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Habitat fragmentation could alter ecological traits including species trophic habits. Here, we used carbon and nitrogen stable isotope ratios to establish differences in isotopic niche width and food resource use between forest fragments and the continuous forest for the phyllostomid frugivorous bat Artibeus lituratus. Using mist nests, we captured bats from two forest fragments and two sites in continuous forest, and sampled from each individual captured three body tissues with contrasting turnover rates (skin, muscle, and liver). Samples were collected between February and March (austral summer) and between August and September (austral winter). In addition, in each sampling site and season we collected potential food resources (fruits and insects) consumed by our A. lituratus. Our findings indicate that A. lituratus had a predominantly omnivorous diet, with high consumption of insects during summer in forest fragments. The increasing consumption of insects in these fragments seems to have led to a wider isotopic niche, in relation to the continuous forest. Because A. lituratus is typically a seed disperser, changes in trophic habits in the forest fragments from frugivory to insectivory may diminish their role in forest regeneration. Abstract in Portuguese is available with online material.

Litterfall is an essential component of tropical forest productivity, transferring nutrients from the vegetation back to soils. Here, we summarize the data from 105 estimates of fine litterfall production from 45 sites in the Atlantic Forest domain, including two types of forests, evergreen and seasonal, and two successional stages, secondary and old growth. The overall litterfall average was 8.0 ± 2.5 Mg/ha. Litterfall was significantly in higher seasonal forests than in evergreen forests and in old growth versus secondary forests. Leaves were the major component of litterfall, contributing 68 percent to the total. The second most important component was branches, contributing 22 percent, followed by reproductive organs (flowers and fruits), at 6 percent. Accurate measurements of tropical forest productivity are crucial for estimating their role in sequestering atmospheric carbon, and we suggest some ways to standardize litterfall sampling to obtain better estimates.

We investigated the variation of stable (δ13C) soil carbon isotopes in relation to depth in seven of the most important savanna areas to adjacent contiguous forests in the Amazon region. The δ13C of bulk organic matter in all profiles from forested sites increased with soil depth. In forest profiles from Amapa, Alter do Chao, and Roraima, the enrichment was less than 3.5‰ between deeper soil and surface layers, suggesting that C3 plants have remained the dominant vegetation cover. On the other hand, in forest soil profiles from Humaita and Carolina sites, the δ13C enrichment was greater than 3.5‰, indicating the influence of past C4 vegetation or a mixture of C3/C4 vegetation (woody savanna). The surface δ13C values in the savanna profiles were 5–13‰ greater than the comparable forest profiles, indicating the influence of C4 vegetation. Two kinds of isotopic distribution were observed in deeper layers. The savanna profiles at Alter do Chao, Chapada dos Parecis, and Redencao had relatively constan...

In order to characterize the organic and isotopic compositions and the origin of the sediment deposited in the Amazon river floodplain, samples from lake bottom, grass cover, and vegetation free sediments were studied. The results obtained showed that after deposition the organic characteristics of these sediments were altered according to their environment. Thus, compared to river-transported fine particulate organic matter (FPOM), samples from the lake bottom sediments showed increases in carbon and nitrogen concentrations, and decreases in 6'3C values due to the low isotopic composition of the particulate organic carbon in the lakes. Samples from areas covered by grasses had lower nitrogen and carbon relative to FPOM. The isotopic composition was changed by organic matter produced by the grasses, becoming less negative in 6'3C in the downriver direction. In the vegetation-free samples, collected over areas that had been recently drained, the isotopic composition did not change in relation to FPOM, but a decrease in carbon and nitrogen was observed.