Despite being considered beneficial by providing a clean and renewable source of energy, the construction of hydroelectric dams has extremely negative implications for Amazonian fisheries. This study ...investigated the impacts of the Santo Antônio and Jirau hydroelectric dams on the fishery stocks of the Madeira River. This investigation was based on fish catch data from the Z‐31 fishing colony, located in the municipality of Humaitá, in Amazonas State, Northern Brazil. Data were collected daily and provided information on the date of return from each trip, the fish species targeted, and the total catch (kg) between January 2002 and September 2017. The results indicated reductions of 39% in the mean annual catch and 34% in the mean monthly catches. These results highlight the high price paid by local fish communities for the development of hydroelectric power in the Amazon basin.
•Differences in forest seasonal productivity cannot be explained by access to water or sunlight.•Equatorial climates benefit species that support high levels of dry-season photosynthesis.•PAR levels ...predicted the degree to which canopy photosynthetic capacity drives GEP.•Converted sites at Central Amazon show the disruption of the productivity cycle.
We investigated the seasonal patterns of Amazonian forest photosynthetic activity, and the effects thereon of variations in climate and land-use, by integrating data from a network of ground-based eddy flux towers in Brazil established as part of the ‘Large-Scale Biosphere Atmosphere Experiment in Amazonia’ project. We found that degree of water limitation, as indicated by the seasonality of the ratio of sensible to latent heat flux (Bowen ratio) predicts seasonal patterns of photosynthesis. In equatorial Amazonian forests (5° N–5° S), water limitation is absent, and photosynthetic fluxes (or gross ecosystem productivity, GEP) exhibit high or increasing levels of photosynthetic activity as the dry season progresses, likely a consequence of allocation to growth of new leaves. In contrast, forests along the southern flank of the Amazon, pastures converted from forest, and mixed forest-grass savanna, exhibit dry-season declines in GEP, consistent with increasing degrees of water limitation. Although previous work showed tropical ecosystem evapotranspiration (ET) is driven by incoming radiation, GEP observations reported here surprisingly show no or negative relationships with photosynthetically active radiation (PAR). Instead, GEP fluxes largely followed the phenology of canopy photosynthetic capacity (Pc), with only deviations from this primary pattern driven by variations in PAR. Estimates of leaf flush at three non-water limited equatorial forest sites peak in the dry season, in correlation with high dry season light levels. The higher photosynthetic capacity that follows persists into the wet season, driving high GEP that is out of phase with sunlight, explaining the negative observed relationship with sunlight. Overall, these patterns suggest that at sites where water is not limiting, light interacts with adaptive mechanisms to determine photosynthetic capacity indirectly through leaf flush and litterfall seasonality. These mechanisms are poorly represented in ecosystem models, and represent an important challenge to efforts to predict tropical forest responses to climatic variations.
•Soil CO2 efflux measured in seven pristine Amazon rain forest sites.•Mean soil respiration depends on soil type, texture and moisture.•The respiration-temperature time-lags differ between the ...sites.•Time-lags are often minimal if surface temperature is used.•The longest time-lags occur for the slowest-growing vegetation.
We analysed soil respiration measurements made in seven distinctly different pristine rain forests in Central Amazon, ranging from stunted heath forest (Campina) to tall terra-firme rain forest. The differences in soil respiration fluxes between sites and their causes were investigated, as well as diurnal patterns and their dependency on temperature. Ensemble averages of hourly fluxes were calculated for both wet and dry seasons (as far as these were sampled). These values were processed using an analytical model estimating soil surface temperature from the temperature measured at two depths. The soil CO2 efflux can be viewed as a proxy for forest productivity. The low productive Campina stunted heath forest site (on leached sandy soils and covered by scleromorphic vegetation) has the lowest respiration (<1.5μmolCO2m−2s−1, dry period). Respiration increased in local patches of taller heath forest on finer textured soil to about 4μmolCO2m−2s−1. In the Cuieiras lowland rain forest respiration changed along a toposequence. The lowest value of 2.5μmolCO2m−2s−1 was observed on the plateau (terra-firme rain forest), whereas a maximum of 6.0μmolCO2m−2s−1 was observed in the valley (Campinarana forest). Soil respiration decreased to about 4μmolCO2m−2s−1 close to the river (riparian forest) where soils remained close to saturation. To find the optimum correlation between soil temperature and respiration flux, relationships were derived between the amplitudes and phases of respiration and soil temperatures measured at different depths. Compared to the use of soil temperatures measured at 5cm and 10cm depth, the use of (modelled) soil surface temperatures strongly reduced the hysteresis between respiration and temperature, and improved the coefficient of determination (R2) for the Cuieiras forest sites, whereas the Campina sites still showed time lags of several hours between respiration and soil temperature diurnal patterns. With respect to the surface temperature, Q10 ranged from 1.7 (bare soil, dry season) to 2.0–2.5 (Cuieiras slope and plateau sites, dry season) and 3.3–5.2 (ibidem, wet season) to 5.5–7.7 (Cuieiras Campinarana and valley forests, dry/wet season).
Abstract Objectives 10-Methacryloyloxy-decyl-dihydrogen-phosphate (10-MDP) is currently considered as one of the most effective functional monomers for dental bonding, this in part thanks to its long ...and relatively hydrophobic spacer chain, adequately separating the polymerizable from the phosphate functionalities. This study compared functional monomers with different spacer chains’ length and hydrophilicity to 10-MDP on their dentin and enamel bonding performance. Methods Atomic absorption spectroscopy (AAS) was used to characterize the chemical interaction. Micro-tensile bond strength (μTBS) and fractographic analyses were performed after 24 h and one year. Confocal micro-permeability and SEM nanoleakage assessments were also undertaken. The tested functional monomers were 2-MEP (2-carbon spacer), 10-MDP (10-carbon), 12-MDDP (12-carbon), MTEP (high hydrophilic polyether spacer chain) and CAP-P (intermediate hydrophilic ester spacer). Results AAS revealed clear differences ( p < 0.05) in monomer-calcium salt formation in this order: 12-MDDP = 10-MDP > CAP-P > MTEP > 2-MEP. The highest initial dentin μTBS was obtained using 10-MDP or 12-MDDP. After 1-year aging, a significant drop ( p < 0.05) in μTBS was observed for the adhesives with MTEP (enamel and dentin), 2-MEP (enamel) and CAP-P (enamel). MTEP presented the highest micro-permeability, while 2-MEP, CAP-P and MTEP showed increased nanoleakage after aging. Significance These outcomes showed that more hydrophilic and shorter spacer chains may compromise the chemical interaction with calcium and the dentin/enamel bonding performance.
Soil respiration plays a significant role in the carbon cycle of Amazonian rainforests. Measurements of soil respiration have only been carried out in few places in the Amazon. This study ...investigated the effects of the method of ring insertion in the soil as well as of rainfall and spatial distribution on CO2 emission in the central Amazon region. The ring insertion effect increased the soil emission about 13-20% for sandy and loamy soils during the firsts 4-7 hours, respectively. After rainfall events below 2 mm, the soil respiration did not change, but for rainfall greater than 3 mm, after 2 hours there was a decrease in soil temperature and respiration of about 10-34% for the loamy and sand soils, with emissions returning to normal after around 15-18 hours. The size of the measurement areas and the spatial distribution of soil respiration were better estimated using the Shuttle Radar Topographic Mission (SRTM) data. The Campina reserve is a mosaic of bare soil, stunted heath forest-SHF and tall heath forest-THF. The estimated total average CO2 emissions from the area was 3.08±0.8 µmol CO2 m-2 s-1. The Cuieiras reserve is another mosaic of plateau, slope, Campinarana and riparian forests and the total average emission from the area was 3.82±0.76 µmol CO2 m-2 s-1. We also found that the main control factor of the soil respiration was soil temperature, with 90% explained by regression analysis. Automated soil respiration datasets are a good tool to improve the technique and increase the reliability of measurements to allow a better understanding of all possible factors driven by soil respiration processes.Respiração do solo possui um importante papel no ciclo do carbono em florestas tropicais Amazônicas. Entretanto poucas medidas de respiração do solo foram feitas. Neste estudo são apontados os efeitos na metodologia de instalação dos anéis no solo, bem como os efeitos da precipitação e a distribuição espacial da emissão de CO2 na Amazônia central. Os efeitos da inserção de anéis no solo aumentaram de 13 a 20% para o solo arenoso e argiloso, o efeito durou de 4 a 7 horas, respectivamente. Já os efeitos na precipitação, notamos que os eventos abaixo de 2 mm a respiração do solo permaneceu indiferente, mas para precipitação acima de 3 mm, 2 horas depois, houve uma diminuição da temperatura e respiração em 10 a 34% para o solo argilosos e arenosos, retornando a emissão normal após 15 a 18 horas. Para estimar a distribuição espacial da respiração do solo e o tamanho correto das áreas medidas, foram utilizadas as imagens do Shuttle Radar Topographic Mission (SRTM). Considerando que a Reserva de Campina é um mosaico de solo desnudo, floresta alagável de baixa e alta estatura (SHF e THF). A emissão total média de CO2 para a área foi de 3.08±0.8 µmol CO2 m-2 s-1. Já a Reserva do Cuieiras possui outro mosaico de florestas de platôs, encostas, Campinaranas e riparias, sendo a emissão média total desta área foram de 3.82±0.76 µmol CO2 m-2 s-1. Encontramos também que a respiração do solo foi controlada pela temperatura do solo, sendo uma correlação de 90% encontrada pela análise de regressão. Dados obtidos com sistema automático de respiração do solo é uma grande oportunidade de melhoramento da técnica e o aumento da confiança nas medidas em relação aos possíveis fatores que controlam os processos de emissão de CO2 do solo.
Soil respiration plays a significant role in the carbon cycle of Amazonian rainforests. Measurements of soil respiration have only been carried out in few places in the Amazon. This study ...investigated the effects of the method of ring insertion in the soil as well as of rainfall and spatial distribution on CO2 emission in the central Amazon region. The ring insertion effect increased the soil emission about 13-20% for sandy and loamy soils during the firsts 4-7 hours, respectively. After rainfall events below 2 mm, the soil respiration did not change, but for rainfall greater than 3 mm, after 2 hours there was a decrease in soil temperature and respiration of about 10-34% for the loamy and sand soils, with emissions returning to normal after around 15-18 hours. The size of the measurement areas and the spatial distribution of soil respiration were better estimated using the Shuttle Radar Topographic Mission (SRTM) data. The Campina reserve is a mosaic of bare soil, stunted heath forest-SHF and tall heath forest-THF. The estimated total average CO2 emissions from the area was 3.08±0.8 µmol CO2 m-2 s-1. The Cuieiras reserve is another mosaic of plateau, slope, Campinarana and riparian forests and the total average emission from the area was 3.82±0.76 µmol CO2 m-2 s-1. We also found that the main control factor of the soil respiration was soil temperature, with 90% explained by regression analysis. Automated soil respiration datasets are a good tool to improve the technique and increase the reliability of measurements to allow a better understanding of all possible factors driven by soil respiration processes.
Respiração do solo possui um importante papel no ciclo do carbono em florestas tropicais Amazônicas. Entretanto poucas medidas de respiração do solo foram feitas. Neste estudo são apontados os efeitos na metodologia de instalação dos anéis no solo, bem como os efeitos da precipitação e a distribuição espacial da emissão de CO2 na Amazônia central. Os efeitos da inserção de anéis no solo aumentaram de 13 a 20% para o solo arenoso e argiloso, o efeito durou de 4 a 7 horas, respectivamente. Já os efeitos na precipitação, notamos que os eventos abaixo de 2 mm a respiração do solo permaneceu indiferente, mas para precipitação acima de 3 mm, 2 horas depois, houve uma diminuição da temperatura e respiração em 10 a 34% para o solo argilosos e arenosos, retornando a emissão normal após 15 a 18 horas. Para estimar a distribuição espacial da respiração do solo e o tamanho correto das áreas medidas, foram utilizadas as imagens do Shuttle Radar Topographic Mission (SRTM). Considerando que a Reserva de Campina é um mosaico de solo desnudo, floresta alagável de baixa e alta estatura (SHF e THF). A emissão total média de CO2 para a área foi de 3.08±0.8 µmol CO2 m-2 s-1. Já a Reserva do Cuieiras possui outro mosaico de florestas de platôs, encostas, Campinaranas e riparias, sendo a emissão média total desta área foram de 3.82±0.76 µmol CO2 m-2 s-1. Encontramos também que a respiração do solo foi controlada pela temperatura do solo, sendo uma correlação de 90% encontrada pela análise de regressão. Dados obtidos com sistema automático de respiração do solo é uma grande oportunidade de melhoramento da técnica e o aumento da confiança nas medidas em relação aos possíveis fatores que controlam os processos de emissão de CO2 do solo.
Abstract Objective To investigate the role of chain extender size from Bis-EMA monomers on the polymerization profiles and properties of the crosslinked polymers. Additionally, the influence of ...Bis-GMA was also evaluated. Methods The polymer network from homopolymers Bis-EMA4, Bis-EMA10 and Bis-EMA30 was characterized, as well as copolymers formed among these monomers and Bis-GMA. The degree of conversion from neat and blended monomers as a function of photo-activation time was evaluated by FTIR. Rate of polymerization, network parameter and cross-link density from materials were demonstrated. Water sorption and solubility were determined according to ISO 4049 specification and the data obtained were analyzed by two-way ANOVA/Tukey's test ( α = 0.05). Flexural strength and Young's modulus from polymerized monomers/co-monomers were measured after 24 h water storage at 37 °C and the results were analyzed by one-way ANOVA/Tukey's test ( α = 0.05). Results Monomers with larger ethylene oxide units presented the highest values regarding the degree of conversion and cross-link density. The effect of the chain extender length was also observed in water sorption and solubility polymer characteristics, with Bis-EMA4 being the most hydrophobic polymer. Bis-EMA10 and Bis-EMA30 homopolymers were not able to be tested with the three point bending test due to their great flexibility. The addition of Bis-GMA produced stronger and more rigid Bis-EMA polymers ( p < 0.05). Significance Aromatic dimethacrylates with different chain extender lengths can be a useful alternative in controlling the properties of a dental material, adjusting those to specific applications.
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