Fig 1.
Location of the study area and spatial distribution of the NFI-4 plots where P. pinaster and P. radiata were dominant.
Fig 2.
A typical sample plot used in the fourth National Forest Inventory (NFI-4).
Grey circles represent trees selected on the basis of tree diameter and the distance to the plot centre.
Table 1.
Potential explanatory variables related to height distribution and canopy cover.
Table 2.
Descriptive statistics for the main tree and stand variables corresponding to the sample plots used in this study.
Std. Dev., standard deviation; d, tree diameter; h, total tree height; cl, crown length (defined as the distance from the crown base to the tree top); N, stand density; dg, quadratic mean diameter; G, stand basal area and H, dominant height (estimated as the mean height of the 100 thickest trees per ha).
Fig 3.
Vertical profiles of relative canopy fuel load (CFLrel) in each sample plot of P. pinaster (left) and P. radiata (right) estimated from field data.
Fig 4.
Box plot of the estimated values of the scale and shape parameters of the Weibull function (â1 and â2, respectively) for P. pinaster (Pp) and P. radiata (Pr) sample plots.
Different letters indicate significant differences between mean values (α = 0.05).
Table 3.
Parameter estimates and goodness-of-fit statistics for the systems of models obtained for each species by using stand variables as predictors.
ME is the model efficiency (Eq 9) and RMSE is the root mean square error (Eq 8). All parameter estimates were significant at p < 0.05.
Fig 5.
Scatter diagrams of vertical CFL distributions estimated from field data against predicted vertical CFL distributions obtained using stand variables as predictors.
The solid line represents the linear model fitted, and the broken line is the 1:1 line (left, first column). Box plot of CFL residuals (using stand variables as predictors) against canopy length classes (right, second column). Graphs for P. pinaster are in the first row and for P. radiata in the second row.
Table 4.
Parameter estimates and goodness-of-fit statistics for the systems of models obtained for each species using ALS metrics as predictors.
ME is the model efficiency (Eq 9) and RMSE is the root mean square error (Eq 8). All parameter estimates were significant at p < 0.05.
Fig 6.
Scatter diagram of vertical CFL distributions estimated from field data against vertical CFL distributions predicted using ALS metrics.
The solid line represents the linear model fitted, and the dashed line is the 1:1 line (left, first column). Box plot of CFL residuals (using ALS metrics as predictors) against canopy length classes (right, second column). Graphs for P. pinaster are in the first row and those for P. radiata are in the second row.