Thresholds of riparian forest use by terrestrial mammals in a fragmented Amazonian deforestation frontier

Species persistence in fragmented landscapes is intimately related to the quality, structure, and context of remaining habitat remnants. Riparian vegetation is legally protected within private landholdings in Brazil, so we quantitatively assessed occupancy patterns of terrestrial mammals in these remnants, examining under which circumstances different species effectively use them. We selected 38 riparian forest patches and five comparable riparian sites within continuous forest, at which we installed four to five camera-traps per site (199 camera-trap stations). Terrestrial mammal assemblages were sampled for 60 days per station during the dry seasons of 2013 and 2014. We modelled species occupancy and detection probabilities within riparian forest remnants, and examined the effects of patch size, habitat quality, and landscape structure on occupancy probabilities. We then scaled-up modelled occupancies to all 1915 riparian patches throughout the study region to identify which remnants retain the greatest potential to work as habitat for terrestrial vertebrates. Of the ten species for which occupancy was modelled, six responded to forest quality (remnant degradation, cattle intrusion, palm aggregations, and understorey density) or structure (remnant width, isolation, length, and area of the patch from which it originates). Patch suitability was lower considering habitat quality than landscape structure, and virtually all riparian remnants were unsuitable to maintain a high occupancy probability for all species that responded to forest patch quality or structure. Beyond safeguarding legal compliance concerning riparian remnant amount, ensuring terrestrial vertebrate persistence in fragmented landscapes will require curbing the drivers of forest degradation within private landholdings

Soil water-holding capacity and monodominance in Southern Amazon tropical forests

Background and aims: We explored the hypothesis that low soil water-holding capacity is the main factor driving the monodominance of Brosimum rubescens in a monodominant forest in Southern Amazonia. Tropical monodominant forests are rare ecosystems with low diversity and high dominance of a single tree species. The causes of this atypical condition are still poorly understood. Some studies have shown a relationship between monodominance and waterlogging or soil attributes, while others have concluded that edaphic factors have little or no explanatory value, but none has accounted for soil-moisture variation other than waterlogging. This study is the first to explicitly explore how low soil water-holding capacity influences the monodominance of tropical forests. Methods: We conducted in situ measurements of vertical soil moisture using electrical resistance collected over 1 year at 0–5; 35–40 and 75–80 cm depths in a B. rubescens monodominant forest and in an adjacent mixed-species forest in the Amazon-Cerrado transition zone, Brazil. Minimum leaf water potential (Ψmin) of the seven most common species, including B. rubescens, and soil water-holding capacity for both forests were determined. Results: The vertical soil moisture decay pattern was similar in both forests for all depths. However, the slightly higher water availability in the monodominant forest and Ψmin similarity between B. rubescens and nearby mixed forest species indicate that low water-availability does not cause the monodominance. Conclusions: We reject the hypothesis that monodominance of B. rubescens is primarily determined by low soil water-holding capacity, reinforcing the idea that monodominance in tropical forests is not determined by a single factor

Hyperdominance in Amazonian Forest Carbon Cycling

While Amazonian forests are extraordinarily diverse, the abundance of trees is skewed strongly towards relatively few ‘hyperdominant’ species. In addition to their diversity, Amazonian trees are a key component of the global carbon cycle, assimilating and storing more carbon than any other ecosystem on Earth. Here we ask, using a unique data set of 530 forest plots, if the functions of storing and producing woody carbon are concentrated in a small number of tree species, whether the most abundant species also dominate carbon cycling, and whether dominant species are characterized by specific functional traits. We find that dominance of forest function is even more concentrated in a few species than is dominance of tree abundance, with only ≈1% of Amazon tree species responsible for 50% of carbon storage and productivity. Although those species that contribute most to biomass and productivity are often abundant, species maximum size is also influential, while the identity and ranking of dominant species varies by function and by region

Long-term thermal sensitivity of Earth’s tropical forests

The sensitivity of tropical forest carbon to climate is a key uncertainty in predicting global climate change. Although short-term drying and warming are known to affect forests, it is unknown if such effects translate into long-term responses. Here, we analyze 590 permanent plots measured across the tropics to derive the equilibrium climate controls on forest carbon. Maximum temperature is the most important predictor of aboveground biomass (−9.1 megagrams of carbon per hectare per degree Celsius), primarily by reducing woody productivity, and has a greater impact per °C in the hottest forests (>32.2°C). Our results nevertheless reveal greater thermal resilience than observations of short-term variation imply. To realize the long-term climate adaptation potential of tropical forests requires both protecting them and stabilizing Earth’s climate

Avaliação das características físicas do solo da área da mata da galeria na sub-bacia hidrográfica da Mariana para a conservação ambiental

The objective of this work was to characterize soil physical properties of the gallery woods area at the hydrographic Mariana sub-catchment. The physical attributes evaluated were: bulk density, gravimetric humidity, soil porosity and mechanical resistance to penetration. The field work was carried out at Alta Floresta-MT, Brazil. Nine plots of 20 m x 50 m in surface were marked along the upper and middle river course areas in such a way that they were representative of all the subcatchment extension. The experimental design was completely randomized. Soil density of the gallery woods area was higher than that of the native forest, so that development of the root system of the trees even could be restricted. Gravimetric humidity was found to be homogeneous when different areas or different depths were compared. Soil porosity was found to be adequate for native gallery woods. Mean penetration resistance at the 0-0.25 m depth was classified as moderate, bout hint the upper and middle river course areas.El objetivo de este trabajo fue caracterizar las propiedades físicas del suelo de la zona de bosques de galería en la subcuenca hidrográfica de Mariana. Los atributos físicos evaluados fueron: densidad aparente, humedad gravimétrica, porosidad del suelo y resistencia mecánica a la penetración. El trabajo de campo se realizó en Alta Floresta-MT, Brasil. Se marcaron nueve parcelas de 20 m x 50 m de superficie a lo largo de las zonas del curso superior y medio del río, de manera que fueran representativas de toda la extensión de la subcuenca. El diseño experimental fue completamente aleatorio. La densidad del suelo de la zona del bosque de galería era mayor que la del bosque nativo, por lo que el desarrollo del sistema radicular de los árboles incluso podía verse restringido. La humedad gravimétrica resultó ser homogénea cuando se compararon diferentes zonas o diferentes profundidades. La porosidad del suelo resultó ser adecuada para los bosques de galería nativos. La resistencia media a la penetración en la profundidad de 0-0,25 m se clasificó como moderada, lo que sugiere las zonas del curso superior y medio del río.O objectivo deste trabalho era caracterizar as propriedades físicas do solo da área da mata da galeria na sub-bacia hidrográfica da Mariana. Os atributos físicos avaliados foram: densidade aparente, humidade gravimétrica, porosidade do solo e resistência mecânica à penetração. O trabalho de campo foi levado a cabo em Alta Floresta-MT, Brasil. Nove parcelas de 20 m x 50 m de superfície foram marcadas ao longo das zonas do curso superior e médio do rio de tal forma que eram representativas de toda a extensão da sub-bacia hidrográfica. O desenho experimental foi completamente aleatório. A densidade do solo da área da mata de galeria era superior à da floresta nativa, de modo a que o desenvolvimento do sistema radicular das árvores pudesse mesmo ser restringido. Verificou-se que a humidade gravimétrica era homogénea quando diferentes áreas ou diferentes profundidades eram comparadas. Verificou-se que a porosidade do solo era adequada para as matas de galeria nativas. A resistência média à penetração a 0-0,25 m de profundidade foi classificada como moderada, sobre as áreas do curso superior e médio dos rios

Spatiotemporal dynamics in caddisfly (Insecta: Trichoptera) of a Cerrado stream, Brazil

Knowing the patterns and mechanisms that regulate spatiotemporal dynamics in aquatic communities is a great challenge. Theoretically, the distribution of aquatic insects is related to food and shelter availability, and/or to dispersal. In this perspective, we analyzed the spatiotemporal variation of Trichoptera communities of a Cerrado stream for 3 years. The longitudinal and temporal distribution provided a good explanation of the variation of the Trichoptera species composition. Specifically, 21.4 and 11.5% of the variation in composition was explained by longitudinal and temporal variation, respectively, and 8.3% by the interaction of both factors. The variation of environmental conditions (pH, total dissolved solids and dissolved oxygen) and temporal autocorrelation were the most important predictors for the distribution of Trichoptera communities. Accordingly, it is possible to assume that seasonal variation throughout the year is also an important factor for this aquatic community, in addition to water quality, as is widely known. Therefore, climate change should affect both temporal and spatial patterns of Trichoptera communities present in Cerrado streams. Consequently, such effect should be expected to occur in other regions with more marked seasons.The longitudinal distribution (along the stream) is more important than the temporal variation (along the seasons) to explain the variations of the composition of Thichoptera species in streams of the Brazilian Cerrado

Seasonal Variation in the Fate of Seeds under Contrasting Logging Regimes

Seed predators and dispersers may drive the speed and structure of forest regeneration in natural ecosystems. Rodents and ants prey upon and disperse seeds, yet empirical studies on the magnitude of these effects are lacking. Here, we examined the role of ants and rodents on seed predation in 4 plant species in a successional gradient on a tropical rainforest island. We found that (1) seeds are mostly consumed rather than dispersed; (2) rates of seed predation vary by habitat, season, and species; (3) seed size, shape, and hardness do not affect the probability of being depredated. Rodents were responsible for 70% of seed predation and were negligible (0.14%) seed dispersers, whereas ants were responsible for only 2% of seed predation and for no dispersal. We detected seasonal and habitat effects on seed loss, with higher seed predation occurring during the wet season and in old-growth forests. In the absence of predators regulating seed-consumer populations, the densities of these resilient animals explode to the detriment of natural regeneration and may reduce diversity and carrying capacity for consumers and eventually lead to ecological meltdown