Determination of ametryn in river water, river sediment and bivalve mussels by liquid chromatography-tandem mass spectrometry

Analytical methods employing liquid chromatography-mass spectrometry (LC-MS-MS) for ametryn determination in river water, river sediment and in freshwater bivalve mussel Corbicula fluminea are described. Liquid-liquid extraction was used for sample preparation. The analyses of ametryn in samples were performed on a reversed-phase RP-18 column with MS detection in positive electrospray and multi reaction monitoring modes. The quantitation limit of ametryn was 20 ng L-1, 0.1 ng g-1 and 0.5 ng g-1, for water, sediment and bivalve samples, respectively. Linearity, precision, accuracy and recovery were also reported. The results obtained for method validation are within the international limits and in accordance with literature, suggesting that the developed methods are suitable for the quantitation of ametryn in river water, river sediment and in bivalve Corbicula fluminea. These methods were applied for the analysis of samples from Mogi-Guaçu River and Pardo River, São Paulo State. Results indicated that the highest level of ametryn was 1.44 ng g-1 in bivalve samples from Mogi-Guaçu River.Foram descritos métodos analíticos empregando cromatografia líquida acoplada a espectrometria de massas (LC-MS-MS) para a determinação de ametrina em água superficial, sedimento de rio e no molusco bivalve Corbicula fluminea. A técnica de extração líquido-líquido foi utilizada para a preparação das amostras. As análises das amostras foram feitas em coluna RP-18 de fase reversa com detecção no modo electrospray positivo e Multi Reaction Monitoring (MRM). O limite de quantificação de ametrina foi 20 ng L-1, 0,1 ng g-1 e 0,5 ng g-1 para amostras de água, sedimento e bivalves, respectivamente. Na etapa de validação dos métodos foram avaliadas também a linearidade, a precisão, a exatidão e a recuperação. Os resultados obtidos na validação do método estão de acordo com os limites internacionais e com a literatura, sugerindo que o método desenvolvido é adequado para a quantificação de ametrina em amostras de água superficial, sedimento de rio e nos bivalves Corbicula fluminea. Estes métodos foram aplicados na análise de amostras coletadas no Rio Mogi-Guaçu e Rio Pardo, São Paulo, Brasil. O nível mais elevado de ametrina foi 1,44 ng g-1, encontrado nas amostras de bivalves do Rio Mogi-Guaçu.FAPESPCoordenacao de Aperfeicoamento de Pessoal de Nivel Superior (CAPES)CNP

CARBON BALANCE AND VEGETATION DYNAMICS IN AN OLD‐GROWTH AMAZONIAN FOREST

Amazon forests could be globally significant sinks or sources for atmospheric carbon dioxide, but carbon balance of these forests remains poorly quantified. We surveyed 19.75 ha along four 1‐km transects of well‐drained old‐growth upland forest in the Tapajós National Forest near Santarém, Pará, Brazil (2°51′ S, 54°58′ W) in order to assess carbon pool sizes, fluxes, and climatic controls on carbon balance. In 1999 there were, on average, 470 live trees per hectare with diameter at breast height (dbh) ≥10 cm. The mean (and 95% ci) aboveground live biomass was 143.7 ± 5.4 Mg C/ha, with an additional 48.0 ± 5.2 Mg C/ha of coarse woody debris (CWD). The increase of live wood biomass after two years was 1.40 ± 0.62 Mg C·ha−1·yr−1, the net result of growth (3.18 ± 0.20 Mg C·ha−1·yr−1 from mean bole increment of 0.36 cm/yr), recruitment of new trees (0.63 ± 0.09 Mg C·ha−1·yr−1, reflecting a notably high stem recruitment rate of 4.8 ± 0.9%), and mortality (−2.41 ± 0.53 Mg C·ha−1·yr−1 from stem death of 1.7% yr−1). The gain in live wood biomass was exceeded by respiration losses from CWD, resulting in an overall estimated net loss from total aboveground biomass of 1.9 ± 1.0 Mg C·ha−1·yr−1. The presence of large CWD pools, high recruitment rate, and net accumulation of small‐tree biomass, suggest that a period of high mortality preceded the initiation of this study, possibly triggered by the strong El Niño Southern Oscillation events of the 1990s. Transfer of carbon between live and dead biomass pools appears to have led to substantial increases in the pool of CWD, causing the observed net carbon release. The data show that biometric studies of tropical forests neglecting CWD are unlikely to accurately determine carbon balance. Furthermore, the hypothesized sequestration flux from CO2 fertilization (\u3c0.5 Mg C·ha−1·yr−1) would be comparatively small and masked for considerable periods by climate‐driven shifts in forest structure and associated carbon balance in tropical forests

Seasonal Controls on the Exchange of Carbon and Water in an Amazonian Rain Forest

The long-term resilience of Amazonian forests to climate changes and the fate of their large stores of organic carbon depend on the ecosystem response to climate and weather. This study presents 4 years of eddy covariance data for CO2 and water fluxes in an evergreen, old-growth tropical rain forest examining the forest's response to seasonal variations and to short-term weather anomalies. Photosynthetic efficiency declined late in the wet season, before appreciable leaf litter fall, and increased after new leaf production midway through the dry season. Rates of evapotranspiration were inelastic and did not depend on dry season precipitation. However, ecosystem respiration was inhibited by moisture limitations on heterotrophic respiration during the dry season. The annual carbon balance for this ecosystem was very close to neutral, with mean net loss of 890 ± 220 kg C ha−1 yr−1, and a range of −221 ± 453 (C uptake) to +2677 ± 488 (C loss) kg C ha−1 yr−1 over 4 years. The trend from large net carbon release in 2002 towards net carbon uptake in 2005 implies recovery from prior disturbance. The annual carbon balance was sensitive to weather anomalies, particularly the timing of the dry-to-wet season transition, reflecting modulation of light inputs and respiration processes. Canopy carbon uptake rates were largely controlled by phenology and light with virtually no indication of seasonal water limitation during the 5-month dry season, indicating ample supplies of plant-available-water and ecosystem adaptation for maximum light utilization.Earth and Planetary SciencesEngineering and Applied SciencesOrganismic and Evolutionary Biolog

Partitioning of environmental and taxonomic controls on Brazilian foliar content of carbon and nitrogen and stable isotopes

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., δ13C and δ15N); (ii) assess differences in foliar N, C:N ratio, and δ15N among three functional groups: species of N2-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 N2-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 δ13C and δ15N were environmentally constrained. While family was the most important taxonomy level for C, N, and C:N ratio, species played a major role for δ13C and δ15N. 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 δ15N was observed among Fabaceae species, demonstrates the complexity of using δ15N 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

Basin-wide variation in tree hydraulic safety margins predicts the carbon balance of Amazon forests

Funding: Data collection was largely funded by the UK Natural Environment Research Council (NERC) project TREMOR (NE/N004655/1) to D.G., E.G. and O.P., with further funds from Coordenação de Aperfeiçoamento de Pessoal de Nível Superior—Brasil (CAPES, finance code 001) to J.V.T. and a University of Leeds Climate Research Bursary Fund to J.V.T. D.G., E.G. and O.P. acknowledge further support from a NERC-funded consortium award (ARBOLES, NE/S011811/1). This paper is an outcome of J.V.T.’s doctoral thesis, which was sponsored by CAPES (GDE 99999.001293/2015-00). J.V.T. was previously supported by the NERC-funded ARBOLES project (NE/S011811/1) and is supported at present by the Swedish Research Council Vetenskapsrådet (grant no. 2019-03758 to R.M.). E.G., O.P. and D.G. acknowledge support from NERC-funded BIORED grant (NE/N012542/1). O.P. acknowledges support from an ERC Advanced Grant and a Royal Society Wolfson Research Merit Award. R.S.O. was supported by a CNPq productivity scholarship, the São Paulo Research Foundation (FAPESP-Microsoft 11/52072-0) and the US Department of Energy, project GoAmazon (FAPESP 2013/50531-2). M.M. acknowledges support from MINECO FUN2FUN (CGL2013-46808-R) and DRESS (CGL2017-89149-C2-1-R). C.S.-M., F.B.V. and P.R.L.B. were financed by Coordenação de Aperfeiçoamento de Pessoal de Nível Superior—Brasil (CAPES, finance code 001). C.S.-M. received a scholarship from the Brazilian National Council for Scientific and Technological Development (CNPq 140353/2017-8) and CAPES (science without borders 88881.135316/2016-01). Y.M. acknowledges the Gordon and Betty Moore Foundation and ERC Advanced Investigator Grant (GEM-TRAITS, 321131) for supporting the Global Ecosystems Monitoring (GEM) network (gem.tropicalforests.ox.ac.uk), within which some of the field sites (KEN, TAM and ALP) are nested. The authors thank Brazil–USA Collaborative Research GoAmazon DOE-FAPESP-FAPEAM (FAPESP 2013/50533-5 to L.A.) and National Science Foundation (award DEB-1753973 to L. Alves). They thank Serrapilheira Serra-1709-18983 (to M.H.) and CNPq-PELD/POPA-441443/2016-8 (to L.G.) (P.I. Albertina Lima). They thank all the colleagues and grants mentioned elsewhere [8,36] that established, identified and measured the Amazon forest plots in the RAINFOR network analysed here. The authors particularly thank J. Lyod, S. Almeida, F. Brown, B. Vicenti, N. Silva and L. Alves. This work is an outcome approved Research Project no. 19 from ForestPlots.net, a collaborative initiative developed at the University of Leeds that unites researchers and the monitoring of their permanent plots from the world’s tropical forests [61]. The authros thank A. Levesley, K. Melgaço Ladvocat and G. Pickavance for ForestPlots.net management. They thank Y. Wang and J. Baker, respectively, for their help with the map and with the climatic data. The authors acknowledge the invaluable help of M. Brum for kindly providing the comparison of vulnerability curves based on PAD and on PLC shown in this manuscript. They thank J. Martinez-Vilalta for his comments on an early version of this manuscript. The authors also thank V. Hilares and the Asociación para la Investigación y Desarrollo Integral (AIDER, Puerto Maldonado, Peru); V. Saldaña and Instituto de Investigaciones de la Amazonía Peruana (IIAP) for local field campaign support in Peru; E. Chavez and Noel Kempff Natural History Museum for local field campaign support in Bolivia; ICMBio, INPA/NAPPA/LBA COOMFLONA (Cooperativa mista da Flona Tapajós) and T. I. Bragança-Marituba for the research support.Tropical forests face increasing climate risk1,2, yet our ability to predict their response to climate change is limited by poor understanding of their resistance to water stress. Although xylem embolism resistance thresholds (for example, Ψ50) and hydraulic safety margins (for example, HSM50) are important predictors of drought-induced mortality risk3-5, little is known about how these vary across Earth's largest tropical forest. Here, we present a pan-Amazon, fully standardized hydraulic traits dataset and use it to assess regional variation in drought sensitivity and hydraulic trait ability to predict species distributions and long-term forest biomass accumulation. Parameters Ψ50 and HSM50 vary markedly across the Amazon and are related to average long-term rainfall characteristics. Both Ψ50 and HSM50 influence the biogeographical distribution of Amazon tree species. However, HSM50 was the only significant predictor of observed decadal-scale changes in forest biomass. Old-growth forests with wide HSM50 are gaining more biomass than are low HSM50 forests. We propose that this may be associated with a growth-mortality trade-off whereby trees in forests consisting of fast-growing species take greater hydraulic risks and face greater mortality risk. Moreover, in regions of more pronounced climatic change, we find evidence that forests are losing biomass, suggesting that species in these regions may be operating beyond their hydraulic limits. Continued climate change is likely to further reduce HSM50 in the Amazon6,7, with strong implications for the Amazon carbon sink.Publisher PDFPeer reviewe

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

Consistent patterns of common species across tropical tree communities

Trees structure the Earth’s most biodiverse ecosystem, tropical forests. The vast number of tree species presents a formidable challenge to understanding these forests, including their response to environmental change, as very little is known about most tropical tree species. A focus on the common species may circumvent this challenge. Here we investigate abundance patterns of common tree species using inventory data on 1,003,805 trees with trunk diameters of at least 10 cm across 1,568 locations1,2,3,4,5,6 in closed-canopy, structurally intact old-growth tropical forests in Africa, Amazonia and Southeast Asia. We estimate that 2.2%, 2.2% and 2.3% of species comprise 50% of the tropical trees in these regions, respectively. Extrapolating across all closed-canopy tropical forests, we estimate that just 1,053 species comprise half of Earth’s 800 billion tropical trees with trunk diameters of at least 10 cm. Despite differing biogeographic, climatic and anthropogenic histories7, we find notably consistent patterns of common species and species abundance distributions across the continents. This suggests that fundamental mechanisms of tree community assembly may apply to all tropical forests. Resampling analyses show that the most common species are likely to belong to a manageable list of known species, enabling targeted efforts to understand their ecology. Although they do not detract from the importance of rare species, our results open new opportunities to understand the world’s most diverse forests, including modelling their response to environmental change, by focusing on the common species that constitute the majority of their trees.Publisher PDFPeer reviewe

Composition of particulate and dissolved organic matter in a disturbed watershed of southeast Brazil (Piracicaba River basin).

The elemental and isotopic composition of particulate and dissolved organic matter was investigated in the Piracicaba River basin, São Paulo State, Brazil. Comparison of riverine organic matter from the Piracicaba River basin, a region where rivers and streams receive urban sewage and industrial effluents, with data reported for the pristine Amazon system revealed significant differences associated with anthropogenic impacts. One important difference was N enrichment in the particulate organic material of the Piracicaba basin rivers, due to (a) urban and industrial effluents, and (b) enhanced phytoplankton growth, which results from the combination of nutrient enrichment and damming of sections of the rivers. Radiocarbon concentrations were overall more depleted (older 14C age) in the Piracicaba basin rivers than in the Amazon, which may reflect the importance of soil erosion in the former. Analyses of stable and radioactive carbon isotopes and lignin-derived compounds indicated that coarse particulate organic material is composed of a mixture of soil particles and degraded organic matter from C3 and C4 vascular plants. Fine particulate organic material was composed mainly of soil particles and phytoplankton cell remains, the latter especially during low water. Ultrafiltered dissolved organic matter was the most degraded fraction according to its lignin oxidation products, and showed the greatest influence of C4 plant sources

Do plant species influence soil CO(2) and N(2)O fluxes in a diverse tropical forest?

To test whether plant species influence greenhouse gas production in diverse ecosystems, we measured wet season soil CO(2) and N(2)O fluxes close to similar to 300 large (>35 cm in diameter at breast height (DBH)) trees of 15 species at three clay-rich forest sites in central Amazonia. We found that soil CO(2) fluxes were 38% higher near large trees than at control sites >10 m away from any tree (P < 0.0001). After adjusting for large tree presence, a multiple linear regression of soil temperature, bulk density, and liana DBH explained 19% of remaining CO(2) flux variability. Soil N(2)O fluxes adjacent to Caryocar villosum, Lecythis lurida, Schefflera morototoni, and Manilkara huberi were 84%-196% greater than Erisma uncinatum and Vochysia maxima, both Vochysiaceae. Tree species identity was the most important explanatory factor for N(2)O fluxes, accounting for more than twice the N(2)O flux variability as all other factors combined. Two observations suggest a mechanism for this finding: (1) sugar addition increased N(2)O fluxes near C. villosum twice as much (P < 0.05) as near Vochysiaceae and (2) species mean N(2)O fluxes were strongly negatively correlated with tree growth rate (P = 0.002). These observations imply that through enhanced belowground carbon allocation liana and tree species can stimulate soil CO(2) and N(2)O fluxes (by enhancing denitrification when carbon limits microbial metabolism). Alternatively, low N(2)O fluxes potentially result from strong competition of tree species with microbes for nutrients. Species-specific patterns in CO(2) and N(2)O fluxes demonstrate that plant species can influence soil biogeochemical processes in a diverse tropical forest.U.S. Forest ServiceNSF-PIR