Fig 1.
Map of ground survey plot locations within the Cabuyal and Zapotillal estuaries.
Plots classified as containing or not containing mangroves or associate species. Map data copyrighted OpenStreetMap contributors and reprinted under a CC BY-SA 2.0 license and available from https://www.openstreetmap.org.
Fig 2.
Model workflow of the accuracy assessment of ground data and aerial survey forest structure measurements.
Data on forest structure collected from ground surveys was compared to forest structure data derived from canopy height (CHM) and canopy cover (CCM) models applied to support vector machine (SVM) classified UAS imagery maps.
Table 1.
Number of individuals, mean, minimum & maximum tree height, diameter at breast height (DBH), and total above-ground (ABG) and belowground (BGB) biomass for 259 mangrove and mangrove associate (C. erectus) trees (≥5 cm DBH) encountered in 21 plots in the Cabuyal and 1 plot in the Zapotillal mangrove stands.
Table 2.
Species frequency, tree density, mean basal area and relative density, dominance, frequency and importance value indices for ≥ 5 cm diameter at breast height (DBH) mangrove and mangrove associate (C. erectus) trees found in 21 plots in the Cabuyal and 1 plot in the Zapotillal mangrove stands.
Fig 3.
Maps of a southwest 500m x 500m portion of the Cabuyal estuary created from UAS imagery.
(A) NDVI index map, (B) support vector machine (SVM) classification of non-vegetation and vegetation land cover, (C) canopy height model of vegetation land cover based on SVM, and (D) canopy coverage model of vegetation land cover based on SVM overlaid with natural jenks break NDVI classification.
Table 3.
Root mean square (RMS) error in the x, y, and z directions for absolute geolocation variance for photo geolocation and calibration for wet (10cm/pixel resolution), dry (10cm/pixel resolution) and dry (100cm/pixel resolution) maps.
Maps created in and geolocation information provided by Pix4D (Pix4D, Inc., Lausanne, Switzerland).
Fig 4.
Residuals of UAS and ground measurements of forest structure.
These include (A) maximum and (B) mean canopy height (m) and (C) percent canopy cover for 10 cm/pixel and 100 cm/pixel resolution dry season maps of the Cabuyal and Zapotillal estuaries.
Table 4.
Root mean square errors (RMSE) for 10cm and 100cm UAS imagery derived measurements of maximum and mean canopy heights (n = 22) and percent canopy (n = 27) in the Cabuyal and Zapotillal estuaries.
UAS imagery and field measurements collected between January and February 2018.
Fig 5.
Mean NDVI values for three dominant (90% of overstory biomass) tree species in the Cabuyal estuary.
Measurements derived from 10cm/pixel resolution UAS imagery taken September through November 2017 for wet season (n = 13) and January through February 2018 for dry season (n = 23) measurements. * represents significant difference of means for between season measurements of plot NDVI from paired t-tests. • represents significant difference of means for within season measurements of plot NDVI from one-way ANOVA and Tukey-HSD post-hoc tests. Error bars represent standard error from the mean.