Agricultura e mudanças do clima no Estado do Tocantins: vulnerabilidades, projeções e desenvolvimento

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Factors driving the biogeochemical budget of the Amazon River and its statistical modelling Facteurs denext term contrôle du bilan biogéochimique previous termdenext term l'Amazone et modélisation statistique associée

International audienceThe seasonal and interannual fluctuations of the biogeochemical budget (solutes, suspended matter, isotopes) of the Amazon River basin were analyzed, with a special focus on 44 physicochemical parameters monitored over the period 1982-1984 during the Carbon in the AMazon River Experiment (CAMREX) project. The relevant factors driving this variability were identified and sorted through the implementation of a statistical-regressive model coupled to variance analysis. Basically, the compositional fluctuations in the Amazon River are related (1) to the variable contribution of major tributaries (variable regional source) to the river flow but also (2) to the variable contribution of hydrological sources, (3) to river processes, i.e. in-stream diagenesis and sediment dynamics and (4) to the hydrological budget of the floodplains. Their respective contributions to the variability of chemical signals observed in the stream waters depend on which parameter was investigated but their combination explains on average 85% of the observed variability. The variability related to regional sources was captured by the compared measures of flow discharge and biogeochemical fluxes at the outlet of the major tributaries. The variability of hydrological sources was described by the variable contribution of three runoffs of distinct but constant composition: forwarded direct runoff, delayed floodplain runoff and baseflow. Several methods were tested to depict the seasonal and interannual variations of their individual discharges. Biologically-mediated processes were related to a hydrobiological index IBIO = [O2]-[CO2] which allows tracking the nature of the dominant ecological regime (autotrophy vs. heterotrophy). The alteration of chemical signals related to the intermittent discharge of the floodplains (where specific processes occur such as: gas exchanges at the air-water interface, sorption of dissolved organic matter, chemical weathering, deposition vs. remobilization of sediments, etc.) was simulated by taking into account the default of hydrological balance between inflows and outflows, used as a marker of floodplains discharge. This analysis shows that the chemical baseline observed in the waters of the Amazon River is mostly acquired upstream from the junction of major tributaries with the Amazon main reach. Les fluctuations saisonnières et interannuelles du bilan biogéochimique (solutés, matière particulaire, isotopes) du fleuve Amazone ont été analysées, avec une attention particulière apportée à 44 paramètres physicochimiques mesurés entre 1982 et 1984 dans le cadre du programme CAMREX. Les facteurs exerçant une influence significative sur cette variabilité ont été identifiés et hiérarchisés par le biais d'un modèle statistique couplé à une analyse previous termdenext term variance. Les variations previous termdenext term composition des eaux previous termdenext term l'Amazone sont fondamentalement associées (1) à previous termlanext term contribution variable previous termdenext term ses affluents majeurs (source régionale variable) au débit total, mais aussi (2) à previous termlanext term contribution variable des pôles previous termdenext term mélange hydrologiques, (3) à des processus fluviaux correspondant au régime hydrobiologique et à previous termlanext term dynamique sédimentaire et (4) au bilan hydrologique des plaines d'inondation. Leurs contributions respectives à previous termlanext term variabilité des signaux chimiques observés dans les eaux du fleuve dépendent du paramètre considéré, mais leur combinaison explique en moyenne 85 % previous termde lanext term variabilité observée. previous termLanext term variabilité associée aux contributions régionales variables est appréhendée en procédant aux bilans entrées-sorties des débits et flux biogéochimiques. previous termLanext term variabilité previous termdenext term contribution des pôles previous termdenext term mélange est décrite par previous termlanext term contribution variable previous termdenext term trois écoulements previous termdenext term compositions distinctes mais constantes : l'écoulement direct à expression précoce, l'écoulement local previous termdenext term vidange alluviale à expression différée et l'écoulement previous termdenext term base. Douze méthodes ont été testées afin previous termdenext term décrire les variations saisonnières et interannuelles des débits individuels previous termdenext term chaque pôle previous termdenext term mélange. Les processus contrôlés par le vivant sont appréhendés à partir d'un indice hydrobiologique IBIO = [O2]-[CO2] qui permet previous termdenext term déterminer previous termlanext term nature du régime hydro-écologique dominant (autotrophe vs. hétérotrophe). L'altération des signaux chimiques générée par previous termlanext term vidange intermittente des plaines d'inondation (au niveau desquelles ont lieu des processus spécifiques : échanges gazeux, sorption previous termdenext term matière organique dissoute, érosion chimique, dépôt vs. remise en suspension previous termdenext term sédiments, etc.) est simulée en prenant en compte le défaut previous termdenext term bilan hydrologique entrées-sorties utilisé comme marqueur previous termdenext term débit des plaines d'inondation. Cette analyse montre que le bruit previous termdenext term fond chimique observé dans les eaux du fleuve Amazone est principalement acquis en amont des confluences entre le tronçon fluvial étudié et les principaux affluents qui l'alimentent

Biogeochemistry of the Amazonian Floodplains: Insights from Six End-Member Mixing Models

International audienceThe influence of Amazonian floodplains on the hydrological, sedimentary, and biogeochemical river budget was investigated along the Vargem Grande–Óbidos reach, by applying six mixing models based on variable regional and/or variable hydrological sources. By comparing the output of many different models designed for different purposes, the nature and the magnitude of processes linking water and biogeochemical budgets of the Amazonian floodplains were clarified. This study reveals that most of the chemical baseline of the Amazon River basin is acquired before the studied 2000-km Amazonian reach. However, the tight connection between the hydrograph stage of the river and the chemical signals provides insightful information on the dynamics of its floodplains. The chemical expression of biotic and abiotic processes occurring in the Amazonian floodplains can be particularly perceived during falling waters. It appears delayed in time compared to the maximum extension of submerged area, because the alternating water circulation polarity (filling versus emptying) between the main channel and the adjacent floodplains determines delayed emptying of floodplains during falling waters. It results also in a longer time of residence in the hydrograph network, which strengthens the rate of transformation of transiting materials and solutes. Biotic and biologically mediated processes tend to accentuate changes in river water chemistry initiated upstream, in each subbasin, along river corridors, indicating that processes operating downstream prolong those from upstream (e.g., floodplains of the large tributaries). Conversely, the flood wave propagation tends to lessen the seasonal variability as a result of the water storage in the floodplains, which admixes waters of distinct origins (in time and space). The morphology of floodplains, determining the deposition and the diagenesis of the sediments as well as the variable extension of submerged areas or the chronology of floodplains storage/emptying, appears to be the main factor controlling the floodplains biogeodynamics. By coupling classical end-member mixing models (providing insight on hydrological source) with a variable regional contribution scheme, relevant information on the biogeochemical budget of the Amazonian floodplains can be achieved

Variabilidade clínica na determinação da dose tóxica oral em intoxicação experimental por fluoroacetato de sódio em gatos

O fluoroacetato de sódio (FAS) ou composto 1080 é um potente rodenticida utilizado no controle de roedores e predadores mamíferos. Sua utilização está proibida por lei em diversos países devido à sua alta toxicidade, mas no Brasil há evidências do uso ilegal e sem critérios causando intoxicações, principalmente em crianças e animais domésticos. O FAS age por meio do seu metabólito tóxico, o fluorocitrato, no bloqueio do ciclo de Krebs com conseqënte diminuição da produção de energia do organismo, provocando principalmente manifestações clínicas neurológicas e cardíacas. No presente estudo compararam quatro doses orais tóxicas do fluoroacetato de sódio, descritas em gatos, na literatura, observando-se o aparecimento dos sinais clínicos predominantes da intoxicação, as diferenças entre as doses quanto a variabilidade clínica em relação ao período de latência para o aparecimento dos sinais clínicos e sua respectiva intensidade. A dose oral tóxica que melhor caracterizou o quadro clínico da intoxicação por FAS em gatos, sem causar a letalidade aguda, foi de 0,45mg/kg. As diferenças entre as manifestações clínicas foram dose-dependentes e em ordem crescente de intensidade, caracterizando-se como sinais leves (dose 1: 0,3mg/kg), leves a moderados (dose 2: 0,4mg/kg), moderados a graves (dose 3: 0,45mg/kg) e graves (dose 4: 0,5mg/kg). Houve também variabilidade clínica individual entre animais intoxicados com a mesma dosagem do tóxico.The sodium monofluoroacetate (FAC) or compound 1080 is a potent rodenticide used for a rodents and vertebrate pest control. It was prohibited in many countries because of its high toxicity, but in Brazil exist evidences of ilegal use causing the intoxication in children and domestic animals. The fluoroacetate metabolite, fluorocitric acid, blocks body energy production by inhibit the Krebs cycle, resulting in neurological and cardiacs signs. In the present study, four group of oral toxic dosis of the FAC were compared in cats. The best oral toxic dose for clinical signs presentation, without cause acute lethality, was 0,45mg/kg. The clinical variability was dosis dependent and its intensity , in crescent order, was: light signs (dose 1: 0,3mg/kg), light to moderate (dose 2: 0,4mg/kg), moderate to severe (dose 3: 0,45mg/kg) and severe (dose 4: 0,5mg/kg). There was individual clinical variability between animals that received the same oral toxic dose

Associação entre o porte da planta do feijoeiro e o tamanho dos grãos

The widest use of technology in bean culture in Brazil has required cultivars to present more upright architecture. However, every available cultivated material which showed that sort of architecture, possesses small seeds which have less commercial acceptance. For this reason, this work was conducted over the period from February 1993 to November 1994, to verify whether there is any association between these two traits. For this goal, the F2, F3, F4 and F5 generations from the crosses Milionário x Flor de Mayo, EMGOPA 201-Ouro x Manteigão Fosco 11 and Rio Vermelho x Roxo PV were used. The screening experiments of the F3, F4 and F5 families were carried out at the Universidade Federal de Lavras, in Lavras, MG, Brazil. This latter generation was also evaluated at Patos de Minas, MG, Brazil. The results obtained showed that the existence of correlation between the score of architecture and yield was not found, but a general bias of positive association between the weight of 100 seeds and yield was verified. In an overall way, no association between the architecture score and the seed weight was observed, showing to be possible to select upright plants with any seed size. However, the frequency of upright architecture families (score inferior to 3) and 100 seeds weight above 25 grams was very low.O maior emprego de tecnologia na cultura do feijoeiro no Brasil tem exigido que as cultivares apresentem porte mais ereto. Contudo, todos os materiais cultivados disponíveis que apresentam porte ereto possuem sementes pequenas, e por isso têm menor aceitação comercial. Foi realizado este trabalho no período de fevereiro de 1993 a novembro de 1994, para verificar se existe associação entre o porte do feijoeiro e o tamanho de suas sementes. Foram utilizadas, para isso, as gerações F2, F3, F4 e F5 dos seguintes cruzamentos: Milionário x Flor de Mayo, EMGOPA 201-Ouro x Manteigão Fosco 11 e Rio Vermelho x Roxo PV. Os experimentos de avaliação das famílias F3, F4 e F5, foram conduzidos na Universidade Federal de Lavras, em Lavras, MG. Esta última geração foi também avaliada em Patos de Minas, MG. A correlação entre a nota do porte da planta e a produção de grãos é inexpressiva. Já a correlação entre o peso de 100 sementes e a produção de grãos é positiva. Não há associação entre a nota do porte e o peso de 100 sementes, o que indica ser possível selecionar plantas eretas com qualquer tamanho de sementes. Contudo, a freqüência de famílias com porte ereto (nota inferior a 3) e peso de 100 sementes acima de 25 gramas, foi muito pequena

Implicações das mudanças do clima no zoneamento agroclimático da cana-de-açúcar no estado do Tocantins, considerando o modelo GFDL.

Tem havido a expansão do complexo sucroalcooleiro para as regiões Centro-Norte do país, devido ao aumento da demanda pelo etanol, tornando relevante a elaboração do zoneamento agroclimático para a cultura da cana-de-açúcar para essas regiões, notadamente para o estado do Tocantins. As informações climáticas e edáficas favorecem a determinação de áreas mais aptas ao cultivo e à mecanização. Por outro lado poderá ocorrer a elevação do risco climático nas regiões produtoras devido à possível influência das mudanças do clima. O presente estudo visou simular o impacto das mudanças do clima sobre o zoneamento agroclimático para a cana-de-açúcar no Tocantins, considerando os dados do modelo GFDL e cenários de emissão B1 e A1B, para o período de 2021 a 2050. Os resultados mostraram que tanto para as condições climáticas atuais, quanto para projeção do modelo, não há restrição térmica para o desenvolvimento da cultura, e que para obter boa produtividade no Estado será necessário, de forma geral, a utilização de irrigação nos períodos de deficiência hídrica. Constatou-se que, existe potencial para a produção, apesar da predominância da classe de aptidão ?restrita?, e que as regiões potenciais com condições agroclimáticas favoráveis, estão localizadas no sul, sudeste e centro do Estado. As simulações dos cenários de emissões indicam fortes restrições hídricas para o Tocantins, com grande redução de áreas consideradas ?aptas? e ?marginais?, e aumento das áreas ?restritas? ao cultivo da cana-de-açúcar

Potenciais efeitos dos cenários futuros do clima na aptidão agroclimática da cana-de-açúcar no estado do Tocantins.

O presente trabalho teve como objetivo geral de elaborar o zoneamento agroclimático para a cultura da cana-de-açúcar no Estado do Tocantins, considerando a condição do clima atual e projeções de possíveis impactos das mudanças climáticas com base nos resultados dos modelos GFDL e HadCM3 para dois cenários de emissões, que integram o AR4 do IPCC (2007), bem como dos modelos Eta MIROC5 e Eta HadGEM2-ES, para dois cenários do AR5 (IPCC, 2013), considerando o período de 2021 a 2050