Estimating Stand Height and Tree Density in Pinus taeda plantations using in-situ data, airborne LiDAR and k-Nearest Neighbor Imputation

ABSTRACT Accurate forest inventory is of great economic importance to optimize the entire supply chain management in pulp and paper companies. The aim of this study was to estimate stand dominate and mean heights (HD and HM) and tree density (TD) of Pinus taeda plantations located in South Brazil using in-situ measurements, airborne Light Detection and Ranging (LiDAR) data and the non- k-nearest neighbor (k-NN) imputation. Forest inventory attributes and LiDAR derived metrics were calculated at 53 regular sample plots and we used imputation models to retrieve the forest attributes at plot and landscape-levels. The best LiDAR-derived metrics to predict HD, HM and TD were H99TH, HSD, SKE and HMIN. The Imputation model using the selected metrics was more effective for retrieving height than tree density. The model coefficients of determination (adj.R2) and a root mean squared difference (RMSD) for HD, HM and TD were 0.90, 0.94, 0.38m and 6.99, 5.70, 12.92%, respectively. Our results show that LiDAR and k-NN imputation can be used to predict stand heights with high accuracy in Pinus taeda. However, furthers studies need to be realized to improve the accuracy prediction of TD and to evaluate and compare the cost of acquisition and processing of LiDAR data against the conventional inventory procedures.

Modeling and mapping basal area of Pinus taeda L. plantation using airborne LiDAR data

ABSTRACT Basal area (BA) is a good predictor of timber stand volume and forest growth. This study developed predictive models using field and airborne LiDAR (Light Detection and Ranging) data for estimation of basal area in Pinus taeda plantation in south Brazil. In the field, BA was collected from conventional forest inventory plots. Multiple linear regression models for predicting BA from LiDAR-derived metrics were developed and evaluated for predictive power and parsimony. The best model to predict BA from a family of six models was selected based on corrected Akaike Information Criterion (AICc) and assessed by the adjusted coefficient of determination (adj. R²) and root mean square error (RMSE). The best model revealed an adj. R²=0.93 and RMSE=7.74%. Leave one out cross-validation of the best regression model was also computed, and revealed an adj. R² and RMSE of 0.92 and 8.31%, respectively. This study showed that LiDAR-derived metrics can be used to predict BA in Pinus taeda plantations in south Brazil with high precision. We conclude that there is good potential to monitor growth in this type of plantations using airborne LiDAR. We hope that the promising results for BA modeling presented herein will stimulate to operate this technology in Brazil.

Remoção de propágulos em fragmento de floresta nativa e reflorestamentos numa região de Floresta Ombrófila Mista do estado do Paraná / Propagules removal in fragments of native forest and in reforested areas in an Araucaria Forest region of Paraná State

Uma questão que tem sido discutida é o papel das monoculturas florestais exóticas na manutenção da fauna nativa e vários estudos têm mostrado que a remoção de propágulos é menor nesses ambientes. O presente trabalho comparou a taxa de remoção de propágulos (pinhão, amendoim, milho) entre áreas de Floresta Nativa (FN), Reflorestamentos de Pinus taeda L. (RP), de Eucalyptus saligna Sm. (RE) e Araucaria angustifolia (Bertol) Kuntze (RA). Na FN, todos os propágulos foram removidos e não houve diferença significativa na remoção de pinhão entre a FN e o RA. A remoção de propágulos nessas áreas diferiu da remoção no RP e RE. No RP, houve alta remoção de amendoim, enquanto que o RE apresentou os menores valores de remoção dos três propágulos. As baixas taxas de remoção nos reflorestamentos de pinus e eucalipto refletem a menor exploração desses habitas pela fauna, o que pode estar relacionado com um subosque pouco estruturado.

A question that has been discussed is the role that reforestations with exotic species in native fauna and several studies have shown that removal of propagules is lower in these environments. This study compared the removal rate of propagules (araucaria seeds, peanuts, corn) from areas of native forest (FN), reforestations of Pinus taeda L. (RP), Eucalyptus saligna Sm. (RE) and Araucaria angustifolia (Bertol) Kuntze (RA). In FN all propagules were removed. There was no difference in the removal of araucaria seeds between FN and RA, and removal rate in both areas differ from the removal rate in the RP and RE. In RP there was high removal of peanuts, while the RE showed the lowest value of removal of the three propagules. The low removal rates in reforestation of pine and eucalyptus reflect the decreased exploitation of these habitats for wildlife, which may be related to a poorly structured understory.

Comparação de parâmetros bióticos e abióticos entre fragmento de floresta secundária nativa e um reflorestamento de Pinus taeda L / Comparison of biotic and abiotic parameters between a native secondary forest fragment and a Pinus taeda L. reforestation

A substituição das florestas naturais por plantios florestais comerciais, pode ser tão prejudicial quanto a agricultura ou a ocupação urbana. Porém, estudos sobre regeneração natural nessas áreas, apresentam resultados no desenvolvimento de espécies nativas no sub-bosque, sugerindo um processo sucessional favorável à recuperação da biodiversidade e também uma alternativa para a restauração. Este estudo teve como objetivo comparar parâmetros bióticos e abióticos entre fragmento de floresta secundária nativa e reflorestamento com Pinus taeda. O trabalho foi realizado no Parque Ecológico da Klabin, Fazenda Monte Alegre, Telêmaco Borba, Paraná. Foram avaliados dados bióticos (altura total, diâmetro à altura do peito (DAP - 1,30 m do solo) e área basal (AB), das espécies arbóreas com DAP ≥ 2,5 cm) e dados abióticos ( pH e compactação do solo, cobertura de herbáceas, cobertura de dossel, espessura da serapilheira, temperatura e umidade relativa do ar). A maioria dos parâmetros diferiu entre o reflorestamento de pinus e a floresta secundária, como pH e compactação do solo, cobertura do dossel, presença de herbáceas e também a estrutura de tamanho da vegetação (diâmetro e altura). Observou-se também, uma baixa regeneração no reflorestamento, evidenciada pela diferença na área basal. No entanto, houve regeneração no reflorestamento de pinus, e isso sugere que, com o tempo, poderá haver um incremento na regeneração da vegetação nativa, aumentando a riqueza de espécies e a complexidade estrutural da vegetação.

The substitution of natural forests for commercial forest plantations can be as damaging as farming or urban occupation. However, studies on natural regeneration in these areas show results in the development of native species in the understory, suggesting a successional process in favor of restoring biodiversity as well as an alternative forrestoration. This work aimed at comparing biotic and abiotic parameters between native secondary forest fragments and Pinus taeda reforestation. The study sites are located at Klabin Ecological Park, Monte Alegre Farm, Telêmaco Borba, Paraná. The following biotic data were evaluated: total height, diameter at breast height (DBH - 1.30 m above the ground) and basal area (BA), in tree species with DBH ≥ 2.5 cm. The following abiotic data were also evaluated: pH, soil compaction, herb cover, canopy cover, litter thickness, air temperature, and relative humidity. Most parameters differed between pine reforestation and secondary forest, such as pH and soil compaction, canopy cover, herb presence and the size structure of vegetation (diameter and height). It was also observed a low regeneration in reforestation, evidenced by the difference in the basal area. However, there was regeneration in pine reforestation, suggesting that, over time, there will be an increase in the regeneration of the native vegetation, increasing the wealth of species and the structural complexity of the vegetation.