Uniformity measures for young Eucalyptus sp. plantations using attributes extracted from UAV flights

Abstract

Background: Studies show that forest uniformity has a direct correlation with productivity, and uniformity measures can serve as indicators of the silvicultural quality of plantations. In this context, this work aimed to determine uniformity and survival in young Eucalyptus sp. plantations using attributes obtained from passive sensors boarded on Unmanned Aerial Vehicles (UAV).

Methods: Tree height was underestimated by the UAV compared to those measured in the Quality Forest Inventory (QFI). Thus, a correction factor applied to size classes was proposed to estimate these heights. The plantations’ uniformity was obtained through the uniformity indices (UI). The UIs were spatialised and integrated, resulting in two uniform surfaces, with and without planting failures.

Results: The UAV survival estimates did not show significant differences compared to the inventory estimates at the 1% or the 5% significance levels. The classification of uniformity surfaces showed that the Eucalyptus saligna Sm plantation was the least uniform compared to the E. grandis W. Hill × E. urophylla S. T. Blake plantations.

Conclusions: Measures of survival and uniformity by the UAV can be jointly employed to generate uniformity surfaces and to determine the areas that need more attention from silvicultural management.