Biometric assessment of early stem growth at a commercial stand of African mahogany (Khaya grandifoliola)

African mahogany species (Khaya spp.) have proven to be promising in the Brazilian forestry scenario, replacing native mahogany owing to their medium-fast growth and relevant timber value. This study aimed to carry out forest inventory and assessments of a Khaya grandifoliola plantation in the first years after planting, test hypsometric models to describe tree growth, and identify the maximum commercial stem yield (i.e., greater than 6 m in height). The stand was located in the municipality of Piracanjuba (GO), where seedlings of seed origin were used. Twenty random plots with a 15 m radius were allocated, and the total height (HT), stem height (HS), diameter at breast height (DBH), crown area, and forest canopy were measured. Four hypsometric models were employed in this study. The best equation was selected based on determination coefficients and standard errors. Further, the models were cross-validated to evaluate predictability and bias. At four years of planting, the largest class of HS was found to range from 3.1 to 4.1 m, and most trees had a DBH ranging from 0.084 to 0.126 m. The percentage of trees with stems > 6 m was 8.35%. The linear model ensured more consistent results for estimating HT, while the quadratic and Weibull models led to more consistent results for HS. By using models, stem measurements can be measured based on DBH, ultimately aiding the selection of stem management strategies for the growth of forests with greater commercial value.

Native species valuable timber plantations in Northern Guatemalan Humid Lowlands: ecological features and silvicultural feasibility / Plantaciones con especies nativas valiosas en Tierras Bajas del Norte de Guatemala: rasgos ecológicos y viabilidad silvícola

The Northern Humid Guatemalan Lowlands contains a significant diversity of tree species, including some valuable-timber producers; these species are threatened by commercial overexploitation and habitat loss due to deforestation. The cultivation of these species in forest and agroforest plantations is a potentially viable option for balancing their conservation and commercial harvesting, something that has been promoted with Government Incentives in Guatemala during the past two decades. However, these species have not been widely planted, among other constraints, because knowledge on their ecological requirements and silviculture is scarce. A characterization of monoculture and mixed plantations with 14 native valuable-timber species was made in the Humid Lowlands of Northern Guatemala, analyzing for each species frequency of association and accompanying species, planted area, the main ecological features and growth rates. To gather information, we combined field observation and measurements with interviews and literature review. Based on our survey, main management challenges for cultivation of the species were identified and described. Valuable-timber native trees could potentially be sustainably cultivated in the study zone in different types of forest plantations and agroforestry schemes of coffee, cacao, cardamom and cattle; considering their suitability to fit in diversified systems, growth performance and farmer's preferences, Swietenia macrophylla, Cedrela odorata, Tabebuia donnell-smithii, Calophyllum brasiliense and Cordia alliodora were the species with the higher potential for inclusion in plantations. However, several unsolved problems continue restricting the cultivation of these species in plantations; therefore, is essential a careful design and management.

Las Tierras Bajas y Húmedas del Norte de Guatemala contienen diversidad relevante de especies arbóreas, incluyendo algunas de madera valiosa; estas especies están amenazadas por sobre explotación comercial de su madera y deforestación. El cultivo de estas especies en plantaciones forestales y agroforestales es una opción potencialmente viable para equilibrar su conservación y aprovechamiento, lo cual ha sido promovido en Guatemala durante las dos décadas pasadas. Sin embargo, estas especies no se cultivan extensivamente, entre otras limitantes, debido al escaso conocimiento sobre su ecología y silvicultura. Se caracterizaron plantaciones puras y mixtas con 14 especies nativas maderables valiosas en Tierras Bajas y Húmedas del Norte de Guatemala, analizando para cada especie, presencia de especies, superficies plantadas, rasgos ecológicos y crecimiento. Para obtener información se combinó observaciones de campo, mediciones, entrevistas, consultas de archivo y revisión bibliográfica. Se identifican y describen los principales desafíos de manejo para cultivar las especies. Las especies nativas de madera valiosa podrían potencialmente ser cultivadas de manera sostenible, en diferentes tipos de plantación forestal y agroforestal con café, cacao, cardamomo y ganadería; considerando idoneidad para encajar en sistemas diversificados, tasas de crecimiento y preferencias de productores, Swietenia macrophylla, Cedrela odorata, Tabebuia donnell-smithii, Calophyllum brasiliense y Cordia alliodora fueron las especies que mostraron mayor potencialidad para ser incluidas en plantaciones en la zona. Sin embargo, aún persisten diferentes aspectos no resueltos que limitan el cultivo de estas especies en plantación, requiriéndose un cuidadoso diseño y manejo.

Von Thünen e o abastecimento madeireiro de centros urbanos pré-industriais / Von Thünen and wood supply of pre-industrial urban centers / Von Thünen y el abastecimiento maderero de centros urbanos preindustriales

A madeira era um recurso natural indispensável ao metabolismo dos centros urbanos pré-industriais, tanto como material construtivo quanto como fonte energética. Em razão da baixa relação valor/volume dos produtos madeireiros, a espacialidade desse setor econômico era largamente determinada pelo custo de transporte. Deste modo, um arcabouço teórico que pode ser importante para a compreensão do fenômeno do abastecimento madeireiro das cidades pré-industriais é a clássica teoria de von Thünen sobre o efeito da distância do mercado sobre a estrutura da produção agrária. O artigo tem como objetivo discutir as potencialidades e limitações desta abordagem. Inicialmente, é apresentada a teoria do "Estado Isolado" e revisam-se os estudos históricos que a utilizaram, tanto como alicerce interpretativo quanto como teoria empírica. Em seguida, é formulado um modelo teórico-conceitual em que a atividade madeireira responde às variações da intensidade agrícola, procurando mostrar a utilidade desse esquema na interpretação do caso da cidade do Rio de Janeiro, no final do período colonial.

Wood was a critical natural resource to the metabolism of pre-industrial urban centers, both as a building material and as an energy source. Due to the low value/volume ratio of wood products, wood economy was largely determined by transport costs. Thus, a theoretical framework that may be important to understanding the phenomenon of pre-industrial wood supply is Von Thünen's theory about the effect of distance from market on the spatial structure of agricultural production. The article aims to discuss the potential and limitations of this approach. At first, we present the theory of "Isolated State"; then we review the historical studies that used the theory, both as a comprehensive framework and as an empirical theory. Later, we formulate a theoretical-conceptual model in which woodcutting responds to changes in agricultural intensity, as to show the usefulness of this scheme in interpreting the case of the city of Rio de Janeiro in the late colonial period.

La madera era un recurso natural indispensable para el metabolismo de los centros urbanos preindustriales, tanto como material constructivo, así como fuente energética. Debido a la baja relación valor/volumen de los productos madereros, la envergadura de ese sector económico estaba profundamente determinada por el coste del transporte. Por este motivo, un armazón teórico que puede resultar importante para la comprensión del fenómeno de abastecimiento maderero de las ciudades preindustriales es la clásica teoría de von Thünen sobre el efecto de la distancia del mercado sobre la estructura de la producción agraria. El artículo tiene como objetivo discutir las potencialidades y limitaciones de este enfoque. Inicialmente, se presenta la teoría del "Estado Aislado" y se revisan los estudios históricos que la utilizaron, tanto como base interpretativa, así como teoría empírica. Enseguida, se formula un modelo teórico-conceptual en el que la actividad maderera responde a las variaciones de la intensidad agrícola, procurando mostrar la utilidad de ese esquema en la interpretación del caso de la ciudad de Río de Janeiro, al final del período colonial.