Nairam Félix de Barros

ESTOQUES DE CARBONO NO SOLO E NA BIOMASSA EM PLANTAÇÕES DE EUCALIPTO

Eucalypt is the main commercial forest species in Brazil, but very little information is available in the literature on the amount of carbon stored in the soil and in the biomass of these forest stands. The main objective of this study was to estimate the amount of soil-stored carbon (SSC) of eucalypt plantations and determine soil and climate characteristics that influence SSC. The study was carried out in the Central-Eastern region of Minas Gerais State, Brazil, in five micro-regions (CO, RD, SB, SA, and VI) with varying soil and climatic conditions. Soil carbon was determined to a depth of 100xa0cm. Carbon in the forest floor was estimated by allometric equations. The carbon stored in the soil-plant system differed among micro-regions and soil classes. SSC ranged from 183.1xa0txa0ha-1 in Red Latosol to 95.1xa0txa0ha-1 in Inceptisol, and was negatively correlated to soil K, Ca2+; and Mg2+ content and density in the top soil layer. SSC was highest in the micro-region VI (141.2xa0txa0ha-1; average value for all soil types) and lowest in RD (80.8xa0txa0ha-1). Considering the soil-plant ecosystem and the usual rotation age (84 months), the absolute SSC value was greatest in the micro-region SA (251.6xa0txa0ha-1) and lowest in RD (186.8xa0txa0ha-1). Regression equations showed that the clay and aluminum content and altitude and water stress explained most of the SSC variation.

Estimativa de biomassa de plantios de eucalipto no Brasil

The aim of this work was to model growth of eucalypt plantations in Brazil. It was intended to evaluate influence of key climatic variables on eucalypt productivity. The database employed was obtained from the Soil and Eucalypt Nutrition Program of the Soil Department of the Federal University of Vicosa. Climatic characteristics and age were a model important component. The region with the highest productivity produced three times more aboveground biomass than the poorest region. Regions with low water availability exhibited the lowest biomass production. Strong reduced in canopy proportion was observed within 3.5 years following planting. After that the canopy proportion reduced more slowly.

Relações entre variáveis climáticas com produção e enraizamento de miniestacas de eucalipto

The purpose of this study was to evaluate the degree of linear association among climate variables with the production and rooting of Eucalyptus minicuttings cultivated in two types of mini garden (sand bed and sub-irrigation tubes). CENIBRA data were used for minicutting rooting, number of minicuttings per ministump and climate monitoring data. The number of minicuttings produced per ministump and their rooting rate were correlated with climatic data (light, temperature and air relative humidity) .Temperature influences minicuting rooting in different ways, with the effect varying according with the clone and type of clonal mini garden. As for the number of minicuttings, temperature increase favors the production of minicuttings, regardless of the type of mini garden. Light influenced rooting and number of minicuttings positively , while air relative humidity had a negative effect, regardless of the type of mini garden evaluated. The data of this study indicates that increased light intensity and reduced air relative humidity favor minicutting rooting and the number of minicuttings produced by ministumps, as well.

Nutrient cycling in two sites of semideciduous forest in mata do paraíso forest reserve in Viçosa, MG, Brazil.

A Semideciduous Seasonal Forest in different successional stages (initial forest and mature forest), in Vicosa, Minas Gerais State, in the southeast region of Brazil, was studied aiming at quantifying litter annual production, decomposition, N, P, K, Ca, and Mg contents and use efficiency. The annual litter production was 6,310 kg.ha-1 for the initial forest and 8,819 kg.ha-1 for the mature forest. Nutrient annual deposition in the litter was estimated at 137 and 180 kg.ha-1 N, 5 and 8 kg.ha-1 P, 17 and 45 kg.ha-1 K, 89 and 179 kg.ha-1 Ca, 21 and 26 kg.ha-1 Mg for the initial forest and mature forest, respectively. The average forest floor biomass was 4,647 kg.ha-1 for the initial forest and 7,006 kg.ha-1 for the mature forest. The instantaneous decomposition rate (k) was estimated at 1,36 for the initial forest and 1,26 for the mature forest, with a turn over time of 270 and 288 days, respectively. The smallest litter production in the initial forest reflects the less developed structure in the site of forest in initial successional stage, with litter production of lower quality compared to the mature forest, but with faster renovation and efficient use of the nutrients.

Transporte de boro no solo e sua absorção por eucalipto

The mechanism and magnitude of B transport to plant roots depend on both water and B soil contents. The contribution of mass flow and diffusion to the B transport in soil to eucalypt roots was evaluated in response to the water potential and B rates. Two water potentials (-10 and -40 kPa) and six B levels (0; 0.5; 1; 2; 3 and 5 mg dm-3 of B) were evaluated. The plants were grown in 2.5 dm3 plastic pots with soil, in a greenhouse. The water potential was controlled by a tensiometer in each pot and soil moisture adjusted with distilled water. The maximum root dry weight was produced at rates of 0.98 and 2.38 mg dm-3 of B, at potentials of -10 and -40 kPa, respectively, and the maximum shoot dry weight at rates of 0.96 and 1.82 mg dm-3 of B, at potentials of -10 and -40 kPa, respectively. Positive and highly significant relationships were observed between B rates, soil extractable B, B in soil solution and B plant content at both water potentials. Mass flow was the predominant mechanism for B transport in soil, supplying 100 % of the plant demand in the soils treated with the highest B rates. Diffusion was a complementary mechanism, but its relative increased substantially under conditions of low soil B and greater water deficit.

Produção de serapilheira em dois estádios sucessionais de floresta estacional semidecidual na Reserva Mata do Paraíso, em Viçosa, MG

RESUMO – Dois trechos de floresta em distintos estadios sucessionais (floresta inicial e floresta madura) foram avaliados quanto a producao de serapilheira durante o periodo compreendido entre novembro/ 2003 e outubro/2004. Os objetivos foram estimar a producao anual de serapilheira, verificar a variacao temporal de deposicao da serapilheira e investigar a existencia de correlacoes entre a estrutura da vegetacao e a producao de serapilheira. O estudo foi realizado na Reserva Mata do Paraiso, em Vicosa, MG, onde foram instalados 20 coletores de 1 m², colocados a 20 cm acima da superficie do solo. Os coletores foram distribuidos no centro de parcelas de for mato retangular, medindo 10 x 30 m cada um, e cada trecho de floresta recebeu 10 coletores. A serapilheira coletada mensalmente foi separada nas fracoes folhas, ramos, flores e frutos/sementes. A producao anual de serapilheira foi estimada em 6.310 kg.ha -1 na floresta inicial e 8.819 kg.ha -1 na floresta madura. A fracao predominante foi a foliar (64,6% e 55,9%), seguida das fracoes ramos (31,2% e 36,4%), frutos e sementes (3,2% e 6,2%) e flores (1,0% e 1,5%), nas florestas inicial e madura, respectivamente. A producao de serapilheira total foi continua ao longo do periodo analisado, apresentando modelo sazonal, com os maiores valores no periodo da primavera. Na fracao foliar, o pico de producao foi verificado em setembro, no final da estacao seca. A producao de serapilheira esteve mais relacionada a densidade de individuos nas parcelas e a sua biomassa do que a presenca de especies pioneiras nos ambientes estudados.

Influência do estado nutricional de minicepas no enraizamento de miniestacas de eucalipto

The adventitious rooting of cuttings is influenced by intrinsic and extrinsic factors of the plant material. The knowledge about the way of the action of these factors upon rooting is essential for the success of the seedling production by minicuttings. Among the factors involved in rooting the mineral nutrition can be emphasized because there is a significant relation between it and rooting, but the importance of various nutrients in this process has not been completely explained yet. Thus, the objective of this work was to evaluate the linear association degree between the nutritional status of ministumps with the rooting of eucalyptus minicuttings. Data from the CENIBRA enterprise were used, and those of rooting of minicuttings and the nutrient contents found in chemical analyses of leaf tissues of the ministumps were analyzed. The data used were from a clonal minigarden grown in sand beds, with fertirrigation by dripping. With these data, analyses were performed to evaluate the existence of a linear correlation among the concentrations of macro and micronutrients in the ministumps and the rooting rate of the minicuttings. The results indicate that the mineral nutrition plays an important role on the adventitious rooting of the minicuttings produced by the ministumps, generating different responses according to the nutrient considered. The results of this study indicate that the nutritive solution used in the clonal minigarden must be specific for each clone.

Relações hídricas em povoamento de eucalipto com diferentes densidades populacionais

In a trial carried out at Santa Barbara, MG, Brazil, the influence of plant population on throughfall, crop evapotranspiration (ETc) and soil moisture regime of Eucalyptus grandis stands was evaluated. Plant population varied from 500 to 5000xa0trees ha-1. Soil moisture was measured down to a depth of 285xa0cm by a neutron probe, every 15xa0days. Rain water interception increased linearly with increasing plant population, whereas ETc was not significantly influenced. Soil moisture level tended to increase as plant population decreased. During the experimental period, soil moisture level was never below that corresponding to retained water at 1.5xa0MPa.

Isolamento e seleção de fungos causadores da podridão-branca da madeira em florestas de Eucalyptus spp. com potencial de degradação de cepas e raízes

The aim of this work was to isolate native wood white-rot fungi from fungal fruit-bodies and eucalyptus wood fragments from different regions of Brazil and to test their potential for degrading dead stumps and roots in Eucalyptus plantings after harvest. Fungi isolates were obtained in a culture medium composed by Eucalyptus sawdust and agar. Among 292 isolates submitted to the Banvedamm test, 144 were classified as phenoloxidases producing isolates. Among nine C/N ratios tested, it was observed a tendency of occurring larger chip decay in the C/N ratios equal to 60 : 1, 200 : 1 and 300 : 1. Two decay assays were performed in wood chips of Eucalyptus saligna using the C/N ratio 60 : 1 in order to verify which isolates were able to cause larger reduction of dry matter. In the first assay, which was evaluated at 90 days of incubation, seven isolates that stood out in relation to Trametes versicolor were selected. The second assay evaluated the capacity of 46 isolates in promoting decay. The isolates selected in the first assay were among the 11 most efficient in the second assay. Based on DNA analysis, six isolates were identified as Pycnoporus sanguineus (3 isolates), Peniophora sp., Pestalotiopsis sp. e Ganoderma sp.

Acúmulo e distribuição de nutrientes em Eucalyptus grandis sob diferentes densidades populacionais

This experiment was carried out in Santa Barbara county, Minas Gerais State, Brazil to evaluate the effect of plant population (PP) on nutrient accumulation and distribution in Eucalyptus grandis. Plant population varied from 500 to 5,000 trees ha-1, laid out in a randomized block design with three replicates. The assessments were performed when the trees were 31 month-old, by sampling tissues from the above ground components of an average tree per plot, forest floor, and soil to the depth of 195 cm. The relations among P, N, K and Mg contents in the above ground biomass of the tree, the P, Ca and Mg utilization efficiency by the stem, and PP were better described by quadratic equations. A nutrient balance sheet, estimate based on the nutrients accumulated in the biomass and on the amount available or exchangeable in the soil, indicated the P, K and Ca would limit tree growth in the next cycle, 31 months after planting, for PP above 833 trees ha-1.