Bragantina Region Research Articles

Damage caused by Tuckerella ornata (Acari: Tuckerellidae) on cocoa fruits (Theobroma cacao) in the Amazon region, state of Pará, Brazil

The study aimed to report peacock mites (Acari: Tuckerellidae) on cocoa fruits (Theobroma cacao L.; Malvaceae) in the northeast Bragantina region, state of Pará, Brazil. Two mite species were identified, Tuckerella ornata, with 149 specimens, 32.89% on leaves and 67.11% on fruits, and Tuckerella knorri, with only two specimens on leaves. It was found that green fruits with T. ornata significantly reduced the size and weight of seeds. More attacked fruits, with more severe damage, showed deformations and thick cracks. Significant damage was noted in the Forastero cocoa seeds, visible to the naked eye, with light brown spots and a fine crack on the epidermis.

Biostratigraphy and paleoenvironment correlation based on benthic foraminifera from the cenozoic Marajó and Pirabas formations, Eastern Amazon Coast, Brazil

The Oligocene-Miocene foraminifera biostratigraphy correlation has been applied successfully as a geological tool for establishing the paleoenvironmental conditions during the deposition of siliciclastic and carbonate strata in the Eastern Amazon coastal basins. In this region, previously interpreted tectonic compartments represented by the Marajó Basin and Bragantina Platform were the main sites of siliciclastic and carbonate sedimentation influenced by Late Paleogene-Neogene transgressive–regressive events. In the subsident Marajó basin, a siliciclastic estuary was developed, supplied by the Cratonic Amazon River. The transcontinental river did not influence the Bragantina region to the East, allowing the implantation of a shallow carbonate platform. These Neogene segments require further sedimentological, stratigraphic, and paleontological studies to define these limits. The use of foraminifera content has been considered an important tool to assist in this differentiation, providing a paleoenvironmental and paleoecological reconstruction model. This work used qualitative and quantitative analyses integrating several diversity indices, complementing the R-mode cluster and the correlation of planktonic and benthic (P/B) ratios. The similarity in faunal diversity indicated that these siliciclastic and carbonate units represented by the Marajó and Pirabas formations are chronocorrelated. Marajó Formation is interpreted as a restricted, suboxic, marginal marine environment (lagoons/mangroves) with variable salinity and abundance of the species as Cribroelphidium williamsoni, Ammonia tepida, and A. beccari. In contrast, the Pirabas Formation was deposited in a brackish, oxic, and carbonate platform characterized by Cibicidoides subhaidingerii, Cibicides pachyderma A. beccarii, and Cassidulina laevigata species. These foraminifera assemblages confirm the previous stratigraphic and paleoenvironmental interpretations providing new insights into understanding the Late Paleogene-Neogene evolution of the Eastern Amazonia Coast.

Usos da terra e potencial de regeneração natural da vegetação nativa na bacia do rio Apeú, Castanhal, Pará

This study analyzes the use and cover land as well as the potential use of natural regeneration for forest restoration in the Apeú River Basin (BHRA), located in the Bragantina region in Pará, the oldest colonization region of the Amazon. Remote sensing and geoprocessing techniques were used for the mapping and classification of the Landsat-8 satellite image of the year 2017. Data treatment and analysis, preparation and editing of the use and coverage map were performed using ArcGis version 10.1. Areas with natural regeneration represent more than 18%, considering dirty pasture and secondary vegetation, and are considered areas under the process of succession. Little over 20% of the areas used for agricultural use and 20% of areas with exposed soil were found, which is due to increasing urbanization. The BHRA analysis shows that conserved and degraded primary forests dominate 47% of the basin territory. Thus, the percentage of secondary vegetation and dirty pasture indicates that the region has average potential for natural regeneration for restoration purposes.

Usos da terra e potencial de regeneração natural da vegetação nativa na bacia do rio Apeú, Castanhal, Pará

This study analyzes the use and cover land as well as the potential use of natural regeneration for forest restoration in the Apeú River Basin (BHRA), located in the Bragantina region in Pará, the oldest colonization region of the Amazon. Remote sensing and geoprocessing techniques were used for the mapping and classification of the Landsat-8 satellite image of the year 2017. Data treatment and analysis, preparation and editing of the use and coverage map were performed using ArcGis version 10.1. Areas with natural regeneration represent more than 18%, considering dirty pasture and secondary vegetation, and are considered areas under the process of succession. Little over 20% of the areas used for agricultural use and 20% of areas with exposed soil were found, which is due to increasing urbanization. The BHRA analysis shows that conserved and degraded primary forests dominate 47% of the basin territory. Thus, the percentage of secondary vegetation and dirty pasture indicates that the region has average potential for natural regeneration for restoration purposes.

Perfil epidemiológico da hipospádia na região Bragantina do estado de São Paulo, Brasil

Modelo de estudo: Estudo de prevalência. Objetivo do estudo: Avaliar o perfil epidemiológico dos casos de hipospádia atendidos no Hospital São Francisco na Providência de Deus da Universidade São Francisco (HUSF), Bragança Paulista/SP nos últimos 10 anos (2007-2017), relacionando os tipos de hipospádia com as malformações associadas e idade à primeira cirurgia corretiva. Metodologia: Foi realizado um levantamento de casos de hipospádia atendidos entre 2007 e 2017 no HUSF, com pacientes oriundos das cidades da Região Bragantina do estado de São Paulo. Os tipos de hipospádia foram relacionados com as malformações associadas. Foram pesquisados nos prontuários: tipo de hipospádia, idade à primeira cirurgia, laudo de exame ultrassonográfico, etnia, local de nascimento e malformação associada. Os dados foram analisados estatisticamente utilizando os testes Qui-quadrado, teste F e de Kruskal-Wallis. Resultados: Em 1401 atendimentos pediátricos no período avaliado, foram encontrados 45 casos de hipospádia com prevalência igual a 0,7/1000 nascidos vivos. Do total de casos, 29 foram classificados como do tipo distal, seis casos de hipospádia média e 10 casos do tipo proximal [F-test (2,8)=5,552; P=0,003; χ2=9,3117; P=0,009]. Nos casos de hipospádia distal, foram detectadas 16 malformações associadas e, nos tipos média e proximal, foram observadas sete malformações associadas em cada uma (KW=3,322, P=0,19). O maior número de casos foi abordado cirurgicamente no intervalo entre os três e quatro anos de idade. Conclusão: A hipospádia distal foi a mais prevalente, com idade à primeira cirurgia em desacordo com o intervalo proposto para a correção da hipospádia.

Conservação de recursos naturais e práticas turísticas sustentáveis em Vargem (SP)

O crescimento acelerado do turismo em áreas protegidas tem gerado debates quanto às dificuldades de integrar ações sustentáveis no planejamento turistico-ambiental dos municípios. Neste contexto, este artigo busca discutir a conservação dos recursos naturais através de práticas turísticas - ambientais sustentáveis no município de Vargem/SP – pertencente à Área de Proteção Ambiental do Sistema Cantareira, Região Bragantina, utilizando o diagnóstico ambiental e a identificação dos atrativos naturais reais e potenciais como instrumento de planejamento local. Além de fortalecer a educação ambiental aliada a práticas sustentáveis, sempre envolvendo os turistas nesses processos, visando proporcionar a sustentabilidade dos recursos naturais e a melhoria da qualidade de vida dos envolvidos. Esta APA possui várias nascentes e pontos de captação de importância regional e remanescentes significativos de Mata Atlântica, apresentando uma problemática ambiental centrada
 na conservação de recursos hídricos gerados, principalmente, a partir das alterações decorrentes da construção do Sistema Cantareira e da duplicação da Rodovia Fernão Dias. Ambos foram determinantes nos processos de expansão industrial e urbana e de incremento turístico na região. Assim, o município de Vargem vem passando por transformações socioambientais e de urbanização, prejudicando a qualidade dos recursos naturais locais. Mesmo possuindo alguns remanescentes vegetais e uma variada fauna, as consequências dos usos e ocupação do solo, ações predatórias e antrópicas vêm dificultando a conservação da biodiversidade e dos recursos hídricos. Esta realidade tem exigido a elaboração e implantação de estudos, projetos e planos de ação, que visem minimizar os impactos negativos gerados a partir da atividade turística e maximizar os positivos, contribuindo para a melhoria da qualidade de vida dos moradores e na conservação dos recursos naturais da região. Este artigo é fruto da pesquisa Qualidade de vida, turismo e sustentabilidade na APA do Sistema Cantareira: um estudo de caso em Vargem / SP (conta com apoio financeiro da FAPESP - Processo 2007/59833-0), que e é parte integrante da tese de doutorado da pesquisadora Cristiane Ferraz e Silva Suarez no Programa de Doutorado em Ambiente e Sociedade do Núcleo de Pesquisas Ambientais – NEPAM da Universidade Estadual de Campinas - SP/ Brasil.

A framework for creating and validating a non-linear spectrum-biomass model to estimate the secondary succession biomass in moist tropical forests

Uncertainties remain in the use of remote sensing technologies to provide validated model-derived estimates of the biomass of the secondary succession (SS) forests in the Amazon Basin. The objectives of this study were to develop a modeling framework for creating a valid spectrum-biomass model to estimate the SS biomass, to assess the utility of the framework and the accuracy and validity of the model, and to identify the model’s determinants. Data sources for this study include 1992–1993 vegetation inventory data and 1991 Landsat Thematic Mapper (TM) data on the Altamira region of Para, Brazil, and 1994–1995 vegetation inventory data and 1994 Landsat TM data on the nearby Bragantina region. The allometric approach was used to estimate the biomass of the sampled sites based on the vegetation inventory data. A framework for the spectrum-biomass regression model was developed based on the estimated biomass of the sampled sites and the Landsat data. The framework includes (1) the pooling of data from Bragantina and the use of ANCOVA to justify this approach; (2) image calibration; (3) biomass data age-adjustment, (4) selection of independent variables, (5) regression model development, and (6) model assessment and validation. The cubic regression model with TM Band5-related predictors was found to best fit the data as evidenced by an adjusted R-squared value of 0.865, mean square error (MSE) of the model, and the analysis of residuals. Residual analysis showed that the model might yield a better estimation on a lower biomass values than on higher biomass values. In addition, further analyses identified several determinants that can impact the accuracy of the spectrum-biomass model. ANCOVA confirmed that the relationship between the biomass and the spectrum is independent of the Altamira and Bragantina regions, and that it was appropriate to pool sampled data from both regions in the proposed model. The model development methodology and the model produced from this research will be of value to researchers using the spectrum-biomass modeling approaches to estimate the biomass and study the SS rates in moist tropical forests.

Degraded pasture distribution and woody enrichment strategies for pasture fertility preservation in the Bragantina region, north-eastern Amazon

In the densely settled Bragantina region, northern Brazil, smallholder cattle pastures start into compulsory degradation processes indicated, among other factors by the woody encroachment of the resprouting secondary vegetation, nationally called capoeira. By means of Landsat and QuickBird satellite imagery techniques different stages of treedominated pastures were identified and the distribution of degraded pastures quantified. This was tested in a supervised Landsat classification from 2006 and 2007, taking QuickBird imageries from 2004 and 2005 as additional ground checks. We found that 42% of the rural Bragantinian landscape has already converted into pastures, 28% in advanced stages of above ground pasture degradation. Our reclassification means that the region is still confronted with a serious ecological pasture problem and that conventional land use classifications, climatological models and carbon calculations, based on Landsat imageries only, underestimate pasture distribution and thus lead to inaccurate extrapolations. As the resprouting shrubs of the capoeira are a permanent problem on tropical lowland pastures but, on the other hand, are also the ecological basis of the sustainable slash-and-burn systems of smallholders, we tested some innovative strategies to tolerate various useful woody components of the capoeira on pastures to stabilise them ecologically: first, a buffet trial shows that the ten tested capoeira and some other common domesticated tree species obtain a comparable palatability as well-known woody forage legumes. Thus, Cecropia palmata and Tithonia diversifolia, among others, were as palatable for cattle as the well-known multi-purpose legume Cratylia argentea. As a consequence, these freely accessible tree species should not be slashed but fostered on pastures, like supplementary forage plants. Secondly, it is demonstrated that the multi-purpose forage legumes C. argentea and Flemingia macrophylla perform better under smallholder management than under large scaled farming or even intense management due to the associated prolonged restoration times. In sum, we could demonstrate that woody components (capoeira and/ or woody legumes) are more appropriate for the humid tropics than pure grass-monocultures. Based on these experiences, we modified the model of a grass-capoeira-legume pasture, incorporating pastures just as an interim stage of the slash-andburn system. Forage production could be enhanced in that system by selective slashing of the capoeira (palatable species are tolerated) and by incorporating woody forage legumes. As this biome is known to restore its ecosystem fertility rather in its above-ground biomass than in its poor soils, woody components on pastures are recommended for ecologically sustainable production systems. Furthermore, they might be requisite to mitigate the proclaimed climatic change in the Amazon.

“The Nature We All Want”—Influences of São Paulo Metropolis on Tourism Development in the Bragantina Region, São Paulo, Brazil

The metropolis of São Paulo comprises the largest urban conglomerate and the most important industrial park in the southern hemisphere and its urban expansion has taken place without any significant concern for its cultural, historical or natural patrimony and tourist potential, leading to a gradual homogenization and depersonalization of the urban area. The Bragantina region, located in the north of the São Paulo metropolis, is nowadays its last urban frontier. Due to difficult access, this region underwent a slow urbanization process that allowed the conservation of an historical and cultural patrimony dating back to the colonial period and of significant remnants of Atlantic forest, one of the tropical forests most threatened with extinction in the world. The doubling of the regional highways that took place in the last 15 years has brought profound changes to the Bragantina region. Nowadays this region is intensively used as a tourist destination for weekend homeowners, events and environmental tourism. Visitors come mainly to explore its natural and cultural aspects, that are sold by real-estate agents and tourism agents, mainly through the use of images in advertisements and folders, as a piece of “wild nature” still preserved on the borders of São Paulo. This approach creates a perspective, described as a simulacrum, a false reality, that is reflected in the ideas of nature held by different tourists and other social actors, but that doesn't express the regional reality. Because intensification of land use has not been accompanied by effective conservation, public policies or involvement of local communities in regional planning, the historical, cultural and environmental patrimony is suffering a range of impacts. In this study we analyse the problems generated by tourism and urbanization in the Bragantina region that have resulted from the expansion of the São Paulo metropolis and characterize ideas of nature that are expressed by different social actors, including tourists, that seem to relate to and to perceive the Bragantina region as an unspoiled and preserved natural area where “nature” can still be found, and where natural resources are saved from environmental degradation, in spite of the actual environmental and cultural changes.

Bird records from the rural landscape of Igarapé-Açu municipality, Northeastern Pará

This paper reports on bird records from the little studied Bragantina region, in the densely populated Northeastern Amazon. This region was a center of human colonization in the last century, resulting in the nearly complete replacement of rainforests by a dynamic, mosaic-like rural landscape pattern. From February 1999 to January 2001, I surveyed birds at three sites: a 25-ha smallholding farm, and around two small lakes, in the municipality of Igarapé-Açu. Bird species were recorded along 36 days during an agricultural experiment. As would be expected, species lists from these sites show reduced bird diversity in comparison to primary forests. They also reveal a preponderance of robust, widespread generalists, such as Crotophaga ani (Linnaeus, 1758), Ramphocelus carbo (Pallas, 1764), and Columbina passerina (Linnaeus, 1758). However, endemic Xipholena lamellipennis (Lafresnaye, 1839), Tachybaptus dominicus (Linnaeus, 1766), and Primolius maracana (Vieillot, 1816) (high count of 34 at one time), were also observed. In all, 110 bird species (representing 95 genera and 40 families) are listed with information about abundance and habitat. More detailed surveys of this region are recommended, which should focus on gallery forests that might serve as refuges for some forest species

Oropouche fever epidemic in Northern Brazil: Epidemiology and molecular characterization of isolates

Background Oropouche fever virus is an important arbovirus associated with febrile disease that re-emerged in 2006 in several municipalities of Pará State, Bragantina region, Amazon, Brazil, 26 years after the last epidemic. Objective To investigate an Oropouche fever outbreak in this region. Study design A serologic survey and prospective study of acute febrile cases were performed in Magalhães Barata (urban and rural areas) and Maracanã (rural area) municipalities. Serology (IgM-ELISA and hemagglutination-inhibition [HI]), virus isolation, RT-PCR and real-time-PCR were used to confirm Oropouche virus (OROV) as responsible for the febrile outbreaks. Results Real-time-PCR showed high titers of OROV in acute-phase serum samples from febrile patients. From 113 of 119 acutely febrile patients with paired serum samples, OROV infections was confirmed by serologic conversion ( n = 76) or high titers ( n = 37) for both HI and IgM-ELISA. Patients had a febrile disease characterized by headache, chills, dizziness, photophobia, myalgia, nausea, and vomiting. Females and children under 15 years of age were most affected. Nucleotide sequencing of six OROV isolates identified that genotype II was associated with the human disease epidemic. Conclusions Oropouche fever, which has re-emerged in the Bragantina region in eastern Amazon 26 years after the last epidemic, is caused by genotype II, a lineage previously found only in Peru and western Brazil.

Poor but allocatively efficient—evidence from the Eastern Amazon

AbstractThis research empirically investigates the well‐known “poor‐but‐efficient” hypothesis formulated by Schultz (1964) assuming that small‐scale farmers in developing countries are reasonably efficient in allocating their scarce resources by responding positively to price incentives. Deviating from Schultz it is assumed here that scale effects explain a considerable proportion of small‐scale farmers' relative efficiency. The theoretical underpinnings of the scale efficiency concept are briefly reviewed before a normalized generalized Leontief (GL) profit function is modeled by using its output supply and input demand system to capture the joint production of cassava flour and maize by a sample of small‐scale farmers in the Bragantina region of the Eastern Amazon, Brazil. The discussion of theoretical consistency and functional flexibility is considered by imposing convexity on the GL profit framework. The empirical results confirm our revised hypothesis that small farmers in traditional development settings are “poor‐but‐allocatively efficient” by clearly suggesting considerable inefficiency with respect to the scale of operations.

Feasibility of mulching technology as an alternative to slash-and-burn farming in eastern Amazon: A cost–benefit analysis

AbstractThis paper addresses the question as to whether it is profitable to apply a mechanical mulching technology (MT) in the Bragantina region of Brazil and assesses the technology's feasibility as an alternative to the slash-and-burn practices of the Amazon. Using empirical data collected from a prototype assessment and a few secondary sources, the paper employs a cost–benefit analysis of ‘with’ and ‘without’ technology cropping systems (plots that applied the technology are compared with those that did not) to assess the financial and economic feasibility of investing in the MT. The analysis showed that the technology is profitable, both financially and socially, mainly because it is able to produce yields that are high enough to offset the costs, including the hiring of the mulching equipment. However, it may not be a feasible alternative to slash-and-burn farming unless certain conditions are fulfilled by farmers. Most of these conditions relate to farmers' adherence to a set of rules for the successful application of the technology. These rules include the abandonment of a single cropping cycle, typical for the traditional slash-and-burn system, and the adoption of two cycles of crop cultivation. In addition, farmers have to choose profitable crop combinations, such as cassava and beans for both cycles. Since most of the trial farmers did not meet these conditions, the technology received a notably low acceptability (8%). Further analysis indicated that the main reason for this trend was the increase of total labor requirement (by 32%), though the technology reduced labor demand during land preparation to almost zero. Similarly, there was a 22% increase in requirement for inorganic fertilizers. Thus, compared with the slash-and-burn practices of the Amazon, the MT can be regarded as a more intensive method of farming which gives higher crop yields but demands higher quantities of inputs such as labor and inorganic fertilizers. The paper concludes by deriving policy implications for the feasibility of the MT as an alternative to slash-and-burn agriculture in the Amazon. Among these is the importance of creating incentives to extend the cropping period from one to two consecutive cycles. Moreover, the necessity to conduct further studies after the technology has been adopted by the farmers is underscored.

Integrating cattle into the slash-and-burn cycle on smallholdings in the Eastern Amazon, using grass-capoeira or grass-legume pastures

Abstract In the humid tropics of northern Brazil, where slash-and-burn cropping is the prevailing smallholder land use system, pastures ecologically degrade after 7–10 years of use, mostly due to invading vegetation, decline of soil fertility (N, P) and insect pests. Degraded pasture areas cannot be easily restored or returned to cropping, so large areas are abandoned. To avoid this degradation process, two alternative pastures were tested to incorporate cattle into the slash-and-burn cropping cycle. It was thought that the inclusion of secondary woody fallow vegetation, locally called capoeira, or of legumes in pastures restores the soil for a subsequent cropping phase while allowing an acceptable level of animal performance. This hypothesis was tested in a researcher-managed on-farm experiment in Igarape-Acu (Bragantina region, Para). A grass-legume pasture (GLP), combining the grass Brachiaria humidicola with three multi-purpose legumes, was compared with a pasture, where controlled regrowth of capoeira was tolerated (GCP), and tested against two controls in the form of a conventional B. humidicola pasture (GP) and undisturbed regrowth of capoeira (UC). The pastures were grazed in a rotational system for 2 years at 1.5 livestock units (LU) ha−1 in the first year and at 1.2 LU ha−1 in the following year. The results showed that the GCP kept the full regenerative potential of the capoeira, showing no significant loss of phytodiversity (GCP 67 species 100 m−2; UC 72 species 100 m−2) and low dissimilarity in species composition measured by Euclidian distance (UC/GCP = 51; UC/UC = 52; GCP/GCP = 33). On the GLP, the legumes Arachis pintoi and Cratylia argentea almost disappeared due to the grazing pressure, while Chamaecrista rotundifolia var. grandiflora was little palatable and invaded the plots by seed propagation. None of the legumes produced a meaningful quantity of nodules, and no difference in total soil N was found between GLP and the other pasture treatments. With regard to animal production, both alternative pastures were less productive than GP over 21 months of grazing (GLP = 384 kg liveweight ha−1, GCP = 474 kg ha−1, GP = 659 kg ha−1), which was attributed to overstocking in the second year. GCP was considered to be an interesting option for smallholdings, provided the balance between the vigorous regrowth of capoeira and forage grass cover can be maintained. In contrast, on GLP a more palatable Ch. rotundifolia accession would be desirable and the establishment of all legumes needs to be improved. It was concluded that GCP would support a subsequent cropping phase better than GLP. However, on both pastures stocking rates would have to be frequently adjusted a management practice that is of secondary consideration in a crop/livestock system in which cattle are kept as cash-generating assets.

Dimensões humanas do uso e cobertura das terras na Amazônia: uma contribuição do LBA

O entendimento das mudanças em paisagens amazônicas depende de documentação das alterações na cobertura da terra. Este artigo parte de resultados do Experimento de Larga Escala de Biosfera-Atmosfera na Amazônia (LBA) relativos ao tema para focalizar um estudo transversal que analisa as dimensões sociais e biofísicas dessas transformações. As áreas de estudo representam um gradiente de fertilidade de solos e inclui distintos mosaicos de paisagens, desde o estuário Amazônico e a Região Bragantina até o nordeste de Rondônia. Áreas de assentamento rural são enfatizadas, devido a sua relevância social e a seus impactos sobre a cobertura das terras em escala local e regional. Para exemplificar o potencial destes estudos, apresentamos resultados comparativos para Machadinho d'Oeste e Vale do Anari, RO. A análise multitemporal utilizou imagens do satélite Landsat e levantamentos de campo. Proprietários, seringueiros, madeireiros e outros atores locais foram entrevistados sobre seus sistemas de produção e a história de uso das terras. O cálculo de métricas espaciais embasou nossas conclusões. Os resultados indicam que o desenho do assentamento e aspectos institucionais têm um papel importante no processo de alteração da paisagem. A combinação de lotes privados com reservas comuns, manejadas por populações locais, pode produzir efeitos positivos na manutenção de maiores manchas de floresta. A metodologia utilizada oferece potenciais de integração, análise e monitoramento do uso e cobertura das terras na Amazônia, visando fornecer subsídios a políticas que valorizem as dimensões sociais e ambientais do desenvolvimento da região.

Nutrient balance of shifting cultivation by burning or mulching in the Eastern Amazon – evidence for subsoil nutrient accumulation

For over a hundred years shifting cultivation with slash-and-burn land preparation has been the predominant type of land use by smallholders in the Bragantina region of the Brazilian Eastern Amazon. This study contrasts the nutrient balance of slash-and-burn agriculture with a fire-free cultivation. Therefore, one half of a 3.5-year-old (28.7 t DM ha–1) and a 7-year-old woody fallow vegetation (46.5 t DM ha–1) was burnt and the other half mulched, leaving the biomass as a surface residue. Subsequently, a sequence of maize, beans and cassava was cropped for 1.5 year. Burning the 3.5- and 7-year-old fallow removed 97 and 94% of the C, 98 and 96% of the N, 90 and 63% of the P-stocks, and between 45 and 70% of the cations K, Mg and Ca of the aboveground biomass by volatilization or ash-particle transfer. These losses were avoided with the slash-and-mulch land preparation. Mulching did not increase the losses of nutrients by leaching, despite the high amount of rapidly decomposing surface mulch. Also the length of preceding fallow had no significant influence on leaching losses. At a depth of 3 m, leached nutrients were quantitatively negligible in both treatments. Comparing the nutrient fluxes at soil depths of 0.9 m, 1.8 m and 3 m, the amounts of all mobile nutrients, and also of chloride and sodium were markedly reduced during percolation and must have been retained. It is likely that nutrient retention in the subsoil layer is only temporary, emphasizing the need for a rapid re-establishment of the naturally deep-rooting secondary vegetation after abandonment of sites to enable uptake of these nutrients. The overall nutrient balance was highly negative for slash-and-burn. 291 and 403 kg N ha–1, 21 and 18 kg P ha–1, and 70 and 132 kg K ha–1 were removed from the burnt plots with a preceding fallow of 3.5 and 7 years, respectively. A reduced fallow period (3.5 years), which is a common trend in the region, resulted in a higher mean annual rate of nutrient loss averaged over the duration of the cycle than a fallow period of 7 years. Eliminating the burning losses by mulching brought the agricultural system back to an equilibrated or even slightly positive nutrient balance, even after a reduced fallow period. Thus, slash-and-mulch is a viable alternative to maintain agricultural productivity and ecosystem functioning.

Labile Phosphorus in Soils of Forest Fallows and Primary Forest in the Bragantina Region, Brazil

ABSTRACTWe used the Hedley sequential extraction procedure to measure nine different organic inorganic soil phosphorus fractions in forest soil of the Bragantina region of Para, Brazil. We compared the labile fractions (resin‐extractable P + HCO3‐extractable inorganic and organic P) in Oxisols from three secondary forests (10, 20, and 40 years old) and a primary forest. These stands were located in an area that has supported shifting agriculture for approximately a century. After agricultural use, total P and labile P in soils of young secondary forests are diminished compared to the amounts presents in the primary forest soil. Within each stand, organic carbon content was a good predictor of labile organic and inorganic P, consistent with the large body of research indicating that mineralization of organic matter is important to plant nutrition in tropical ecosystems. During the reorganization of P pools during forest development, the pool of labile organic P (HCO3‐extractable) diminishes more than the other labile fractions, suggesting that it is directly or indirectly an important source of P for the regrowing forest vegetation. Across the four age classes of forest, the soil reservoir of labile P was equal to or greater than the total amount of P in the vegetation. If labile P measured by this method adequately represents P available to plants in the short term (as suggested by the current consensus), we would conclude that plant‐available P is reasonable abundant, and that the effects of agriculture on available P pools are detectable but not sufficient to compromise forest regrowth in this area.

Labile Phosphorus in Soils of Forest Fallows and Primary Forest in the Bragantina Region, Brazil1

Abstract We used the Hedley sequential extraction procedure to measure nine different organic and inorganic soil phosphorus fractions in forest soils of the Bragantina region of Para, Brazil. We compared the labile fractions (resin-extractable P + HCO3-extractable inorganic and organic P) in Oxisols from three secondary forests (10, 20, and 40 years old) and a primary forest. These stands were located in an area that has supported shifting agriculture for approximately a century. After agricultural use, total P and labile P in soils of young secondary forests are diminished compared to the amounts present in the primary forest soil. Within each stand, organic carbon content was a good predictor of labile organic and inorganic P, consistent with the large body of research indicating that mineralization of organic matter is important to plant nutrition in tropical ecosystems. During the reorganization of P pools during forest development, the pool of labile organic P (HCO3-extractable) diminishes more than ...

Landscape dynamics and equilibrium in areas of slash-and-burn agriculture with short and long fallow period (Bragantina region, NE Brazilian Amazon)

Fallow periods used in slash-and-burn agriculture in the Bragantina region, the oldest agricultural frontier in the Brazilian Amazon, are being reduced. The objective of this study was to analyze the effects of a shortened fallow period on the Bragantina landscape dynamics and equilibrium. Dynamics were characterized by landscape structural changes, particularly in the spatial distribution of secondary forests, and by transition matrix. Equilibrium was defined by temporal and spatial parameters, and by the increment of agricultural areas from 1985 to 1996, analyzed with 6 LANDSAT-TM images. I worked with 6 areas of 250 ha each, 3 with short fallow periods (2‐4 years) and 3 with long fallow periods (about 10 years). Results showed that short fallow period areas did not present an equilibrium situation. In these areas, developed secondary vegetation tended to disappear and agricultural areas were being expanded at an average rate of 3% per year. Landscape structure changes pointed out that a reduction in fallow period was occurring in already short fallow period areas. Long fallow period areas presented a shifting mosaic steady-state condition, where punctual changes due to agricultural uses were compensated by field abandonment rate. Both agricultural uses and field abandonment rates were lower in long fallow period areas when compared with short ones. Comparisons with indigenous traditional cropping-fallow cycles indicate that sustainable conditions could be maintained with 11 years of fallow for each cropping year, while shorter cycles would break down the system if agricultural improvements are not implemented.

White-thread blight: five new hosts in the state of pará, brasil

Since the first description of Pellicularia koleroga Cooke, at present classified as Ceratobasidium stevensii (Burt) Venkat. (sin: Corticium koleroga (Cooke) v. Hohn., Koleroga noxia Donk, Botryobasidium koleroga Cooke) by Deslandes (Bol. Fitossanitario 1:197, 1944), more than 40 important agricultural and forestry species were reported to be damaged by the white-thread blight, making evident the importance of that pathogen to the Amazon region (Albuquerque, Seminario Tecnico, EMBRAPA-IPEAN, 1973; Silva et al., Fitopatol. bras., 8:601, 1983; Lourd & Alves, Fitopatol. bras., 12:88, 1987; Furtado, Manual de Fitopatol., 1997; Benchimol & Muller, Embrapa-CPATU, Comunicado Tecnico 99, 1999; Gasparotto & Silva, Fitopatol. bras., 24:469, 1999). C. stevensii penetrates the plant by natural chaps or twig axils, showing up as whitish mycelial cords (rhizomorphs) that develop upon the host twigs and leaves, causing them to dry. The dead leaves remain hanged on the twigs by the pathogen mycelium as a characteristic sign of the white-thread blight (Figure 1). Morphological and physiological characteristics of the pathogen and disease control were described by Roger, L. (Phytopathologie des Pays Chauds, Lechevalier, 1949). Surveys on Bragantina region plantings, State of Para, Brazil, detected damages caused by C. stevensii on Neem (Azadirachta indica A. Juss.), African mahogany (Khaya ivorensis A. Chev.), coconut (Cocos nucifera L.), banana (Musa L. cv. yangambi) and ornamental Ixora (Ixora coccinea L.). Reproduction of white-thread blight symptoms under greenhouse conditions was obtained about one week after mycelial PDA plug inoculation on the abaxial face of the young leaves of these hosts left in a dew chamber for 48 h. FIG. 1 Signs of Ceratobasidium stevensii (arrows) on (a) K. ivorensis; (b) A. indica; (c) I. coccinea; (d) C. nucifera; (e) Musa sp.