The nutrient demands of regrowing tropical forests are partly satisfied by nitrogen-fixing legume trees, but our understanding of the abundance of those species is biased towards wet tropical regions. Here we show how the abundance of Leguminosae is affected by both recovery from disturbance and large-scale rainfall gradients through a synthesis of forest inventory plots from a network of 42 Neotropical forest chronosequences. During the first three decades of natural forest regeneration, legume basal area is twice as high in dry compared with wet secondary forests. The tremendous ecological success of legumes in recently disturbed, water-limited forests is likely to be related to both their reduced leaflet size and ability to fix N, which together enhance legume drought tolerance and water-use efficiency. Earth system models should incorporate these large-scale successional and climatic patterns of legume dominance to provide more accurate estimates of the maximum potential for natural nitrogen fixation across tropical forests.

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We tested the following hypotheses on the dynamics of a dung beetle community in a Brazilian Seasonally Dry Tropical Forest: (1) successional changes of dung beetle community, with species composition, richness and overall abundance increasing with the successional stages; (2) dung beetle community changes between dry and wet seasons, with species composition, richness and abundance decreasing in the dry season. Dung beetles were sampled in 15 plots from three different successional stages in both wet and dry seasons. We sampled a total of 2,752 individuals, representing 38 beetle species and 14 genera. The composition, richness, and abundance of dung beetles changed along the successional gradient and was strongly related to seasonal variation. The highest diversity of dung beetles was found in the intermediate aged forest fragments. These findings highlight the importance of secondary forests to biodiversity conservation and restoration programs in seasonally dry tropical ecosystems.

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