Allometric models to estimate tree height in northern Amazonian ecotone forests

The aim if this work was to assess and propose projection models for diameter at breast height and total height of individual pine trees and the contribution of competition indexes in these models. Data was obtained from 1056 permanent sampling units of non-thinned Pinus taeda L. stands located in the Telêmaco Borba region, Paraná, Brazil, with ages between 3.4 and 19.5 years. In order to project the diameter and total height of the trees, linear models were tested according to the variable in the current age, the projection age in the future, the basal area, and the site index, as well as their transformations. The Spearman correlation was obtained between competition indexes and dendrometric and stand variables, with the GH (Glover and Hool), LO (Lorimer) and ST (Stage) indexes being selected. These indexes were assessed as independent variables in the models, whose contributions were verified through the “F ci ” test on the incremental contribution. The models were assessed through the adjusted coefficient of determination, standard error of the estimate, and boxplots of residuals. The models provided precise and bias-free projections. The competition indexes statistically contributed to diameter and total height projection according to the “F ci ” test, increasing the precision of projected values for the majority of models tested. The indexes with major contributions to individual tree modelling for diameter and total height projection of Pinus taeda were Glover and Hool (GH) and Lorimer (LO), respectively.

This paper developed and evaluated the performance of the current functional tree taper and volume models. The models were applied to some selected economically important natural tree species common to central Sudan, namely, Combretum hartmannianum and, Lonchocarpus Laxiflorus. The tree variables measured were the diameter at breast height (DBH, cm), diameter at the base of the tree (d0, cm), upper stem diameters (di), total tree height (H), and height to the base of the crown (Hb). In total, 19 taper and 32 volume models were tested and evaluated (22 models were two-variable models (Diameter at breast height and total tree height or bole height) and 10 were three-variable models (Diameter at ground level, Diameter at breast height and total tree height or bole height). The model goodness of fit was evaluated in terms of adjusted coefficient of determination (Ra2), standard error (SE), mean absolute residual (MAR), bias (BI) Akaike’s information criterion (AIC), homogeneity of the residuals and significance of the regression parameters. As far as taper models is concerned, Models, some of the models were found to yield satisfactory results for the tow selected species with R2 range of 0.94 – 0.96. For the within species variation of models on the basis of the AIC values, the ranking of the models (smaller AIC first) were in consistant with the rankings due to SE and Ra2 values although AIC penalizes models in proportion to the number regression parameters. In general the results of the study indicated that higher residuals valuse are in most of the cases associated with the lower parts of the bole, the butress portion of the stem. This suggests that care should be taken during the application of such models for hardwood species, especially in open woodlands where butress is a common characteristic.The results for volume models revealed differences in the behaviour of different models for each species as the degree of significance of the regression parameters varies between tree species. However, the replacement of the total tree height by the bole height (merchantable height) improves both the level of parameter significance and the coefficient of determination. The results also reveal that inclusion of diameter at grown level to the original two variables (DBH, Ht) and the replacement of the original model total height with the bale height results in quite significant improvement of the Ra2 values. In general, the study concluded that taper and volume models can provide precise and accurate estimation of tree growth variables for the studied species with reasonable cost and time, but care should be taken when dealing with same model for the same species across varying growth and management condition, or when dealing with different species. country.

Cultivation of energy crops is concerned with estimation of the total lignified biomass (dendromass) production, which is based on the plantation density and individual plant dendromass. The main objective of this study was to investigate the allometry of aboveground leafless biomass of juvenile black poplar hybrids (Populus deltoides x P. nigra ), traditionally used for timber and cellulose production, and to derive generic allometric models for dendromass prediction, relevant to energy crop cultivation in Bulgaria. The study material comprised a variety of growth sites, tree ages and clones, specific to poplar plantings in Bulgaria. We used three principal quantitative predictors: diameter at breast height, total tree height and mean stand (stock) height. The models were not differentiated by clone, because the black poplar hybrids tested were not equally represented in the data, and the inclusion of tree age as a predictor variable seemed unreliable, because of the significant, up to 3 years, variation, which was possible within the narrow age range investigated. We defined the mean stand (stock) height as a composite quantitative variable, which reflected the interaction between the time since planting (age), site quality and the intrinsic growth potential. Stepwise and backward multiple regression analyses were applied to these quantitative variables and their products and sets of adequacy and goodnessof-fit criteria were used to derive individual biomass models for stem and branches. Then we developed compatible additive systems of models for stem, branch and total lignified biomass in log-transformed form. Finally, the prediction data were back-transformed, applying correction for bias, and were cross-validated. Three systems of generic equations were derived to enable flexible model implementation. Equation system M1 proposes a stem biomass model based on tree and stand heights and stem diameter, and a model for branches including mean stand height and breast height diameter; this model displayed the best goodness-of-fit characteristics. Model system M2 uses only the tree height and diameter and therefore is most relevant to dendromass determination in single trees or harvested saplings, while model M3 allows fast and sufficiently accurate biomass estimation of standing poplar stock, because it employs the average stand height and the individual tree diameters. All models are applicable to predict lignified aboveground biomass of juvenile Populus deltoides x P. nigra trees of diameter up to 21 cm and total height up to 16 m.

Accurate forest parameters are essential for forest inventory. Traditionally, parameters such as diameter at breast height (DBH) and total height are measured in the field by level gauges and hypsometers. However, field inventories are usually based on sample plots, which, despite providing valuable and necessary information, are laborious, expensive, and spatially limited. Most of the work developed for remote measurement of DBH has used terrestrial laser scanning (TLS), which has high density point clouds, being an advantage for the accurate forest inventory. However, TLS still has a spatial limitation to application because it needs to be manually carried to reach the area of interest, requires sometimes challenging field access, and often requires a field team. UAV-borne (unmanned aerial vehicle) lidar has great potential to measure DBH as it provides much higher density point cloud data as compared to aircraft-borne systems. Here, we explore the potential of a UAV-lidar system (GatorEye) to measure individual-tree DBH and total height using an automatic approach in an integrated crop-livestock-forest system with seminal forest plantations of Eucalyptus benthamii. A total of 63 trees were georeferenced and had their DBH and total height measured in the field. In the high-density (>1400 points per meter squared) UAV-lidar point cloud, we applied algorithms (usually used for TLS) for individual tree detection and direct measurement of tree height and DBH. The correlation coefficients (r) between the field-observed and UAV lidar-derived measurements were 0.77 and 0.91 for DBH and total tree height, respectively. The corresponding root mean square errors (RMSE) were 11.3% and 7.9%, respectively. UAV-lidar systems have the potential for measuring relatively broad-scale (thousands of hectares) forest plantations, reducing field effort, and providing an important tool to aid decision making for efficient forest management. We recommend that this potential be explored in other tree plantations and forest environments.

The paper evaluated the performance of the current functional tree taper and volume models. The models were applied to some selected economically important natural Terminalia tree species common to central Sudan, namely, Terminalia laxiflora and, Terminalia brownii. 22 two-variable models (Diameter at breast height and total tree height or bole height) and 10 three-variables models (Diameter at ground level, Diameter at breast height and total tree height or bole height) were evaluated. The tree variables measured were the diameter at breast height (DBH, cm), diameter at the base of the tree (d0, cm), upper stem diameters (di), total tree height (H), and height to the base of the crown (Hb). Data were extracted from a natural reserved forest in the Blue Nile state. The models goodness of fit were evaluated in terms of adjusted coefficient of determination (Ra2), standard error (SE), mean absolute residual (MAR), bias (BI) Akaike’s information criterion (AIC), homogeneity of the residuals and significance of the regression parameters. Taper-17 and Taper-19 were found to be among the best two models for the two species with R2 range of 0.94 – 0.93, but with different rankings for each species. Comparison of the range of data for the tow studied species suggested that representation of various diameter at breast height (DBH, cm), diameter at the base of the tree (d0, cm), upper stem diameters (di), total tree height (H), and height to the base of the crown (Hb), had significant influence on the accuracy of prediction outside the range of the fitted data. This implies that application of the selected models is only useful at local stand level or at best in similar biological and stand structure conditions. For volume models, The results indicated that individual equations act differently in each species as there were great variations in the values of the same parameter of a given model accross the species. Some regression parameters of a given model were found to be significant in some species and insignificant in others. Comparison between the two versions of each group reveals that the replacement of the total tree height by the bole height (merchantable height) improves both the level of parameter significance and the coefficient of determination. From the first, the regression parameters of only 5 models (VOL-1, VOL-5, VOL-8, VOL-17, and VOL-20) were found to be significant at 0.05 probability level for all the tow species. The results also reveal that inclusion of variable D0 to the original two variables (DBH, Ht) to the volume equations results in insignificant improvement of the Ra2 values, while the replacement of the original model Ht variable with the Hb results in quite significant improvement of the Ra2 values. However, substantial improvement of the Ra2 values were obtained when both D0 and Hb were added. For this group of models, VOL-23, VOL-25- VOL-29 VOL30- and VOL-31were found to be the best for almost all the tow species. In general, the study concluded that taper and volume models can provide precise and accurate tree growth variables for the studied species with reasonable cost and time, but care should be taken when dealing with same model for the same species across the varying growth and management condition.

Wood quality and growth are two important parameters that need to be analyzed for the utilization and selection of superior genotypes. The objective of this research was to investigate the ten provenances growth characteristics and their physical and mechanical properties of Acacia mangium at Parung Panjang, Bogor. The provenance trial was arranged in three blocks of a randomized completely blocks design. In every provenance, 18 trees were sampled resulting in a total of 180 trees in each block representing each provenance measured for their total height, clear bole height, stem diameter at breast height, stem form, branching system, and crown form. Three individual trees were selected randomly from each provenance for wood properties traits, i.e. moisture content, density, modulus of elasticity (MOE) and modulus of rapture (MOR). Significant differences among provenances were detected for stem diameter, clear bole height, branching system and crown form, while total height and stem form revealed not significantly different. Most of growth parameters was not significantly correlated with physical and mechanical wood traits, except for MOR, it revealed significant correlation with the total tree height, stem form, and branching system. Generally, some growth characteristics were not a good indicator for selecting the best provenance in wood properties. The best growth performance was revealed by Kiriwo/Serisa WP, Bimadebun Village, and Balimo District, but from wood quality, the superior provenance was revealed by Bimadebun Village with the lower moisture content, the highest wood density, the highest MOE and MOR. The Bimadebun Village provenance is potential to be developed as provenance seed stand, especialy for solid (contruction) wood.

Aim of Study: As an innovative prediction technique, Artificial Intelligence technique based on a Deep Learning Algorithm (DLA) with various numbers of neurons and hidden layer alternatives were trained and evaluated to predict the relationships between total tree height (TTH) and diameter at breast height (DBH) with nonlinear least squared (NLS) regression models and nonlinear mixed effect (NLME) regression models.Area of Study: The data of this study were measured from even-aged, pure Turkish Pine (Pinus brutia Ten.) stands in the Kestel Forests located in the Bursa region of northwestern Turkey.Material and Methods: 1132 pairs of TTH-DBH measurements from 132 sample plots were used for modeling relationships between TTH, DBH, and stand attributes such as dominant height (Ho) and diameter (Do).Main Results: The combination of 100 # neurons and 8 # hidden layer in DLA resulted in the best predictive total height prediction values with Average Absolute Error (0.4188), max. Average Absolute Error (3.7598), Root Mean Squared Error (0.6942), Root Mean Squared error % (5.2164), Akaike Information Criteria (-345.4465), Bayesian Information Criterion (-330.836), the average Bias (0.0288) and the average Bias % (0.2166), and fitting abilities with r (0.9842) and Fit Index (0.9684). Also, the results of equivalence tests showed that the DLA technique successfully predicted the TTH in the validation dataset.Research highlights: These superior fitting scores coupled with the validation results in TTH predictions suggested that deep learning network models should be considered an alternative to the traditional nonlinear regression techniques and should be given importance as an innovative prediction technique.Keywords: Prediction; artificial intelligence; deep learning algorithms; number of neurons; hidden layer alternatives.Abbreviations: TTH (total tree height), DBH (diameter at breast height), OLS (ordinary least squares), NLME (nonlinear mixed effect), AIT (Artificial Intelligence Techniques), ANN (Artificial Neural Network), DLA (Deep Learning Algorithm), GPU (Graphical Processing Units), NLS (nonlinear least squared), RMSE (root mean squared error), AIC (Akaike information criteria), BIC (Bayesian information criterion), FI (fit index), AAE (average absolute error), BLUP (best linear unbiased predictor), TOST (two one-sided test method).

Species of the genus Paulownia have been introduced to Bulgaria since the beginning of the XXth century and their multipurpose uses - as ornamental trees, for wood and biomass production - have been tested ever since. We present a study, which examines the early growth of four Paulownia clones at southern locations in Bulgaria and derives biometric models for dendromass estimation of juvenile Paulownia trees. The data originated from two experimental plantations established on nursery land using one-year-old in vitro propagated plant material. Forty six, 1 to 3 year-old saplings from two clones of P. tomentosa and two P. elongata × P. fortunei hybrids were sampled. Their stem biomass was modeled as a function of the breast height tree diameter and total tree height or the stem diameter alone and a set of goodness-of-fit criteria was applied to select the most adequate among the 29 tested formulations. The regression models were fitted in log-transformed form to the logarithm of the stem biomass and MM correction factor for bias was applied to the back-transformed prediction data. Two allometric relationships were derived, which adequately assess stem dendromass of young Paulownia sp. from easily measurable tree characteristics. Both models are applicable for stem biomass estimation of juvenile Paulownia trees of diameter up to 5 cm and total height up to 3.5 m.

Parameters influencing gum yield such as tapping techniques and soil mineral elements had earlier been investigated while there is dearth of information on effect of morphological characteristics on gum yield. This study investigated effects of height and girth on yield of Acacia senegal L. in the natural forest. Three heights and girth classes were purposely selected. Trees which heights and girth fell within those classes were selected randomly and tapped at constant height classes with varying girth clas ses. 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 yield increased as tree girth goes higher from 35 - 54cm (163.6 - 209.7g).Tree girth significantly affected gum yield (p≤0.05) and trees which total heights were lower than 2.0 m (maximum of 1.95m) with girth higher than 54cm (maximum of 65cm) produced the highest mean gum yield. Silvicultural practices that could bring about increase in girth such as early pruning and re-spacing which is applicable to plantation trees could also be carried out on the natural forest trees to increase gum yield. Key words: Savanna woodland, Acacia senegal, height, girth, gum yield

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.

Background and objectives: Intraspecific interaction is important because it occurs between the same species individuals that have similar ecological nests. The objective of this study was to evaluate intera-specific interaction of poplar trees (Populus euhratira Olivier.) using mark correlation functions. Materials and methods: The position of all trees with DBH>2.5 cm were recorded in two pure and mixed stands in Behbahan Chaharasyab area with area of 4.5 and 9.1 ha, respectively. Tree height (H), diameter at breast height (DBH), crown diameter (CD) and light crown length (LCL) were measured as mark variables. Point spatial pattern analysis was used to study the spatial pattern and intraspecific interaction. Marked correlation (MCF) function was used to reveal the spatial relationships between the poplar individuals trees in terms of various characteristics such as total tree height, diameter at breast height, crown diameter and light crown length. Results: The results showed that in pure stand, a significant negative correlation was observed between the DBH of trees at a distance of less than 5 and more than 20 m. Between distances of 5 to 20 m, an independent state was observed between the individuals. There was a positive and negative correlation between the crown diameter of poplar trees from a distance of 5 to 40 m and more than 45 m, respectively. There was a significant positive correlation between the total height and the light crown length of the trees from a distance of 5 to 30 m. At a distance of more than 30 m, the independence was seen between the individuals. In mixed stand, the independence status was observed between DBH of trees up to a distance of 40 meters. A positive correlation was observed at distances greater than 40 m. There was a negative correlation between trees CD at all distances. The independence was seen between H and LCL of trees at most distances. Conclusion: In pure stand, depending on different distances and marks, various states of interaction including negative, positive and independence were seen between the tree individuals. While in mixed stand, except for the state of negative interaction that was seen in relation to the crown diameter, in other cases, the condition of independence between different individuals was observed in terms of the studied marks. DBH showed similar conditions in both pure and mixed stands. CD showed positive and negative correlations between individuals in pure and mixed stands, respectively. There was a positive correlation between H and LCL of individuals in pure stand while independence was observed in mixed stand. Overall, it is useful to study the interaction between poplar trees to understand the dynamics, growth process and mechanisms that endanger this valuable species.

Influence of biomechanics and growing space on tree growth in young Pinus sylvestris stands

I investigated the relationships between stem surface area outside bark and other stem dimensions for Japanese cedar (Cryptomeria japonica D. Don) and Japanese cypress (Chamaecyparis obtusa Endl.) trees. The stem dimensions used here were the basal area and the product of diameter at breast height (dbh) and total tree height. The regression equation of the stem surface area s against basal area g was s = 184.216 g for the cedar trees and s = 156.878 g for the cypress trees. The slope of the equation was significantly different between the two species. For the same dbh, the cedar trees tended to have a higher total tree height than the cypress trees. The cedar trees also had a larger surface area of relative stem form than the cypress trees. These results indicated that the difference in the slope was produced by the differences in both the stem slenderness and tapering between the two species. On the other hand, the regression equation between the stem surface area and the product of dbh and total tree height dh was s = 1.937 dh for the cedar trees and s = 1.921 dh for the cypress trees, whereas no significant difference in the slope was found. The obtained slopes for the cedar and cypress trees seemed to be in accord with that for other coniferous species reported in earlier studies, suggesting that the variation in the slope among coniferous species would be small. The estimation from the basal area would provide a simpler means for estimating the stem surface area and would be useful in obtaining an approximation of the surface area. By contrast, the estimation from the product of dbh and total tree height would provide a more accurate and precise estimate as well as a wider applicable range, i.e., a parameter for physiological growth models. In conclusion, it could not be judged which regression equation examined in the present study was superior to the other, and thus it was important to select an appropriate equation depending both on the purpose and on the time and labor available.

Aim of study: The objective of this study is to test the validity of the DBH and total height allometric models fitted to the crown polygon data obtained by the application of a crown delineation and individualisation algorithm which uses the geometrical relationships between the points in the original LiDAR point clouds in the Pinus sylvestris L. stands.Area of study: The study area is located in the province of Álava in the Autonomous Community of the Basque Country.Material and Methods: The crowns are delineated using data from airborne LiDAR point clouds obtained in the 2008 overflight of the Basque Autonomous Community. The DBH and total height data for field trees are obtained from the plots in the 4th National forest inventory.Main Results: For the adjusted total height and DBH models coefficients of determination of 0.87 and 0.74 respectively were obtained. The root mean squared errors were 10.67% and 18.97% respectively. The distributions of obtained DBH and total height fitted values and the distributions of the DBH and total height of the field trees are very similar except for the DBH below 15 cm.Research highlights: For stands of Pinus sylvestris L. in Álava, the geometrical relationships between the points that correspond to laser signal echoes obtained with airborne LiDAR sensors can be used directly to delineate approximations of the horizontal projections of the crowns of the trees. Although the procedure set out here was developed for stands of P. sylvestris L. in Álava, it can be applied to other conifers in regular stands by adjusting the working parameters of the function which delineates the crowns on the basis of the point cloud.Abbreviations used: IFN4: 4th National Forest Inventory; Ht: Field Tree Height; Hl: LiDAR Tree Height; DCL: LiDAR Crown Diameter.

Tree allometry and stand structure in dryland forests relics of northern Côte d’Ivoire