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Human activities pose a major threat to tropical forest biodiversity and ecosystem serv-ices. Although the impacts of deforestation are well studied, multiple land-use andland-cover transitions (LULCTs) occur in tropical landscapes, and we do not knowhow LULCTs differ in their rates or impacts on key ecosystem components. Here, wequantified the impacts of 18 LULCTs on three ecosystem components (biodiversity,carbon, and soil), based on 18 variables collected from 310 sites in the BrazilianAmazon. Across all LULCTs, biodiversity was the most affected ecosystem component,followed by carbon stocks, but the magnitude of change differed widely amongLULCTs and individual variables. Forest clearance for pasture was the most prevalentand high-impact transition, but we also identified other LULCTs with high impact butlower prevalence (e.g., forest to agriculture). Our study demonstrates the importanceof considering multiple ecosystem components and LULCTs to understand the conse-quences of human activities in tropical landscapes Made available in DSpace on 2022-10-06T16:05:22Z (GMT). No. of bitstreams: 1 pnas.2202310119.pdf: 1994033 bytes, checksum: 7b87b3ce0f689008a66ab5755a038d75 (MD5) Previous issue date: 2022

Made available in DSpace on 2022-04-28T19:52:03Z (GMT). No. of bitstreams: 0 Previous issue date: 2022-07-01 Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) Empresa Brasileira de Pesquisa Agropecuária Fundação de Amparo à Pesquisa do Estado de Minas Gerais (FAPEMIG) The Amazon rainforest is a heterogeneous ecosystem and its soils exhibit geographically variable concentrations of trace elements. In this region, anthropic activities - e.g., agriculture and mining - are numerous and varied, and even natural areas are at risk of contamination by trace elements, either of geogenic or anthropogenic origin. A reliable dataset of benchmark values for selenium (Se), barium (Ba), and iodine (I) concentrations in soils is needed for use as a reference in research and public policies in the region. In this study, 9 selected sites in the Brazilian Amazon rainforest within areas represented by Oxisols and Ultisols were assessed for relevant soil physicochemical characteristics, along with the concentrations of total Se (SeTot), total Ba (BaTot), and sequentially-extracted soluble Se (SeSol) and adsorbed Se (SeAd) in 3 different soil layers (0–20, 20–40, and 40–60 cm). In addition, organically bound-Se (SeOrg) and total I (ITot) concentrations in the surface layer (0–20 cm) were measured. Soil Se concentrations (SeTot) were considered safe and are likely a result of contributions of sedimentary deposits from the Andes. Available Se (SeSol + SeAd) accounted for 4.5% of SeTot, on average, while SeOrg in the topsoil accounted for more than 50% of SeTot. Barium in the western Amazon (state of Acre) and central Amazon (Anori, state of Amazonas) exceeded national prevention levels (PVs). Furthermore, the average ITot in the studied topsoils (5.4 mg kg−1) surpassed the worldwide mean. Notwithstanding, the close relationship found between the total content of the elements (Se, Ba, and I) and soil texture (clay, silt, and sand) suggests their geogenic source. Finally, our data regarding SeTot, BaTot, and ITot can be used to derive regional quality reference values for Amazon soils and also for updating prevention (PV) and investigation (IV) values established for selected elements by the Brazilian legislation. Department of Soil Science Federal University of Lavras, MG Embrapa Rondônia, RO Embrapa Amazônia Ocidental, AM Embrapa Roraima, RR Embrapa Amapá, AP Embrapa Amazônia Oriental, PA São Paulo State University (UNESP) School of Sciences and Engineering, SP School of Biosciences University of Nottingham, Sutton Bonington Campus São Paulo State University (UNESP) School of Sciences and Engineering, SP CAPES: 001

Multiscalar topography influence on soil distribution has a complex pattern that is related to overlay of pedological processes which occurred at different times, and these driving forces are correlated with many geomorphologic scales. In this sense, the present study tested the hypothesis whether multiscale geomorphometric generalized covariables can improve pedometric modeling. To achieve this goal, this case study applied the Random Forest algorithm to a multiscale geomorphometric database to predict soil surface attributes. The study area is in phanerozoic sedimentary basins, in the Alter do Chao geological formation, Eastern Amazon, Brazil. The multiscale geomorphometric generalization was applied at general and specific geomorphometric covariables, producing groups for each scale combination. The modeling was run using Random Forest for A-horizon thickness, pH, silt and sand content. For model evaluation, visual analysis of digital maps, metrics of forest structures and effect of variables on prediction were used. For evaluation of soil textural classifications, the confusion matrix with a Kappa index, and the user’s and producer’s accuracies were employed. The geomorphometry generalization tends to smooth curvatures and produces identifiable geomorphic representations at sub-watershed and watershed levels. The forest structures and effect of variables on prediction are in agreement with pedological knowledge. The multiscale geomorphometric generalized covariables improved accuracy metrics of soil surface texture classification, with the Kappa Index going from 43% to 62%. Therefore, it can be argued that topography influences soil distribution at combined coarser spatial scales and is able to predict soil particle size contents in the studied watershed. Future development of the multiscale geomorphometric generalization framework could include generalization methods concerning preservation of features, landform classification adaptable at multiple scales.

Understanding the pronounced seasonal and spatial variation in leaf carboxylation capacity (Vc,max ) is critical for determining terrestrial carbon cycling in tropical forests. However, an efficient and scalable approach for predicting Vc,max is still lacking. Here the ability of leaf spectroscopy for rapid estimation of Vc,max was tested. Vc,max was estimated using traditional gas exchange methods, and measured reflectance spectra and leaf age in leaves sampled from tropical forests in Panama and Brazil. These data were used to build a model to predict Vc,max from leaf spectra. The results demonstrated that leaf spectroscopy accurately predicts Vc,max of mature leaves in Panamanian tropical forests (R2 = 0.90). However, this single-age model required recalibration when applied to broader leaf demographic classes (i.e. immature leaves). Combined use of spectroscopy models for Vc,max and leaf age enabled construction of the Vc,max -age relationship solely from leaf spectra, which agreed with field observations. This suggests that the spectroscopy technique can capture the seasonal variability in Vc,max , assuming sufficient sampling across diverse species, leaf ages and canopy environments. This finding will aid development of remote sensing approaches that can be used to characterize Vc,max in moist tropical forests and enable an efficient means to parameterize and evaluate terrestrial biosphere models.

A florestas secundárias são fonte de recursos florestais para as populações tradicionais. Portanto, o objetivo do estudo é analisar a distribuição espacial da vegetação secundária na APA de Aramanaí e na comunidade de Maguari, na FLONA Tapajós, avaliando o potencial dessas áreas em fornecer espécies uteis, com destaque, a utilização de sementes florestais, para confecção de bijuterias pelos comunitários de Maguari. Foram realizadas entrevistas com os artesãos em Maguari, sobre a utilização de espécies florestais e posteriormente foi analisado a distribuição espacial dessa vegetação através do mapeamento do TerraClass, de uso e cobertura da terra dessas UCs. As principais espécies vegetais apontadas nas entrevistas foram o morototó (Schefflera morototoni (Aubl.) Maguire, Steyerm. & Frodin), o tento vermelho (Ormosia arborea L. /Adenanthera pavonina L.), tento amarelo (Ormosia excelsa Beth), saboneteira (Sapindus saponaria L.), jutaí (Hymenaea courbaril L.), tucumã (Astrocaryum aculeatum G.F.W Meyer) e o caracaxá ou jupati (Raphia taedigera Mart.), destacando o morototó como a semente mais utilizadas por todos os entrevistados. Foi apontado, através do estudo de distribuição espacial, o agrupamento da população do morototó em áreas de vegetação secundárias, que corresponde cerca de 17% das duas UCs, demonstrando que a população da região utiliza as espécies uteis de áreas de vegetação secundária. A vegetação secundária se tornou uma fonte de recursos florestais paras as comunidades inseridas em UCs. Dessarte, é importante para economia das comunidades e ao mesmo tempo, promove a preservação da vegetação primária do desmatamento, sendo uma forma de conservar a floresta e o estoque de recursos para as gerações futuras.

This article aims to identify the use of non-timber forest products (NTFPs) by the traditional populations living in the communities of São Domingos, Maguari, and Jamaraquá, PA, Brazil, to understand the issues related to the main species collected, their uses, and product pricing. A rapid rural appraisal (RRA) was conducted with community NTFP collectors, followed by interviews with the artisans, including a total of 10 people. The most cited species in the RRA were morototó, bead tree, tento amarelo, wingleaf soapberry, açaí palm, jutaí, and Job’s tears, which are used to produce handicrafts and bio-jewels. In addition, buriti, tucumã, and curuá fiber and lapachillo, itaúba, cedar, arara castanha, and molongó wood were used. The price of bio-jewels varies from BRL 2 to 30, and of the wood ornamental pieces from BRL 10 to 300. The main advantages of working with NTFP highlighted in the interviews were that seed collection is easy, that there is demand, and that income is generated for community members. The difficulties mentioned were the collection and processing of morototó and paricá seed, and access to trees. Jamaraquá, Maguari, and São Domingos are successful examples of forest products that consolidated the market and are cultural and social representation of the forest peoples. &nbsp, O objetivo deste artigo é caracterizar o uso dos produtos florestais não madeireiros (PFNM) pelas populações ribeirinhas em comunidades na Flona Tapajós, compreendendo as questões relacionadas às principais espécies coletadas, seus usos e atribuição de valor aos produtos confeccionados. Foi realizado um Diagnóstico Rápido Rural (DRR) com os coletores de PFNMs, e entrevistas com um total de 10 artesãos. As espécies mais citadas foram: morototó, tento vermelho, tento amarelo, saboneteira, açaí, jutaí e lágrima de nossa senhora que são utilizadas na produção de artesanatos e biojóias; também se utiliza as fibras (buriti, tucumã e curuá) e as madeiras (coração de negro, itaúba, cedro, arara castanha e molongó). As biojóias variam de valor entre R$2,00 a R$20,00 e as peças ornamentais de madeira de R$10,00 a R$300,00. As principais vantagens de trabalhar com PFNM apontadas na entrevista são a facilidade de coletar sementes, o fato de ter demanda e gerar renda aos artesãos envolvidos. As dificuldades mencionadas são a coleta das sementes do morototó e paricá e o acesso as árvores na floresta. Jamaraquá, Maguari e São Domingos são exemplos bem-sucedidos de que os produtos oriundos da floresta têm mercado consolidado e são representação cultural e social dos povos da floresta. Palavras-chave: artesanato; biojóias; população tradicional; Amazônia. Use of non-wooden forest products in the National Forest of Tapajós communities ABSTRACT: The aim of this article is to characterize the use of non-timber forest products (NTFP) by riverine populations in communities in Flona Tapajós, including issues related to the main species collected, their uses and attribution of value to the manufactured products. the use of non-timber forest products (NTFP) by riverine populations in communities in Flona Tapajós, including issues related to the main species collected, their uses and attribution of value to the products made. A rapid rural appraisal (RRA) was conducted with community NTFP collectors, followed by interviews with the artisans, including a total of 10 people. The most cited species in the RRA were morototó, bead tree, tento amarelo, wingleaf soapberry, açaí palm, jutaí, and Job’s tears, which are used to produce handicrafts and bio-jewels. In addition, buriti, tucumã, and curuá fiber and lapachillo, itaúba, cedar, arara castanha, and molongó wood were used. The price of bio-jewels varies from BRL 2 to 20, and of the wood ornamental pieces from BRL 10 to 300. The main advantages of working with NTFP highlighted in the interviews were that seed collection is easy, that there is demand, and that income is generated for community members. The difficulties mentioned were the collection and processing of morototó and paricá seed, and access to trees. Jamaraquá, Maguari, and São Domingos are successful examples of forest products that consolidated the market and are cultural and social representation of the forest peoples. Keywords: handicrafts; bio-jewels; traditional population; Amazon.

Deforestation and land use change (LUC) to expand the agricultural frontier in the Brazilian Amazon deplete soil carbon (C) stocks, and negatively impact climate regulation. The variety of soil types, land-transition options, and management practices present in the Amazon region require detailed inventories to reduce the uncertainties associated with estimates of soil C change. Therefore, we conducted a study covering ca. 1 million hectares to estimate the soil C stock changes due to LUC in Paragominas and Santarem, Para state, eastern Brazilian Amazon, for the period of 1990–2010. Soil C stocks for 1990 were modeled based on land cover at the time. In 2010, we carried out a field work taking soil samples to measure soil C stock changes in 356 transects across contrasting land uses (logged and burnt forest, young secondary forest, intermediate secondary forest, old secondary forest, pasture, and cropland). The response ratios for the conversion from undisturbed forest to new land uses were calculated considering the differences in soil C stocks, with the undisturbed forest as reference. Between 1990 and 2010, LUC induced a total loss of 1.51 Tg C year-1 (over an area of 7350 km2). For this period, the uncertainty of estimates was ± 23.2%. The land transitions to pasture and cropland were the main drivers of soil C losses. Thus, deforestation contributes to climate change not only through losses of forest biomass but also subsequently soil C losses. These results can inform national and international climate change initiatives associated with LUC in the eastern Brazilian Amazon.

The production and emission of CO2 in native, pasture and cultivated areas is a result of microbiological activity and mineralization of organic matter, and depends on favorable environmental factors, such as temperature, availability of water and of land use. The results of this work show that the no tillage system (NT) has the potential to mitigate 37.7% of C-CO2 efflux from cultivation of soy compared to conventional tillage (CT). The temperature of the soil accounted for 65% of the variability of the flux of CO2-C in CT. The variation of soil moisture explained 73 and 51% of the flux of CO2-C in CT and NT, respectively. These results indicate that soil moisture and soil temperature were controlling factors of CO2-C emissions from soil to atmosphere because these parameters directly affect soil microbial activity. The results also show that the active pasture had the highest outflows of soil CO2-C to the atmosphere in relation to forests and degraded pasture in Western Pará. Furthermore, it was shown that both the pastures and forests have seasonality in the fluw, which mainly related to precipitation patterns and water potential between soil and air. We observed a strong correlation between the efflux and soil moisture of both capoeira and in the pastures, as the soil temperature was a controlling factor of the active efflux only in the pasture. The average fluw of CO2-C obtained in pasture active was 218.9 mg C m-2 h-1 value of 40.7% higher than the primary forests and 155.5 mg C m-2 h-1. Finally, the results presented here suggest that the conventional tillage and pasture management are activities strongly associated to human enhance biogeochemical changes in the balance of carbon in these ecosystems, since the efflux of CO2-C is related to soil primary productivity of these ecosystems. Made available in DSpace on 2017-09-02T06:14:36Z (GMT). No. of bitstreams: 1 MIERCIO2017.pdf: 1461174 bytes, checksum: 3d0790981ef7478130a49e8caa8af156 (MD5) Previous issue date: 2017-08-29

This work examines whether management causes changes in evapotranspiration (ET) surface conductance (gs), aerodynamic conductance (ga) and the decoupling factor (Ω) in managed and natural forest sites in a tropical rain forest in the Amazon. The study was conducted in the Tapajós National Forest (FNT) in managed (logged) and natural (unlogged) forests, which have micrometeorological towers for data capture. For ET estimation, the Penman-Monteith (PM) and Eddy Covariance (EC) equations were used. The models were significantly different only for unlogged (PM 134.9±15.9 mm.month-1 and EC 100.9±11.1 mm.month-1), while the means of the logged site were PM 111.1±15.7 mm.month-1 and EC 108.5±18.3 mm.month-1. Each area has different characteristics for the surface variables, ga, gs and Ω, and therefore the sites were different from each other for the study variables. However, logged ET did not differ for the PM, while EC decreased in the year after the management intervention, and was then followed by an increase. Made available in DSpace on 2017-09-02T06:14:41Z (GMT). No. of bitstreams: 1 DIEGO2017.pdf: 722861 bytes, checksum: 3aa40db1e1ebf7e2f423ed3cea3b119a (MD5) Previous issue date: 2017-08-29

The FLUXNET2015 dataset provides ecosystem-scale data on CO2, water, and energy exchange between the biosphere and the atmosphere, and other meteorological and biological measurements, from 212 sites around the globe (over 1500 site-years, up to and including year 2014). These sites, independently managed and operated, voluntarily contributed their data to create global datasets. Data were quality controlled and processed using uniform methods, to improve consistency and intercomparability across sites. The dataset is already being used in a number of applications, including ecophysiology studies, remote sensing studies, and development of ecosystem and Earth system models. FLUXNET2015 includes derived-data products, such as gap-flled time series, ecosystem respiration and photosynthetic uptake estimates, estimation of uncertainties, and metadata about the measurements, presented for the frst time in this paper. In addition, 206 of these sites are for the frst time distributed under a Creative Commons (CC-BY 4.0) license. This paper details this enhanced dataset and the processing methods, now made available as open-source codes, making the dataset more accessible, transparent, and reproducible., European Union (EU), United States Department of Energy (DOE)

Tropical forests may be vulnerable to climate change1–3 if photosynthetic carbon uptake currently operates near a high temperature limit4–6. Predicting tropical forest function requires understanding the relative contributions of two mechanisms of high-temperature photosynthetic declines: stomatal limitation (H1), an indirect response due to temperature-associated changes in atmospheric vapour pressure deficit (VPD)7, and biochemical restrictions (H2), a direct temperature response8,9. Their relative control predicts different outcomes—H1 is expected to diminish with stomatal responses to future co-occurring elevated atmospheric [CO2], whereas H2 portends declining photosynthesis with increasing temperatures. Distinguishing the two mechanisms at high temperatures is therefore critical, but difficult because VPD is highly correlated with temperature in natural settings. We used a forest mesocosm to quantify the sensitivity of tropical gross ecosystem productivity (GEP) to future temperature regimes while constraining VPD by controlling humidity. We then analytically decoupled temperature and VPD effects under current climate with flux-tower-derived GEP trends in situ from four tropical forest sites. Both approaches showed consistent, negative sensitivity of GEP to VPD but little direct response to temperature. Importantly, in the mesocosm at low VPD, GEP persisted up to 38 °C, a temperature exceeding projections for tropical forests in 2100 (ref. 10). If elevated [CO2] mitigates VPD-induced stomatal limitation through enhanced water-use efficiency as hypothesized9,11, tropical forest photosynthesis may have a margin of resilience to future warming. Photosynthesis in tropical forests shows an apparent sensitivity to temperature. This Letter teases apart the effects of temperature and correlated atmospheric water demand on ecosystem productivity.

O objetivo desse trabalho foi comparar a estrutura da regeneração natural de palmeiras de fragmentos florestais nas comunidades de Agrovila Araipá e São Tomé no município de Aveiro (PA). Foi realizado o método de transecção em linha, sendo quatro transecções: duas em cada comunidade e distribuídos em dois ecossistemas diferentes: um em ecossistemas de floresta primária remanescente e outro em ecossistema de floresta secundária. Todos os indivíduos não reprodutivos da parcela foram registrados, sendo classificados em seis estádios de vida, mas apenas os quatros primeiros estádios foram inclusos no estudo. Cada transecção media 300m de comprimento e 10m de largura dentro de cada fragmento. Na floresta primária, foram 390 indivíduos distribuídos em duas espécies (Astrocaryum aculeatum Meyer e Attalea maripa (Aublet) Martius) e 226 indivíduos distribuídos em três (Attalea sp., Astrocaryum aculeatum Meyer e Attalea maripa (Aublet) Martius) espécies na floresta secundária. A análise da estrutura revelou alta ocorrência de indivíduos da espécie A. maripa em estádios iniciais de desenvolvimento, causa essa provável pela ausência e/ou ineficiência dos dispersores dessa espécie. A espécie A. aculeatum, não apresentou diferença em sua ocorrência nos dois tipos de florestas (primária e secundária). Entretanto, na floresta secundária, a ocorrência de Attalea sp. foi considerada relevante na área, ocorrendo exclusivamente nessa vegetação; isso, possivelmente porque a floresta primária está fragmentada, cercada de pastagens e plantios agrícolas, causando um desiquilíbrio no recrutamento da A. maripa, sendo a provável uma característica da espécie uma alta produção de frutos e consequentemente um maior número de indivíduos em estádios iniciais de vida.

The following authors were omitted from the original version of this Data Descriptor: Markus Reichstein and Nicolas Vuichard. Both contributed to the code development and N. Vuichard contributed to the processing of the ERA-Interim data downscaling. Furthermore, the contribution of the co-author Frank Tiedemann was re-evaluated relative to the colleague Corinna Rebmann, both working at the same sites, and based on this re-evaluation a substitution in the co-author list is implemented (with Rebmann replacing Tiedemann). Finally, two affiliations were listed incorrectly and are corrected here (entries 190 and 193). The author list and affiliations have been amended to address these omissions in both the HTML and PDF versions. © 2021, This is a U.S. government work and not under copyright protection in the U.S.; foreign copyright protection may apply.

A análise das oscilações dos estoques de biomassa em florestas tropicais permite descrever o comportamento desses ecossistemas diante de alterações naturais ou antropogênicas. O objetivo deste trabalho foi avaliar o estoque e a dinâmica de biomassa no período (2007-2010) em Floresta Ombrófila Densa de duas áreas de pesquisa na FLONA - Tapajós: Amazônia oriental, denominadas Área 1 e Área 2, distantes aproximadamente 45 km uma da outra. A biomassa foi estimada através de equação alométrica e medidas de DAP, proveniente de 12 parcelas permanentes, sendo 6 em cada área. Os resultados mostraram que houve diferença significativa no estoque médio anual de biomassa entre a Área 1 (293,19 ± 27,74; 298,21 ± 31,73; 299,60 ± 29,46; 298,11 ± 29,40 Mg.ha-1) e a Área 2 (254,35 ± 69,61; 259,10 ± 70,05; 261,00 ± 69,43; 248,92 ± 61,78 Mg.ha-1). Notou-se variação anual no estoque de biomassa em intervalos de medições superiores a um ano, devido às oscilações na taxa de mortalidade, recrutamento e incremento, além da área basal e abundância dos indivíduos em cada área. A maior concentração de indivíduos ocorreu nas classes diamétricas 10 ≤ DAP ≤ 30 cm, porém, verificou-se que os indivíduos com DAP ≥ 60 cm em concentração menor estocam biomassa equivalente à da classe diamétrica 10 ≤ DAP ≤ 30 cm. Concluiu-se que as oscilações na taxa de mortalidade, recrutamento e incremento, além da abundância e área basal nestes locais afetaram os estoques de biomassa. Made available in DSpace on 2018-10-03T01:02:28Z (GMT). No. of bitstreams: 1 FABIOPLINIOCOSMECIENCIAFLORESTAL2018.pdf: 753273 bytes, checksum: cf651299c16d1ca8b5315dcfb3a17f5b (MD5) Previous issue date: 2018-10-02

Amazonian Dark Earths (ADEs) are highly fertile soils in areas with predominance of unfertile soils. However, the variation in nutrient availability between regions and the resilience of ADEs to modern agricultural use is still little known, particularly regarding micronutrient contents. Hence, the present study synthesized current information of ADE impacts on extractable micronutrient (Cu, Ni, Fe, Mn, Zn, B) contents at different soil depths and assessed in detail the role of both soil depth and land-use type on extractable Cu, Ni, Fe, Mn and Zn in nine ADEs and adjacent (ADJ) soils from different Amazonian regions. The land-use systems chosen were secondary old (OF) or young (YF) forests, and agricultural systems (AS) in Iranduba, Belterra and Porto Velho. Only eight studies compared extractable (Mehlich-1) micronutrient contents at 21 sites with ADEs and ADJ soils, but only four studies included depths greater than 30 cm, and B and Ni were evaluated in only one study. Higher Mn and Zn, but lower Fe contents were found in ADEs both from literature data and in the present study, especially in the first 30 cm depth. Increases in extractable Ni and Cu in ADEs varied according to the site and the land use considered. Micronutrient contents tended to decrease with depth, but varied depending on the element, site, soil type and land use. Sites with modern agriculture showed few differences in extractable micronutrient contents, except for a decrease in Fe in Belterra and Mn in Porto Velho. Considering the high amounts of some micro- and macronutrients in ADEs further work is warranted concerning soil management and nutrient balance in plants grown on these soils.

The association between spectral reflectance and canopy processes remains challenging for quantifying large-scale canopy phenological cycles in tropical forests. In this study, we used a tower-mounted hyperspectral camera in an eastern Amazon forest to assess how canopy spectral signals of three species are linked with phenological processes in the 2012 dry season. We explored different approaches to disentangle the spectral components of canopy phenology processes and analyze their variations over time using 17 images acquired by the camera. The methods included linear spectral mixture analysis (SMA); principal component analysis (PCA); continuum removal (CR); and first-order derivative analysis. In addition, three vegetation indices potentially sensitive to leaf flushing, leaf loss and leaf area index (LAI) were calculated: the Enhanced Vegetation Index (EVI), Normalized Difference Vegetation Index (NDVI) and the entitled Green-Red Normalized Difference (GRND) index. We inspected also the consistency of the camera observations using Moderate Resolution Imaging Spectroradiometer (MODIS) and available phenological data on new leaf production and LAI of young, mature and old leaves simulated by a leaf demography-ontogeny model. The results showed a diversity of phenological responses during the 2012 dry season with related changes in canopy structure and greenness values. Because of the differences in timing and intensity of leaf flushing and leaf shedding, Erisma uncinatum, Manilkara huberi and Chamaecrista xinguensis presented different green vegetation (GV) and non-photosynthetic vegetation (NPV) SMA fractions; distinct PCA scores; changes in depth, width and area of the 681-nm chlorophyll absorption band; and variations over time in the EVI, GRND and NDVI. At the end of dry season, GV increased for Erisma uncinatum, while NPV increased for Chamaecrista xinguensis. For Manilkara huberi, the NPV first increased in the beginning of August and then decreased toward September with new foliage. Variations in red-edge position were not statistically significant between the species and across dates at the 95% confidence level. The camera data were affected by view-illumination effects, which reduced the SMA shade fraction over time. When MODIS data were corrected for these effects using the Multi-Angle Implementation of Atmospheric Correction Algorithm (MAIAC), we observed an EVI increase toward September that closely tracked the modeled LAI of mature leaves (3–5 months). Compared to the EVI, the GRND was a better indicator of leaf flushing because the modeled production of new leaves peaked in August and then declined in September following the GRND closely. While the EVI was more related to changes in mature leaf area, the GRND was more associated with new leaf flushing.

Amazonian rainforests once thought to hold an innate pristine wilderness, are increasingly known to have been densely inhabited by populations showing a diverse and complex cultural background prior to European arrival. To what extent these societies impacted their landscape is unclear. Amazonian Dark Earths (ADEs) are fertile soils found throughout the Amazon Basin, created by pre-Columbian societies as a result of more sedentary habits. Much is known of the chemistry of these soils, yet their zoology, have been neglected. Hence, we characterised soil macroinvertebrate communities and activity in these soils at nine archaeological sites in three Amazonian regions. We found 667 morphospecies and a tenacious pre-Columbian footprint, with 43% of species found exclusively in ADEs. The soil biological activity is higher in the ADEs when compared to adjacent reference soils, and it is associated with higher biomass and richness of organisms known to engineer the ecosystem. We show that these habits have a unique pool of species, however, the contemporary land-use in ADEs drives nutrient decay and threats biodiversity. These findings support the idea that Humans have built and sustained a contrasting high fertile system that persisted until our days and irreversibly altered the biodiversity patterns in Amazonia.

A precipitação é uma importante fonte de entrada de nutrientes para ecossistemas, principalmente em floresta tropical, que depende extremamente dessa fonte para a sua sobrevivência. A pesquisa objetivou quantificar os fluxos de potássio (K+), fósforo (P), cálcio (Ca2+), magnésio (Mg2+) e ferro (Fe2+) presentes na precipitação direta (PD) e precipitação interna (PI), e também verificar a influência do efeito de borda na composição química da PI. O estudo foi realizado na Floresta Nacional do Tapajós (FLONA Tapajós), no município de Belterra, Pará, na zona de influência da rodovia BR 163 (Santarém-Cuiabá), em duas áreas, km 67 e km 126. Para a realização da amostragem delimitou-se um transecto, da borda até 100 m dentro da floresta, onde as coletas de PI ocorreram nas bordas da FLONA e de PD nas respectivas zonas de entorno. Somente no km 67, também, foram considerados os fluxos de nutrientes presentes na PI, do centro da FLONA Tapajós. O fluxo de nutrientes, de uma forma geral, mostrou a ordem decrescente: K+>Ca2+>Mg2+>P>Fe2+. Foi possível verificar que a PI é uma importante fonte de entrada para potássio e que as atividades de agricultura de grande porte influenciam expressivamente a composição química da PI, na zona de planalto e da FLONA Tapajós. Made available in DSpace on 2019-12-20T18:07:43Z (GMT). No. of bitstreams: 1 FluxoCosme.pdf: 1116974 bytes, checksum: 36a074c45b6efe025c57f15d097ebfc0 (MD5) Previous issue date: 2018

A mudança de uso e manejo do solo vem ocorrendo de forma dinâmica e intensa, sobretudo na região Amazônica, o que pode resultar em fonte ou dreno de gases do efeito estufa para a atmosfera. Este trabalho quantificou as trocas gasosas de metano (CH4) e óxido nitroso (N2O) entre solo e atmosfera em diferentes tipos de cobertura, e analisou as variáveis ambientais reguladoras das trocas gasosas em diferentes microbacias da região Oeste do estado do Pará. As medidas foram realizadas através de câmaras instaladas no campo, posteriormente analisadas por cromatografia gasosa. Não houve diferença significativa no fluxo de metano mediante os efeitos da mudança no uso da terra em campos agrícolas de soja (0,23mg-C/m2/h), pastagens (0,31mg-C/m2/h) e capoeira (0,42mg-C/m2/h). Encontrou-se diferença estatística entre o fluxo de óxido nitroso relacionado ao tipo de cobertura do solo, onde o fluxo de capoeira (19,57 mg-N/m2/h) foi menor que o da pastagem (36,81mg-N/m2/h) e agricultura (40,08mg-N/m2/h). Houve diferença entre os fluxos de metano encontrados na soja em sistema de plantio direto (0,29mg-C/m2/h) em relação ao sistema de plantio convencional (0,11mg-C/ m2/h). Também se encontrou diferença no fluxo de óxido nitroso do plantio direto (40,7mg-N/m2/h) que foi maior que o plantio convencional (38,8mg-N/m2/h). Frente às mudanças no uso da terra cada vez mais frequentes, há a necessidade de novas formas de manejo que busquem reduzir as emissões desses gases ou aumentar seus sumidouros. Made available in DSpace on 2019-12-20T18:07:24Z (GMT). No. of bitstreams: 1 TrocasCosme.pdf: 1726450 bytes, checksum: ded049f80a429cdc114de8708acaa3a8 (MD5) Previous issue date: 2018 Edição Especial do Congresso de Gestão Ambiental do Baixo Amazonas (CONGABA) - Ago 2018.

This research estimated litter production and analyzed its relation to environmental variables such as maximum temperature, insolation, and rainfall. The study was conducted on a 300 × 300 m experiment as part of the project titled mapping of native Brazil nut stands and socio-environmental and economic characterization of Brazil nut production systems (MapCast), in the Tapajós National Forest (FLONA Tapajós). Every 30 days for one full year (August 2015 to July 2016), litterfall was collected and stored in a laboratory. After drying, the material was separated into leaves, wood, flowers and fruits, and miscellaneous and weighed. Statistical tests conducted were Shapiro-Wilk (5%), Principal coordinate analysis, t-test, Pearson?s linear correlation, cross-correlation, and canonical redundancy analysis. Rainfall and temperature data were inferior and superior, respectively, to normal climate conditions in the region, and data for solar insolation had an abnormal pattern compared to normal climate conditions. Leaf production varied between 169.9 and 965.6 kg ha-1 month-1, and that of wood between 26.7 and 501.3 kg ha-1 month-1, while that for flowers and fruit varied from 0.6 to 19.6 kg ha-1 month-1. The greatest leaf production was measured during the months with the lowest amount of rainfall and highest temperatures, and variation in leaf production and total litterfall was partially explained by temperature and insolation. Made available in DSpace on 2018-02-07T23:36:55Z (GMT). No. of bitstreams: 1 QUEZIAETALAJAR2018.pdf: 1413271 bytes, checksum: 50143c256223e6e324c90e02b20ee0bc (MD5) Previous issue date: 2018-02-07 Article Number: 1A6396E55865.

Made available in DSpace on 2019-10-06T15:46:53Z (GMT). No. of bitstreams: 0 Previous issue date: 2019-10-15 Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) Fundação de Amparo à Pesquisa do Estado de Minas Gerais (FAPEMIG) Arsenic (As) in native soils of the Amazon rainforest is a concern due to its likely origin from the Andean rivers, which transport loads of sediments containing substantial amounts of trace elements coming from the cordilleras. Yet, unveiling soil As baseline concentrations in the Amazon basin is still a need because most studies in Brazil have been performed in areas with predominantly high concentrations and cannot express a real baseline value for the region. In this study, 414 soil samples (0–20, 20–40 and 40–60 cm layers) were collected from different sites throughout the Amazon basin - including native Amazon rainforest and minimally disturbed areas - and used to determine total and extractable (soluble + available) As concentrations along with relevant soil physicochemical properties. Descriptive statistics of the data was performed and Pearson correlation supported by a Principal Component Analysis (PCA) provided an improved understanding of where and how As concentrations are influenced by soil attributes. Total As concentration ranged from 0.98 to 41.71 mg kg−1 with values usually increasing from the topsoil (0–20 cm) to the deepest layer (40–60 cm) in all sites studied. Considering the proportional contribution given by each fraction (soluble and available) on extractable As concentration, it is noticeable that KH2PO4-extractable As represents the most important fraction, with >70% of the As extracted on average in all the sites studied. Still, the extractable fractions (soluble + available) correspond to ~0.24% of the total As, on average. Total, available, and soluble As fractions were strongly and positively correlated with soil Al3+. The PCA indicated that soil pH in combination with CEC might be the key factors controlling soil As concentrations and the occurrence of each arsenic fraction in the soil layers. Department of Soil Science Federal University of Lavras Vale Institute of Technology Embrapa Rondônia Embrapa Amazônia Ocidental Embrapa Roraima Embrapa Amapá Embrapa Amazônia Oriental São Paulo State University (UNESP) School of Sciences and Engineering, Rua Domingos da Costa Lopes 780 School of Biosciences University of Nottingham, Sutton Bonington Campus São Paulo State University (UNESP) School of Sciences and Engineering, Rua Domingos da Costa Lopes 780

Seasonal dynamics in the vertical distribution of leaf area index (LAI) may impact the seasonality of forest productivity in Amazonian forests. However, until recently, fine-scale observations critical to revealing ecological mechanisms underlying these changes have been lacking. To investigate fine-scale variation in leaf area with seasonality and drought we conducted monthly ground-based LiDAR surveys over 4 yr at an Amazon forest site. We analysed temporal changes in vertically structured LAI along axes of both canopy height and light environments. Upper canopy LAI increased during the dry season, whereas lower canopy LAI decreased. The low canopy decrease was driven by highly illuminated leaves of smaller trees in gaps. By contrast, understory LAI increased concurrently with the upper canopy. Hence, tree phenological strategies were stratified by height and light environments. Trends were amplified during a 2015-2016 severe El Nino drought. Leaf area low in the canopy exhibited behaviour consistent with water limitation. Leaf loss from short trees in high light during drought may be associated with strategies to tolerate limited access to deep soil water and stressful leaf environments. Vertically and environmentally structured phenological processes suggest a critical role of canopy structural heterogeneity in seasonal changes in Amazon ecosystem function.

Forest biophysical structure - the arrangement and frequency of leaves and stems - emerges from growth, mortality and space filling dynamics, and may also influence those dynamics by structuring light environments. To investigate this interaction, we developed models that could use LiDAR remote sensing to link leaf area profiles with tree size distributions, comparing models which did not (metabolic scaling theory) and did allow light to influence this link. We found that a light environment-to-structure link was necessary to accurately simulate tree size distributions and canopy structure in two contrasting Amazon forests. Partitioning leaf area profiles into size-class components, we found that demographic rates were related to variation in light absorption, with mortality increasing relative to growth in higher light, consistent with a light environment feedback to size distributions. Combining LiDAR with models linking forest structure and demography offers a high-throughput approach to advance theory and investigate climate-relevant tropical forest change.

A Floresta Nacional do Tapajós (FLONA Tapajós) possui 600 mil hectares de floresta protegida, e está situada a 50 km ao sul da cidade de Santarém, Pará, Brasil, uma cidade portuária de 250 mil habitantes, localizada na confluência dos rios Tapajós e Amazonas. Há abundância de terras agrícolas na região, que oferecem muitas oportunidades para estudar mudanças no uso da terra, e um tipo de uso da terra, a colheita seletiva de madeira, é particularmente importante para a economia de Santarém. A deposição úmida e seca pode ser uma importante fonte de nutrientes para as plantas, e isto é especialmente verdade quando os solos são pobres, o que é o caso na região do planalto Santarém-Belterra, a área de estudo da presente investigação. Nesta região, a deposição de nutrientes atmosférico natural é reforçada pela frequente queima de biomassa que libera uma grande parte dos nutrientes da biomassa acima do solo para a atmosfera. Os objetivos deste estudo foram: 1) Estimar a deposição úmida total via precipitação direta e através da copa, incluindo a deposição seca; 2) Verificar potenciais fontes de nutrientes encontrados na deposição úmida total e deposição seca; e, 3) Verificar possíveis efeitos da cobertura vegetal no teor de nutrientes na precipitação e precipitação interna. Este estudo foi realizado na FLONA Tapajós no km 67 da rodovia Santarém - Cuiabá, ao sul da cidade de Santarém. A área de estudo consistiu de uma parcela de 100 x 100 m dividida em transectos de 10 x 10 m que foi localizada próximo de uma torre meteorológica de 65 m que com medidas de vários parâmetros climáticos, como precipitação, velocidade e direção do vento, radiação solar incidente e temperatura e umidade do ar, entre outros. Coletores de precipitação direta (PD) e de precipitação interna (PI) consistiram de frascos de 2 L de polietileno com um funil de diâmetro de 115 mm. As amostras foram coletadas semanalmente durante abril de 2003 a março de 2006. O volume da amostra foi medido individualmente para cada coletor (25 coletores para a precipitação interna e 4 para a precipitação direta). As conclusões que podem ser tiradas a partir deste estudo são: 1) A estação seca apresenta a maior variação no fluxo de íons; 2) A sazonalidade exerce uma forte influência sobre a concentração de cátions básicos; 3) A deposição seca é um das mais importantes caminhos para a entrada de nutrientes na FLONA Tapajós; 4) Há uma entrada significativa de macronutrientes, Cl e Na da agricultura de grãos intensivo nas proximidades; 5) Deposição seca é o processo mais importante para o enriquecimento de água que atinge o chão da floresta; 6) A análise de componentes principais facilita a interpretação e caracterização de águas pluviais e, neste estudo, mostra a influência de fontes antropogênicas como a agricultura, queima de biomassa, e poeira. The Tapajós National Forest (FLONA Tapajós) has 600,000 hectares of protected forest, and is situated 50 km south of the city of Santarém, Pará, Brazil, a port city of 250,000 inhabitants that is located at the confluence of the Tapajós and Amazon Rivers. There is a lot of farmland in the region, which offers many opportunities to study changes in land use. Selective wood harvesting is one type of land use that is particularly important to the economy of Santarém. Wet and dry deposition of organic material can be an important source of nutrients for plants, and this is especially true when the soil is poor, which is the case in Santarém-Belterra plateau region, the study area of this research. In this region, the natural atmospheric deposition of nutrients is often enhanced by the burning of biomass, which releases a large part of the above-ground biomass nutrients into the atmosphere. The objectives of this study were: 1 - estimate the total wet deposition via direct precipitation and through the canopy, including dry deposition; 2 - verify potential sources of nutrients found in the total wet deposition and dry deposition; and 3 - investigate the effects of coverage vegetation on nutrient content in precipitation and throughfall. The study was conducted in FLONA Tapajós at km 67 of Santarém- Cuiabá Highway, south of the city of Santarém. The study area consisted of a portion of 100 x 100 m transects divided into 10 x 10 m plots. The area was located next to a meteorological tower 65 m tall that measures various climate parameters such as rainfall, wind speed and direction, solar radiation, temperature and humidity, among others. Direct precipitation (PD) and internal precipitation (IP) collectors consisted of 2 L polyethylene bottles with a 115 mm diameter funnel. Samples were collected weekly from April 2003 to March 2006. The volume of the sample was measured individually for each collector (25 traps for internal precipitation and 4 for direct precipitation). The conclusions that can be drawn from this study are: 1 - the dry season has the highest variation in ion flux; 2 - seasonality has a strong influence on the concentration of basic cations; 3 - dry deposition is one of the most important ways that nutrients are acquired in FLONA Tapajos; 4 - there is a significant inflow of nutrients Cl and Na due to intensive grain farming nearby; 5 - dry deposition is the most important process for the enrichment of water that reaches the forest floor; 6 - principal component analysis facilitates the interpretation and characterization of rainwater and in this study shows the influence of anthropogenic sources such as agriculture, biomass burning, and dust.

A castanha-do-brasil é considerada uma das árvores mais nobres do bioma Amazônia e contém ecossistemas e importância econômica para esta região. O estudo da variância espacial das propriedades edáficas em árvores nativas podem direcionar pesquisas futuras sobre amostragens mais eficientes. A geostatística é a metodologia utilizada para este tipo de estudo, uma vez que considera as características estruturais e aleatórias de uma variável espacialmente distribuída. Este trabalho buscou obter um maior conhecimento sobre a distribuição dos nutrientes no solo, verificando a relação com a ocorrência desta espécie, desse modo, fornecer subsídios para o futuro manejo florestal e manutenção / ampliação do produtividade nessas áreas. As amostras de solo foram coletadas a partir de 30 × 30 m na linha, em todas as linhas em parte do estudo, totalizando 60 amostras. Todos os pontos foram georreferenciados. A preparação do amostras para o preparo da amostra para a análise química e os métodos e cálculos para determinação das variáveis ​​físico-químicas estudadas foram descritos por Nogueira e Souza (2005). As análises estatística e geoestatística foram realizadas no ambiente computacional R, versão 3.2.2. A maioria das variáveis ​​estudadas apresentou nível definido. Para as variáveis ​​físicas, houve predomínio do ajuste ao modelo do variograma gaussiano, seguidor pelo modelo esférico. No caso das variáveis ​​químicas, houve duas ocorrências para cada modelo de ajuste (esférico, exponencial e gaussiano). As variáveis ​​que melhor apresentaram relação espacial com o ocorrência de árvores de castanha do Brasil foram o lodo, argila, macroporosidade, pH, fósforo, zinco e cobre. The Brazil nut is considered one of the noblest trees of the Amazon biome and contains social, ecologic and economic importance to this region. The study of the spatial variance of the edaphic properties in native nut trees can direct future researches about more efficient samplings. The Geostatistics is the methodology utilized for this type of study, once that it considers the structural and random characteristics of a variable spatially distributed. This work sought to get a higher knowledge about the distribution of the nutrients in the soil, verifying the relationship with the occurrence of this species, to thereby provide subsidies to future forest management and maintenance/enlargement of the productivity in these areas. The soil samples were collected from 30 × 30 m on the line, in all of the lines in part of the study, totaling 60 samples. All of the points were georeferenced. The preparation of the samples for the sample preparation for the chemical analysis and the methods and calculations to determine the physicochemical variables studied were described by Nogueira and Souza (2005). The statistical and geostatistical analysis were conducted using the R computational environment, version 3.2.2. Most of the studied variables presented defined level. For the physical variables, there was predominance of the adjustment to the model of the gaussian variogram, follower by the spherical model. In the case of the chemical variables, there were two occurrences for each adjustment model (spherical, exponential and gaussian). The variables that best presented spatial relation with the occurrence of Brazil nut trees were the silt, clay, macroporosity, pH, phosphorus, zinc and copper.

Satellite and tower-based metrics of forest-scale photosynthesis generally increase with dry season progression across central Amazônia, but the underlying mechanisms lack consensus. We conducted demographic surveys of leaf age composition, and measured the age dependence of leaf physiology in broadleaf canopy trees of abundant species at a central eastern Amazon site. Using a novel leaf-to-branch scaling approach, we used these data to independently test the much-debated hypothesis – arising from satellite and tower-based observations – that leaf phenology could explain the forest-scale pattern of dry season photosynthesis. Stomatal conductance and biochemical parameters of photosynthesis were higher for recently mature leaves than for old leaves. Most branches had multiple leaf age categories simultaneously present, and the number of recently mature leaves increased as the dry season progressed because old leaves were exchanged for new leaves. These findings provide the first direct field evidence that branch-scale photosynthetic capacity increases during the dry season, with a magnitude consistent with increases in ecosystem-scale photosynthetic capacity derived from flux towers. Interactions between leaf age-dependent physiology and shifting leaf age-demographic composition are sufficient to explain the dry season photosynthetic capacity pattern at this site, and should be considered in vegetation models of tropical evergreen forests. © 2018 The Authors. New Phytologist © 2018 New Phytologist Trust

Background: The dynamics of gaps plays a role in the regimes of tree mortality, production of coarse woody debris (CWD) and the variability of light in the forest understory. Aims: To quantify the area affected by, and the carbon fluxes associated with, natural gap-phase disturbances in a tropical lowland evergreen rain forest by use of ground measurements and high-resolution satellite images. Methods: We surveyed two large forest inventory plots of 114 and 53 ha of the Tapajos National Forest (TNF) in the Brazilian Amazon during 2008 and 2009, respectively. We mapped all gaps and collected data on light availability, CWD stocks and tree mortality in the field. Gap location, canopy openness (CO) and leaf area index (LAI) estimated in the field were compared with two IKONOS–2 high-resolution satellite images acquired at approximately the time of the field measurements. Results: In the two large plots (167 ha total area) we found 96 gaps. The gaps represented 1.42% of the total area and gaps

Across the tropics, there is a growing financial investment in activities that aim to reduce emissions from deforestation and forest degradation, such as REDD+. However, most tropical countries lack on-the-ground capacity to conduct reliable and replicable assessments of forest carbon stocks, undermining their ability to secure long-term carbon finance for forest conservation programs. Clear guidance on how to reduce the monetary and time costs of field assessments of forest carbon can help tropical countries to overcome this capacity gap. Here we provide such guidance for cost-effective one-off field assessments of forest carbon stocks. We sampled a total of eight components from four different carbon pools (i.e. aboveground, dead wood, litter and soil) in 224 study plots distributed across two regions of eastern Amazon. For each component we estimated survey costs, contribution to total forest carbon stocks and sensitivity to disturbance. Sampling costs varied thirty-one-fold between the most expensive component, soil, and the least, leaf litter. Large live stems (≥10 cm DBH), which represented only 15% of the overall sampling costs, was by far the most important component to be assessed, as it stores the largest amount of carbon and is highly sensitive to disturbance. If large stems are not taxonomically identified, costs can be reduced by a further 51%, while incurring an error in aboveground carbon estimates of only 5% in primary forests, but 31% in secondary forests. For rapid assessments, necessary to help prioritize locations for carbon- conservation activities, sampling of stems ≥20cm DBH without taxonomic identification can predict with confidence (R2 = 0.85) whether an area is relatively carbon-rich or carbon-poor—an approach that is 74% cheaper than sampling and identifying all the stems ≥10cm DBH. We use these results to evaluate the reliability of forest carbon stock estimates provided by the IPCC and FAO when applied to human-modified forests, and to highlight areas where cost savings in carbon stock assessments could be most easily made.

A perturbação florestal antropogênica e a mudança no uso da terra(LUC) na região amazônica são principal fonte de emissões de gases de efeito estufa para a atmosfera no Brasil, devido ao carbono (C)e nitrogênio (N) emitido da limpeza da vegetação. Conversão de uso da terra associada à gestão práticas desempenham um papel fundamental na distribuição e origem de C em diferentes matérias orgânicas do solo (MOS)frações. Aqui, mostramos como a mudança nos sistemas de uso da terra tem influenciado os estoques de C e N do solo,Frações físicas da OMS e a origem da MOS na região de Santarém, no leste brasileiro Amazônia Os estoques de solo C e N foram calculados para a camada superficial de 0 a 30 cm. Antropogênico distúrbios na floresta em pé, como a extração seletiva de madeira e os incêndios florestais, levaram a declínios significativos em estoques de C e N no solo. No entanto, a longo prazo, a conversão da floresta amazônica para pastagem não teve um efeito perceptível nos estoques de C e N do solo, presumivelmente por causa de de pastagens. No entanto, a conversão para terras de cultivo levou a reduções no solo C e N conteúdo. De acordo com o fracionamento físico da MOS, a LUC alterou a qualidade da MOS, mas silte e argila permaneceu a fração combinada que mais contribuiu para o armazenamento de solo C. Nossos resultados enfatizam a importância de implementar sistemas de manejo florestal mais sustentáveis, ao mesmo mais atenção à necessidade de sistemas de monitoramento de incêndio, ajudando a assegurar a resiliência de C e Estoque e seqüestro de N em solos florestais; contribuindo assim para a necessidade urgente de esforços para mitigar a mudança climática. Anthropogenic forest disturbance and land use change (LUC) in the Amazon region is the main source of greenhouse gas emissions to the atmosphere in Brazil, due to the carbon (C) and nitrogen (N) emitted from vegetation clearance. Land use conversion associated with management practices plays a key role in the distribution and origin of C in different soil organic matter (SOM) fractions. Here, we show how changing land use systems have influenced soil C and N stocks, SOM physical fractions, and the origin of SOM in the Santarém region of the eastern Brazilian Amazon. Soil C and N stocks were calculated for the surface layer of 0–30 cm. Anthropogenic disturbances to the standing forest, such as selective logging and wildfires, led to significant declines in soil C and N stocks. However, in the long-term, the conversion of the Amazon forest to pasture did not have a noticeable effect on soil C and N stocks, presumably because of additional inputs from pasture grasses. However, the conversion to cropland did lead to reductions in soil C and N content. According to the physical fractionation of SOM, LUC altered SOM quality, but silt and clay remained the combined fraction that contributed the most to soil C storage. Our results emphasize the importance of implementing more sustainable forest management systems, whilst also calling further attention to the need for fire monitoring systems, helping to ensure the resilience of C and N stocks and sequestration in forest soils; thereby contributing towards urgently needed ongoing efforts to mitigate climate change.

Forest inventory studies in the Amazon indicate a large terrestrial carbon sink. However, field plots may fail to represent forest mortality processes at landscape-scales of tropical forests. Here we characterize the frequency distribution of disturbance events in natural forests from 0.01 ha to 2,651 ha size throughout Amazonia using a novel combination of forest inventory, airborne lidar and satellite remote sensing data. We find that small-scale mortality events are responsible for aboveground biomass losses of ~1.7 Pg C y−1 over the entire Amazon region. We also find that intermediate-scale disturbances account for losses of ~0.2 Pg C y−1, and that the largest-scale disturbances as a result of blow-downs only account for losses of ~0.004 Pg C y−1. Simulation of growth and mortality indicates that even when all carbon losses from intermediate and large-scale disturbances are considered, these are outweighed by the net biomass accumulation by tree growth, supporting the inference of an Amazon carbon sink., The world’s tropical forests represent a terrestrial carbon sink, yet its size is uncertain. Espírito-Santo et al. characterize full Amazon disturbances combining forest inventories and remote sensing data, and use statistical modelling to quantify the Amazon aboveground forest carbon balance.

Eucalyptus grandis and other clonal plantations cover about 3.5 million ha in Brazil. The impacts of intensively-managed short-rotation forestry on soil aggregate structure and Carbon (C) dynamics are largely undocumented in tropical ecosystems. Long-term sustainability of these systems is probably in part linked to maintenance of soil organic matter and good soil structure and aggregation, especially in areas with low-fertility soils. This study investigated soil aggregate dynamics on a clay soil and a sandy soil, each with a Eucalyptus plantation and an adjacent primary forest. Silvicultural management did not reduce total C stocks, and did not change soil bulk density. Aggregates of the managed soils did not decrease in mass as hypothesized, which indicates that soil cultivation in 6 year cycles did not cause large decreases in soil aggregation in either soil texture. Silt, clay, and C of the sandy plantation soil shifted to greater aggregate protection, which may represent a decrease in C availability. The organic matter in the clay plantation soil increased in the fractions considered less protected while this shift from C to structural forms considered more protected was not observed. Este trabalho teve como objetivo investigar a dinâmica dos agregados do solo e das suas frações derivadas dos mesmos em duas texturas de solo, cada uma com uma plantação de Eucalipto e uma floresta primaria imediatamente adjacente. Eucalyptus grandis e outros clones cultivados em plantações cobrem aproximadamente 3,5 milhões de hectares no Brasil. Os impactos de manejo intensivo de plantações de rotação curta sobre a estrutura de solo e a dinâmica de carbono (C) são em grande parte desconhecidos em ecossistemas tropicais. No longo prazo, a sustentabilidade desses sistemas é provavelmente ligada à manutenção da matéria orgânica e à estrutura de agregação do solo, principalmente em áreas de solos de baixa fertilidade. Manejo silvicultural não diminuiu os estoques de C total, e não mudou a densidade do solo. Agregados dos solos manejados não diminuíram em massa, o que indica que a subsolagem e o manejo em ciclos de 6 anos não causaram um efeito negativo na agregação do solo em ambas as texturas. Os agregados do solo arenoso sob plantio aumentaram seus conteúdos de silte, argila e C, indicando que, na estrutura de agregação do solo, C está mudando para um ambiente de maior proteção contra decomposição. O solo argiloso sob plantio teve um aumento de matéria orgânica contida nas frações consideradas menos protegidas, e não demonstrou essas mudanças de C para formas estruturais consideradas mais protegidas.