International audienceThe seasonal climate drivers of the carbon cycle in tropical forests remain poorly known, although these forests account for more carbon assimilation and storage than any other terrestrial ecosystem. Based on a unique combination of seasonal pan-tropical data sets from 89 experimental sites (68 include aboveground wood productivity measurements and 35 litter productivity measurements), their associated canopy photosynthetic capacity (enhanced vegetation index, EVI) and climate, we ask how carbon assimilation and aboveground allocation are related to climate seasonality in tropical forests and how they interact in the seasonal carbon cycle. We found that canopy photosynthetic capacity seasonality responds positively to precipitation when rainfall is < 2000 mm yr(-1) (water-limited forests) and to radiation otherwise (light-limited forests). On the other hand, independent of climate limitations, wood productivity and litterfall are driven by seasonal variation in precipitation and evapotranspiration, respectively. Consequently, light-limited forests present an asynchronism between canopy photosynthetic capacity and wood productivity. First-order control by precipitation likely indicates a decrease in tropical forest productivity in a drier climate in water-limited forest, and in current light-limited forest with future rainfall < 2000 mm yr(-1)

a b s t r a c tTree mortality in Amazonia has been related to regional variation in soil, topography and climatic disturbances, but the magnitude of the effect of these factors on tree mortality at local and mesoscales remains poorly determined. We investigated tree mortality in 72 1-ha permanent plots spanning 64 km 2 of tropical moist forest in Reserva Ducke, Manaus, Brazil. Plots were censused three times (resulting in two census intervals. The relationships of soil and topography to tree mortality were dependent on tree size. Small-and medium-sized trees (1 6 dbh < 30 cm) had similar relationships of mortality with soil and topography, while large trees (dbh P 30 cm) showed different (or no) relationships. The effects of soil and topography on tree mortality also varied temporally. In the second census interval after storms, soil and topography explained about one-fourth of the spatial variation in mortality of small-and medium-sized trees (<30 cm dbh), whereas no effects were detected in the first census interval. In particular, soil fertility was the most important predictor of tree mortality in the study area. Topography alone (altitude and slope) was associated with only 12% of the spatial variation in tree mortality and the magnitude of the effect of soil and topography on tree mortality also increased after storms. In general, plots on more fertile soils, on steep slopes and sandy soils in valleys showed greater tree mortality than those on plateau with well-drained clayey soils. Therefore, disturbance history and tree size should be included when scaling up tree mortality from local to regional scales. As much variation remains unexplained, other landscape features, such as watershed morphology and wind exposure, may be necessary to make more precise predictions on patterns of tree mortality in Central Amazonia.

a b s t r a c tTree mode of death provides insights as to why soil and topography explain only about 25% of the spatial variation in tree mortality in Central Amazonia, and permit predictions about what types of mortality are most probable under climate change. We studied tree mortality by mode of death in 72 1-ha permanent plots spanning 64 km 2 of tropical moist forest in Reserva Ducke, Manaus, Amazonas, Brazil. Plots were recensused twice (2003-2005 and 2005-2008). Tree mode of death was assigned for trees P4 cm dbh as standing, uprooted or snapped. We also recorded whether trees died alone or were pushed over by treefalls. Standing death was predominant, representing 54% of deaths of trees with dbh P 10 cm, followed by snapping (26%) and uprooting (14%). Trees that fell alone represented 25% of deaths, while 16% were pushed over. Most small fallen dead trees (4 6 dbh < 30 cm) were pushed over by other trees, while most large dead trees (dbh P 30 cm) died alone. Standing mortality was weakly related to soil and topography, but 20% of variation in uprooted mortality and 11% in snapped mortality of trees with dbh P 10 cm was explained by soil and topography. The variation in mortality explained for small trees (18% for uprooted mortality and 13% for snapped mortality) was higher than for large trees (14% for mortality by snapping only). In spite of little variation in mortality associated directly with soil and slope, analyses assessing the effect of topographic categories (plateaux, slope, and valley) on tree mortality detected higher differences, even though causal factors remain unidentified because topographic position may encompass both topographic and soil properties. There was an increase from the first to the second census interval in the effects associated with soil and topography on tree mortality by uprooting and snapping, and this was likely due to storms, which led to a disproportional increase in tree mortality for these tree modes of death. Presently, uprooting and snapping mortality are not dominant and the use of soil and topographic variables for modeling of tree mortality is therefore limited. However, under predicted climate-change scenarios of higher frequency of extreme storms, soil and topography may become more useful to improve estimates of tree mortality and biomass losses over large areas in Amazonia.

An Amazonian savanna in northern Brazil known as the Cerrado of Amapá is under imminent threat from poor land-use planning, the expansion of large-scale agriculture and other anthropogenic pressures. These savannas house a rich and unique flora and fauna, including endemic plants and animals. However, the area remains under-sampled for most taxa, and better sampling may uncover new species. We estimate that only ~9.16% of these habitats have any kind of protection, and legislative changes threaten to further weaken or remove this protection. Here we present the status of knowledge concerning the biodiversity of the Cerrado of Amapá, its conservation status, and the main threats to the conservation of this Amazonian savanna. To secure the future of these unique and imperilled habitats, we suggest urgent expansion of protected areas, as well as measures that would promote less-damaging land uses to support the local population.

Tropical forests are known for their high diversity. Yet, forest patches do occur in the tropics where a single tree species is dominant. Such “monodominant” forests are known from all of the main tropical regions. For Amazonia, we sampled the occurrence of monodominance in a massive, basin-wide database of forest-inventory plots from the Amazon Tree Diversity Network (ATDN). Utilizing a simple defining metric of at least half of the trees ≥ 10 cm diameter belonging to one species, we found only a few occurrences of monodominance in Amazonia, and the phenomenon was not significantly linked to previously hypothesized life history traits such wood density, seed mass, ectomycorrhizal associations, or Rhizobium nodulation. In our analysis, coppicing (the formation of sprouts at the base of the tree or on roots) was the only trait significantly linked to monodominance. While at specific locales coppicing or ectomycorrhizal associations may confer a considerable advantage to a tree species and lead to its monodominance, very few species have these traits. Mining of the ATDN dataset suggests that monodominance is quite rare in Amazonia, and may be linked primarily to edaphic factors.

Amazonian forests are extraordinarily diverse, but the estimated species richness is very much debated. Here, we apply an ensemble of parametric estimators and a novel technique that includes conspecific spatial aggregation to an extended database of forest plots with up-to-date taxonomy. We show that the species abundance distribution of Amazonia is best approximated by a logseries with aggregated individuals, where aggregation increases with rarity. By averaging several methods to estimate total richness, we confirm that over 15,000 tree species are expected to occur in Amazonia. We also show that using ten times the number of plots would result in an increase to just ~50% of those 15,000 estimated species. To get a more complete sample of all tree species, rigorous field campaigns may be needed but the number of trees in Amazonia will remain an estimate for years to come.

Xenarthrans—anteaters, sloths, and armadillos—have essential functions for ecosystem maintenance, such as insect control and nutrient cycling, playing key roles as ecosystem engineers. Because of habitat loss and fragmentation, hunting pressure, and conflicts with domestic dogs, these species have been threatened locally, regionally, or even across their full distribution ranges. The Neotropics harbor 21 species of armadillos, 10 anteaters, and 6 sloths. Our data set includes the families Chlamyphoridae (13), Dasypodidae (7), Myrmecophagidae (3), Bradypodidae (4), and Megalonychidae (2). We have no occurrence data on Dasypus pilosus (Dasypodidae). Regarding Cyclopedidae, until recently, only one species was recognized, but new genetic studies have revealed that the group is represented by seven species. In this data paper, we compiled a total of 42,528 records of 31 species, represented by occurrence and quantitative data, totaling 24,847 unique georeferenced records. The geographic range is from the southern United States, Mexico, and Caribbean countries at the northern portion of the Neotropics, to the austral distribution in Argentina, Paraguay, Chile, and Uruguay. Regarding anteaters, Myrmecophaga tridactyla has the most records (n = 5,941), and Cyclopes sp. have the fewest (n = 240). The armadillo species with the most data is Dasypus novemcinctus (n = 11,588), and the fewest data are recorded for Calyptophractus retusus (n = 33). With regard to sloth species, Bradypus variegatus has the most records (n = 962), and Bradypus pygmaeus has the fewest (n = 12). Our main objective with Neotropical Xenarthrans is to make occurrence and quantitative data available to facilitate more ecological research, particularly if we integrate the xenarthran data with other data sets of Neotropical Series that will become available very soon (i.e., Neotropical Carnivores, Neotropical Invasive Mammals, and Neotropical Hunters and Dogs). Therefore, studies on trophic cascades, hunting pressure, habitat loss, fragmentation effects, species invasion, and climate change effects will be possible with the Neotropical Xenarthrans data set. Please cite this data paper when using its data in publications. We also request that researchers and teachers inform us of how they are using these data.

The effects of soil on tree species composition and trait distributions in tropical forest, and how these interactions affect tree biomass and dynamics, are poorly understood because variation in soil is confounded with variation in climate over large areas. We excluded confounding due to climate by studying variation among 72 1-ha plots within 64 km 2 , and minimized within-plot variation in soil and stand properties by using long narrow plots oriented along altitudinal contours in Reserva Ducke, Central Amazonia, Brazil. Soil variation caused shifts in tree species composition, which determined stand-level wood density. Soil clay content, cation exchange capacity, plot mean wood density and one-dimensional ordination of tree species composition explained about 40% of variation in tree biomass, 24% of variation in tree mortality and 18% of variation in coarse wood production. As pioneer species were not abundant, lower biomass and higher mortality on sandy soils is a consequence of dominance of species with low to medium wood density adapted to waterlogged and nutrient-poor sandy soils. Therefore, mesoscale variation in biomass and dynamics is caused by co-occurrence of species with similar traits in different parts of the edaphic gradient. Identification of mechanisms controlling tree biomass and dynamics in Amazonian forest will require better understanding of tree-soil physiologic interactions.