Litterfall Chemistry Is Modulated by Wet-Dry Seasonality and Leaf Phenology of Dominant Species in the Tropics

Litterfall has a large influence on carbon and nutrient cycling of ecosystems, particularly in light-limited forested streams, as most nutrients return in the form of litter. Although recent evidence points to the prevalence of seasonal litterfall in species-rich and evergreen tropical riparian forests, there is a limited understanding of how riparian plant diversity intersects with stream and riparian ecosystem functions. To explore this question, we investigate litterfall chemistry across wet and dry seasons and the congruence between litter traits and plant species composition of litterfall in the wet-dry tropics. Using generalized additive models, we observed consistent seasonal patterns of litterfall chemistry over 2 years, mostly influenced by dominant species in litterfall. While drier seasons showed litter lower in nutrients and structural compounds and higher in polyphenols, litter from wetter seasons were nutrient rich but lower in polyphenols. We also found contrasting seasonal patterns in litterfall chemistry, one showing that litterfall nutrient, structural compounds, and secondary metabolite concentrations declined in drier seasons while the other showed that mass-based litterfall inputs increased markedly in drier seasons. Our findings suggest that litterfall chemistry may be altered by shifts in the identity of dominant plant species and seasonality, possibly leading to changes in carbon and nutrient fluxes in tropical riparian ecosystems

New Materials to Solve Energy Issues through Photochemical and Photophysical Processes: The Kinetics Involved

Kinetic rates of energy production are extremely controlled by the competing processes that occur in systems capable of energy transfer. Besides organic and inorganic compounds already known as electronically actives, supramolecular systems can be thought to form energy transfer complexes to efficiently convert, for instance, light into electricity and the mechanisms for that can be of any kind. Photophysical and photochemical processes can simultaneously occur in such systems to provide energy conversion, by competing mechanisms or collaborative ones. Thus, to investigate the kinetic rates of each process and to understand the dynamics of the electronic excited states population and depopulation in strategically structured materials, can offer important tools to efficiently make use of this not always so evident power of supramolecular materials. In this chapter, we present the state-of-the-art of the use of photophysical processes and photochemical changes, presented by new materials and devices to provide a control of energy transfer processes and enable distinct applications, since energy conversion to sensing and imaging techniques to material characterization

A novel approach for the characterisation of proteoglycans and biosynthetic enzymes in a snail model

Proteoglycans encompass a heterogeneous group of glycoconjugates where proteins are substituted with linear, highly negatively charged glycosaminoglycan chains. Sulphated glycosaminoglycans are ubiquitous to the animal kingdom of the Eukarya domain. Information on the distribution and characterisation of proteoglycans in invertebrate tissues is limited and restricted to a few species. By the use of multidimensional protein identification technology and immunohistochemistry, this study shows for the first time the presence and tissue localisation of different proteoglycans, such as perlecan, aggrecan, and heparan sulphate proteoglycan, amongst others, in organs of the gastropoda Achatina fulica. Through a proteomic analysis of Golgi proteins and immunohistochemistry of tissue sections, we detected the machinery involved in glycosaminoglycan biosynthesis, related to polymer formation (polymerases), as well as secondary modifications (sulphation and uronic acid epimerization). Therefore, this work not only identifies both the proteoglycan core proteins and glycosaminoglycan biosynthetic enzymes in invertebrates but also provides a novel method for the study of glycosaminoglycan and proteoglycan evolution. (C) 2011 Elsevier B.V. All rights reserved.Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)NIHUniversidade Federal de São Paulo, Dept Bioquim, BR-04044020 São Paulo, BrazilUniv Texas El Paso, Dept Biol Sci, Border Biomed Res Ctr, El Paso, TX 79912 USAUniversidade Federal de São Paulo, Dept Bioquim, BR-04044020 São Paulo, BrazilNIH: 2G12RR008124-16A1NIH: 2G12RR008124-16A1S1Web of Scienc

Rarity of monodominance in hyperdiverse Amazonian forests.

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

Modeling biomass and nutrients in a eucalyptus stand in the cerrado

The prediction of biological processes, which involve growth and plant development, is possible via the adjustment of mathematical models. In forest areas, these models assist in management practices, silviculture, harvesting, and soil fertility. Diameter, basal area, and height are predictors of volume and biomass estimates in forest stands. This study utilized different non-linear models for estimating biomass and nutrient values in the aerial biomass and roots of an unmanaged eucalypt stand in Cerrado dystrophic soil. It was hypothesized that the models would estimate the nutrients of the aboveground biomass and roots after meeting the selection and validation criteria. By statistical analysis of the parameters and subsequent validation, the Schumacher–Hall model was presented to be the best fit for biomass and nutrients. This result confirmed the ability of different variables, including diameter, basal area, and height, to be predicted. Estimating the nutrient values in the aboveground biomass and roots allowed a better understanding of the quality of the vegetal residues that remained in the soil. For dystrophic soils, which occur in the Cerrado, these estimates become even more relevant

Macro-scale (biomes) differences in neotropical stream processes and community structure

The definition of conservation strategies and ecological assessment schemes requires understanding ecosystem patterns over multiple spatial scales. This study aimed to determine if macro-scale structural and functional (processes) patterns associated with stream ecosystems differed among three neotropical biomes (Cerrado, Amazon, Atlantic Forest). We compared the aquatic communities (benthic invertebrates and hyphomycetes) and processes (decomposition rates, primary production and biofilms growth and aquatic hyphomycetes reproduction rates-sporulation) of Cerrado stream sites (neotropical savannah) against those of stream sites in the connecting biomes of the Atlantic Forest and Amazon (rainforests). We expected that, contrary to the biome dependency hypothesis the community structure and processes rates of streams at the biome-scale would not differ significantly, because those ecosystems are strongly influenced by their dense riparian forests, which have a transitional character among the three biomes. Fifty-three stream sites were selected covering a wide range of geographic locations (Table 1), from near the Equator (2° S) in the Amazon, to intermediate latitudes in the Cerrado (12-19° S), and latitudes closer to the tropic of Capricorn in the Atlantic Forest (19º-25° S). We found that: 1) at the abiotic level, the aquatic ecosystems of the three biomes differed, which was mostly explained by large-scale factors such as temperature, precipitation and altitude; 2) functional and structural variables did not behave similarly among biomes: decomposition and sporulation rates showed larger differences among biomes than invertebrate and aquatic hyphomycete assemblages structure; 3) invertebrate assemblages structure differed between the rainforests and Cerrado but not between rainforests (Amazon and Atlantic Forest) whereas aquatic hyphomycetes were similar among all biomes; 4) biofilm growth and algae concentration in biofilms of artificial substrates were highly variable within biomes and not significantly different between biomes. Overall, aquatic ecosystem processes and community structure differed across biomes, being influenced by climatic variables, but the variation is not as pronounced as that described for terrestrial systems. Considering the potential use of these functional and structural indicators in national-wide ecological assessments, our results indicate the need to define different reference values for different biomes, depending on the variable used. The approach followed in this study allowed an integrative analysis and comparison of the stream ecosystems across three tropical biomes, being the first study of this kind. Future studies should try to confirm the patterns evidenced here with more sites from other areas of the three biomes, and especially from the Amazon, which was the least represented biome in our investigation. © 201