José Márcio de Mello

Effects of past disturbance and edges on tree community structure and dynamics within a fragment of tropical semideciduous forest in south-eastern Brazil over a five-year period (1987–1992)

Tree community structure and dynamics of a 5.8 ha fragment of montane semideciduous forest in south-eastern Brazil are described based on two successive surveys of trees with dbh ≥5 cm carried out in 1987 and 1992 in 126 20 × 20 m quadrats. The main purpose was to assess whether the spatial variation of dynamic and structural variables were related to edge-effects and past disturbance regimes. The totals for the two surveys were, respectively, 6528 and 6770 trees, and 94.89 and 108.53 m2 of basal area. The forest fragment was at an aggrading sylvigenetic phase, indicated by an overall net increase in density and basal area, and by a declining proportion of trees of smaller size. The overall annual mortality and recruitment rates were 2.6% and 3.0%, respectively. The dynamic process, however, was strongly affected by spatial heterogeneity. The more severely disturbed sectors had lower average canopy heights and basal areas per hectare, and higher tree densities, proportions of smaller trees, and relative area of canopy gaps. They also had higher mortality and recruitment rates, resulting in higher turnover rates compared to the sectors which suffered only moderate disturbance regimes. Edge sectors were also affected by different past disturbance regimes. However, they stood out by having a particularly high frequency of liana tangles and the highest rates of net increase both in density and basal area. A canonical correspondence analysis indicated that the effects of past disturbance regimes and edges were highly related to the species distribution in the area. Pioneer species were concentrated on the edges and more severely disturbed sectors, shade-tolerant species were particularly more abundant on the moderately disturbed sites, while light-demanding ones were more widely distributed. Tree community structure was also undergoing important changes, with less common species enjoying higher recruitment rates and density increase compared to the more common ones. Shade-tolerant species were increasing in relative abundance and had comparatively lower mortality rates and higher recruitment rates. On the other hand, pioneer species were under retreat, with a decreasing relative abundance, higher mortality rates and lower recruitment rates.Nomenclature: Oliveira-Filho et al. 1994a,d.

Continuidade espacial de chuvas intensas no estado de Minas Gerais

O mapeamento de variaveis climaticas, como chuvas intensas, e de fundamental importância para o manejo ambiental. Para isto, ferramentas estatisticas para interpolacao espacial devem ser devidamente analisadas e caracterizadas. Assim, objetivou-se com este trabalho analisar modelos e metodos de modelagem do semivariograma que melhor se ajustem a chuvas intensas com duracao de 20, 60, 360 e 1440 minutos e tempos de retorno de 5, 50 e 100 anos, fornecendo subsidios primordiais para espacializacao da mesma pelo interpolador geoestatistico, para o Estado de Minas Gerais. Foram testados os modelos esferico, exponencial e gaussiano pelos metodos de ajuste da Maxima Verossimilhanca (MV) e Minimos Quadrados Ponderados (MQP). Utilizou-se como criterio de escolha do melhor modelo, o menor erro medio gerado pela validacao cruzada, e em caso de similaridade, tambem foram considerados o maior grau de dependencia espacial e o menor efeito pepita, alem da analise visual do ajuste do modelo ao semivariograma experimental. O modelo exponencial se sobressaiu em nove das doze situacoes analisadas, o gaussiano em duas e o esferico em uma situacao. Quanto aos metodos de ajuste, o MQP sobressaiu em todos os casos estudados, o que permite sugerir o modelo exponencial ajustado pelo metodo dos minimos quadrados ponderados como sendo o mais adequado para o mapeamento da chuva intensa para as condicoes do Estado de Minas Gerais.

Métodos de interpolação espacial para o mapeamento da precipitação pluvial

A espacializacao de variaveis climaticas, notadamente a precipitacao pluvial, necessita de estudos constantes, visando ao aperfeicoamento de interpoladores e desenvolvimento de mapas sem tendencia. Objetivou-se, neste contexto, avaliar o desempenho dos interpoladores krigagem (KG), a partir do melhor modelo de semivariograma, cokrigagem (CA), introduzindo a altitude como variavel secundaria, modelagem estatistica (ME), na qual a precipitacao media pode ser estimada a partir de coordenadas geograficas, e inverso do quadrado da distância (IQD), para espacializacao da precipitacao media mensal, precipitacao media do periodo seco e precipitacao media anual, em Minas Gerais; para isto se utilizaram informacoes de 232 postos pluviometricos para modelagem e de 70 para validacao, com base no erro medio absoluto, alem de um modelo digital de elevacao com resolucao de 270 m. Quanto a avaliacao dos metodos de interpolacao, constatou-se bom desempenho das metodologias abordadas, com erro absoluto medio variando de 12,84 a 19,96%, com destaque para a cokrigagem, que obteve menor erro em 50% das situacoes analisadas.

Continuidade espacial para características dendrométricas (numero de fustes e volume) em plantios de eucalyptus grandis

O objetivo deste estudo foi verificar a continuidade espacial do numero de fustes e do volume nas diferentes formas e intensidades amostrais de Eucalyptus grandis com idade entre 3 e 4 anos. A area de estudo abrangeu quatro talhoes, totalizando 104,71 ha, pertencentes a Ripasa S/A Celulose e Papel. Os dados para a realizacao do estudo de variabilidade espacial foram coletados em parcelas circulares e em parcelas em linhas distribuidas sistematicamente na area, nas intensidades de 1:4 (1 parcela a cada 4 ha), 1:7 e 1:10. Foi possivel verificar que, tanto em numero de fustes quanto em volume, os dados apresentaram distribuicao aproximadamente normal. Pela analise variografica, foi verificado que as caracteristicas numero de fustes e volume de madeira apresentaram-se estruturadas espacialmente. O modelo exponencial foi o que se ajustou melhor aos semivariogramas experimentais das caracteristicas nas diferentes formas de parcela e intensidade amostral. A continuidade espacial foi detectada em todas as intensidades amostrais e formas de parcelas avaliadas, quanto a numero de fustes. Portanto, o uso da estatistica espacial no processamento dessa variavel aumentara a precisao das estimativas. No caso de volume, na intensidade amostral 1:10 nao foi possivel detectar continuidade espacial. Em tal condicao, deve-se utilizar a estatistica classica para processamento do inventario florestal.

Avaliação de modelos polinomiais não-segmentados na estimativa de diâmetros e volumes comerciais de Pinus taeda .

This study aimed at constructing equations with fractionary, unitary and ten magnitude power, in an attempt of representing the top, medium and basis portion of the stem; at constructing polynomial equations compatible with volume equations; at evaluating the accuracy of three non-segmented polynomial taper models for estimating diameters and volumes along the stem of Pinus taeda; and at verifying if the more accurated model for diameters estimates is also the more accurated for estimating partial and total volumes. The database used was composed of 58 trees of Pinus taeda cubed by the Smalian’s method, in the farms of “PISA – Papel de Imprensa S/A” enterprise, located in Jaguariaiva county (PR). The 58 trees were separated in 8 diameter classes. The models were fitted for each diameter class and for the total group of data. Three non-segmented polynomial models were tested: Schoepfer (1966); Hradetzky (1976); and Goulding and Murray (1976). The accuracy of the models in estimating diameters and volumes along the stem of Pinus taeda was evaluated through the following statistics: coefficient of determination; residual standard error; graphic analysis of the medium profile of the stem; mean deviation of the diameters and volumes for each position along the stem; standard deviation of the differences of the diameters and volumes; sum of square of the relative residue; and percentage of the residues of the diameters and volumes. Starting from the last four statistics, it was elaborated a ranking to detect the more accurated model for each position along the stem. It can be pointed out that among the non-segmented models tested, the model of Hradetzky (1976) is more stable than the others in the estimates of the two studied variables. Goulding and Murray (1976) model presented accurated estimates of diameters and volumes along the whole stem profile only when fitted by diameter classes. The model proposed by Schoepfer (1965) showed biased estimates along the whole stem profile, in all diameter classes.

Spatial Distribution of Aboveground Carbon Stock of the Arboreal Vegetation in Brazilian Biomes of Savanna, Atlantic Forest and Semi-Arid Woodland.

The objective of this study was to map the spatial distribution of aboveground carbon stock (using Regression-kriging) of arboreal plants in the Atlantic Forest, Semi-arid woodland, and Savanna Biomes in Minas Gerais State, southeastern Brazil. The database used in this study was obtained from 163 forest fragments, totaling 4,146 plots of 1,000 m2 distributed in these Biomes. A geographical model for carbon stock estimation was parameterized as a function of Biome, latitude and altitude. This model was applied over the samples and the residuals generated were mapped based on geostatistical procedures, selecting the exponential semivariogram theoretical model for conducting ordinary Kriging. The aboveground carbon stock was found to have a greater concentration in the north of the State, where the largest contingent of native vegetation is located, mainly the Savanna Biome, with Wooded Savanna and Shrub Savanna phytophysiognomes. The largest weighted averages of carbon stock per hectare were found in the south-center region (48.6 Mg/ha) and in the southern part of the eastern region (48.4 Mg/ha) of Minas Gerais State, due to the greatest predominance of Atlantic Forest Biome forest fragments. The smallest weighted averages per hectare were found in the central (21.2 Mg/ha), northern (20.4 Mg/ha), and northwestern (20.7 Mg/ha) regions of Minas Gerais State, where Savanna Biome fragments are predominant, in the phytophysiognomes Wooded Savanna and Shrub Savanna.

Volume equations for the savannah (cerrado), in Minas Gerais state

In this work, the physiognomy Savannah (Cerrado), present in three regions of the Sao Francisco River Basin, in Minas Gerais State, was studied with the following objectives: to adjust and to select equations to estimate total volume and stem volume; to test the similarity among volumetric models; to show the behavior of the volume in the stem and branches of the tree, and to evaluate the bark percentage in each diametric class. For this, the rigorous scaling using the method of Huber was accomplished, in which the data base was composed by 497 trees, distributed in six diameter classes, inside the three study areas. The bark thickness at the heights of 0%, 25%, 50%, 75% and 100% of the commercial height was measured. The accuracy of the models was evaluated by the determination coefficient, standard error of estimate and graphic analysis of the residuals. To test model identity, the method used was the one developed by Graybill (1976). The models selected for all the tested variables were the ones of Schumacher and Hall and of Spurr, transformed in logarithm. According to the identity test of models, for all the tested variables, similarity exists among the areas 2 and 3. Regarding to the behavior of volume, it was observed that the smallest diametric classes possess larger stem volume than the branches and that there is also a tendency of decreasing the bark percentage with the increase of the diametric class for the three studied areas.In this work, the physiognomy Savannah (Cerrado), present in three regions of the Sao Francisco River Basin, in Minas Gerais State, was studied with the following objectives: to adjust and to select equations to estimate total volume and stem volume; to test the similarity among volumetric models; to show the behavior of the volume in the stem and branches of the tree, and to evaluate the bark percentage in each diametric class. For this, the rigorous scaling using the method of Huber was accomplished, in which the data base was composed by 497 trees, distributed in six diameter classes, inside the three study areas. The bark thickness at the heights of 0%, 25%, 50%, 75% and 100% of the commercial height was measured. The accuracy of the models was evaluated by the determination coefficient, standard error of estimate and graphic analysis of the residuals. To test model identity, the method used was the one developed by Graybill (1976). The models selected for all the tested variables were the ones of Schumacher and Hall and of Spurr, transformed in logarithm. According to the identity test of models, for all the tested variables, similarity exists among the areas 2 and 3. Regarding to the behavior of volume, it was observed that the smallest diametric classes possess larger stem volume than the branches and that there is also a tendency of decreasing the bark percentage with the increase of the diametric class for the three studied areas.

Dominant Height Model for Site Classification of Eucalyptus grandis Incorporating Climatic Variables

This study tested the effects of inserting climatic variables in Eucalyptus grandis as covariables of a dominant height model, which for site index classification is usually related to age alone. Dominant height values ranging from 1 to 12 years of age located in the Southeast region of Brazil were used, as well as data from 19 automatic meteorological stations from the area. The Chapman-Richards model was chosen to represent dominant height as a function of age. To include the environmental variables a modifier was included in the asymptote of the model. The asymptote was chosen since this parameter is responsible for the maximum value which the dominant height can reach. Of the four environmental variables most responsible for database variation, the two with the highest correlation to the mean annual increment in dominant height (mean monthly precipitation and temperature) were selected to compose the asymptote modifier. Model validation showed a gain in precision of 33% (reduction of the standard error of estimate) when climatic variables were inserted in the model. Possible applications of the method include the estimation of site capacity in regions lacking any planting history, as well as updating forest inventory data based on past climate regimes.

Spatial distribution of top soil water content in an experimental catchment of Southeast Brazil

Soil water content is essential to understand the hydrological cycle. It controls the surface runoff generation, water infiltration, soil evaporation and plant transpiration. This work aims to analyze the spatial distribution of top soil water content and to characterize the spatial mean and standard deviation of top soil water content over time in an experimental catchment located in the Mantiqueira Range region, state of Minas Gerais, Brazil. Measurements of top soil water content were carried out every 15 days, between May/2007 and May/2008. Using time-domain reflectometry (TDR) equipment, 69 points were sampled in the top 0.2 m of the soil profile. Geostatistical procedures were applied in all steps of the study. First, the spatial continuity was evaluated, and the experimental semi-variogram was modeled. For the development of top soil water content maps over time a co-kriging procedure was used having the slope as a secondary variable. Rainfall regime controlled the top soil water content during the wet season. Land use was also another fundamental local factor. The spatial standard deviation had low values under dry conditions, and high values under wet conditions. Thus, more variability occurs under wet conditions.

Continuidade espacial da condutividade hidráulica saturada do solo na bacia hidrográfica do Alto Rio Grande, MG

Spatial distribution of the saturated hydraulic conductivity (k0) is essential in the study of soil erosion and surface runoff. The purpose of this study was to investigate the spatial continuity of the soil hydrologic characteristic k0 in the watershed Alto Rio Grande, state of Minas Gerais, and to map k0 based on geostatistical procedures, using data without and with logarithmic transformation. Exponential and spherical semi-variogram models were fitted to the experimental semi-variograms in two approaches: ordinary minimum square (MQO) and weighted minimum square (MQP). Cross validation and predictive validation were both applied to choose the best model. The results showed that the use of log (k0) improved the geostatistical applicability due to a reduction in the number of outliers and anisotropy; however, the spatial dependency degree was highest for k0 data without log-transformation. The spherical model fitted by MQO preformed best in the spatial continuity modeling of k0. The spatial distribution in the basin, indicated by the maps developed from data without and with log transformation was not the same; the map developed on the basis of log-transformed data showed a more detailed spatial distribution.