994). Otherwise, these relationships are different in distinct ecological groups and in different taxa (Alves et al 2004). All the eight species studied by O'Brien et al (1995) at a semi-deciduous forest in Panama showed values close to the elastic similarity model.…”

Demographic structure of a threatened palm (Euterpe edulis Mart.) in a fragmented landscape of Atlantic Forest in northeastern Brazil

“…The number of leaves has been shown to vary less than do diameter and height in E. edulis (Reis 1995). The shape of E. edulis plants changes over the course of development, because stem diameter does not correlate directly with height (Alves et al 2004). Plants up to 1.25 m in height will allocate resources to widen the stem base, establishing support for later height gains (Silva 1991;Alves et al 2004).…”

“…The shape of E. edulis plants changes over the course of development, because stem diameter does not correlate directly with height (Alves et al 2004). Plants up to 1.25 m in height will allocate resources to widen the stem base, establishing support for later height gains (Silva 1991;Alves et al 2004). Silva et al (2009) suggested that low soil fertility and a closed canopy environment caused by high plant density influences development in E. edulis in the Una region, resulting in individuals that are taller and thinner than are those in other populations.…”