Species that evolved in high-altitude grasslands, where soils are dystrophic and metal rich, developed adaptations for these extreme conditions, such as metal accumulation and sclerophyllous leaves, and these adaptations may secondarily affect insect herbivory activity. The present study investigates the hypothesis that costs related to accumulation of certain metals may be evolutionarily compensated for by decreasing leaf herbivory in some plant species from rupestrian fields. Studies were conducted in different locations at the Ferriferous Quadrangle, a metal-rich region in south-east Brazil, with four species adapted to high-altitude grasslands: Eremanthus erythropappus, Eremanthus incanus, Lychnophora ericoides and Byrsonima variabilis. Sample design varied according to population sizes and spatial distribution of individuals. We found that concentrations of manganese (Mn) and iron (Fe) significantly reduced the herbivory in the leaves of E. erythroppapus and E. incanus, whereas aluminum (Al) reduced herbivory in L. ericoides, and Mn affected negatively the herbivory in B. variabilis. These results support the hypothesis that metal-accumulating plants, as a response to the harsh environment in which they evolved, are protected against foliar damage caused by insect herbivores in rupestrian fields.
RESUMO -O manguezal é um ecossistema de grande complexidade que ocorre na interface entre os ambientes marinhos e terrestres, mas que apresenta baixa riqueza de espécies vegetais adaptadas às suas condições diferenciadas. Avaliar a estrutura e distribuição da vegetação no manguezal do rio Piraquê-Açu, ES, associando-as com parâmetros abióticos ao longo de um gradiente, foi o objetivo deste estudo. Em seis parcelas de 100 m 2 cada, foram registrados 306 indivíduos vivos e um morto, pertencentes às espécies Laguncularia racemosa, Rhizophora mangle, Avicennia schaueriana, Terminalia catappa e outras quatro indeterminadas, sendo L. racemosa de maior densidade, dominância, área basal e IVI. A altura média das árvores foi de 4,2 m (DP±1,9) e a CAP, de 12,4 cm (DP±9,5), estando a maioria dos indivíduos em classes de CAP até 10 cm. O manguezal encontrava-se em estado juvenil e pouco desenvolvido estruturalmente, e houve distinção na distribuição das espécies na área, com espécies associadas ocorrendo na parcela mais elevada e menos úmida. As variáveis abióticas diferiram entre as parcelas, contudo apenas a umidade do substrato apresentou relação significativa com a abundância de indivíduos e circunferência dos troncos.Palavras-chave: Fitossociologia; Manguezal; Umidade do solo.
STRUCTURE OF THE MANGROVE VEGETATION ASSOCIATED TO FLOOD GRADIENT IN THE NORTH COASTAL ESPÍRITO SANTO, BRAZIL
Despite their extreme importance for environmental balance, riparian forests have been severely disturbed over time. This study aimed to identify grass species and determine their distribution in a disturbed stretch of riparian forest along Pimentas creek, in the municipality of Matutina, which is in the state of Minas Gerais, Brazil. Among four plots established within the study area, we recorded Pennisetum purpureum Schumach., Urochloa mutica (Forssk.) T.Q. Nguyen, Urochloa decumbens (Stapf) R.D. Webster, Paspalum notatum Flüggé and Andropogon bicornis L. The most common species was Pennisetum purpureum, which occurred in all of the plots, more frequently in those that had been disturbed. The proportions of exotic and native grasses, as well as their distribution, differed significantly among the plots. The distribution of the grass species varied according to the level of degradation of the creek bank, occurring more frequently where the bank had been disturbed. Therefore, we assume that grasses can be used as indicators of degradation in riparian zones. We also found that grasses are less efficient in preventing erosion than is the typical riparian vegetation.
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