Forest fragmentation, synergisms and the impoverishment of neotropical forests

It is well documented that the negative effects of habitat fragmentation are strong enough to promote local as well as regional extinction of canopy and emergent trees in neotropical forests. However, forest fragmentation does not occur alone, but is always associated with other human-induced threats to trees, such as logging, forest burning and hunting of key vertebrate seed dispersers within forest remnants. This association occurs because forest resources are, at least during a certain period, the main income source for local human populations. It is now possible to establish how these threats act in concert causing tree species impoverishment. Based on a predictive model, it is predicted that the most fragmented forest regions have lost or will lose an important part of their tree diversity. New integrated research must urgently test this prediction and investigate how human activities might be regulated in both old and new tropical forest frontiers to avoid species loss. If we fail to do this we will miss the opportunity of proposing sound and efficient guidelines to rescue neotropical forests from species impoverishment.     

Effects of frugivore impoverishment and seed predators on the recruitment of a keystone palm

Many plant species are threatened as a result of extinction of their large-bodied frugivores all over the world. Additionally, introduced herbivores and seed predators may cause severe pressure on early stages of plant recruitment. We studied the seed dispersal and seed predation of the keystone palm Euterpe edulis on a land-bridge island with a highly impoverished frugivore fauna and overabundant seed predators, and in a continuous Atlantic forest in Brazil. While the diversity of avian seed dispersers and predators was higher on the mainland, the abundance of seed dispersers was 4-fold higher on the island. Turdus flavipes was responsible for 72% and 96% of seeds removed in the island and mainland, respectively. However, the higher density of T. flaviceps on the island did not result in higher seed removal. In fact, seed removal rate was 1.7 times lower there than on the mainland, probably due to the aggressive behavior of the major seed disperser who defend palm fruits. Seed predation, on the other hand, was markedly higher on the island, where nearly 100% of seeds were preyed upon, but only 0.3% on the mainland. As a consequence of higher seed predation the population of E. edulis has few numbers of seedlings and saplings on the island. Therefore, management of the seed predator populations on the island is a key priority for recovering the natural population of this keystone palm and the frugivores that depend on its fruits.     

Stability of elemental content correlates with plant resistance to soil impoverishment

Plant and Soil - We investigated whether plant resistance to soil impoverishment would depend on their flexibility in taking up nutrients and on maintaining elemental stoichiometry. We mixed sand...