Plant structure predicts leaf litter capture in the tropical montane bromeliad Tillandsia turneri / A estrutura da planta determina a folhagem interceptada pela bromelia Tillandsiaturneri

Abstract Leaves intercepted by bromeliads become an important energy and matter resource for invertebrate communities, bacteria, fungi, and the plant itself. The relationship between bromeliad structure, defined as its size and complexity, and accumulated leaf litter was studied in 55 bromeliads of Tillandsia turneri through multiple regression and the Akaike information criterion. Leaf litter accumulation in bromeliads was best explained by size and complexity variables such as plant cover, sheath length, and leaf number. In conclusion, plant structure determines the amount of litter that enters bromeliads, and changes in its structure could affect important processes within ecosystem functioning or species richness.

Resumo As folhagens interceptadas pelas bromélias é um importante recurso para a comunidade de invertebrados, bactérias, fungos e para a própria planta. Estudou-se a relação entre a estrutura de 55 bromélias de Tillandsia tumeri, definida como o tamanho, a complexidade da planta, a folhagem acumulada por meio de regressão múltipla e o critério de informação de Akaike. Encontrou-se que as variáveis de tamanho, cobertura, comprimento da bainha e a variável de complexidade do número de folhas explicam a acumulação de folhas nas bromélias. Em conclusão, a estrutura do planta determina a quantidade de folhas armazenada na bromélia e os câmbios da estrutura da bromélia poderiam afetar importantes processos de funcionamento do ecossistema ou a riqueza de espécies.

Non-random foraging in certain bird pests of field crops.

Two systems of bird-crop interactions were studied to explain the between- and the within-field variation in the foraging pattern of bird pests in agro-ecosystems. Weaverbirds and munias select rice fields with greater vegetation complexity and not based on the resource status. Within a selected area the concentration of feeding birds was greater close to vegetation cover and decreased non-linearly with increase in distance. Certain structural features and earhead characters of rice plants predisposed particular varieties for intense grain predation by birds. In the parakeet – sunflower system the extent of damage among plants within a field was closely linked to the foraging pattern of parakeets. The extent of achene predation by parakeets was influenced by certain structural features of sunflower plants and not the resource load of each plant. Selective feeding on sunflower plants was governed by the predator vigilance pattern; parakeets prefer to feed on plants that offered better field of vision. The results suggest that the observed pattern of foraging by bird pests in agro-ecosystems is non-random and is dependent on factors favouring predator avoidance behaviour and not on resource maximization.