Heterogeneity of tree diversity and carbon stocks in Amazonian oil palm landscapes

ABSTRACT Background: Quantitative effects of large-scale oil palm expansion in the Neotropics on biodiversity and carbon stocks are still poorly documented. Aims: We evaluated differences in tree species composition and richness, and above-ground carbon stocks among dominant land cover types in Pará state, Brazil. Methods: We quantified tree species composition and richness and above-ground carbon stock in stands in remnant primary rain forest, young secondary forest, oil palm plantation and pastures. Results: We sampled 5,696 trees with a DBH≥2 cm, of 413 species in 68 families, of which 381 species were recorded in primary forest fragments. We found significant differences in species richness and carbon stock among the four land cover classes. Carbon stocks in remnant primary forest were typically over 190 Mg ha −1 , while those in other land cover types were typically less than 60 Mg ha −1 . Conclusion: Oil palm plantations have a species-poor tree community given active manage- ment; old plantations have a standing carbon stock which is comparable to that of secondary forest and far greater than that of pastures. Private forest reserves within oil palm company holdings play an important role in preserving primary forest tree diversity in human-modified landscapes in Amazonia

A large‐scale assessment of plant dispersal mode and seed traits across human‐modified Amazonian forests

1. Quantifying the impact of habitat disturbance on ecosystem function is critical to understanding and predicting the future of tropical forests. Many studies have examined post-disturbance changes in animal traits related to mutualistic interactions with plants, but the effect of disturbance on plant traits in diverse forests has received much less attention. 2. Focusing on two study regions in the eastern Brazilian Amazon, we used a trait-based approach to examine how seed dispersal functionality within tropical plant communities changes across a landscape-scale gradient of human modification, including both regenerating secondary forests and primary forests disturbed by burning and selective logging. 3. Surveys of 230 forest plots recorded 26,533 live stems from 846 tree species. Using herbarium material and literature, we compiled trait information for each tree species, focusing on dispersal mode and seed size. 4. Disturbance reduced tree diversity and increased the proportion of lower wood density and small-seeded tree species in study plots. Disturbance also increased the proportion of stems with seeds that are ingested by animals and reduced those dispersed by other mechanisms (e.g. wind). Older secondary forests had function-ally similar plant communities to the most heavily disturbed primary forests. Mean seed size and wood density per plot were positively correlated for plant species with seeds ingested by animals. 5. Synthesis. Anthropogenic disturbance has major effects on the seed traits of tree communities, with implications for mutualistic interactions with animals. The important role of animal-mediated seed dispersal in disturbed and recovering forests highlights the need to avoid defaunation or promote faunal recovery. The changes in mean seed width suggest larger vertebrates hold especially important functional roles in these human-modified forests. Monitoring fruit and seed traits can provide a valuable indicator of ecosystem condition, emphasizing the importance of developing a comprehensive plant traits database for the Amazon and other biomes

Biodiversity recovery of Neotropical secondary forests.

Old-growth tropical forests harbor an immense diversity of tree species but are rapidly being cleared, while secondary forests that regrow on abandoned agricultural lands increase in extent. We assess how tree species richness and composition recover during secondary succession across gradients in environmental conditions and anthropogenic disturbance in an unprecedented multisite analysis for the Neotropics. Secondary forests recover remarkably fast in species richness but slowly in species composition. Secondary forests take a median time of five decades to recover the species richness of old-growth forest (80% recovery after 20 years) based on rarefaction analysis. Full recovery of species composition takes centuries (only 34% recovery after 20 years). A dual strategy that maintains both old-growth forests and species-rich secondary forests is therefore crucial for biodiversity conservation in human-modified tropical landscapes