Table 1.
Overview of sampling designs across the 18 different National Forest Inventories. In total, the database contains 255,418 plots. For each country we used one cycle of measurements.
Fig 1.
Number of NFI plots per 0.2-degree grid cell on a log scale (log(plot count)) as available in our database.
Colored pixels represent the study area. The log scale was used to make the differences discernible (white cells have no NFI plots). Densities of plots vary because of different sampling densities between countries and within countries (e.g., Germany, France, Spain). These sampling densities and designs are set in countries’ NFIs based on countries’ spatial variation in the forest and, e.g., budget limitations. The varying representativity per plot for scaling to the full forest area is not taken into account in present study. The basemap was produced using giscoR for accessing Eurostat spatial data.
Table 2.
Classification scheme with criteria.
Fig 2.
Conceptual visualization and associated conceptual diameter distributions of the six forest structure classes.
Fig 3.
Spatial distribution of the six forest structure classes over Europe on a 0.2-degree grid scale.
‘Share’ means the fraction of plot counts per pixel which fall into that class as the share of the total. The basemap was produced using giscoR for accessing Eurostat spatial data.
Fig 4.
Distribution of forest area per forest structure class by country showing noticeable variation between countries.
The overall dominance of the single-species regular and the multiple-species regular is apparent.
Fig 5.
Comparison of the share of forest area in the “single-species regular” class (x-axis, this study) and the two categories as reported in [70] and one class in [13].