Comparing Johnson’s SB and Weibull Functions to Model the Diameter Distribution of Forest Plantations through ALS Data

[EN] The analysis of the diameter distribution is important for forest management since the knowledge of tree density and growing stock by diameter classes is essential to define management plans and to support operational decisions. The modeling of diameter distributions from airborne laser scanning (ALS) data has been performed through the two-parameterWeibull probability density function (PDF), but the more flexible PDF Johnson's SB has never been tested for this purpose until now. This study evaluated the performance of the Johnson's SB to predict the diameter distributions based on ALS data from two of the most common forest plantations in the northwest of the Iberian Peninsula (Eucalyptus globulus Labill. and Pinus radiata D. Don). The Weibull PDF was taken as a benchmark for the diameter distributions prediction and both PDFs were fitted with ALS data. The results show that the SB presented a comparable performance to the Weibull for both forest types. The SB presented a slightly better performance for the E. globulus, while theWeibull PDF had a small advantage when applied to the P. radiata data. The Johnson's SB PDF is more flexible but also more sensitive to possible errors arising from the higher number of stand variables needed for the estimation of the PDF parametersSIThis research was funded by the Forest Research Centre, a research Unit funded by Fundação para a Ciência e a Tecnologia I.P. (FCT), Portugal (grant number UID/AGR/00239/2019). The research activities of Diogo N. Cosenza were funded by the Portuguese Science Foundation (grant number PD/BD/128489/2017). The eucalyptus data used in this work were acquired under the framework of the PTDC/AGR-CFL/72380/2006 project (supported by the FCT under grant PTDC/AGR-CFL/72380/2006, co-financed by the European Fund of Regional Development (FEDER) through COMPETE–Operational Factors of Competitiveness Program, POFC). The pine data were acquired under the framework AGL2008-02259/FOR project (supported by the Spanish Ministry of Science and Innovation

ESTIMATING THE DIAMETER OF TREE USING THE NEURO-FUZZY INFERENCE SYSTEM AND ARTIFICIAL NEURAL NETWORKS FROM THE TOTAL HEIGHT VARIABLE

Studies that seek to identify potential techniques for obtaining diameter values at 1.30 m from the ground from tree height data are necessary, especially when considering the use of airborne Lidar in forest inventory activity. In this sense, this work aimed to evaluate two artificial intelligence tools for this purpose, namely the neuro-fuzzy inference systems and the artificial neural networks. Four models were tested to obtain estimates for the diameter variable, which were prepared by combining the independent variables useful area per plant, age and height. After processing, the statistics of bias, square root of the mean squared error in percentage, correlation and mean percentage error were calculated, in addition to the preparation of scatter plots and histogram of residues. It was observed that, for the estimation of the diameter in both techniques, the use of the model with all independent variables obtained the best values for the analysis statistics. It can be concluded that both tools can be used to estimate the diameter, with the neuro-fuzzy inference system being more suitable for its processing speed and small variability between the values obtained in different training sessions for the same database

Airborne laser scanning applied to eucalyptus stand inventory at individual tree level

The objective of this work was to evaluate the application of airborne laser scanning (ALS) to a large-scale eucalyptus stand inventory by the method of individual trees, as well as to propose a new method to estimate tree diameter as a function of the height obtained from point clouds. The study was carried out in a forest area of 1,681 ha, consisting of eight eucalyptus stands with ages varying from four to seven years. After scanning, tree heights were obtained using the local maxima algorithm, and total wood stock by summing up individual volumes. To determine tree diameters, regressions fit using data measured in the inventory plots were used. The results were compared with the estimates obtained from field sampling. The equation system proposed is adequate to be applied to the tree height data derived from ALS point clouds. The tree individualization approach by local maxima filters is efficient to estimate number of trees and wood stock from ALS data, as long as the results are previously calibrated with field datainfo:eu-repo/semantics/publishedVersio

Comparing Johnson's Sb and Weibull functions to model the diameter distribution of forest plantations through ALS data

The analysis of the diameter distribution is important for forest management since the knowledge of tree density and growing stock by diameter classes is essential to define management plans and to support operational decisions. The modeling of diameter distributions from airborne laser scanning (ALS) data has been performed through the two-parameterWeibull probability density function (PDF), but the more flexible PDF Johnson’s SB has never been tested for this purpose until now. This study evaluated the performance of the Johnson’s SB to predict the diameter distributions based on ALS data from two of the most common forest plantations in the northwest of the Iberian Peninsula (Eucalyptus globulus Labill. and Pinus radiata D. Don). The Weibull PDF was taken as a benchmark for the diameter distributions prediction and both PDFs were fitted with ALS data. The results show that the SB presented a comparable performance to the Weibull for both forest types. The SB presented a slightly better performance for the E. globulus, while theWeibull PDF had a small advantage when applied to the P. radiata data. The Johnson’s SB PDF is more flexible but also more sensitive to possible errors arising from the higher number of stand variables needed for the estimation of the PDF parametersinfo:eu-repo/semantics/publishedVersio

Escaneamento a laser aerotransportado aplicado a inventário de povoamentos de eucalipto ao nível de árvores individuais

The objective of this work was to evaluate the application of airborne laser scanning (ALS) to a large-scale eucalyptus stand inventory by the method of individual trees, as well as to propose a new method to estimate tree diameter as a function of the height obtained from point clouds. The study was carried out in a forest area of 1,681 ha, consisting of eight eucalyptus stands with ages varying from four to seven years. After scanning, tree heights were obtained using the local maxima algorithm, and total wood stock by summing up individual volumes. To determine tree diameters, regressions fit using data measured in the inventory plots were used. The results were compared with the estimates obtained from field sampling. The equation system proposed is adequate to be applied to the tree height data derived from ALS point clouds. The tree individualization approach by local maxima filters is efficient to estimate number of trees and wood stock from ALS data, as long as the results are previously calibrated with field data.O objetivo deste trabalho foi avaliar a aplicação do escaneamento a laser aerotransportado (ALS) na realização de inventário de povoamentos de eucalipto, em larga escala, por meio do método de individualização de árvores, bem como propor um novo método para estimativa dos diâmetros das árvores em função das alturas obtidas a partir da nuvem de pontos. O estudo foi conduzido em floresta de 1,681 ha, composta por oito povoamentos de eucalipto com idades entre quatro e sete anos. Após o escaneamento, foram obtidas as alturas das árvores pelo algoritmo de máximos locais, e o estoque total de madeira, pela soma dos volumes individuais. Para determinar os diâmetros das árvores, foram utilizadas regressões ajustadas a partir de dados medidos em parcelas de inventário. Os resultados foram comparados às estimativas obtidas via amostragem de campo. O sistema de equações proposto é adequado para ser aplicado aos dados de altura derivados da nuvem de pontos do ALS. O método de individualização de árvores com o filtro de máximos locais é eficiente para estimar o número de árvores e o estoque de madeira a partir dos dados do ALS, desde que os resultados sejam previamente calibrados com o inventário de campo

Forest biometric characterization through remote sensing applications

Doutoramento em Engenharia Florestal e dos recursos Naturais / Instituto Superior de Agronomia. Universidade de LisboaThe general objective of this thesis was to step forward in the application of aerial 3D-data in the forest characterization context. To meet this goal, the thesis focused on four cutting-edge research topics related to the forestry applications of 3D data collected by airborne laser scanning (ALS) and digital aerial photogrammetry (DAP). Four common algorithms were deeply investigated to filter ALS ground points. The results showed that performing exhaustive filter calibration is not mandatory to derive accurate digital terrain models (DTM), that the applications of software defaults can derive accurate DTM as well, and that filter calibration has a significant but low practical improvement on the prediction of forest attributes using area-based approach (ABA). The application of the high-flexible Johnson’s SB probability density function (PDF) was adapted to the ALS data and compared with the Weibull PDF to estimate diameter distributions in two forest stands, an eucalyptus stand and a radiate pine stand. Johnsons SB was highly sensitive to the prediction of the inputs used to fit the parameters, reasons why this function was just slightly better than Weibull. The ALS data from five different forest sites were used to compare three common modeling approaches used to estimate growing stock volume, ordinary least squares (OLS), random forest (RF), and k-nearest neighbor (kNN). The estimation was more accurate with OLS and RF. The kNNbased models had the worst prediction accuracy and may result in overfitting. The point clouds derived from ALS and DAP presented comparable results when it comes to detect and estimate individual tree volumes in eucalyptus plantations. This result benefits the DAP since it is an inexpensive approach to collect 3D forest data, especially when associated with unmanned aerial vehiclesN/

Application of airborne laser scanner to forest inventory at individual tree level of eucalyptus stands

O setor florestal tem experimentado rápida evolução no que diz respeito aos métodos de mensuração da produção de madeira, seja a nível de equipamentos ou dos sistemas empregados. Dentre estas mudanças está o uso do escaneamento a laser aerotransportado (ALS) para coletar dados do povoamento. O potencial desta técnica está na alta precisão dos sensores, os quais permitem detectar a altitude do terreno e da copa das árvores simultaneamente e extrair daí as informações de altura. Este trabalho avaliou a aplicação deste sistema em povoamentos de eucalipto utilizando a metodologia de individualização de árvores. Também foi proposto um novo método de equacionar as relações entre diâmetro e altura para serem empregadas nas estimativas de volume individuais. O estudo foi conduzido em uma floresta de 1.681 ha, composta por oito povoamentos de eucalipto com idades variando entre quatro e sete anos. Após os escaneamento, foram obtidas as alturas (Ht) das árvores pelo algoritmo de local máxima e o estoque total de madeira foi obtido pela soma dos volumes individuais. Os diâmetros das árvores foram obtidos empregando regressões dap = f(Ht) ajustadas a partir de dados medidos em parcelas de inventário. Os resultados foram comparados com as estimativas via amostragem de campo. As estimativas obtidas foram inferiores aos valores de referência, variando entre entre -9% a -36% para o número de árvores e de -16% a -53% para o estoque de madeira dos projetos. O ALS gerou uma estrutura vertical diferente da amostragem para a maioria dos projetos avaliados. Os erros de estimativa do ALS foram causados especialmente pela omissão de árvores pelo filtro de local máxima. Contudo, verifica-se que mesmo após décadas de pesquisa, a técnica do ALS necessita de mais avaliações para aprimorar a sua exatidão, e para que sua aplicação seja mais prática e acessível ao usuário.The forest sector has experienced rapid development regarding the measurement methods of timber production in terms of both equipment and systems employed. Among these changes, the airborne laser scanning (ALS) to collect stand data has recently emerged. The potential of this technique lies on its high accuracy sensor, which can detect the altitude of the terrain and the treetops simultaneously and extract the height information from it. This study has evaluated the application of this system in eucalypt stands using the tree individualization method. A new method was proposed to equate the relationship between diameter and height to be employed in the individual volume estimates. The study was conducted in an area of 1,681 hectars, composed by eight Eucalyptus stands with ages ranging between four and seven years. After scanning, the tree heights (Ht) were obtained using the local maximum algorithm and the total woodstock was obtained by summing the individual volumes. The tree diameters were obtained using a regression model of the form dap = f(Ht) fitted using data from inventory permanent plots. The results were compared with the estimatives obtained through field sampling. The estimates were below the reference values, ranging from -9% to -36% for the number of trees and from -16% to -53% for the woodstock of the projects. ALS has generated a different vertical structure from the sampling for most of the evaluated projects. The ALS estimation errors were especially caused by the omission of trees by the local maximum filter. However, it appears that even after decades of research, ALS technique needs further evaluation to improve its accuracy and making its application more practical and accessible to the user.Conselho Nacional de Desenvolvimento Científico e Tecnológic

Comparing Johnson’s SB and Weibull Functions to Model the Diameter Distribution of Forest Plantations through ALS Data

The analysis of the diameter distribution is important for forest management since the knowledge of tree density and growing stock by diameter classes is essential to define management plans and to support operational decisions. The modeling of diameter distributions from airborne laser scanning (ALS) data has been performed through the two-parameter Weibull probability density function (PDF), but the more flexible PDF Johnson’s SB has never been tested for this purpose until now. This study evaluated the performance of the Johnson’s SB to predict the diameter distributions based on ALS data from two of the most common forest plantations in the northwest of the Iberian Peninsula (Eucalyptus globulus Labill. and Pinus radiata D. Don). The Weibull PDF was taken as a benchmark for the diameter distributions prediction and both PDFs were fitted with ALS data. The results show that the SB presented a comparable performance to the Weibull for both forest types. The SB presented a slightly better performance for the E. globulus, while the Weibull PDF had a small advantage when applied to the P. radiata data. The Johnson’s SB PDF is more flexible but also more sensitive to possible errors arising from the higher number of stand variables needed for the estimation of the PDF parameters

APPLYING CLASSICAL FOREST REGULATION METHODS TO SMALLHOLDINGS WITH COOPERATIVE CONSTRAINTS

This study aims to assess the cooperative regulation process of forestry producers in comparison to the traditional individual regulation of properties. Twenty (20) forest properties are studied as examples of the development of three forest regulation scenarios: 1) individual regulation, 2) group regulation, and 3) cooperative regulation. The Net Present Value (NPV) of each of the scenarios is optimized according to mathematical programming models and compared to a baseline scenario without forest regulation. According to the proposed cooperative regulation, properties had a proportion factor for annual net revenue distribution calculated from results of the baseline scenario. By comparing the NPV maximization results from scenarios 1 and 3 with the non-regulation scenario, the cost for individual regulation is on average 25%, while being only 11% for cooperative regulation, that is, a 14% reduction in property regulation costs. Additionally, cooperative regulation had the advantage of dividing properties into fewer areas when compared to individual regulation

Avaliação econômica de projetos de sistemas agroflorestais

Por se tratar de uma atividade complexa, os estudos de viabilidade econômica de sistemas agroflorestais (SAFs) exigem maior esforço para avaliação. Dentre os motivos estão a maior quantidade de elementos a serem considerados, a necessidade de prever os efeitos das interações entre as diferentes espécies consorciadas e a dificuldade de valorar os benefícios ambientais do sistema. Dessa forma, o objetivo deste trabalho foi analisar e sintetizar os principais métodos de avaliação econômica descritos na literatura. Através dele é possível determinar quais itens devem ser computados na análise e como atribuir valores a eles para definir as principais receitas e custos do projeto. Ainda, podem ser traçados os principais métodos de análise econômica e de comparação de resultados. Por fim, entende-se que existem dificuldades na valoração de muitos benefícios que os SAFs proporcionam, mas estas podem ser contornadas pelas metodologias apresentadas. Além disso, criou-se a necessidade de promover os benefícios ambientais (externalidades) do sistema, a fim de valorizar os seus serviços frente ao mercado