We used eddy covariance and ecological measurements to investigate the effects of reduced impact logging (RIL) on an old-growth Amazonian forest. Logging caused small decreases in gross primary ...production, leaf production, and latent heat flux, which were roughly proportional to canopy loss, and increases in heterotrophic respiration, tree mortality, and wood production. The net effect of RIL was transient, and treatment effects were barely discernable after only 1 y. RIL appears to provide a strategy for managing tropical forest that minimizes the potential risks to climate associated with large changes in carbon and water exchange.
The net ecosystem exchange of carbon dioxide was measured by eddy covariance methods for 3 years in two old-growth forest sites near Santarém, Brazil. Carbon was lost in the wet season and gained in ...the dry season, which was opposite to the seasonal cycles of both tree growth and model predictions. The 3-year average carbon loss was 1.3 (confidence interval: 0.0 to 2.0) megagrams of carbon per hectare per year. Biometric observations confirmed the net loss but imply that it is a transient effect of recent disturbance superimposed on long-term balance. Given that episodic disturbances are characteristic of old-growth forests, it is likely that carbon sequestration is lower than has been inferred from recent eddy covariance studies at undisturbed sites.
Information on pollutant trophodynamics can be crucial for public health, as contaminated food consumption may lead to deleterious effects. This study was performed in Puruzinho Lake, a remote body ...of water in the Brazilian Amazon from which a riparian human population obtains an important part of its animal protein intake. Samples from 92 individuals, comprising 13 species and four trophic guilds (iliophagous, planktivorous, omnivorous, and piscivorous fish) were analysed for the determination of trace elements (Fe, Cr, Mn, Ni, Zn, Ca, Sr, Cd, Sn, Tl and Pb) and methylmercury concentrations. Samples from the same individuals had already been analysed for stable isotope (SI) measurements (δ13C and δ15N) in a previous investigation and the SI data have been statistically treated with those generated in this study for the evaluation of trophic dynamics of contaminants. Methylmercury was the only analyte that biomagnified, presenting TMF values of 4.65 and 4.55 for total and resident ichthyofauna, respectively. Trace elements presented either trophic dilution or independence from the trophic position, constituting a behaviour that was coherent with that found in the scientific literature. The similarity between Ni behaviour through the trophic web to that of essential elements contributes to the discussion on the essentiality of this metal to fish. Considering the Non-cancer Risk Assessment, the calculated Target Hazard Quotient (THQ) values were higher than 1.0 for all analysed individuals for methylmercury, as well as for only one individual for nickel. No other analyte rendered THQ values higher than 1.0.
•Methylmercury has undergone biomagnification in Puruzinho Lake ichthyofauna.•Elements either went through dilution (TD) or were not influenced by position (TP).•Migratory species have influenced biomagnification of 3 elements: Zn, Ca and Pb.•Methylmercury was the only analyte that presented THQ values higher than 1.0.•Multielement analysis may help distinguishing resident and migratory species.
The properties and components of the peat allow peatlands to function as water reservoirs which participate in the hydrological cycle by modulating water discharge. In particular, mountain peatlands ...from Serra do Espinhaço Meridional (Minas Gerais State, Brazil) provide water of good quality for the nearby cities and also serve as habitats for wildlife and flora, with unique endemic species. In this paper, we present the characterization of four mountain mires (Pau de Fruta, São João da Chapada, Pinheiros and Sempre Viva) based on morphological, physical, chemical, and elemental properties analyzed in five selected peat cores (PdF-I, PdF-II, SJC, PI and SV). Radiocarbon dating indicates that they started to form during the late Pleistocene. Principal components analysis was applied to synthesize their main peat properties and underlying processes. The first principal component, PC1, is related to the relative content in inorganic versus organic matter of the peat, most probably related to the evolution of the soils of the mires' catchments (i.e. soil erosion); PC2 seems to be related to the incorporation of inorganic material by deposition of dust from regional sources; PC3 reflects the content and preservation of plant remains; and PC4 indicates the degree of peat decomposition. Our results suggest that mountain tropical mires from Serra do Espinhaço Meridional are complex peatland ecosytems, with a large potential for the reconstruction of environmental changes (i.e. climate change) occurred since the late Pleistocene, and that they should be fully protected.
•The properties are comparable to those of other mountain peatlands.•The properties show variations in depth and in agreement with the stratigraphy.•The analyzed properties have to be conceived as proxies of the processes/drivers.•Four main processes are related to the genesis and evolution these mires.•These late Pleistocene mires should be preserved and protected in full.
Soil erosion leads to land degradation and translocation of soil particles together with associated particulate organic carbon (POC) and nutrients, thereby influencing the global carbon cycle. In the ...present study, we estimated the contribution of POC delivered to a first-order stream from upslope sugarcane fields and a riparian forest in southeast Brazil. The results show that the amount of surface runoff and soil erosion generated in the riparian forest is significantly lower than in the upslope sugarcane field. However, the contribution of the forest to the total stream bed POC was above 70%, even though most sediments delivered to the stream originated from the upland sugarcane fields. The discrepancy between sediment and POC delivery from both land uses is a consequence of the presence of preferential runoff pathways from the agricultural fields, through the buffer strips, to the stream. This disconnection between the main sources of sediment and POC to the first-order stream is a potentially important mechanism influencing the transfer of POC from upslope areas to waterways. This mechanism should be considered in order to more reliably assess fluxes of OC from upslope areas to first-order streams in landscapes where arable land is separated from streams by a semi-natural buffer zone with permanent vegetation.
•Poor soil conservation allows pathways formation connecting crop lands to streams.•Preferential pathways may severely reduce the buffer strips mitigation capacities.•Lateral fluxes of OC to inland waters due to erosion is an important mechanism.
Objective
The main objective of this study is to investigate diet patterns among rural and urban populations of the Center‐West, Northeast, and Amazon regions of Brazil through the carbon and ...nitrogen isotopic composition of fingernails, recognizing that the extent of market integration is a key driver of food consumption.
Materials and methods
In the Center‐West, Northeast, and Amazon regions of Brazil, fingernails were sampled in clusters encompassing a major city, town, and rural village. A total of 2,133 fingernails were analyzed. Fingernails were clipped by donors using fingernail clippers. In the laboratory, samples were cleaned then weighed in small tin capsules before being isotopically analyzed for carbon and nitrogen.
Results
The overall mean δ13C and δ15N were −19.7 ± 2.8‰ and 10.6 ± 1.1‰, respectively. In the more remote villages, where access to food markets is more challenging, lower δ13C prevails, suggesting that Brazilian staple foods (rice, beans, and farinha) still dominate. In areas with easier access to food markets, δ13C values were higher, suggesting a change to a diet based on C4 plants, typical of a Brazilian supermarket diet. The variability among inhabitants in the same location expressed by a significant inverse correlation between δ13C and δ15N fingernail values suggested that “market integration” does not affect everyone equally in each community.
Discussion and Conclusion
The nutrition transition has not yet reached some remote villages in these regions of Brazil or that the nutrition transition has not yet reached all residents of these remote villages. On the other hand, in several villages there is a considerable adherence to the supermarket diet or that some residents of these villages are already favoring processed food.
Variability in snake venom composition has been frequently reported and correlated to the adaptability of snakes to environmental conditions. Previous studies report plasticity for the venom ...phenotype. However, these observations are not conclusive, as the results were based on pooled venoms, which present high individual variability. Here we tested the hypothesis of plasticity by influence of confinement and single diet type in the venom composition of 13 adult specimens of
snakes, maintained under captivity for more than three years. Individual variability in venom composition was observed in samples extracted just after the capture of the snakes. However, composition was conserved in venoms periodically extracted from nine specimens, which presented low variability restricted to the less abundant components. In a second group, composed of four snakes, drastic changes were observed in the venom samples extracted at different periods, mostly related to snake venom metalloproteinases (SVMPs), the core function toxins of
venom, which occurred approximately between 400 and 500 days in captivity. These data show plasticity in the venom phenotype during the lifetime of adult snakes maintained under captive conditions. Causes or functional consequences involved in the phenotype modification require further investigations.
Global warming can intensify the soil organic matter (SOM) turnover, damaging soil health. Crop residues left on the soil are important to maintain a positive SOM budget and nutrient cycling. But, ...sugarcane (
Saccharum officinarum
) straw has been removed from the field for bioenergy purposes. We hypothesize that global warming, together with straw removal, will negatively impact Brazil’s ethanol carbon footprint. Thus, we conducted an experiment under controlled conditions to evaluate the impacts of warming and straw removal on greenhouse gas (GHG) emissions, soil carbon and nitrogen storage, and nutrient cycling. Two soils (Rhodic Acrisol and Eutric Nitisol) were tested with three rates of sugarcane straw removal (no removal (NR): equivalent to 12 Mg ha
−1
; medium removal (MR): 6 Mg ha
−1
; and total removal (TR): bare soil) and submitted to two temperatures (24 °C and 30 °C) and soil moistures (30% and 50%). Straw decomposition was stimulated by lower rates of straw removal, resulting in increases on carbon dioxide (CO
2
) emissions between 5 to 14 times, and N
2
O between 25 and 40%. There were no significant methane (CH
4
) fluxes. Soil carbon and nitrogen did not change due to straw removal, yet labile carbon fractions (living and non-living) were highly impacted, causing reductions of 15 to 40% on the carbon management index (CMI). Furthermore, straw removal reduced nutrient cycling between 10 and 30%. Overall, in a scenario of warming, our findings point to an intensification of SOM dynamic, resulting in increases of 35% on the GHG emissions and a CMI reduction by 20%. In practical terms, at least 6 Mg ha
−1
of straw should be left in the field, guaranteeing raw-material for bioenergy, without causing major impacts on the GHG emission and soil attributes.
The Neotropics harbor some of the most diversified woody species in the world, and to understand the nutrient dynamics in these ecosystems, it is crucial to understand the role of plant taxonomy. In ...addition, biological nitrogen (N) fixation (BNF) in the tropics is one of the key processes affecting the global N cycle. Our objective was to (i) investigate the role of taxonomy and sampling site as predictors of foliar carbon (C) and N concentration and its stable isotopes (i.e., δ
13
C and δ
15
N); (ii) assess differences in foliar N, C:N ratio, and δ
15
N among three functional groups: species of N
2
-fixers and non-fixers of the Fabaceae family, as well as non-Fabaceae species; and (iii) examine the effect of wood density on tree foliar properties. We hypothesized that Fabaceae specimens in symbiosis with N
2
-fixers would possess a higher foliar N than non-fixing plants, including those of the Fabaceae family, as well as high-density trees would have higher foliar C and C:N ratio relative to low-density trees, where the latter invest in nutrients instead of structural C. We used a data set composed of 3,668 specimens sampled in three main biomes of Brazil: Amazon, Atlantic Forest, and Cerrado. The partitioning of variance had a higher influence of taxonomy on leaf C, N, and C:N ratio. Conversely, foliar δ
13
C and δ
15
N were environmentally constrained. While family was the most important taxonomy level for C, N, and C:N ratio, species played a major role for δ
13
C and δ
15
N. Foliar N followed the pattern fixers > non-fixers > non-Fabaceae, while C:N ratio had an opposite trend. In addition, foliar C was correlated with wood density, where high-density > medium-density and low-density woods. The large variability of δ
15
N was observed among Fabaceae species, demonstrates the complexity of using δ
15
N as an indicator of BNF. The higher foliar N of Fabaceae non-fixers than non-Fabaceae specimens support the hypothesis that an N-demanding lifestyle is an inherent pattern in this family. Lastly, although observed in some studies, the prediction of foliar properties using wood density is challenging, and future research on this topic is needed.
In Brazil most of the urban sewage is dumped without treatment into rivers. Because of this, it is extremely important to evaluate the consequences of organic matter rich sewage on the structure and ...functioning of river ecosystems. In this study we investigated the effects of urban sewage on the dissolved oxygen (O sub(2)), dissolved inorganic (DIC) and organic carbon (DOC), and electrical conductivity (EC) in 10 small streams of the Piracicaba River basin, southeast region of Brazil. In the Piracicaba River basin, which is one of the most developed regions of the country, only 16% of the total sewage load generated is treated. These streams were classified into two groups, one with heavy influence of urban sewage and another with less influence. Both concentrations and seasonal variability were distinct between the two groups. The streams that received sewage effluent had a combination of low O sub(2) with high DIC, DOC, and EC. In the polluted streams, concentrations of dissolved carbon forms and EC were higher and O sub(2) concentration lower during the low water period. In the less polluted streams seasonal variations in concentrations were small. We also investigated the efficiency of a sewage treatment plant installed two years ago in the catchment of one of these streams. It was observed an increase in the O sub(2) concentration after the beginning of the treatment, and a decrease of DIC and DOC concentrations especially during the low water period. However, no significant change was observed in the EC, suggesting that the concentrations of major ions is still unaltered, and that a secondary treatment is necessary in order to reduce ion load into the stream.
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