Aristides Ribeiro

Disponibilidade hídrica do solo e produtividade do eucalipto em três regiões da Bacia do Rio Doce

The productivity of eucalyptus stands found in Belo Oriente, Nova Era and Guanhaes areas in the Rio Doce Basin, Minas Gerais State were analyzed. The precipitation events occurred over the rainy seasons as well as the water balance components by Thornthwaite and Mather, in 1955, relative to the period from January 1985 to December 1998 were studied, in order to determine the influence of these components on the gain of the annual average volume of wood (m3ha-1). To do so, the forest inventory data from the Empresa Florestal Celulose Nipo-Brasileira - CENIBRA, relative to the 3 - 7 year age range, were used. Wood productivity was affected by the total precipitation in the rainy season (PEC). The lowest values of the monthly periodic increment (IPM) were observed in those years preceded by dry (S) or very dry rainy season (MS), whereas the highest IPM values occurred in those years preceded by rainy season so-classified as rainy (C) or very rainy (MC). Taking into account that this fact was more pronounced in both Guanhaes and Nova Era, the correlation between PEC finished at every year and IPM for either the increase (1986 to 1992) and decrease periods (1992 to 1995) in PEC were verified; these correlations reached a r2above 80%. For a 100 mm increase in PEC from a year to another, the increase in IPM averaged 0.445 m3ha-1mo-1, whereas for a reduction of 100 mm the decrease in IPM was 0.64 m3ha-1mo-1 for both regions. Guanhaes showed the highest average site index as well as the highest average productivity, following the Nova Era and Belo Oriente regions.

Mecanismos de controle da variação sazonal da transpiração de uma floresta tropical no nordeste da amazônia

No presente trabalho foram estudadas a variacao sazonal da transpiracao, de uma floresta tropical, e sua dependencia com fatores bioticos e abioticos. Utilizaram-se dados do projeto CARBOPARA, parte integrante do Experimento de Grande Escala da Biosfera-Atmosfera na Amazonia (LBA), coletados na reserva florestal de Caxiuana, regiao nordeste da Amazonia. A evapotranspiracao total num intervalo de 39 dias para o periodo chuvoso foi 108,2 mm, com valor medio de 2,9 mm dia-1, enquanto, durante o periodo menos chuvoso, a evapotranspiracao total num intervalo de 29 dias foi 128,8 mm, com media de 4,3 mm dia-1 para o periodo. Os valores maximos da condutividade de superficie (Cs), nos dois periodos, ocorreram as 08:00 hl, sendo estes valores de 0,060 m s-1 e 0,045 m s-1 para o periodo chuvoso e menos chuvoso, respectivamente. A condutância aerodinâmica media (Ca) foi 0,164 m s-1 e 0,210 m s-1, para os periodos chuvoso e menos chuvoso, respectivamente. Os valores maximos da Ca observados para os periodos chuvoso e menos chuvoso foram, respectivamente, 0,220 e 0,375 m s-1. Verificou-se que Cs guarda uma relacao exponencial inversa com o deficit de vapor de agua atmosferico, para diferentes intervalos de irradiância solar global. A analise horaria do fator de desacoplamento sugere que a evapotranspiracao, durante a manha, tem um maior controle realizado pela disponibilidade de energia, quando comparado ao periodo menos chuvoso. Durante a tarde verifica-se que o dossel da floresta progressivamente tende a estar mais acoplado a atmosfera, para ambos os periodos estudados, demonstrando maior controle superficial na transpiracao.

Zoneamento agroclimático da cultura do café para a Bacia do Rio Doce

It was aimed in this work, through the geospatialization, the identification of the apt, restricted and inapt regions for cultivation of coffee (Coffea arabica L.) in Rio Doce watershed. It was used for such, temperature and water deficit data of 50 meteorological stations installed in the watershed and in bordering watershed. The data of water deficit were determined using the water balance according to Thornthwaite & Mather (1955). They were identified equivalent regions the one third of the watershed, located in the central part and in the northeast of the same, as being inapt to the cultivation of coffee, according to the productivity criterions related with the thermal and hydric demands of culture.

Comments on “The Regional Evapotranspiration of the Amazon”

Werth and Avissar (2004) review four methods of estimation of the seasonal variability of the regional evapotranspiration (ET) of the Amazon region: a net radiation method, a water budget method, a global climate model method, and a data assimilation method. They noted that the seasonal ET estimates fit in two different groups: one that typically follows the net radiation seasonal cycle, while the other typically follows the precipitation seasonal cycle. This division actually encompasses another question, also acknowledged by the authors: What controls the seasonal variation of ET in the Amazon? Is it controlled by the net radiation, or is it controlled by the vegetation, mainly through the surface conductance that would respond to the soil moisture seasonality? Werth and Avissar (2004) also conclude that the net radiation control of ET, initially verified by Shuttleworth (1988), is probably not more credible than the other estimates, and the lack of vegetation control of ET during the dry season in the Amazon may not be realistic, but call for additional ground-based observations to improve the knowledge on the subject. A recent study (Souza-Filho et al. 2004) presents new evidence that supports the argument that the net radiation (and maybe other atmospheric variables) is the major control mechanism of the seasonal variation of ET in Amazonia, leaving the vegetation control to a secondary role. Using meteorological and flux data col

Estimativa da produtividade da cana-de-açúcar para as principais regiões produtoras de Minas Gerais usando-se o método ZAE 1

ABSTRACT The objective of this study was to parameterize, calibrate and test the Agroecological Zone (AEZ) method for estimating the yield of sugarcane in the major producing areas of sugarcane in the State of Minas Gerais. Meteorological data from the Instituto Nacional de Meteorologia and the Agencia Nacional de Aguas, as well as productivity data from Programa de Melhoramento Genetico da Cana-de-Acucar were used. The AEZ method showed good agreement, R2 = 0.89, RMSE = 8.4 t ha-1; MAE = 6.7 t ha-1, MBE = 5.9 t ha-1 and Willmotts coefficient (d) = 0.95. For validation, a series of crop productivity data from the Instituto Brasileiro de Geografia e Estatistica from 1989/90 to 2007/08 was used for the Triângulo Mineiro region. A systematic error with a tendency to overestimate the productivity of about 37 t ha-1 was found. After correcting the tendency of overestimating, the AEZ method showed satisfactory agreement (R2 = 0.55, RMSE = 4.9 t ha-1; MAE = 4.0 t ha-1, MBE = 0.0 t ha-1 and d = 0.80). Therefore, the model has revealed to be an important tool for estimating the yield of sugarcane in a large scale in the state, which could be useful to plan the expansion of optimal activity in the region.

Consumo de água em plantios de eucalipto: parte 2 modelagem da resistência estomática e estimativa da transpiração em tratamentos irrigados e não-irrigados

This paper concludes the last part of the work aimed to calculate water consumption in eucalypt plantations. Stomatal resistance was modeled as a function of the following ambient variables: global solar irradiance, vapor pressure deficit and temperature. Based on stomatal resistance modeled from the values observed in the first part of this work, eucalypt transpiration by the Penman-Monteith method could be calculated in some days during the humid and dry periods of the year. Correlation between stomatal resistance and ambient variables was verified. The models generated by this relation proved efficient in calculating the diurnal variation of stomatal resistance as well as hourly and daily transpiration totals.

Transpiração e temperatura foliar da cana-de-açúcar sob diferentes valores de potencial matricial

The objective of this study was to evaluate the diurnal behaviour of transpiration and leaf temperature of sugarcane (cv. RB867515) under different water matrix potential in the cultivation substrate and greenhouse meteorological conditions. The water stress effect on transpiration and leaf temperature was determined after irrigation suspension, when three measurement campaigns were initiated at 122; 150 and 185 days after planting (DAP) until the matrix water potential in the substrate (Ψ) reached -1,500 kPa, approximately. Under the absence of water stress (Ψ>-50 kPa), plant transpiration reached the maximum value between 10:00 AM and 13:00 PM, near to 60; 70 e 100 gplant-1h-1, for 122; 150 and 185 DAP, respectively. Under severe water stress (Ψ<-1,100 kPa), there was daily transpiration reduction of approximately 73%, compared to measurements performed without water stress and under similar meteorological conditions. Under the absence of water stress and overcast sky conditions, the average value of the difference between leaf temperature and air temperature was -2.9 oC. In contrast, under severe water stress and high values of global solar radiation, the leaf temperature was found to be 6.6 oC above the air temperature.

Albedo da cultura da soja em área de avanço da fronteira agrícola na Amazônia

O avanco da fronteira agricola na Amazonia pode acarretar graves impactos ambientais, constituindo a mudanca no albedo da superficie um dos principais forcantes. Avaliou-se, neste trabalho, o albedo da soja (Glycine Max (L.) Merryl), plantada em condicoes naturais de campo, na cidade de Paragominas, PA, regiao com grande avanco da fronteira agricola na Amazonia, e se observou relacao direta entre o albedo da soja e o seu indice de area foliar, valor maximo diario variando entre 0,24 e 0,25 associado a um IAF de 7,17 correspondente a 1297,62 graus-dia acumulados. Em termos medios, encontrou-se que a o estadio fenologico mais critico da cultura, tendo como base a mudanca no albedo, e o estadio fenologico de frutificacao na qual a mesma apresenta um albedo medio maximo de 23,3% (± 0,0007). Modelos empiricos foram ajustados para simular a variacao diaria do albedo em funcao do IAF e umidade do solo, ao longo do ciclo, e a variacao diurna do albedo na elevacao solar, para cada estadio fenologico da soja.

Geoestatística no estudo de modelagem temporal da precipitação

Geostatistics analysis is a powerful tool which has been used in studies of spatial dependence. With respect to the temporal dependence, few analysis are performed with this kind of methodology. In this study, the geostatistics technique was used to adjust a model to a series of temporal values of precipitation and its performance to predict data was also evaluated. The study was carried out at the Rio Itapemirim Basin in a series of monthly precipitation from 1940 to 2006. The adjusted model was compared to the Box and Jenkins model. The best geostatistics model adjusted was the one which used with 96 neighbors in the prediction and mean relative absolute error of 80.46. Geostatistics methodology showed better results for estimating the monthly precipitation in relation to the SARIMA model (2,1,1)(0,1,1)12.

IMPACTO DAS MUDANÇAS CLIMÁTICAS NA PRODUTIVIDADE DO EUCALIPTO NA REGIÃO NORTE DO ESPÍRITO SANTO E SUL DA BAHIA

Scenarios of climatic change linked to growth models based on ecophysiological processes may be useful to identify risks of serious consequence on the yield of planted forests, presenting the possibility to lessen the gravity of climatic change impacts and also to assess means of adaptation. The main objective of this paper is to analyze climatic change impacts on eucalyptus yield in Northern of Espirito Santo and Southern Bahia. The climate input data used in the 3-PG growth model were from two scenarios of climatic change (A2 and B2) from global model CCSR/NIES, for three periods of time: 2011 -2040, 2041-2070 and 2071-2100. It was found that future climatic changes are most likely to decrease the eucalyptus yield, reaching a 40% reduction in scenario A2 for the 2071-2100 period and 24% for scenario B2. In spite of global models converging on the possible incremental temperatures, there is still skepticism about the change in precipitation, as well as the change in the frequency of climatic extremes, making it impossible to predict the true magnitude of eucalyptus yield losses.