Estimating plant dominance using field-measured structural parameters and remotely sensed data; A case study from Rekawa mangrove forest, southern coast of Sri Lanka

The conventional method of determining plant dominance using the basal area is challenging for inaccessible ecosystems. Thus, the present study aimed to develop a new method to determine plant dominance in such inaccessible ecosystems using a remote sensing (RS) method. The target ecosystem of the study was the Rekawa mangrove forest. In this study, plant dominance was determined using both conventional and RS-based methods for two selected vegetation types in the Rekawa mangrove forest, i.e., monospecific and mixed vegetation stands. Google Earth (GE) satellite images and drone images were used to digitize the crown area using on-screen digitization technique in ArcMap v.10.3. Finally, plant dominance values, determined through the three methods (conventional method, using GE satellite images, and using drone images) were compared in terms of their percentage deviation calculated with reference to the conventional method. This study reveals that there is a weak positive correlation (P < 0.05, r = 0.132) between basal area and individual tree crown area in a mangrove forest. Moreover, for both mangrove vegetation types, the drone imagery method has shown the least average percentage deviation in determination of plant dominance, compared to that of the GE satellite imagery method. For instance, the drone imagery method could be used with 100% and 86.02% average accuracies respectively for monospecific and mixed mangrove vegetation, whereas the GE satellite imagery method could be used with 97.85% and 42.15% average accuracies, respectively for monospecific and mixed mangrove vegetation. Therefore, this RS-based method could be used as an alternative method to the conventional basal area-based method of determining plant dominance in dense mangrove forests.