ABSTRACT. An increase in atmospheric CO2 levels and global climate changes have led to an increased focus on CO2 capture mechanisms. The in situ quantification and spatial patterns of forest carbon stocks can provide a better picture of the carbon cycle and a deeper understanding of the functions and services of forest ecosystems. This study aimed to determine the aboveground (tree trunks) and belowground (soil and fine roots, at four depths) carbon stocks in a tropical forest in Brazil and to evaluate the spatial patterns of carbon in the three different compartments and in the total stock. Census data from a semideciduous seasonal forest were used to estimate the aboveground carbon stock. The carbon stocks of soil and fine roots were sampled in 52 plots at depths of 0-20, 20-40, 40-60, and 60-80 cm, combined with the measured bulk density. The total estimated carbon stock was 267.52 Mg ha-1, of which 35.23% was in aboveground biomass, 63.22% in soil, and 1.54% in roots. In the soil, a spatial pattern of the carbon stock was repeated at all depths analyzed, with a reduction in the amount of carbon as the depth increased. The carbon stock of the trees followed the same spatial pattern as the soil, indicating a relationship between these variables. In the fine roots, the carbon stock decreased with increasing depth, but the spatial gradient did not follow the same pattern as the soil and trees, which indicated that the root carbon stock was most likely influenced by other factors.

ABSTRACT Background: This study aims to evaluate the technical feasibility of simple coppice system, in a planted stand of the native arboreal species Eremanthus erythropappus (DC.) MacLeish (candeia), according to different moments of soil scarification. The experiment is located in Baependi - MG (Brazil), where the mean altitude is 1,165 m and it´s under mild mesothermal climate. The first cycle was harvested under a clear-cutting system at 8 years after planting, with manual soil scarification and exposure of roots around the harvested trees stumps, at 5, 6, 7, and 8 weeks after cutting, i.e., four treatments with four repetitions of 50m2 plots each. In the first months, adventitious buds sprouting from the roots have been observed inside and outside the perimeter around stumps. The area remained fenced, without thinning or application of fertilizers and, until the third year, the selective clearing was done to eliminate weed competition. Six years after the treatment, measurements of diameter at 1.30 m height (DBH), the height of the sprouts, and the circumference at soil height (CSH) of stumps were taken. Results: After six years, the regenerated site under simple coppice system presented a density of established plants 216% higher than the harvested site using a high forest system (first cycle), but with only 4.3% of the commercial volume. The correlation between the density of sprouts and the density of stumps indicated that initial plant density can influence the number of sprouts after harvest. Conclusion: It was verified the simple coppice system feasibility and that scarification technique can be applied up to eight weeks after tree cutting.

RESUMO Períodos de seca prolongados têm impactado as florestas Atlânticas no sudeste do Brasil, demandando investigações para entender os efeitos destas condições estressantes em sua hidrologia. Este estudo objetivou avaliar as mudanças no balanço hídrico de um remanescente de floresta Atlântica semi-decidual e como ela responde à secas. O Índice Padronizado Precipitação-Evapotranspiração (SPEI) foi aplicado para identificar os períodos de seca (de 1961 a 2019) e suas severidades nas escalas de ano hidrológico e verão. Os impactos das secas na evapotranspiração real, na percolação potencial e no armazenamento de água no solo foram analisados por meio do Hydrus-1D, considerando a precipitação efetiva e a evapotranspiração potencial como entradas. As análises de erro (<10%) confirmaram a adequabilidade do Hydrus-1D na simulação da umidade do solo. Incertezas com relação à condutividade hidráulica saturada estão relacionadas à presença de caminhos preferenciais, os quais não são considerados na equação de Richards. A intensificação das secas acarretaram mudanças na hidrologia florestal, ativando respostas fisiológicas. Florestas Atlânticas semi-deciduais são adaptadas a períodos secos devido à suas espécies adaptadas e à ativação de mecanismos fisiológicos. No entanto, a floresta respondeu de maneira diferente considerando as escalas de seca. A intensificação das secas no verão aumentou a evapotranspiração e diminuiu a percolação potencial. A perda de folhas alterou a estrutura do dossel em um intervalo de dois anos em resposta à intensificação da seca no ano hidrológico. Alterações na hidrologia florestal ativam respostas fisiológicas (como a perda de folhas) em um processo atrasado após episódios de seca.

ABSTRACT Since prolonged droughts have impacted Atlantic forests in Southeastern Brazil, further investigations to understand the effects of such stressful conditions in their hydrological behavior are required. This study aimed to assess the changes in the water balance of a semi-deciduous Atlantic forest remnant and how the forest responds to droughts. The Standardized Precipitation-Evapotranspiration Index was applied to identify droughts (from 1961 to 2019) and their severity in both the hydrological year and summer scales. Drought impacts on actual evapotranspiration, potential percolation, and soil water storage were assessed using Hydrus-1D, having net precipitation and potential evapotranspiration as inputs. Error analyses (< 10%) confirmed Hydrus-1D suitability for simulating soil moisture. Uncertainties regarding the soil saturated hydraulic conductivity are due to preferential flows, which are not accounted for in Richards’ equation. Drought intensification changed forest hydrology and triggered physiological responses to deal with it. Semi-deciduous Atlantic forests are adapted to dry conditions because of the existence of dry-affiliated species and the activation of physiological mechanisms. However, such adaptations responded differently regarding the drought scales. The intensification of summer droughts increased evapotranspiration and decreased the potential percolation. Leaf shedding changed the canopy structure in a two-year time lag as a response to the intensification of hydrological year droughts. Changes in forest hydrology are sudden and trigger physiological responses, such as leaf shedding, in a delayed process after droughts take place.

SUMMARY: The increasing awareness of global climate change has drawn attention to the role of forests as mitigators of this process as they act as carbon sinks to the atmosphere. Understanding the process of carbon storage in forests and its drivers, as well as presenting consistent models for their estimation, is a current demand. In this sense, the aim of this study was to evaluate the performance of machine learning techniques: support vector machines (SVM) and to propose a new nonlinear model extracted from the training of an artificial neural network (ANN) in the modeling of above ground carbon stock in a secondary semideciduous forest. SVM and ANN construction and training process considered independent variables selected by stepwise: minimum DBH (diameter of breast height - 1.3 m), maximum DBH, mean DBH, total height and number of trees, all by plot. SVM and the model extracted from ANN were applied to the data set intended for validation. Both techniques presented satisfactory performance in modeling carbon stock by plot, with homogeneous distribution and low dispersion of residues and predicted values close to those observed. Analysis criteria indicated superior performance of the model extracted from the artificial neural network, which presented a mean relative error of 6.94 %, while the support vector machine presented 13.52 %, combined with lower bias values and higher correlation between predictions and observations.

RESUMEN: La conciencia de la sociedad en relación a los cambios climáticos globales ha llamado la atención sobre el papel de los bosques como mitigadores de este proceso, ya que actúan como sumideros de carbono en la atmósfera. Comprender el proceso de almacenamiento de carbono en los bosques y sus determinantes, así como presentar modelos consistentes para su estimación es una demanda actual. En este sentido, el objetivo de este estudio fue evaluar el desempeño de las técnicas de máquina de vectores de soporte (SVM) y proponer un nuevo modelo no lineal extraído del entrenamiento de una red neuronal artificial (RNA) para modelar la cantidad de carbono sobre el suelo en un Bosque secundario estacional semideciduo. El proceso de construcción y entrenamiento de SVM y RNA consideró variables independientes seleccionadas por stepwise: DAP mínimo (diámetro de altura del pecho - 1.3 m), DAP máximo, DAP promedio, altura total promedio y número de árboles, todo por unidad de muestreo. La SVM y el modelo extraído de la RNA se aplicaron al conjunto de datos para su validación. Ambas técnicas mostraron un desempeño satisfactorio en la modelación de la cantidad de carbono por unidad de muestreo, con distribución homogénea y baja dispersión de residuos y valores pronosticados cercanos a los observados. Los criterios de análisis utilizados indicaron un desempeño superior del modelo extraído de la red neuronal artificial, que presentó un error relativo promedio de 6.94 %, mientras que la máquina de vectores de soporte presentó 13.52 % junto con valores de sesgo más bajos y una mayor correlación entre predicciones. y observaciones.

SUMMARY: This study aimed at evaluating the performance of different models based on Artificial neural networks (ANN) to estimate the total height of eucalyptus trees (Eucalyptus spp.), reducing the number of measurements in the field. Forty-eight ANN were tested, different from each other by the number of trees used as training sample, number of trees used to calculate the dominant height and use of variables (a) categorical, (b) categorical and continuous and (c) continuous, except for the diameter at 1.30 meters above the ground (DBH), used in all combinations. Estimates of height obtained by ANN were compared with values observed and estimates obtained by a hypsometric model. The ANN that showed the best results were used for the height estimation in forest inventory data for further application in the Schumacher and Hall volumetric model. The proposed models were efficient to estimate the total height of eucalyptus trees and allowed the expressive reduction of the number of trees to be measured in forest inventory. The best model found is composed of five trees as training sample, one as test sample and one as validation sample; dominant height coming from the height of the tallest tree in the plot; categorical variable Clone and continuous variables DBH, DBH dominant and basal area of the plot.

RESUMEN: El objetivo fue evaluar el desempeño de diferentes modelos basados en Redes Neuronales Artificiales (RNA) en la estimación de la altura total de los eucaliptos, reduciendo el número de mediciones en el campo. Se analizaron 48 RNA, diferentes entre sí por el número de árboles utilizados como muestra de entrenamiento; número de árboles utilizados para calcular la altura dominante; y el uso de (a) variables categóricas, (b) categóricas y continuas y (c) continuas, con la excepción del diámetro a 1,30 m del suelo (DAP), utilizadas en todas las combinaciones. Las estimaciones de altura obtenidas por RNA han sido comparadas con los valores observados y con las estimaciones obtenidas por un modelo hipsométrico. Las RNA que presentaron los mejores rendimientos se utilizaron para estimar la altura en los datos del inventario forestal, para el cálculo posterior del volumen de cada árbol. Los modelos propuestos demostraron ser eficientes para estimar la altura total de los eucaliptos y permitieron la reducción expresiva de la cantidad de árboles que se medirán en el inventario forestal. El mejor modelo encontrado se compone de cinco árboles como muestra de entrenamiento, uno como muestra de prueba y uno como muestra de validación; altura dominante desde la altura del árbol más alto en la parcela; variable categórica clon; y variables continuas DAP, DAP dominante y área basal de la parcela.

ABSTRACT. This study was carried out in an Atlantic forest remnant in Southeastern Brazil and aimed to spatially model the soil water content (SWC) and net precipitation (NP) on a monthly time scale and to assess the spatial behavior of these hydrological variables in the different seasons. NP is defined by summing throughfall and stemflow, which have been collected after each rain event and accumulated monthly. Soil moisture measurements were carried out monthly up to a depth of 1.00 m and then integrated to obtain the SWC. The exponential semivariogram model was fitted for both hydrological variables, and the goodness-of-fit was assessed by a cross-validation procedure, spatial dependence degree (SDD) and spatial dependence index (SDI). This model provided adequate performance for SWC and NP mapping according to the cross-validation statistics. Based on the SDD, both variables have been classified as a ‘strong spatial dependence structure’. Nevertheless, when the SDI was assessed, NP showed less spatial dependence, while the SWC maintained almost the same performance. Kriging maps pictured the regional climate seasonality due to higher values of both variables in spring and summer than in autumn and winter seasons. However, correlations between NP and SWC are not expressive in the studied period.

ABSTRACT The rainfall-forest canopy interaction can impact on the chemical and physical rain-water features and is expected that different forests will have different effects on throughfall rain-water quality parameters. This study aimed (i) to compare chemical and physical rain-water quality variables observed in both gross precipitation and throughfall measured in two different forest stands (Atlantic semideciduous forest remnant - AFR, and a Eucalyptus urograndis plantation - EUP). Each stand was monitored with 8 internal rain-gauges and one external rain-gauge, encompassing the period from March 2015 to March 2016. The results pointed out a seasonal behavior of chemical and physical rain-water variables. Gross precipitation and throughfall presented different behaviors for pH, NH3, NH4+ and Ca hardness for AFR, and NH3, NH4 +, Phosphate, Chloride, Ca hardness, Total Dissolved Solids and Conductivity for EUP. Besides, significant differences between the stands were found in terms of throughfall indicators for some of the rainfall events, remarkably NH3 and NH4 + which were always higher at AFR. Our findings reinforce that trees and forests promote rain water enrichment with nutrients, performing key role on environmental services such as nutrient water and air pollution mitigation.

Resumo As novas condições ambientais impostas por eventos de distúrbios criam um mosaico de manchas em diferentes estágios sucessionais. Nosso objetivo foi descrever a variação temporal de uma floresta estacional semidecidual em função do histórico de perturbação antrópica, verificando possíveis mudanças na dinâmica e estrutura da floresta. Nós amostramos a vegetação arbórea com diâmetro a 1,3 m do solo (DAP) ≥ 5 cm em 15 parcelas permanentes de 20 × 20 m onde realizamos quatro inventários (2003, 2005, 2007 e 2015). Nós verificamos uma diminuição da densidade e aumento da área basal, o que indica que a comunidade arbórea analisada se encontra em estágio tardio de sucessão. A estrutura fitossociológica, a riqueza e a diversidade de espécies da comunidade arbórea não apresentaram mudanças ao longo dos monitoramentos. Entretanto, o predomínio da espécie Protium spruceanum pode ser uma resposta às mudanças ambientais provocadas pela mineração que ocorreu na área há 250 anos. As influências duradouras dos distúrbios antrópicos tornam este tipo de trabalho imprescindível por permitir a compreensão dos processos ecológicos, possibilitando um gerenciamento factual das florestas pelo manejo e conservação efetivos.

Abstract The new environmental conditions imposed by disturbance events often create a mosaic of spots in different successional stages. Our objective was to describe the temporal variation of a semideciduous seasonal forest based on its anthropic disturbance history, verifying possible changes in forest dynamics and structure. We sampled the arboreal vegetation with a diameter at breast height (1.3 m above the ground; DBH) ≥ 5 cm in 15 permanent plots of 20 × 20 m where we performed four inventories (2003, 2005, 2007 and 2015). We observed a density decrease and a basal area increase, which indicates the late successional stage of the analyzed tree community. The phytosociological structure, richness and species diversity of the tree community did not show changes throughout the monitoring. However, the Protium spruceanum predominance may be a response to the environmental changes caused by the mining occurred in the area 250 years ago. The anthropic disturbances enduring influences make this type of work indispensable because it allows the ecological processes understanding, allowing a factual management of the forests by the its effective management and conservation.

RESUMO Este trabalho teve como objetivo analisar a ocorrência de processo sucessional em uma floresta madura, utilizando para isto a distribuição das árvores em fases de desenvolvimento. O fragmento estudado consiste em uma floresta estacional semidecidual em estágio avançado de recuperação com cerca de 11 ha, localizado as margens do Rio Capivari no município de Lavras, estado de Minas Gerais, Brasil. A coleta de dados ocorreu nos anos de 1998, 2003, 2009 e 2014, nos quais foram mensurados e identificados em nível de espécie todos os indivíduos arbóreos que atingiram o critério de inclusão preestabelecido (circunferência a 1,3 m do solo - CAP≥15,7 cm). A partir destes dados foram obtidos os valores de riqueza para cada uma das quatro fases estabelecidas com base em critérios de circunferência (Juvenis, Preestabelecidos, Estabelecidos e Emergentes), bem como informações sobre rotatividade de espécies, estrutura, composição florística e compartilhamento entre essas fases. Os resultados indicaram a inexistência de diferenças temporais quanto à estrutura e distribuição da riqueza em fases de desenvolvimento. Foram observadas movimentações temporais de espécies principalmente entre as fases menores. Com relação à similaridade entre fases, ocorreu a divisão em um grupo contendo as duas menores e outro composto pelas duas maiores, nos quais a composição florística e espécies mais representativas foram mais semelhantes. Ademais, observou-se uma substituição não direcional das espécies mais representativas de cada fase, provavelmente relacionado a não correspondência entre ciclos de vida das populações. Assim, a ocorrência de modificações temporais nos padrões de riqueza na floresta indica a existência de processos sucessionais dinâmicos em uma comunidade em estágio clímax.

ABSTRACT This study aimed to test the occurrence of the successional process in a mature forest using the distribution of the trees in phases of development. The study forest remnant, a 11-ha old-growth seasonal forest, is located in the margins of Rio Capivari in Lavras, Minas Gerais state, Brazil. The data collection was carried out in 1998, 2003, 2009 and 2014, when we measured and identified to species level all trees that have reached the pre-established inclusion criteria (circumference at 1.3 above the ground level - CBH ≥15,7 cm). From these data, we obtained the species richness for each of the four development phases established on the basis of circumference criteria (Juvenile, Pre-established, Established and Emerging), as well as information on the species turnover, structure, floristic composition and the sharing between these phases The results indicated that there are no significant temporal differences in the structure and the distribution of species richness in development phases. Besides, we found a subtle movement of species mainly among the small phases. Concerning to the similarity among phases, we observed a clustering of the two smallest development phases and the clustering of the two largest ones, in which the floristic composition and most representative species were more similar. In addition, there was a non-directional turnover of the most representative species of each phase, probably related to a mismatch among the population life cycles. Thus, the occurrence of temporal changes in richness’ patterns can indicate the existence of dynamic succession processes in a climax stage community.

ABSTRACT The present study seeks to characterize the composition, structure, and functional traits of the tree stratum of a Semideciduous Forest in Pouso Alegre, MG, Brazil (22º12’43”S and 45º59’30”W), by comparing Edge and Interior habitats and their relation to human impacts and soil variables. The tree community (diameter at 1.3 m (DBH) higher than 5 cm) was inventoried using the point-centered quarter method by laying out 12 transects of 450 m each (six transects in the Edge and six in the Interior). Functional traits – wood density and seed mass – were obtained by genus. The impact evaluation and soil sample collection were realized per transect. We found significant differences in terms of the basal area (higher in Interior), diversity (higher in Interior) and community seed mass (higher in Edge). The effects of higher values of soil traits such as Calcium, Magnesium, cation sum (CS) and base saturation (V) on species composition were stronger in the Interior, while human induced impacts and soil Potassium had an overwhelming effect on the Edge.

RESUMO Galhas são resultantes da interação específica entre um indutor e a planta hospedeira. A espécie Heteropterys byrsonimifolia A. Juss. ocorre em abundância em ecótones de floresta estacional semidecidual e formações abertas adjacentes. No Parque Ecológico Quedas do Rio Bonito no estado de Minas Gerais, Brasil, essa espécie é afetada por um único morfotipo de galhas. O presente estudo objetivou avaliar se a complexidade estrutural do hospedeiro (teste da Hipótese da Complexidade Estrutural) e a distância entre hospedeiros (teste da Hipótese da Concentração de Recursos) têm influência sobre a densidade de galhas em H. byrsonimifolia, além de caracterizar a espacialização da infestação. Os resultados corroboram as duas Hipóteses testadas, sugerindo um comportamento metapopulacional das galhas em H. byrsonimifolia. Encontrou-se também um maior sucesso dos galhadores em ambientes de transição abrupta entre floresta-cerrado, o que pode estar associado à maior vulnerabilidade dos hospedeiros ocasionados por estresse que as plantas usualmente sofrem em ambientes ecotonais.

ABSTRACT Galls are the result of a specific interaction between an inducer and a host plant. The species Heteropterys byrsonimifolia A. Juss. occurs in abundance in semideciduous seasonal forest ecotones and adjacent open formations. In the ecological reserve Quedas do Rio Bonito, located in the state of Minas Gerais, Brazil, this species is affected by a single gall morphotype. The present study aimed to evaluate whether the structural complexity of the host (test of the structural complexity hypothesis) and the distance between hosts (test of the resource concentration hypothesis) affect gall density in H. byrsonimifolia and to characterize the spatial distribution of the infestation. The results corroborate the two hypotheses tested, suggesting a metapopulation pattern of gall infestation in H. byrsonimifolia. Gallers were more successful in abrupt forest-savannah transition environments, which may be associated with greater stress-induced host vulnerability that plants usually experience in ecotones.

Compreender as correlações existentes entre variáveis ambientais e a distribuição das espécies em uma floresta, sua dinâmica e estoque de carbono é um dos principais objetivos em ecologia florestal. Nesse sentido o presente trabalho objetivou correlacionar aspectos da vegetação com variáveis topo-edafo-climáticas em um remanescente florestal em Bocaina de Minas, Serra da Mantiqueira, MG. Técnicas multivariadas de ordenação (PCA e CCA) e regressões múltiplas foram utilizadas para representar essas correlações. Altitude teve destaque como fator ambiental síntese, compreendendo vários gradientes existentes na área (em especial edáfico e de conservação) sendo, portanto, a variável que mais explicou distribuição de espécies, dinâmica florestal e estoque de carbono na área.

Understanding the correlations among environmental variables and species distribution in a forest, including its dynamics and carbon storage, is one of the main goals in forest ecology. Therefore, the present study aimed to correlate aspects of vegetation to soil and climatic variables of a forest remnant in Bocaina de Minas, Serra da Mantiqueira, MG. Multivariate ordination techniques (PCA and CCA) and multiple regressions were used to represent these correlations. Altitude was highlighted as a synthetic environmental variable, comprising several gradients within the area (especially edaphic and conservation). This was the variable that best explained the distribution of species, forest dynamics and carbon stock in the area.

O presente trabalho objetivou analisar o comportamento espacial do estoque de carbono presente no fuste da vegetação (ECV) e da matéria orgânica do solo (MO) em uma floresta ombrófila densa na Serra da Mantiqueira, no Estado de Minas Gerais, por meio de krigagem. Pretendeu-se também testar a utilização da MO superficial como variável auxiliar na predição do ECV com o uso da cokrigagem. Para isso, foram analisados dados georreferenciados de 25 pontos amostrais de MO em três profundidades, 0-20 cm (P1), 20-50 cm (P2) e 50-100 cm (P3), e de 12 parcelas amostrais de 400 m2 de vegetação. As variáveis apresentaram estrutura de dependência espacial (maior em ECV e menor em MO em P1) e o semivariograma cruzado refletiu a correlação espacial entre ECV e MO em P1. O mapa de interpolação gerado por cokrigagem foi satisfatório na detecção de tendências da variável ECV, conservando os mesmos padrões do mapa gerado por krigagem ordinária para essa variável. Considera-se que, na área estudada, MO em P1 pode ser utilizada como covariável na caracterização espacial geral do ECV, em situações de subamostragem de ECV.

We aimed to analyze the spatial behavior of carbon present in the stems of trees (ECV) and soil organic matter (OM) in a dense ombrophilous forest at Serra da Mantiqueira, MG, using kriging. Also we tested the use of superficial organic matter as auxiliary variable in predicting ECV by cokriging. In order to achieve this, we analyzed georeferenced data from 25 sampling points of soil organic matter in three depths, 0-20 cm (P1), 20-50 cm (P2) and 50-100 cm (P3) and 12 vegetation sample plots of 400 m2. All variables presented spatial dependence structure (higher ECV and lower OM at P1). The cross semivariogram reflected the spatial correlation between ECV and OM at P1. The interpolation map generated by cokriging provided good notion of general ECV trends keeping the same patterns as the one generated by ordinary kriging for this variable. Our findings pointed that in our studied area, OM at P1 can be used as a covariate for ECV prediction of where ECV is under sampled.