Abstract The objective of this work was to investigate the influence of the qualitative traits canker severity and stem quality on the mean annual increment (MAI) in diameter, total height, and stem height of an African mahogany (Khaya grandifoliola) stand. The study area is located in the state of Minas Gerais, Brazil, where continuous forest inventories were conducted over six years for data collection. Given the nonparametric characteristic of the data, an aligned rank transform analysis of variance was performed for each factor, and the averages were compared by Dunn’s multiple test. There was no significant effect of the interaction between the classes of canker severity and stand age. Increased canker severity has a significant effect on MAI values, causing reductions of 13% in diameter, 11% in total height, and 21% in stem height in trees from the highest canker severity class, when compared with the healthy ones. Age interacts significantly with stem quality, and MAI values tend to be similar in younger trees, differing over time in the oldest ones. In addition, the highest MAI values are recorded in trees with the best stem classification.

Resumo O objetivo deste trabalho foi investigar a influência das características qualitativas severidade do cancro e qualidade do fuste sobre o incremento médio anual (IMA) em diâmetro, altura total e altura de fuste de um talhão de mogno-africano (Khaya grandifoliola). A área do estudo se localiza no estado de Minas Gerais, Brasil, onde inventários florestais contínuos foram realizados por seis anos para a coleta dos dados. Pela característica não paramétrica dos dados, foi realizada uma análise de variância de transformação de postos alinhados para cada fator, e as médias foram comparadas pelo teste múltiplo de Dunn. Não houve interação entre as diferentes classes de severidade de cancro e a idade do talhão. O aumento da severidade do cancro tem efeito significativo sobre os valores de IMA, causando reduções de 13% em diâmetro, 11% em altura total e 21% em altura do fuste nas árvores da classe de severidade mais alta, em comparação às sadias. A idade interage significativamente com a qualidade do fuste, e o valores de IMA tendem a ser semelhantes nas árvores mais jovens, diferenciando-se posteriormente nas mais velhas. Além disso, os maiores valores de IMA são registrados nas árvores com melhor classificação de fuste.

ABSTRACT Background: Managed Caatinga forests in Northeast Brazil are an important source of wood products, however, successful regeneration and regrowth is important to guarantee sustainability in these forests. The main objective of this study was to evaluate the natural regeneration and forest regrowth ability of a Caatinga forest under varying clear-cut treatments, as well as to estimate the recovery time of stand parameters. Results: An experiment was set up in Petrolina, Pernambuco state, Brazil, comparing five clear-cut strip widths: 0, 40, 60, 80 and 100 meters. Forest inventory data was gathered before and eight years after harvesting in 19 plots of 10 x 40 m. Tree seedling regeneration (individuals with circumference at breast height < 6 cm and minimum height of 0.5 m) was also monitored in 5 x 5 m sub plots, before harvesting, one, three and eight years after harvesting. Conclusions: No influence of the clear-cut strip width on regeneration and forest regrowth ability was detected, with all treatments presenting similar growth and tree species diversity and similarity values. The estimated growth rates of the clear-cut plots were of 0.12 m2·ha-1·year-1 and 0.39 m3·ha-1·year-1 for basal area and volume, respectively, resulting in recovery times of 35 and 49 years, longer than the 15 years cycles generally adopted in Caatinga forest management plans.

RESUMO A estratificação de uma floresta resulta em inventários mais precisos e mais baratos. Este estudo teve como objetivo selecionar a variável estratificadora que estima inventários mais precisos e estáveis ao longo dos anos para um plantio de eucalipto no estado de Minas Gerais, Brasil. Foi realizado inventário florestal contínuo na área anualmente dos anos 2,7 a 6,8, sendo posteriormente calculados o diâmetro médio aritmético (d), altura (h), altura dominante (Hdom), área basal (G), volume (V) e incremento médio anual em volume (MAI). Foram gerados semivariogramas e os modelos exponencial, esférico e Gaussiano foram ajustados para cada variável estratificadora em cada época de medição. Os modelos foram avaliados pelo erro médio reduzido e seu desvio, sendo o modelo exponencial selecionado. Mapas mostrando a distribuição espacial de todas as variáveis foram construídos para cada idade de medição, utilizando krigagem ordinária. Em seguida, a área de estudo foi dividida em quatro estratos com base em cada variável estratificadora para cada idade de medição. A estabilidade de cada variável estratificadora para cada idade de medição foi avaliada por: 1) área coincidente dos estratos; 2) estabilidade da área total dos estratos; 3) permanência da parcela em cada estrato; e 4) erro de inventário utilizando formulação de amostragem casual estratificada. Todas as variáveis em todas as idades apresentaram estrutura de dependência espacial. G e Hdom foram as variáveis estratificadoras que geraram mais e menos área coincidente entre estratos ao longo dos anos, respectivamente. G e altura (h e Hdom) foram as variáveis estratificadoras que apresentaram menor e maior número de parcelas com mudança de estrato, respectivamente. A mesma tendência foi observada para a estabilidade da área total dos estratos. As estratificações baseadas em MAI e V renderam os menores erros de inventário, enquanto as estratificações baseadas em h e Hdom renderam os maiores erros. G foi selecionada como a melhor variável estratificadora, pois apresentou pequenos erros de inventário e foi a variável mais estável em termos da área coincidente dos estratos, estabilidade da área total dos estratos e permanência das parcelas no mesmo estrato.

ABSTRACT Stratifying a forest results in more precise and cheaper inventories. This study aimed to select the stratifying variable that estimates more precise and stable inventory over the years for a eucalyptus plantation in Minas Gerais state, Brazil. The continuous forest inventory was performed annually from 2.7 to 6.8 years, and based on the field measurements, arithmetic mean diameter (d), height (h), dominant height (Hdom), basal area (G), volume (V), and mean annual increment in volume (MAI) were calculated. Semivariograms were generated and the exponential, spherical and Gaussian models were fit for each stratifying variable for each measurement date. The models were assessed by the reduced mean error and its deviation, being the exponential model selected. Maps showing the spatial distribution of all variables were generated for each measurement age, using ordinary kriging. Next, the study area was divided in four strata based on each stratifying variable for each measurement age. The stability of each stratifying variables for each measurement age were assessed by: 1) coincident strata area; 2) stability of total strata area; 3) plot permanency on each stratum; and 4) inventory error using stratified random sampling procedures. All variables in all ages presented spatial dependence structure. G and Hdom were the stratifying variables that generated the most and the least coincident strata area over the years, respectively. G and height (h and Hdom) were the stratifying variables yielding the least and most plot stratum changes, respectively. The same trend was observed for the total strata area stability. Stratifying based on MAI and V yielded the smaller inventory error, and h and Hdom yielded the largest. G was selected as the best stratifying variable because it yielded small inventory errors and was the most stable variable in terms of coincident strata area, total strata area and plot stratum changes over the years.

ABSTRACT Background: The conservation and restoration of forest landscapes is an important aspect of sustainable development. In semi-arid regions these practices are difficulted by the harsh climate of these environments, with low precipitation values and prolonged dry seasons. The objective of this study is to identify tree species from the south of the Brazilian state of Piauí that have potential to be used in forest restoration programs. Results: Data from forest inventory and tree characteristics were used to select eight tree species using target species definition, focusing on species with desirable wood properties, abundance in the study region, favorable dendrometric variables, seed availability, ease of seed germination and seedling growth in nursery and field conditions, among others. These species were then evaluated as candidates for restoration using a framework species approach focusing on the following attributes: (i) 70% or higher seedling survival in the field; (ii) seedling height of 45 cm or taller after the first growing season in the field and (iii) 70% or greater nursery seedling survival. Conclusion: The species Combretum glaucocarpum, Cenostigma macrophyllum, and Pityrocarpa moniliformis are suitable to be employed in forest restoration programs in the southern region of Piauí, Brazil. Further studies must be carried out to assess the behavior of these and other potential tree species in long term field conditions and under varying silvicultural regimes, a key aspect for forest restoration.

ABSTRACT Pinus palustris Mill. ecosystem is considered one of the most threatened of North America. In this context, studies on biomass quantification are fundamental for forest management plans. Thus, the objective of this study was to develop a set of allometric equations to predict total P. palustris stump-biomass. Biomass data were collected at different locations in the southeastern United States. A total of 119 allometric equations were fitted from the combination of explanatory variables: diameter at breast height (DBH), height (H), age (I), basal area (G), number of trees per hectare (N), site index (S) and quadratic diameter (Dq). One of the models that presented the lowest residual standard error (Sy.x) and root mean square error (RMSE) was ln(W) = -0.9978+0.7082.(H)+0.1009.ln(H.DBH)-0.5310.(N)-0.0003.ln(Dq). Therefore, the insertion of dendrometric variables characteristic of forest stands has great efficacy in biomass prediction for trees from different sites.

Abstract: Here we model and describe the wood volume of Cerrado Sensu Stricto, a highly heterogeneous vegetation type in the Savanna biome, in the state of Minas Gerais, Brazil, integrating forest inventory data with spatial-environmental variables, multivariate regression, and regression kriging. Our study contributes to a better understanding of the factors that affect the spatial distribution of the wood volume of this vegetation type as well as allowing better representation of the spatial heterogeneity of this biome. Wood volume estimates were obtained through regression models using different environmental variables as independent variables. Using the best fitted model, spatial analysis of the residuals was carried out by selecting a semivariogram model for generating an ordinary kriging map, which in turn was used with the fitted regression model in the regression kriging technique. Seasonality of both temperature and precipitation, along with the density of deforestation, explained the variations of wood volume throughout Minas Gerais. The spatial distribution of predicted wood volume of Cerrado Sensu Stricto in Minas Gerais revealed the high variability of this variable (15.32 to 98.38 m3 ha-1) and the decreasing gradient in the southeast-northwest direction.

ABSTRACT This study aimed to evaluate the growth of Eremanthus erythropappus (DC.) MacLeish submitted to different planting spacing and growth modelling based on the diameter and crown area projection, as well as to identify the best management strategy to be applied to control the competition, period and intensity of thinning. The evaluated planting spacings were: 1.5 × 1.5 m; 1.5 × 2.0 m; 1.5 × 2.5 m and 1.5 × 3.0 m. Diametric growth modelling in function of the age and crown area projection according to the mixed models methodology was efficient and the individual tree modelling allowed for defining a correct thinning prescription for tree plantations in relation to the percentage of removal needed at each spacing, thus permitting the trees to grow free from competition and produce trees with larger diameters.

Abstract African mahogany (Khaya spp.) plantations are in expansion in Brazil and in the world. This fact justifies the need for studies related to its growth and yield. This paper aimed to evaluate the performance of single-entry and double-entry models for estimating merchantable and total volume for Khaya ivorensis plantations before the first thinning (7 years) and expected final cut (15 years). Volume data was from 100 and 46 trees in Minas Gerais and Pará states, respectively, by using an electronic dendrometer (Criterion RD 1000). Observed volumes were calculated by Smalian’s formula. To validate the optical dendrometer, 10 trees were felled and had their volume measured, and compared with the volumes measured indirectly. The results showed that observed and estimated volumes were statistically equal, and that double-entry models were more precise than single-entry models. Schumacher and Hall model was the best equation to estimate merchantable volume for first thinning and for final cut in Minas Gerais stands. Spurr logarithmized model was the best equation to estimate total volume for first thinning and Spurr model for final cut in Pará stands. All chosen equations can be used to quantify merchantable and total volumes of Khaya ivorensis grown under similar conditions.

ABSTRACT The use of height-diameter models have important applications in the management of eucalyptus plantations. The aim of this paper is to provide adequate height models based on the diameter and stand variables that could be easily used and applied to plantation’s management. The data was based on tests located in Espírito Santo and Bahia. A total of 312 plots, including 35 different treatments (different initial planting densities, number and severity of thinning operations, fertilization regimes, among others), and four different clones. This resulted in 2,407 conditions for 85,608 tree measurements. The constructed equations were based on mixed-effect models, in order to accommodate possible autocorrelations, to address variations between sites and to obtain locally calibrated estimates. Among the different model structures and combination of variables tested and presented, the best model showed a coefficient of determination of 0.953 and 0.988, for the fixed and fixed+random parts, respectively. The model included a random factor for measurements-within-tree and tree-within-plot. The bias of the fixed part was 0.208 cm (0.0659%). We believe the models in this study can have broad applications in management and inventory methods applied to plantations.

RESUMO O crescimento da demanda por madeira se dá em qualidade e quantidade, sendo os estudos econômicos fundamentais na análise da viabilidade de projetos florestais. Tais estudos estão alinhados aos estudos de manejo e silvicultura, destacando a modelagem do crescimento e produção. Este trabalho propõe a avaliação econômica da implantação do mogno africano no Brasil sob diferentes perspectivas de manejo florestal. Os dados são provenientes de plantios com idades variando de 1,1 a 15 anos localizados em diferentes regiões do Brasil. Uma análise financeira foi realizada utilizando o Valor Presente Líquido (VPL), Taxa Interna de Retorno (TIR) e Valor Anual Equivalente (VAE) para uma rotação de 20 anos de idade considerando diferentes regimes de desbaste (A - não desbastado, B - um desbaste aos 10 anos de idade com 150 árvores por hectare remanescentes e C - dois desbastes, primeiro na idade de 8 anos remanescendo 150 árvores por hectare e segundo aos 15 anos com 75 árvores por hectare remanescentes) considerando uma densidade inicial de 278 árvores por hectare. Uma simulação de Monte Carlo foi realizada levando em consideração diferentes variáveis de risco. Os resultados mostraram que a taxa de desconto foi a variável que mais influenciou a viabilidade do investimento. Todas as classes de sítio nos diferentes regimes de manejo apresentaram valores de VPL positivos, variando de 25.053 a 125.780 reais por hectare, sendo os regimes B e C os melhores. A simulação de Monte Carlo mostrou que a probabilidade de insucesso do investimento é praticamente zero, destacando o mogno africano como uma boa opção para investimento florestal, uma vez que possui altos valores de taxa interna de retorno (14% a 25%), superiores à maioria das taxas de investimento disponíveis no mercado.

ABSTRACT Wood demand is increasing in quality and quantity, and economic studies are fundamental to analyze the feasibility of forest projects. These researches are in line with management and silvicultural studies, highlighting growth and yield modeling. This paper proposes an economic evaluation of implementation of African mahogany stands in Brazil under different perspectives of forest management. Data are from plantations ranging from 1.1 to 15 years old in different Brazilian regions. Financial analysis was undertaken using Net Present Value (NPV), Internal Rate of Return (IRR) and Equal Annual Equivalent (EAE) for a 20-year period considering three thinning management regimes (A - unthinned, B - one thinning at age 10 years remaining 150 trees ha-1 and C - two thinnings, first at age 8 remaining 150 trees ha-1 and second at age 15 years remaining 75 trees ha-1) considering an initial density of 278 trees ha-1. A Monte Carlo simulation was performed considering six risk variables. Results showed that the discount rate is the variable that most influences the viability of the project. All site indexes in all management regimes lead to a feasible financial return, with NPV values ranging from 25,053 to 125,780 Brazilian reais per hectare, being regimes B and C the best ones. The probability for an unfeasible investment is almost zero, highlighting African mahogany as a great forest investment opportunity, providing high interest rates values (14% to 25%), superior to most available market rates of return.

SUMMARY: Tree height measurement is one of the most difficult activities in forest inventory data gathering, although it is a fundamental variable to support forest management, since it is an input for modelling growth and yield. To overcome this obstacle and ensure that the heights of trees are estimated accurately, hypsometric relationships are used. Therefore, the objective of this study was to compare different fitting strategies (i.e. nonlinear least squares and mixed-effects) to predict tree height in African mahogany Brazilian plantations using well know local (using only tree height and diameter) and generalized (using height, diameter and plot level variables) models. Data were gathered on 149 permanent plots sampled in different Brazilian regions and ages, totaling 4,201 height-diameter pairs. Different models were evaluated and the best method to estimate the height-diameter relationship was based on statistical and graphical criteria. A local model using mixed-effects with correction of heteroscedasticity was efficient and superior to other models evaluated. However, when using an independent data base, the generalized model fitted by nonlinear least squares generates adequate results that are scaled to the plots’ productivity, since the inclusion of dominant height into the model helps to predict height locally.

RESUMEN: La medición de la altura del árbol es de difícil realización en inventarios forestales, aunque es una variable fundamental para apoyar el manejo forestal una vez que es dato de entrada para la modelación del crecimiento y producción. Para superar este obstáculo y garantizar un cálculo de alturas de los árboles con precisión se utiliza la relación hipsométrica. Por lo tanto, el objetivo de este estudio fue comparar diferentes estrategias de ajuste (mínimos cuadrados no lineales e efecto mixto) para predecir la altura de los árboles en plantaciones brasileñas de caoba africana (Khaya ivorensis) utilizando conocidos modelos locales (apenas diámetro e altura) y generalizados (diámetro, altura y variables de la parcela). Los datos fueron recogidos en 149 parcelas permanentes muestreadas en diferentes regiones brasileñas y edades, totalizando 4.201 pares de altura-diámetro. Diferentes modelos fueron evaluados y el mejor método para estimar la relación altura-diámetro se basó en los criterios estadísticos y gráficos. El modelo local usando efectos mixtos con la corrección de heterocedasticidad fue eficiente y superior a otros modelos evaluados. Sin embargo, cuando se utiliza una base de datos independiente, el modelo generalizado ajustado por mínimos cuadrados no lineales genera resultados adecuados que se ajustan a la productividad de las parcelas, ya que la inclusión de la altura dominante en el modelo ayuda a predecir la altura a nivel local.

RESUMO O setor florestal brasileiro está em plena expansão e com um aumento gradativo de investidores florestais optando pelo cultivo de espécies de madeira nobre. O mogno africano (Khaya spp.) é uma espécie que vêm se destacando na preferência dos empresários como opção no investimento florestal. Porém, estudos e pesquisas sobre a espécie, principalmente no Brasil, são escassos. Assim, a presente revisão procurou reunir diversas fontes de publicação, nacionais e internacionais, abordando aspectos históricos do mogno, buscando aclarar as características da espécie e a experiência de outros países no manejo dessa cultura.

ABSTRACT The Brazilian forest sector is fast growing with a gradual increase of forest investors choosing valuable hardwood species for tree crops. African mahogany (Khaya spp.) is a species that has been preferred by many entrepreneurs as a forestry investment. However, there are few studies and research on the species, especially in Brazil. Therefore, this review aimed to bring together diverse sources of national and international publications, discussing the history of the mahogany and characteristics of the species as well as the experience of other countries on the management of this crop.

RESUMO A estimativa da qualidade de sítio é uma importante ferramenta para o manejo florestal, uma vez que auxilia na modelagem do crescimento e produção de florestas equiâneas. Dados de plantios brasileiros de mogno africano (Khaya ivorensis A. Chev.) foram utilizados para avaliar modelos de crescimento em altura dominante comparando modelos dinâmicos invariantes com a idade padrão e modelos estáticos (método da curva guia). Para a avaliação dos modelos foram utilizados critérios quantitativos e qualitativos. Também foi verificada a estabilidade dos modelos candidatos, sendo preferido o modelo que resultou em menos mudanças de classes na predição da mesma parcela em diferentes idades. O modelo de Lundqvist-Korf com o método da curva guia se mostrou eficiente, sendo recomendado para a classificação de sítios e para a predição de altura dominante em povoamentos de mogno africano. A amplitude dos índices de sítio, na idade de referência de 15 anos, foi de 17 a 33 metros.

ABSTRACT Site quality estimation is an important tool in forest management since it is useful for modeling growth and yield for even-aged stands. Data from African mahogany (Khaya ivorensis A. Chev.) Brazilian plantations were used to develop a model to predict dominant height growth, comparing dynamic base-age invariant site index models with the guide curve method (static models). For the evaluation of the candidate models qualitative and quantitative criteria were used. We also verified the stability of the candidate models, preferring a model providing fewer site class changes when predicting site index from different ages. The Lundqvist-Korf function fitted with the guide curve method proved to be effective and accurate for site classification and dominant height predictions of African mahogany stands. The range of observed site index, at a reference age of 15, was between 17 and 33 meters.

RESUMO Eremanthus erythropappus, conhecida vulgarmente por candeia, é uma árvore nativa do Brasil, geradora de renda devido à elevada durabilidade apresentada por sua madeira e, também, pelo seu óleo produzido conter, como ingrediente majoritário, o alfa bisabolol. Apesar deste potencial econômico, até o início do ano 2000, a espécie não contemplava estudos sobre seu sistema de cultivo, tanto para o manejo sustentável em áreas de ocorrência natural quanto para o estabelecimento de plantios comerciais. Este estudo propõe estudar novas estratégias de manejo com base em modelo de árvore individual, e avaliar o crescimento da candeia em diferentes espaçamentos. O experimento teve início em março de 2002, no município de Carrancas, Minas Gerais, Brasil. A área experimental foi dividida em quatro blocos, com quatro diferentes espaçamentos como tratamentos. O modelo avaliado para definir o melhor sistema de manejo foi baseado na relação entre o desenvolvimento da área de copa e do DAP das árvores. Os resultados mostraram que a candeia foi sensível a variação no espaçamento inicial. Aumentando o espaçamento inicial, a competição entre as árvores de candeia ocorre mais tarde, ou seja, à medida que o espaçamento aumenta demora-se mais para que o plantio perca o ritmo desejado de crescimento. O modelo testado foi consistente e a técnica baseada na árvore individual apresentou flexibilidade, fornecendo alternativas para diferentes estratégias de manejo. As melhores respostas de crescimento foram obtidas para densidades iniciais de plantio a partir de 3,75 m² por planta, área que corresponde a um espaçamento de 1,5m x 2,5m.

ABSTRACT Eremanthus erythropappus, commonly known as candeia, is an income-generating tree native to Brazil. This is due to the high durability of its wood and its essential oil containing the active component alpha bisabolol. Despite this economic potential, until the early 2000's no studies existed to explore the sustainable management in areas in which the species naturally occurs or for establishing commercial plantations. This study proposes new management strategies based on an individual tree model, and evaluates the growth behavior of candeia trees planted in different spacing. The experiment was installed in March 2002, in Carrancas municipality, Minas Gerais state, Brazil. The experimental area was divided into 4 blocks with 4 different spacings as treatments. The individual model used to propose the best management system uses development of crown area as a function of DBH. The results showed that candeia trees were sensitive to initial spacing variation. With increased initial spacing, candeia trees reached competition later, as demonstrated by crown area development. Thus, candeia trees planted at a wider spacing maintain a desirable growth rate without need for thinning for a longer time, compared to trees planted at narrower spacing. The fitted individual tree model presented in this study showed consistent results and flexibility, providing alternatives for different management strategies. The best growth response was obtained for planting densities greater than 3.75 m² per tree, which corresponds to a spacing of 1.5 x 2.5 m.

Resumo:O objetivo deste trabalho foi desenvolver e validar um sistema de prognose para produção em volume e área basal de povoamento de Pinus taeda manejado intensamente, com uso de modelos de povoamento e de classes diamétricas compatíveis em estimativas de área basal. Os dados utilizados no estudo foram obtidos de plantios localizados no norte do Uruguai. Para a validação dos modelos sem perda de informação, foi aplicado um esquema de validação em três fases: primeiro, as equações foram ajustadas sem a base de dados de validação; depois, a validação do modelo foi realizada; e, por fim, a base de dados foi reagrupada para recalibrar os valores dos parâmetros. Após a validação e a parametrização final dos modelos, foi realizada uma simulação do primeiro desbaste comercial. O sistema de prognose desenvolvido foi preciso e acurado na estimativa de produção em área basal por hectare ou por classes diamétricas. Houve compatibilidade nas estimativas de área basal entre os modelos de classes diamétricas e do talhão como um todo, com diferença média de -0,01 m2 ha-1. O esquema de validação aplicado é lógico e consistente, uma vez que informações sobre a acurácia e a precisão dos modelos são obtidas sem perda de informação nas estimativas dos parâmetros dos modelos.

Abstract:The objective of this work was to develop and validate a prognosis system for volume yield and basal area of intensively managed loblolly pine (Pinus taeda) stands, using stand and diameter class models compatible in basal area estimates. The data used in the study were obtained from plantations located in northern Uruguay. For model validation without data loss, a three-phase validation scheme was applied: first, the equations were fitted without the validation database; then, model validation was carried out; and, finally, the database was regrouped to recalibrate the parameter values. After the validation and final parameterization of the models, a simulation of the first commercial thinning was carried out. The developed prognosis system was precise and accurate in estimating basal area production per hectare or per diameter classes. There was compatibility in basal area estimates between diameter class and whole stand models, with a mean difference of -0.01 m2ha-1. The validation scheme applied is logic and consistent, since information on the accuracy and precision of the models is obtained without the loss of any information in the estimation of the models' parameters.