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Altitude above sea level in classes of 400 m. Reference: Digital height model DHM 25 from Swisstopo

Altitudinal vegetation belts in the system used in the guidelines for monitoring the sustainability and performance of protection forests (NaiS; Frehner et al. 2005), reduced to six classes. The variable represents a simplification of the NaiS altitudinal vegetation belts with ten classes (NAISHSTKOMB) in which the classes «hyperinsubric» and «colline» are merged with «colline with beech» to form the class «hyperinsubric and colline» and the class «lower montane» with «upper montane» and «lower/upper montane» to form the class «lower and upper montane». The information is based on the altitudinal vegetation belts determined by experts (accessible forest sample plots of NFI4 on the 1.4-km network; Arge Frehner et al. 2020), as well as on the altitudinal vegetation belts modelled for the period 1981-2010 (other sample plots; Zischg et al. 2021). n/a: located above the forest boundary modelled by Zischg et al. and sometimes in the area of lakes, which were relatively roughly cut out by Zischg et al.

Measure of inter-tree crowding of the tree crowns in a stand. Reference: Field Survey (MID 266: Schlussgrad)

Proportions of conifers and broadleaves making up the stand structure, classified according to their proportional basal areas into four classes: pure conifer forest: 91-100 % conifers, mixed conifer forest: 51-90 % conifers, mixed broadleaved forest: 11-50 % conifers and pure broadleaved forest: 0-10 % conifers. Reference: Field Survey (MID 265: Mischungsgrad)

Combination of the 18 groups of NaiS site types, each with a similar objective for the main tree species (NAISGGROB20), into 10 large associations known as «forest formations». *As the characterisation of the site types in the NaiS-NFI project is on a small scale, it is possible that non-forest site types such as meadow, pasture and rock may be present in sample plots that are classified as «forest» in NFI. Similarly, «forest without shrub forest“ may also contain «shrub forest» site types.

NFI's sampling grid with a mesh size of 1.4 km. The 1.4-km grid is the grid size covering all the previous terrestrial Inventories, which is why it is also called the base grid.