Amazon forest structure generates diurnal and seasonal variability in light utilization.

The complex three-dimensional (3-D) structure of tropical forests generates a diversity of light environments for canopy and understory trees. Understanding diurnal and seasonal changes in light availability is critical for interpreting measurements of net ecosystem exchange and improving ecosystem models. Here, we used the Discrete Anisotropic Radiative Transfer (DART) model to simulate leaf absorption of photosynthetically active radiation (lAPAR) for an Amazon forest. The 3-D model scene was developed from airborne lidar data, and local measurements of leaf reflectance, aerosols, and PAR were used to model lAPAR under direct and diffuse illumination conditions. Simulated lAPAR under clear-sky and cloudy conditions was corrected for light saturation effects to estimate light utilization, the fraction of lAPAR available for photosynthesis. Although the fraction of incoming PAR absorbed by leaves was consistent throughout the year (0.80?0.82), light utilization varied seasonally (0.67?0.74), with minimum values during the Amazon dry season. Shadowing and light saturation effects moderated potential gains in forest productivity from increasing PAR during dry-season months when the diffuse fraction from clouds and aerosols was low. Comparisons between DART and other models highlighted the role of 3-D forest structure to account for seasonal changes in light utilization. Our findings highlight how directional illumination and forest 3-D structure combine to influence diurnal and seasonal variability in light utilization, independent of further changes in leaf area, leaf age, or environmental controls on canopy photosynthesis. Changing illumination geometry constitutes an alternative biophysical explanation for observed seasonality in Amazon forest productivity without changes in canopy phenology.

Biomarker analysis in soils of the Amazon rainforest after vegetation fire.

The objective of this study was to determine the origin of organic matter incorporated in Amazon forest soils subjected to vegetation fire by analyzing the aliphatic biomarkers (n-alkanes) present in lipid extracts of soil samples.

Dendrochronological potential of Copaifera lucens Dwyer (Fabaceae): endemic species of a hotspot in the Atlantic Forest of Brazil.

2016

Dendroecology of Araucaria angustifolia under two geomorphological conditions in the seasonal semideciduous forest and mixed ombrophilous forest ecotone of Paraná, Brazil.

2016

Communities of parasite metazoans in Piaractus brachypomus (Pisces, Serrasalmidae) in the lower Amazon River (Brazil).

The aim of this study was to investigate the component community of parasite metazoans of Piaractus brachypomus in the lower Amazon River, northern Brazil. From 34 necropsied fish, 27,384 metazoan parasites were collected, such as Anacanthorus spathulatus, Mymarothecium viatorum and Notozothecium janauachensis (Monogenoidea); Spectatus spectatus and Contracaecum sp (Nematoda); Clinostomum marginatum and Dadaytrema oxycephala (Digenea); and Argulus carteri and Ergasilus sp. (Crustacea). The dominant species was S. spectatus followed by monogenoidean species, and there was aggregated dispersion of parasites, except for D. oxycephala and Contracaecum sp., which presented random dispersion. Positive correlation among the abundance of the three monogenoideans species were found, thus indicating that there was no competition between the species of these parasites on the gills of hosts. The abundances of some parasite species showed positive correlations with the size of the hosts, but the condition factor of the fish was not affected by the parasitism levels. It showed that this host had a metazoan community characterized by high species richness of metazoans, low evenness and high diversity of parasites, with prevalence of endoparasites, including larval stages. This was the first record of C. marginatum, A. carteri, Ergasilus sp. and Contracaecum sp. for P. brachypomus.

Typologies and spatialization of agricultural production systems in Rondônia, Brazil: linking land use, socioeconomics and territorial configuration.

The current Amazon landscape consists of heterogeneous mosaics formed by interactions between the original forest and productive activities. Recognizing and quantifying the characteristics of these landscapes is essential for understanding agricultural production chains, assessing the impact of policies, and in planning future actions. Our main objective was to construct the regionalization of agricultural production for Rondônia State (Brazilian Amazon) at the municipal level. We adopted a decision tree approach, using land use maps derived from remote sensing data (PRODES and TerraClass) combined with socioeconomic data. The decision trees allowed us to allocate municipalities to one of five agricultural production systems: (i) coexistence of livestock production and intensive agriculture; (ii) semi-intensive beef and milk production; (iii) semi-intensive beef production; (iv) intensive beef and milk production, and; (v) intensive beef production. These production systems are, respectively, linked to mechanized agriculture (i), traditional cattle farming with low management, with (ii) or without (iii) a significant presence of dairy farming, and to more intensive livestock farming with (iv) or without (v) a significant presence of dairy farming. The municipalities and associated production systems were then characterized using a wide variety of quantitative metrics grouped into four dimensions: (i) agricultural production; (ii) economics; (iii) territorial configuration, and; (iv) social characteristics. We found that production systems linked to mechanized agriculture predominate in the south of the state, while intensive farming is mainly found in the center of the state. Semi-intensive livestock farming is mainly located close to the southwest frontier and in the north of the state, where human occupation of the territory is not fully consolidated. This distributional pattern reflects the origins of the agricultural production system of Rondônia. Moreover, the characterization of the production systems provides insights into the pattern of occupation of the Amazon and the socioeconomic consequences of continuing agricultural expansion.

Population dynamics of Tachigali rubiginosa (Mart. ex Tul.). Oliveira-Filho (Fabaceae) (2007-2014) in the Forest Gallery / Ecotone / Campo Sujo transition at Água Limpa Farm, Federal District, Brazil.

2016

Diversity of new root nodule bacteria from Erythrina velutina Willd., a native legume from the Caatinga dry forest (Northeastern Brazil).

This study aims to evaluate the phenotypical characteristics of bacterial isolates from mulungu (Erythrina velutina Willd.) nodules and determinate their Box-PCR fingerprinting. All bacteria were evaluated by the following phenotypic characteristics: growth rate, pH change, colony color and mucus production. The bacterial isolates able to re-nodulate the original host were also evaluated regarding its tolerance to increased salinity and different incubation temperatures, ability to growth using different carbon sources, intrinsic antibiotic resistance and ?in vitro? auxin biosynthesis. The molecular fingerprints were set up using the Box-PCR technique and the isolates were clustered by their profiles. Among the 22 bacterial isolates obtained, eight were able to re-nodulate the original host. Among the nodule inducing isolates, some were tolerant to 1% of NaCl and 39° C and all of them metabolized the maltose, fructose, glucose, sucrose and arabinose, were resistant to rifampicin and produced auxin. The bacteria showed low genetic similarity among them and reference strains, which indicates the great genetic variability of the isolates. The results of this work are the first reports about the bacterial isolates able to nodulate this species. A more deep study of these bacteria may reveal the existence of isolates tolerant to environmental stresses and suitable as a future mulungu inoculant.

Agriculture and forest: A sustainable strategy in the Brazilian Amazon.

Large-scale agriculture is increasing in anthropogenically modified areas in the Amazon Basin. Crops such as soybean, maize, oil palm, and others are being introduced to supply the world demand for food and energy. However, the current challenge is to enhance the sustainability of these areas by increasing efficiency of production chains and to improve environmental services. The Amazon Basin has experienced a paradigm shift away from the traditional slash-and-burn agricultural practices, which offers decision makers the opportunity to make innovative interventions to enhance the productivity in previously degraded areas by using trees to ecological advantage. This study describes a successful experiment integrating the production of soybean and paricá (Glycine max L. and Schizolobium amazonicum) based on previous research that indicated potential topoclimatic zones for planting paricá in the Brazilian state of Pará. This paper shows that a no-tillage system reduces the effects of drought compared to conventional tillage still used by many farmers in the region. The integrated system was implemented during the 2014/2015 season in 234.6 ha in the high-potential zone in the municipality of Ulianópolis, Pará. Both soybean and paricá were planted simultaneously. Paricá was planted in 5 m x 2 m inter-tree spacing totaling 228x103 trees per hectare and soybean, in 4 m x 100 m spacing, distributed in nine rows with a 0.45 m inter-row distance, occupying 80% of the area. The harvested soybean production was 3.4 t ha-1, higher than other soybean monocultures in eastern Pará. Paricá benefited from soybean fertilization in the first year: It exhibited rapid development in height (3.26 m) and average diameter (3.85 cm). Trees and crop rotation over the following years is six years for forest species and one year for each crop. Our results confirm there are alternatives to the current production systems able to diminish negative impacts resulting from monoculture. In addition, the system provided environmental services such as reduced soil erosion and increased carbon stock by soil cover with no-tillage soybean cultivation. The soybean cover contributes to increased paricá thermal regulation and lower forestry costs. We concluded that innovative interventions are important to show local farmers that it is possible to adapt an agroforest system to large-scale production, thus changing the Amazon.

Regeneration in felling gaps after logging in Acre state, Western Amazon.

Regeneration of tree species in felling gaps were studied during the first two years following harvesting in a tropical forest in Acre state, Brazil. Felling gaps averaged 340 m2 in size, while canopy openings averaged 17%. Seedling mortality in adjacent undisturbed forest was 4.6% yr', and 59.6% yr·1 and 100% yr' in the crown and trunk zones respectively, two years after logging. Recruitment of new seedlings inthe undisturbed forest understorey averaged 462 plants ha' yr', two years after gap creation. Inthe crown zones of the gaps, recruitment of seedlings averaged 1350 ha' yr', and in the trunk zones 1392 ha' yr'. The entire seedling community in trunk zones after logging was composed of new recruits. lhere was a tendency for seedling growth rates to increase from the natural forest (0,21cm yr-1) to the crown zone (0.40cm yr'), Before gap creation, species richness and diversity and seedling density were quite similar. After gap creation a sharp decrease could be verified in the gap.zones, however the differences between gap and undisturbed forest decreased rapidly in the second year after gap creation. lhe regeneration of commercial species was not affected by gap creation apart from the increase in growth rates.

Sustainable forest management for smallholder farmers in the Brazilian Amazon.

The paper describes a forest management system to be applied on smallholder farms, particularly on settlement projects in the Brazilian Amazon. The proposed forest management system was designed to generate a new source of family income and to maintain forest structure and biodiversity. The system is new in three main characteristics: the use of short cycles in the management of tropical forests, the low harvesting intensity and environmental impact, and the direct involvement of the local population in ali forest management activities. It is based on a minimum felling cycle of ten years and an annual timber harvest of 5-10 m3 ha-1.