Total Tree Height Research Articles

VARIATION OF SPECIFIC GRAVITY WITHIN Eucalyptus grandis TREES GROWING IN DIFFERENT SITE CLASSES.

Wood is a very remarkable material with variability and flexibility The variability of woodincreases its utility It may be also a major drawback to its efficient use as raw materialTherefore understanding of pattern of wood properties within the tree has becomeimportant. In addition, growth rate and its effect on wood properties are of practicalimportance to maximize wood and fiber production. In this study, variations of specificgravity within the trees of 30-years old Eucalyptus grandis extracted from Pattipola,Saruhipura and Piduruthalagala in Nuwara-Eliya districts were studied. Data werecollected in relation to site class (growth rate) as determined by tree height. The objectiveof the study was to find out whether specific gravity is affected by growth rate of tree.Specific gravity values were collected in a systematic manner, which are essential incommercial utilization of this species. Three sites, namely Slow Growth Site (SGS),Medium Growth Site (MGS) Fast Growth Site (FGS) were chosen. Five trees from eachsite were taken for the investigation. Tree height difference between SGS (33.8 meters )FGS (45 meters) was significantly different (PS:005) but not between SGS and MGS (387meters)Variation patterns of specific gravity in racial direction were studied using two linearsections extracted across the diameter of every sample disc, from north to south and cast towest at different height levels at breast height and at 20'Yo,40%, 60% and 80% of total treeheight. 3021 wood samples of 2*2* 1 em dimensions were used for specific gravitydetermination.In general, low specific gravity values were observed at pith in all three sites. In fastgrowth site, specific gravity increased from uith; thereafter it remained constant towardsthe bark with small fluctuation. In slow and medium growth sites, however specific gravityincreased gradually towards the bark. Fast growth site maintained the highest specificgravity values throughout piths to bark The specific gravity of SGS and MGS increasedrapidly with increasing distance from pith.In general, specific gravity increased with tree height in all sites except at 20% height levelin SGS and MGS. Mean specific gravity values in SGS at breast height, 20%, 40'%, 60'Y<,and 80% height levels were 0.432, 0.431, 0433, 0.468 and 0.475 respectively. Specificgravity values for these levels in MGS were 0.441,0.435,0.467,0.477,0.542 and Specificgravity values were 0.479.0.482,0.493,0525, .J.553 for FGS respectively.

Ecuación para estimar la biomasa arbórea en los bosques tropicales de Costa Rica

<p>Una de las medidas más relevantes para la mitigación del cambio climático es la conservación y regeneración del bosque en nuestros países. La cantidad de carbono que se almacena en la biomasa arbórea pasa a ser una medida relevante para la política pública. El presente trabajo analiza la asociación que tienen algunas variables dasométricas, fácilmente medibles, asociadas a la biomasa, con el propósito de estimarla indirectamente, dado que la medición directa de la biomasa arbórea es un trabajo complejo y tiene un costo muy elevado. El objetivo general del estudio fue hacer un análisis del comportamiento de las variables dasométricas fácilmente medibles para predecir biomasa arbórea con datos de dos bosques tropicales de Costa Rica, con el propósito de analizar su posible aplicación generalizada en los bosques tropicales de todo el país.</p> <p>Mediante una revisión bibliográfica, se determinaron cuatro posibles modelos que estiman biomasa en bosques tropicales. Se evaluaron 907 árboles con diámetro a la altura de pecho (dap) mayor a 10 cm en dos bosques tropicales de Costa Rica (Parque Nacional Corcovado en el suroeste y Fila Carbón en el sureste, vertiente del Caribe), generando una estimación de biomasa lo más precisa posible. Se realizó un análisis de las variables de los árboles (densidad específica de la madera, altura total y dap) y su biomasa, con el fin de desarrollar el modelo que facilitara la predicción de esta. El modelo final utiliza como variables independientes el dap y la densidad. Con el dap se da el hecho de que existe una alta correlación con la altura total, la cual es muy difícil de obtener en el campo, de modo que se decidió no utilizarla. La variable densidad es importante, ya que dos árboles con la misma estructura pero distinta densidad van a mostrar diferente cantidad de biomasa. Para la estimación de este modelo se utilizó una regresión segmentada (por la relación que tienen el dap y la altura total con la variable biomasa transformada) y cuadrados medios ponderados para resolver el problema de heterocedasticidad. El modelo final cumplió con los supuestos estadísticos de una regresión lineal general, evaluados por el comportamiento de los residuos y otras pruebas paramétricas, y obtiene un coeficiente de determinación de 0,992.</p> <p>Como conclusión, este estudio propone un enfoque metodológico para estimar la biomasa a nivel general en los bosques, lo cual se considera de utilidad para fundamentar la toma de decisiones sobre el almacenamiento a largo plazo del carbono en los bosques tropicales. Se espera que en estudios futuros se disponga de parcelas de otros bosques con mediciones de la biomasa real, para seguir calibrando el modelo propuesto para la estimación de la biomasa almacenada en los bosques tropicales.</p>

Benchmarking and Calibration of Forest Vegetation Simulator Individual Tree Attribute Predictions Across the Northeastern United States

This study used permanent sample plot data from the USDA Forest Service’s Forest Inventory and Analysis database to benchmark and calibrate three key submodels of the Forest Vegetation Simulator-Northeast variant (FVS-NE). Model predictions for total tree height (ht) and 5-year diameter (dbh5) and height increment (ht5) for the 20 most abundant species did not indicate any serious spatial trends. FVS-NE predictions for total ht performed moderately well, as mean bias averaged 0.9 5.2 ft (mean SD) across all species. FVS-NE dbh5 predictions fell within 15% of observed values between 8.4 and 17.3% of the time and performed best for shade-tolerant species and worst for intermediate shade intolerants. For ht 5 , the number of predictions that fell within 15% of observed values averaged 7.7%. Submodel performance generally improved after calibrating FVS-NE predictions using tree size, site, and climate variables. After employing a calibrated dbh5, 5-year basal area growth continued to be underpredicted across all ecoregions and forest types. Results indicate that (1) an assessment of overall model performance should be conducted if calibrated submodels are used and (2) alternative modeling strategies be explored to better represent the allometry and growth of the important trees species across the northeastern United States.

Available residual biomass obtained from pruning Morus alba L. trees cultivated in urban forest

Large quantity of residual biomass with possible energy and industrial end can be obtained from management operations of urban forests. The profitability of exploiting these resources is conditioned by the amount of existing biomass within urban community ecosystems. This research was focused on direct and indirect quantification of lignocellulosic waste from urban tree pruning of Morus alba, which is widely deployed as ornamental vegetation in Mediterranean countries. The mean quantity of dried pruned biomass obtained in street and park location was 31.67 kg/tree and 77.78 kg/tree with standard deviation 16.88 kg/tree and 29.51 kg/tree, respectively. Mathematical models for predicting the available amount of pruning residues for this species were developed from easily measurable dendrometric parameters, such as diameter at breast height, crown diameter and total tree height. The best functions were obtained when several variables were combined in quadratics models. R2 was 0.96 for topping type of pruning practice and street location, and 0.88 in maintenance pruning applied in park areas. Good results were also found when correlating apparent crown volume with kilograms of yielded residues. These models can be used for urban inventories and the application of logistic models. The analysis indicates that an abundant amount of residual biomass originating from pruning operations of ornamental species can be used to achieve ecological and energy targets.

Effect of Tree Height and Girth on Gum Yield of Acacia senegal L. in Savanna Woodland of Nigeria

Parameters influencing gum yield such as tapping techniques and soil mineral elements had earlierbeen investigated while there is dearth of information on effect of morphological characteristics on gumyield. This study investigated effects of height and girth on yield of Acacia senegal L. in the naturalforests. Three heights and girth classes were purposely selected. Trees which heights and girth fell withinthose classes were selected randomly and tapped at constant height classes with varying girth classes.Exudates were collected, weighed and recorded according to height and girth class respectively.Descriptive and ANOVA results showed that when total tree height was lower than 2.0 m, gum yieldincreased as tree girth goes higher from 35 - 54cm (163.6 - 209.7g). Tree girth significantly affected gumyield (p≤0.05) and trees which total heights were lower than 2.0m (maximum of 1.95m) and girth higherthan 54cm (maximum of 65cm) produced the highest mean gum yield. Silvicultural practices that couldbring about increase in girth such as early pruning and re-spacing which is applicable to plantation treescould also be carried out on the natural forest trees to increase gum yield.Key words: Savanna woodland, Acacia senegal, Gum yield.

Comparison of stem volume of Eastern white pine (Pinus strobus L.) and Scotch pine (Pinus sylvestris L.)

This study deals with mensurational and volumetric characteristics of introduced Eastern white pine (Pinus strobus) in comparison with native Scotch pine (Pinus sylvestris) of the similar age and habitat. Municipal forests of Hradec Králové city (an area with the natural occurrence of Scotch pine and introduced Eastern white pine; east part of Bohemia, altitude from 250 to 280 m a.s.l.) belong to typological unit – nutrient-very poor, and acidic sites. There comparative analysis of basic stem variables (stem diameter at the breast-height – DBH, total tree height – H and stem volume – V) of dominant trees (10 individuals with the highest DBH of both species) in four suitable forest stands of age from 42 to 102 years was done. Statistical analysis showed similar trends in all forests stands. Eastern white pine compared to Scotch pine reached larger mean DBH (up to 16%). H – values do not have a clear trend across the forest stands and did not show large differences in all cases. Eastern white pine compared to Scotch pine showed also larger mean stem volume (up to 47%). Therefore, introduced Eastern white pine reached higher stem size parameters and wood production compared to native Scotch pine in studied forest district.

Residual biomass calculation from individual tree architecture using terrestrial laser scanner and ground-level measurements

Large quantity of residual biomass with possible energy and industrial end can be obtained from management operations of urban forests. The profitability of exploiting this resource is conditioned by the amount of existing biomass within urban community ecosystems. Prior research pointed out that residual biomass from Platanus hispanica and other tree species can be calculated from dendrometric parameters. In this study, two approaches have been analyzed: First, applicability of TLS was tested for residual biomass calculation from crown volume. In addition, traditional models for residual biomass prediction were developed from dendrometric parameters (tree height, crown diameter, and diameter at breast height). Next, a comparison between parameters obtained with both methodologies (standard methodologies vs TLS) was carried out. The results indicate a strong relationship (R2=0.906) between crown diameters and between total tree heights (R2=0.868). The crown volumes extracted from the TLS point cloud were calculated by 4 different methods: convex hull; convex hull by slices of 5cm height in the XY plane; triangulation by XY flat sections, and voxel modeling. The highest accuracy was found when the voxel method was used for pruned biomass prediction (R2=0.731). The results revealed the potential of TLS data to determine dendrometric parameters and biomass yielded from pruning quitar of urban forests.

Nonlinear growth functions for modeling tree height–diameter relationships for Gmelina arborea (Roxb.) in south-west Nigeria

Tree height–diameter relationship can be used as an important input component in forest growth and yield models, and description of stand dynamics. Five nonlinear growth functions were fitted to tree height–diameter data of a 21-year-old Gmelina arborea plantation in Ibadan, Nigeria. The data consisted of three sets obtained in 2004, 2008 and 2011 for total tree height and diameter at breast height (DBH). According to the model statistics, the five growth functions fitted the data equally well, but resulted in different asymptote estimates. Modified exponential fit was observed to give the best fit for the three data sets based on least square error, coefficient of determination and significance. The predicted values follow the same nonlinear pattern and formed close to the line of best fit without much outlier. The result of this study revealed that the ability of DBH in determining height is not strong enough based on the model's goodness of fit and the model's ability for predictive purposes. Hence, more variables such as age, crown area and soil fertility were recommended to be incorporated in future prediction of the tree height in the study area.

Secondary forest floristic composition, structure, and spatial pattern in subtropical China

Secondary evergreen broadleaved forests are precious remnants for biodiversity conservation and templates for sustainable management of natural forests in subtropical China. Floristic composition, size structure, and spatial pattern of dominant tree species have been investigated for a subtropical secondary evergreen broadleaved forest in the Huitong Yingzuijie National Forest Reserve, Hunan, China. The location of all trees greater than 4 cm in diameter at breast height (DBH) were mapped within a 0.96-ha plot in which species, DBH, and total tree height were recorded. Ripley's K(t) function was used to analyze spatial patterns and associations. The secondary forest consisted of 74 tree species and 1,596 stems per hectare. A reverse-J shaped DBH classes distribution was observed for all stems and trees of later seral species whereas trees of earlier successional species were distributed irregularly. Significant aggregated spatial patterns were observed for all trees within the forest and for conspecific trees of each dominant species. This result, and a repulsive spatial pattern for interspecific trees of Choerospondias axillaries and Cyclobalanopsis glauca against other dominant tree species, support segregation hypothesis. Contributions of seed dispersal, topographic heterogeneity, and competition to spatial patterns of conspecific trees vary depending on tree species. Attractive spatial pattern among interspecific trees of Liquidambar fortunei, Liquidambar formosana, and Pinus massoniana reflects stochastic colonization of pioneer tree species and a facilitation relationship. Although deciduous species are long-lived and persist over long successional processes, they will eventually be replaced by late seral evergreen species within the secondary forest if no disturbance events occur.

Tree species composition and stand structure of woody savanna in Dahomey Gap

The Dahomey gap is a savanna region separating the West African rainforests to two regions. We set two sites in this woody savanna, at north and south regions in purpose to examine the differences in tree community properties between sites and among canopy-closure types, and to reveal the factors affecting the differences. Two sites are ca. 225 km distant from each other and have different rainfall patterns. Six 1-ha plots in each site were studied, which cover three types of canopy-closure (closed, semi-open and open). We recorded 3,720 trees that are equal to or more than 5 cm diameter at the breast height, consisted of 70 species belonging to 34 families. Most abundant three species, Isoberlinia doka, Vitellaria paradoxa and Pericopsis laxiflora appeared in both sites. The detrended correspondence analysis (DCA) based on species abundance divided 12 plots into groups of north and south sites along the first axis, whereas canopy-closure types were not associated with DCA axes. At any given total tree height, trees in the north site had slenderer stems with narrower crowns than those in the south site. The specific leaf area was smaller in the north site. Between-site differences in species abundance and allometry are possibly driven by rainfall variation.

Influence of silvicultural regimes on the volume and proportion of juvenile- and mature wood in boreal Scots pine

Trees from 48 to 78 years old, exposed to three different long-term silvicultural regimes, were examined for transition ages between juvenile (JW), transition (TW) and mature wood (MW), total wood volume and proportions of the same wood types, as defined by fibre length. Twenty one sample trees were collected at sites with similar growing conditions within the same geographical area. Stem discs and fibre samples from breast height (BRH), 20% of tree height, green crown height and 70% of tree height were analysed. Trees growing in an environment with few neighboring trees (Sparse regime) started to produce MW, on average, five years later at BRH and six to nine years later at 20% of total tree height than trees in stands with high stem numbers (Dense regime) and trees growing in stands where the stem number had been heavily reduced after an initial high stand density (Dense/Sparse regime). For all regimes, the greatest mean fibre length was found below the green crown and high initial stem numbers were found to positively influence fibre length. The proportion of MW in the whole stem was 34% at Sparse regime sites, 57–69% at Dense/Sparse sites and 63–64% in sites where there was a Dense regime. The proportion of MW was significantly lower for trees from the Sparse regime on each stem section compared. In conclusion, the results suggest that the initial condition a tree faces affects the stem wood properties and quality output at the end of the rotation period.

Geographic Patterns and Stand Variables Influencing Growth and Vigor of Populus tremuloides in the Sierra Nevada (USA)

Awareness of geographic patterns and stand variables that influence tree growth will help forest managers plan appropriate management and monitoring strategies. We quantified influences of stand location, species composition, stand density, and tree size on aspen tree growth and vigor around the Lake Tahoe Basin in the Sierra Nevada Mountains of California and Nevada, USA. Radial growth data were taken from increment cores. Aspen trees on the south and west sides of the lake grew 20–25% faster than aspen in north and east side stands. Diameter growth at 2,400 m elevation was 58% of growth at 1,900 m near lake level. Aspen grew faster with less competition from neighbor trees. At any level of competition, aspen growth was slower beside conifer neighbors and correlated with crown ratio (CR: length of live crown relative to total tree height, a proxy for tree vigor). Analysis of independent CR data for 707 aspen trees in nine additional stands indicated that aspen had smaller crowns in the presence of greater competition, and that composition of neighbor trees also affected CR: aspen trees had shorter crowns in the presence of conifer at higher stand densities. Taken collectively, our analyses point towards a cascading decline in aspen growth and vigor incited by succession of aspen stands to conifers. Our findings suggest that conifer removal and stand density control in aspen-conifer stands at Lake Tahoe will enhance aspen growth and vigor.

Estructura, composición florística, biomasa y carbono arriba del suelo en los manglares Laguna de Gandoca y Estero Moín, Limón, Costa Rica

Se delimitó el área de dos manglares del Caribe Sur deCosta Rica, se analizó su estructura horizontal y verticaly la composición florística. Se cuantificó la biomasay el carbono arriba del suelo respecto al gradiente dedistanciamiento al borde del canal; en ambos sitios.Sobre transeptos perpendiculares al borde del canal,se establecieron parcelas circulares de siete metros deradio, dispuestas cada 25 m. Se evaluó el diámetro (d) decada individuo mayor a 5 cm (a 1,30 m del suelo o arribade la raíz más alta de los individuos con raíces aéreas).Se determinó la densidad de árboles (árboles/ha), el áreabasal (m2/ha), la distribución de los individuos por clasediamétrica, la altura total (m), la densidad de árboles porpisos de altura, el índice de valor de importancia de lasespecies, los índices de diversidad de Shannon–Wiener(H´) y Alpha de Fisher, la biomasa y la reserva de carbonoarriba del suelo. Se utilizó un diseño experimental debloques incompletos al azar (BIA). Se realizaron análisisde varianza (ANDEVA) y pruebas Duncan. El áreadelimitada del manglar de Gandoca fue de 13,34 ha y 10,73 ha en Moín. En Gandoca y Moín se encontrarondiámetros promedio de los árboles de 21,43 cm y20,01 cm, alturas totales promedio de 12,8 m y 10,5 m,densidades de 687 árboles/ha y 708 árboles/ha, áreasbasales de 26,35 m2/ha y 26,37 m2/ha respectivamente.La especie más importante en Gandoca fue Rhizophoramangle y en Moín Pterocarpus officinalis. En ambossitios también se encontraron Laguncularia racemosa yAvicennia germinans junto a otras 20 especies asociadas.El sitio más diverso fue Moín. La biomasa fue de 330, 27Mg/ha y 257,10 Mg/ha, el carbono fue de 153,25 Mg/hay 119,29 Mg/ha para Gandoca y Moín respectivamente.La composición florística y las variables estructurales seasemejaron a otras reportadas en manglares del Caribey sugieren que los manglares estudiados son madurosy se encuentran en constante renovación; sin embargo,Moín presenta un grado de disturbio mayor. Las reservasde biomasa y carbono superaron a las reportadas parabosques secundarios y primarios de Costa Rica y lasde algunos manglares del Indo - Pacífico. El manglar deGandoca presentó un aumento de área, con respecto alo reportado por Coll et al. (2001), para el manglar de Moínno se encontraron registros anteriores de este dato, porlo que este estudio no reporta aumento o disminucióndel área.

Reconstructing the post-glacial sediment budget of a mountain valley-fill system, Chilliwack Valley, British Columbia, Canada

Large quantity of residual biomass with possible energy and industrial end can be obtained from management operations of urban forests. The profitability of exploiting these resources is conditioned by the amount of existing biomass within urban community ecosystems. This research was focused on direct and indirect quantification of lignocellulosic waste from urban tree pruning of Morus alba, which is widely deployed as ornamental vegetation in Mediterranean countries. The mean quantity of dried pruned biomass obtained in street and park location was 31.67 kg/tree and 77.78 kg/tree with standard deviation 16.88 kg/tree and 29.51 kg/tree, respectively. Mathematical models for predicting the available amount of pruning residues for this species were developed from easily measurable dendrometric parameters, such as diameter at breast height, crown diameter and total tree height. The best functions were obtained when several variables were combined in quadratics models. R2 was 0.96 for topping type of pruning practice and street location, and 0.88 in maintenance pruning applied in park areas. Good results were also found when correlating apparent crown volume with kilograms of yielded residues. These models can be used for urban inventories and the application of logistic models. The analysis indicates that an abundant amount of residual biomass originating from pruning operations of ornamental species can be used to achieve ecological and energy targets.

Assessing a reliable modeling approach of features of trees through neural network models for sustainable forests

Financial exploitation of forests comprises an important part of man activity. There are efforts being made to conserve the sustainable exploitation while simultaneously avoiding degradation of the environment. One tool used in these efforts is the modeling of tree features, such as total tree height, sawn-timber tree height, merchantable tree height, and total or sawn-timber tree volume, which yields an estimate of the forest in finance recoverable goods. Sustainable forest management design must be supported by the adjustment of computational techniques. The purpose of this paper is to assess a reliable modeling approach for estimating individual tree heights for the maturity of trees for logging through determining the applicability of different types of neural network models and identifying a neural network procedure for accurate estimation of these variables. These models serve as an alternative to the traditional regression approach. All types of model estimations are evaluated and compared in this paper. Back Propagation Artificial Neural Network (BPANN), Cascade Correlation Artificial Neural Network (CCANN), and Generalized Regression Neural Network (GRNN) models are developed to estimate individual tree heights for the logging of mature trees, such as sawn-timber height and merchantable height. The results reported in this research suggest that the selected BPANN and CCANN models are reliable and demonstrate their adequacy and potential for estimating sawn-timber and merchantable tree height. The results also illustrate that the CCANN models are superior to the BPANN and GRNN models and lead to higher estimation accuracy. Moreover, the NN models were found to be superior to the tested nonlinear regression models.

Intercepción de precipitación en tres estadios de sucesión de un Bosque húmedo Tropical, Parque Nacional Guanacaste, Costa Rica

<p>La intercepción de precipitación fue determinada por medio de la precipitación bruta (PB), precipitación de copas (PC) y flujo caulinar (FC) en tres estadios de sucesión secundaria en un Bosque húmedo Tropical en el Parque Nacional Guanacaste, Costa Rica. En cada estadío se identificaron las especies y se midió la altura total y el diámetro de todos los árboles mayores a 5 cm de diámetro presentes en las parcelas de medición. El Índice de Área Vegetal (IAV) y el Índice de Complejidad de Holdridge (ICH) fueron estimados para describir la estructura de cada bosque. El ensayo se realizó entre julio y octubre del 2007, registrando una precipitación total de 491,2 mm en el estadío intermedio, y de 706,1 mm para el estadio temprano y tardío. Los resultados indican que la intercepción de precipitación aumentó conforme avanza la madurez del estado de sucesión del bosque.</p>

Ponto de amostragem ao longo do fuste para estimativa do poder calorífico da madeira

Este trabalho teve como objetivo verificar a variação do poder calorífico superior (PCS) ao longo do fuste das espécies florestais Acacia mearnsii De Wild, Eucalyptus grandis W. Hill, Mimosa scabrella Benth. e Ateleia glazioveana Baill e também avaliar o número e as posições das amostras ao longo do fuste para a estimativa do PCS dessas espécies. Para tanto, foram retirados discos de aproximadamente dois centímetros de espessura, ao longo de 0 %, 25 %, 50 % e 75 % da altura total de árvores com um ano de idade para determinação do PCS em bomba calorimétrica (C5000, IKA WORKS). Para Eucalyptus grandis e Ateleia glazioveana, é possível estimar o PCS a partir de um disco, respectivamente, nas posições 50% e 0% da altura total, para Mimosa scabrella em dois discos, nas posições 0+75% e para Acacia mearnsii em três discos, nas posições 0+25+75% da altura total.

Deriving individual tree competition indices from airborne laser scanning

This article deals with quantification of competition on the single-tree level. Three new classes (non-spatially explicit, spatially explicit and hybrid) of tree competition indices based on airborne laser scanning were derived. By comparison to a selection of existing competition indices both spatially and non-spatially explicit, it was concluded by the performance of a growth model fitted using the competition indices as independent variables, that the ability to predict the diameter growth at breast height of individual trees of Norway spruce (Picea abies (L.) Karst.) was better for many of the derived competition indices, than for the existing competition indices. In addition, the Spearman rank correlation for the best derived index calculated on plot level revealed a highly significant correlation (p<0.001) between diameter growth at breast height and competition ranging from −0.81 to −0.18 on plot basis. For data pooled from 20 plots used in the study the best of the derived indices increased the adjusted R2 of the growth model by 18%, when compared to the adjusted R2 of a growth model excluding competition as an independent variable. The best of the existing indices increased it by 10%. Some of the derived indices only require the spatial location and properties (diameter at breast height, crown width, height to base of crown and total height) of the subject tree, and not of the competing trees. Logic shows that such indices eliminate plot edge bias, which was supported empirically. When airborne laser scanning data is available, these competition indices should be preferred.

Desempenho silvicultural e seleção precoce de clones de híbridos de eucalipto

O objetivo deste trabalho foi avaliar a variabilidade genética e o desempenho silvicultural de clones de híbridos interespecíficos de Eucalyptus urophylla, E. globulus, E. maidenii, E. saligna, E. grandis, E. pellita, E. resinifera, E. kirtoniana e E. dunnii, e determinar a viabilidade da seleção precoce em selecionar clones superiores. Os diâmetros do tronco à altura do peito aos três (DAP3) e sete (DAP7) anos de idade e a altura total das árvores aos sete anos de idade foram mensurados. Utilizou-se o delineamento experimental de blocos ao acaso, com 138 clones, 10 repetições e seis plantas por parcela. Os dados foram submetidos à análise de variância e agrupados pelo método das k-médias, tendo-se realizado a comparação de médias e determinado a correlação de Pearson (r) entre as variáveis avaliadas. A validação do agrupamento foi realizada por meio de análise de variância e do teste de Tukey. Os clones de híbridos interespecíficos de Eucalyptus apresentaram variabilidade genética. Foram estabelecidos cinco grupos de clones com base no desempenho silvicultural (DAP3, DAP7 e altura). O DAP3 é altamente correlacionado ao DAP7 e à altura aos sete anos de idade. A seleção com base no DAP3 pode ser utilizada para identificar clones superiores de Eucalyptus com grande vigor de crescimento.

Evaluation of nonlinear equations for predicting diameter from tree height

With the emergence and advancement of airborne laser scanning technology over the past decade, individual tree height can be easily measured over a large area of forests with a comparable degree of accuracy to conventional ground-based methods. In laser scanning based large-scale forest inventories, the need to predict diameter from remotely sensed tree height calls for a systematic evaluation of equation forms as the first step towards a well-developed approach to developing diameter–height equations. This study evaluated more than 30 height–diameter equations in the forest biometrics literature to select candidates for deriving equation forms for diameter–height equations. The evaluation was based on four criteria: (i) the height–diameter function is inversable; (ii) the inverse function is continuous and monotonically increasing over a specified working range of total tree height; (iii) diameter at breast height is equal to zero when tree height equals breast height in the inverse function; and preferably, (iv) the inverse function has an inflection point that is consistent with biological expectations. A total of 12 candidate equation forms were derived, which included five two-parameter and seven three-parameter equations. The estimation properties and predictive performance of these 12 equation forms were further evaluated and compared through repeated sampling and fitting using data from 3581 trees destructively sampled for taper measurements from Pinus radiata D. Don plantations across New South Wales, Australia. Three equation forms, including the constrained Richards, Weibull, and the combined power and exponential function, displayed superior prediction accuracy and estimation properties and so were recommended as the primary equation forms for developing diameter–height equations. The remaining equation forms were marred by either lower prediction accuracy or poorer estimation properties or both. The three recommended equation forms should only serve as basic deterministic specifications upon which other tree and stand variables should be incorporated as predictors to further improve their predictive performance.