UAV-Based Digital Terrain Model Generation under Leaf-Off Conditions to Support Teak Plantations Inventories in Tropical Dry Forests. A Case of the Coastal Region of Ecuador

Aguilar, Fernando J.; Rivas, José R.; Nemmaoui, Abderrahim; Peñalver, Alberto; Aguilar, Manuel A.

doi:10.3390/s19081934

Cited by 26 publications

(22 citation statements)

References 64 publications

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“…These climate conditions cause alternating leaf-on (April to September) and leaf-off (November to December) seasons in the case of the teak plantations located at the coastal region of Ecuador. The data on which this research is based were collected during the leaf-off canopy conditions in order to facilitate the field work avoiding shadows and occlusions [34].…”

Section: Study Areamentioning

confidence: 99%

“…A TLS field campaign was carried out in November 2018 (leaf-off conditions) over 58 reference plots of even-aged teak trees according to the following distribution: Thirty plots were located in Morondava teak plantation, eight in El Tecal plantation, and the remaining 20 in Allteak plantation (see location in Figure 1). Some key features of the reference plots located in the plantations of Morondava, El Tecal, and Allteak can be found in Aguilar et al [34].…”

Section: Field Datamentioning

confidence: 99%

“…This is a very early developing plantation that shows a certain heterogeneity with both a low average basal area of 4 m 2 /ha (from 0.6 to 6.28 m 2 /ha) and a low average Lorey's mean height of 7.83 m (from 3.84 to 9.57 m). The average slope of the reference plots was 23.4%, ranging from 3.9% to 55.5% [34]. Understory vegetation was mainly composed of shrubs (Mimosa pudica Linn.)…”

Section: Field Datamentioning

confidence: 99%

“…Considering that both basal area [38] and Lorey's mean height [39] are dasometric variables positively correlated to forest stand volume, it can be inferred that the reference plots located in El Tecal presented a forest stand volume larger than those of Morondava. The average slope of the reference plots was 11.7%, ranging from 8.3% to 14.7% [34]. Understory vegetation was mainly composed of an herbaceous layer (Amaranthus retroflexus L. and different species of grasses).…”

Section: Field Datamentioning

confidence: 99%

“…The main objective of this study aims at developing locally calibrated allometric equations based on TLS data obtained in leaf-off conditions teak plantations located in the Coastal Region of Ecuador. Together with the unmanned aerial vehicle structure from the motion (UAV-SfM) method tested in a previous work [34], it could make up the skeleton of an efficient remote sensing based method to estimate and update the aboveground biomass and tree stem commercial volume dynamic over small sample areas of the teak plantations located in the study area (i.e., at project level scale within the context of REDD), thus contributing to their sustainable management and carbon stock estimation.…”

Section: Introductionmentioning

confidence: 99%

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Developing Allometric Equations for Teak Plantations Located in the Coastal Region of Ecuador from Terrestrial Laser Scanning Data

Aguilar

Nemmaoui

Peñalver

et al. 2019

Forests

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Traditional studies aimed at developing allometric models to estimate dry above-ground biomass (AGB) and other tree-level variables, such as tree stem commercial volume (TSCV) or tree stem volume (TSV), usually involves cutting down the trees. Although this method has low uncertainty, it is quite costly and inefficient since it requires a very time-consuming field work. In order to assist in data collection and processing, remote sensing is allowing the application of non-destructive sampling methods such as that based on terrestrial laser scanning (TLS). In this work, TLS-derived point clouds were used to digitally reconstruct the tree stem of a set of teak trees (Tectona grandis Linn. F.) from 58 circular reference plots of 18 m radius belonging to three different plantations located in the Coastal Region of Ecuador. After manually selecting the appropriate trees from the entire sample, semi-automatic data processing was performed to provide measurements of TSCV and TSV, together with estimates of AGB values at tree level. These observed values were used to develop allometric models, based on diameter at breast height (DBH), total tree height (h), or the metric DBH2 × h, by applying a robust regression method to remove likely outliers. Results showed that the developed allometric models performed reasonably well, especially those based on the metric DBH2 × h, providing low bias estimates and relative RMSE values of 21.60% and 16.41% for TSCV and TSV, respectively. Allometric models only based on tree height were derived from replacing DBH by h in the expression DBH2 x h, according to adjusted expressions depending on DBH classes (ranges of DBH). This finding can facilitate the obtaining of variables such as AGB (carbon stock) and commercial volume of wood over teak plantations in the Coastal Region of Ecuador from only knowing the tree height, constituting a promising method to address large-scale teak plantations monitoring from the canopy height models derived from digital aerial stereophotogrammetry.

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Section: Study Areamentioning

confidence: 99%

Section: Field Datamentioning

confidence: 99%

Section: Field Datamentioning

confidence: 99%