Data from: How to map forest structure from aircraft, one tree at a time

Forest structure is strongly related to forest ecology and it is a key
parameter to understand ecosystem processes and services. Airborne laser
scanning (ALS) is becoming an important tool in environmental mapping. It
is increasingly common to collect ALS data at high enough point density to
recognize individual tree crowns (ITCs) allowing analyses to move beyond
classical stand level approaches. In this paper an effective and simple
method to map ITCs, and their stem diameter and above ground biomass is
presented. ALS data were used to delineate ITCs and to extract ITCs’
height and crown diameter; then using newly developed allometries the
ITCs’ DBH and AGB were predicted. Gini coefficient of DBHs was also
predicted and mapped aggregating ITCs predictions. Two datasets from
spruce dominated temperate forests were considered: one was used to
develop the allometric models, while the second was used to validate the
methodology. The proposed approach provides accurate predictions of
individual DBH and AGB (R2 = 0.85 and 0.78, respectively) and of tree size
distributions. The proposed method had a higher generalization ability
compared to a standard area based method, in particular for the prediction
of the Gini coefficient of DBHs. The delineation method used detected more
than 50% of the trees with DBH >10 cm. The detection rate was
particularly low for trees with DBH below 10 cm, but they represent a
small amount of the total biomass. The Gini coefficient of the DBH
distribution was predicted at plot level with R2 = 0.46. The approach
described in this work, easy applicable in different forested areas, is an
important development of the traditional area based remote sensing tools
and can be applied for more detailed analysis of forest ecology and
dynamics.