Preselection of the inventory

Horizontal distance that the timber travels on a road with limited truck drivability to the point of sale (timber yard or railway station) in four classes. Restricted truck access means that the road cannot be used by trucks with fewer than 4 axles due to permanent bottlenecks or places with a load capacity of less than 28 tonnes. Reference: Forest Service Survey (MID 3060: Vortransportlinie)

Altitude above sea level in classes of 200 m. Reference: Digital height model DHM 25 from Swisstopo

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) – in ten classes, whereby the classes «hyperinsubric», «colline» and «colline with beech» and «lower and upper montane» only occur in the Southern Alps (S), the classes «submontane», «lower montane», «upper montane» only in the Northern Alps (N) and the classes «high montane», «subalpine» and «upper subalpine» on both sides of the Alps. 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).

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 three classes. The variable represents a simplification of the NaiS altititudinal vegetation belts in six classes (NAISHSTKOMB6KL) in which the class «hyperinsubric and colline» is mearged with «submontane» to form the class «hyperinsubric, colline, submontane», the class «lower and upper montane» with «high montane» to form the class «montane» and the class «subalpine» with «upper subalpine» to form the class «subalpine». 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).

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).

Sample plots classified: «no», «one», «two» or «more than two» red wood ant-heaps in the 500 m² circle. Reference: Field Survey (MID 837: Ameisenhaufennummer)

Sample plots without/with gaps ≥100 m² from canopy edge to canopy edge that intersect with the interpretation area (50 × 50 m), classified according to the area of the largest gap into five classes. Reference: aerial photo interpretation

Aspect, classified into the following five classes: North, East, South, West and indeterminate. «Indeterminate» means that the slope is ≤10%. Reference: Field Survey (MID 191: Azimut der Exposition)

Aspect, classified into the following nine classes: North, North-East, East, South-East, South, South-West, West, North-West and indeterminate. «Indeterminate» means that the slope is ≤10%. Reference: Field Survey (MID 191: Azimut der Exposition)

Basal area of standing living trees and shrubs ≥12 cm in diameter at breast height (dbh) per hectare – in four classes. Reference: Field Survey (MID 60: Brusthöhendurchmesser, MID 62: Umfang)

Type of subsidised measure implemented since the last Inventory as part of the biodiversity promotion programme. Reference: Forest Service Survey (MID 2016: Biodiversitätsmassnahmen)

Ecological value of the forest as a habitat for animals and plants – in three classes. Its value as a biotope is based on the three indicators «naturalness of the proportion of conifers», «diversity of woody species» and «structural diversity».

Obstruction directly at the forest edge that makes it difficult or impossible for humans or animals to enter or leave the forest or restricts the spread of the shrub belt or herbaceous fringe - in ten classes. Reference: Field Survey (MID 982: Art der Waldrandbegrenzung)

Cause of the damage gap, e.g. storm, drought, insect or fungal infestation or timber harvesting. Reference: Forest Service Survey (MID 600: Art der Schadenflächen)

Cause of damage to trees and shrubs ≥12 cm in diameter at breast height (dbh) – in ten classes. Eight of these classes focus exclusively on standing living trees and shrubs with dbh ≥12 cm, while one class applies to lying living trees and shrubs with dbh ≥12 cm, and one to dead trees and shrubs with dbh ≥12 cm. Reference: Field Survey (MID 1029: Baumschadenursache, MID 1018: Baumzustand)

Reason why trees and shrubs ≥12 cm in diameter at breast height (dbh) have died or disappeared since the last Inventory. Reference: Forest Service Survey (MID 2046: Absterbegrund - toter/fehlender Probebaum)

Type of certificate: FSC and/or PEFC (NFI4, NFI5) or FSC and/or Q (PEFC) (NFI3). Reference: Forest Service Survey (MID 602: Zertifizierungs-Label)

Type of trees and shrubs ≥12 cm in diameter at breast height (dbh) in two classes (conifers or broadleaves). Reference: Field Survey (MID 50: Baumart)

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

Size of the adjacent areas on which the trees were so severely damaged during an event (e.g. storm, drought, insect or fungal infestation, or timber harvest) that they died immediately or are most likely to soon die – in five classes..Reference: Field Survey (MID 996: Fläche des Schadens am Probeflächenzentrum), together with Forest Service Survey (MID 600: Art der Schadenflächen)

Damage to young forest plants ≥10 cm in height and ≤11.9 cm in diameter at breast height (dbh), whereby browsing is only assessed on specimens ≤129 cm in height, – in eight classess. Reference: Field Survey (MID 127: Gipfeldürre, MID 174: Verbiss des Leittriebes, MID 977: Fegeschaden, MID 987: Schälschaden, MID 184: Krankheit; MID 183: Holzereischaden, MID 185: anderer Schaden)

Proportion of bark cover on dead trees and shrubs (standing and lying) ≥12 cm in diameter at breast height (dbh) – in three classes. Reference: Field Survey (MID 418: Totholz - Rindendeckung)

Number of shrubs ≥10 cm in length growing on a lying dead tree or shrub ≥12 cm in diameter at breast height (dbh) – in five classes. Reference: Field Survey (MID 425: Strauchpflanzen auf Totholz)

Species group (conifers or broadleaves) of lying deadwood. Reference: Field Survey (MID 907: LIS-Totholz – Laub- oder Nadelholz)

Stage of wood decay in dead trees and shrubs (standing and lying) ≥12 cm in diameter at breast height (dbh) – in three classes. Reference: Field Survey (MID 419: Totholz - Festigkeit)

Stage of decay of wood in dead trees and shrubs (standing and lying) ≥12 cm in diameter at breast height (dbh) – in five classes. Reference: Field Survey (MID 419: Totholz - Festigkeit)

Number of young broadleaves or conifers ≥10 cm growing on a lying dead tree or shrub ≥12 cm in diameter at breast height (dbh) – in three classes. Reference: Field Survey (MID 426: Verjüngung auf Totholz)

Proportion of the ground area covered by tree crowns according to the aerial photo interpretation – in five 20-percent classes. The percentage is calculated using the 25 grid points on the interpretation area (50 × 50 m). Reference: aerial photo interpretation

Proportion of the ground area that is covered by established regeneration, i.e. by living coniferous and broadleaved trees ≥1.3 m in height and 11.9 cm in diameter at breast height (dbh). Reference: Field Survey (MID 273: Deckungsgrad der gesicherten Verjüngung)

Proportion of ground area covered by ferns, grasses, herbs, Rubus species, (tall) herbaceous perennials and dwarf shrubs (e.g. vaccinia, Alpenrose or juniper). Reference: Field Survey (MID 278: Bodenvegetations-Deckungsgrad).

Proportion of the ground area covered by trees and shrubs with a height of 0.5-3.0 m and by branches of taller individuals of the same species in the same area. Reference: Field Survey (MID 277: Strauchschicht-Deckungsgrad)

Proportion of the ground area covered with berry bushes (blackberry, raspberry, blueberry, cowberry, bog bilberry, and cranberry). Reference: Field Survey (MID 279: Beerensträucher-Deckungsgrad)

Degree of damage to trees and shrubs ≥12 cm in diameter at breast height (dbh) classified into six classes according to the damage occurred. Reference: Field Survey (MID 1027: Baumschadenart, MID 1018: Baumzustand)

Degree of damage to forest stands in six classes, derived from the mean degree of damage to trees and shrubs ≥12 cm in diameter at breast height (dbh) weighted with the basal area. Reference: Field Survey (MID 1027: Baumschadenart, MID 1018: Baumzustand)

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)

Proportion of the area covered by regeneration, i.e. broadleaves and conifers ≥10 cm in height and ≤11.9 cm in diameter at breast height (dbh) - in seven classes. The variable has been in use since NFI3 (2004-2006). For comparisons going back to NFI2 (1993-1995), the variable «degree of regeneration cover (6 classes)» can be used. Reference: Field Survey (MID 270: Verjüngungs-Deckungsgrad)

Density of shelterbelt (forest mantle) and shrub belt with foliage from the ground to a height of 2 m - in four classes. Reference: Field Survey (MID: 43: Waldranddichte)

Stage of stand development, defined by the dominant diameter at breast height (dbhdom = dbh of the 100 largest [thickest] trees per hectare). Young growth/thicket: dbhdom <12 cm, pole timber: dbhdom 12-30 cm, young timber: dbhdom 31-40 cm, medium timber : dbhdom 41-50 cm, old timber: dbhdom >50 cm, mixed: trees of different development stages, no development stage predominant or groups of different development stages covering < 500 m². Reference: Field Survey (MID 261: Entwicklungsstufe)

Diameter at breast height (dbh) of trees and shrubs ≥12 cm dbh in the two classes: «≤30 cm dbh» or «>30 cm dbh. Reference: Field Survey (MID 60: Brusthöhendurchmesser, MID 62: Umfang)

Diameter at breast height (dbh) of trees and shrubs ≥12 cm – in classes of 20 cm. Reference: Field Survey (MID 60: Brusthöhendurchmesser, MID 62: Umfang)

Diameter at breast height (dbh) of trees and shrubs ≥12 cm dbh - in classes of 4 cm. Reference: Field Survey (MID 60: Brusthöhendurchmesser, MID 62: Umfang)

Diameter at breast height (dbh) of trees and shrubs ≥12 cm dbh, classified in main diameter classes. Reference: Field Survey (MID 60: Brusthöhendurchmesser, MID 62: Umfang)

Diameter at breast height (dbh) of the trees and shrubs ≥12 cm dbh – in ten classes. Reference: Field Survey (MID 60: Brusthöhendurchmesser, MID 62: Umfang)

Diameter of lying deadwood – in 4 classes. Reference: Field Survey (MID 459: Durchmesser 1, MID 460: Durchmesser 2)

Ecological value of the forest edge according to the number of woody species present, as well as the weighted proportion of thorny shrubs, short-lived, light-demanding softwoods (birches, alders, poplars and willows) and other ecologically valuable woody species (e.g. oaks and rowan) – in three classes. Reference: Field Survey (MID 568: Pflanzenarten am Waldrand)

Ecological value of the forest stand according to the number of woody species present, as well as the presence of woody species of special ecological importance (willows, birches, alders, native poplars, native oaks, chestnut, cherry tree, Malus spp., Pyrus spp., Sorbus spp. and Scots pine) in the upper layer – in three classes. Reference: Field Survey (MID 50: Baumart, MID 65: Schicht)

Indication of whether alien woody species (tree or shrub neophytes) ≥12 cm in diameter at breast height (dbh) dominate the growing stock, i.e. account for at least 50% of the growing stock – in two classes. Reference: Field Survey (MID 50: Baumart, MID 1018: Baumzustand, MID 60: Brusthöhendurchmesser, MID 62: Umfang)

Indication as to whether invasive or non-invasive alien woody species («tree or shrub neophytes») ≥12 cm in diameter at breast height (dbh) dominate the growing stock, i.e. account for at least 50% of the growing stock – in three classes. The classification as «invasive» is based on the 2022 publication «Invasive alien species in Switzerland» of the Federal Office for the Environment (FOEN) (UW-2220-E). Reference: Field Survey (MID 50: Baumart, MID 1018: Baumzustand, MID 60: Brusthöhendurchmesser, MID 62: Umfang)

Indication as to whether introduced woody species (tree- or shrub-like neophytes) ≥12 cm in diameter at breast height (dbh) dominate the growing stock, i.e. account for at least 50% of the growing stock, classified into the three classes: «not dominated by introduced species», «dominated by introduced species other than black locust», «dominated by introduced, invasive black locust». Black locust is the only invasive introduced species that has been recorded separately in all NFI inventories to date. The classification as «invasive» corresponds to the publication «Alien species in Switzerland» of the Federal Office for the Environment (FOEN) from 2022 (UW-2220-E). Reference: Field Survey (MID 50: Baumart, MID 1018: Baumzustand, MID 60: Brusthöhendurchmesser, MID 62: Umfang)

Mean age of the 100 largest standing living trees and shrubs ≥12 cm in diameter at breast height (dbh) per hectare – in five classes. Reference: Field Survey (MID 826: Baumalter)

Diameter at breast height (dbh) of the 100 largest (thickest) standing living trees and shrubs ≥12 cm dbh per hectare – in eight classes. Reference: Field Survey (MID 60: Brusthöhendurchmesser, MID 62: Umfang)

Mean diameter at breast height (dbh) of the 100 largest standing living trees ≥12 cm in diameter at breast height (dbh) per hectare – in five classes. Reference: Field Survey (MID 60: Brusthöhendurchmesser, MID 62: Umfang)

Location inside or outside the catchment area of a spring whose water is fed either directly and unfiltered into the drinking-water supply, or is used at least temporarily or partially as drinking water for the public. Reference: Forest Service Survey (MID 603: Wald im Einzugsgebiet von gefassten Trinkwasserquellen)

Sample plots with/without dry stone walls and piles of stones on the interpretation area (50 × 50 m), classified according to the type of objects. Reference: Field Survey (MID 217: Trockenmauer und Steinhaufen)

Ecological value of the forest edge as a habitat for animals and plants, classified into three classes according to the structural diversity and diversity of woody species along the forest edge. Reference: Field Survey (various attributes)

Sample plots without/with damage gaps on the interpretation area, and the extent of damage classified into ten classes according to the proportion of the forested interpretation area that is damaged. Reference: Field Survey (MID 601: Ausmass der Schadenfläche)

Distance - measured horizontally - that the timber is transported from the felling site to a road that is at least 2.50 m wide and dimensioned for an axle load of at least 10 tonnes - in four classes. Any hauling on a road does not count to the extraction distance. Reference: Forest Service Survey (MID 3000: Rückelinie)

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.

Forest functions of considerable local importance according to forest plans or an assessment by the local forest service. It's possible for there to be several forest functions of considerable local importance at the same time. Reference: Forest Service Survey (MID 327: Spezielle Waldfunktionen)

Presence of the forest function 'agricultural use' according to forest plans or an assessment by the local forest service. The forest function 'agricultural use' generally includes wooded pastures and nut orchards. Reference: Forest Service Survey (MID 327: Spezielle Waldfunktionen)

Presence of the forest function «carbon sink» according to forest plans or an assessment by the local forest service. Reference: Forest Service Survey (MID 327: Spezielle Waldfunktionen)

Presence of the forest function 'drinking-water protection' according to forest plans or an assessment by the local forest service. The forest function «drinking-water protection» generally includes groundwater protection zones and drinking-water catchment areas. Reference: Forest Service Survey (MID 327: Spezielle Waldfunktionen)

Presence of the forest function 'game protection' according to forest plans or an assessment by the local forest service. As a rule, the forest function 'game protection' includes seasonal grazing areas and game reserves. Reference: Forest Service Survey (MID 327: Spezielle Waldfunktionen)

Presence of the forest function 'landscape protection' according to forest plans or an assessment by the local forest service. Reference: Forest Service Survey (MID 327: Spezielle Waldfunktionen)

Presence of the forest function 'military' according to forest plans or an assessment by the local forest service. Reference: Forest Service Survey (MID 327: Spezielle Waldfunktionen)

Presence of the forest function 'nature conservation' according to forest plans or an assessment by the local forest service. Reference: Forest Service Survey (MID 327: Spezielle Waldfunktionen)

Presence of the forest function «protection against natural hazards» according to forest plans or an assessment by the local forest service. The term «natural hazards» refers to avalanches, rockfall, landslides, landslides and channel processes. Reference: Forest Service Survey (MID 327: Spezielle Waldfunktionen)

Presence of the forest function 'recreation' according to forest plans or an assessment by the local forest service. Reference: Forest Service Survey (MID 327: Spezielle Waldfunktionen)

Presence of the forest function 'timber production' according to forest plans or an assessment by the local forest service. Reference: Forest Service Survey (MID 327: Spezielle Waldfunktionen)

Presence of the forest function 'windbreak' according to forest plans or an assessment by the local forest service. The forest function 'windbreak' generally includes the forests or forest strips that protect agricultural land against wind. Reference: Forest Service Survey (MID 327: Spezielle Waldfunktionen)

Intensity of forest management, classified in three classes according to site quality and the time of the last treatment. Reference: Forest Service Survey (MID 607: Anzahl Jahre seit dem letzten Eingriff); modelled site quality (total growth performance according to Keller 1978)

Indication as to whether forest planning documents exist at the local level (operational plan, silvicultural project, etc.) and/or at the cantonal level (forest development plan or regional/cantonal forest plan). These documents provide the basis for the forest manager to make silvicultural or operational decisions, irrespective of the year they were produced. Reference: Forest Service Survey (MID 2028: lokale forstliche Planungswerke, MID 803: Stand der Waldentwicklungspläne WEP)

STRBREITE gibt an, wie breit der betreffende Strecken-/Strassenabschnitt ist. Lastwagenstrassen im Schweizer Wald müssen, um in der Erschliessungserhebung erfasst zu werden, eine Mindestbreite von 2.50 m aufweisen, wobei der Strassenoberbau mindestens für eine Achslast von 10 t ausgelegt sein muss. Im Rahmen der Försterumfrage des LFI4 wurden zusätzliche Informationen erhoben. Dabei steht nicht die lastwagenbefahrbare Strasse nach LFI mit 10 t Achslast und einer Mindestbreite von 2.50 m im Fokus, sondern die für die Holzabfuhr relevante Strasse mit mindestens 3 m Fahrbahnbreite und genügender Tragfähigkeit für Fahrzeuge mit einem Gesamtgewicht ab 26 t.

Classification of forests into 12 classes («types») according to their development, structure and management. Unlike in the 17-class forest-type classification, in this 12-class classification all development stages (from young growth to timber) are subsumed in the class «uniform high forest». Reference: Field Survey (MID 255: Nutzungskategorie, MID 257: Waldtyp nach Aufnahmeanleitung LFI, MID 260: Waldform, MID 267: Bestandesstruktur, MID 261: Entwicklungsstufe)

Classification of forests according to their establishment, structure and management into 17 classes («types»). In contrast to the forest typology with 12 classes, the forest typology with 17 classes defines each development stage (young growth to timber) as an individual class. Reference: Field Survey (MID 255: Nutzungskategorie, MID 257: Waldtyp nach Aufnahmeanleitung LFI, MID 260: Waldform, MID 267: Bestandesstruktur, MID 261: Entwicklungsstufe)

Classification of the forest according to the forest decision and accessibility into the three classes «accessible forest without shrub forest», «inaccessible forest without shrub forest» and «shrub forest».

Type of forest in two classes: «forest without shrub forest» or «shrub forest». Reference: Field Survey (MID 816) or - if the forest is inaccessible – aerial photo interpretation

Land cover, classified as one of three categories: 'forest without shrub forest', 'shrub forest' and 'non-forest', based on the NFI forest definition. Reference: Field Survey (MID 816), or if inaccessible, aerial photo interpretation.

Land cover classified into the two classes: «forest» (i.e. forest without shrub forest or shrub forest) and «non-forest» according to the forest definition of the NFI. Reference: Field Survey or, in if inaccessible – aerial photo interpretation

Sample plots without/with geomorphological objects (e.g. bands of rock, boulders, limestone pavements or gullies) on the interpretation area (50 × 50 m), classified according to the type of the largest object. Reference: Field Survey (MID 218: Geomorphologische Objekte, Kleinrelief)

Zones around groundwater wells and groundwater recharging facilities that are designated by the canton as in the public interest for protecting drinking water. How strict the property restrictions and/or management requirements are depends on the protection zone,. The variable reflects the protection zone categories applicable since 2016 in accordance with Art. 121 of the Waters Protection Ordinance (SR 814.201) and the status of designation by the cantons on 8 July 2022 (download of data from geodienste.ch).

Habitat quality assessed according to the types of deadwood present. It is considered «high» if the three deadwood types «snagss», «branch and wood piles» and «stumps and lying deadwood» are present on the interpretation area, «moderate» if two types are present, and «low» if none or only one type is present.

Indication as to whether the timber harvesting (felling, processing, extraction and hauling) is carried out wholly or in part by the forest enterprise itself or by a contractor. If an intervention has been carried out since the last Inventory, the information is based on the actual type of operation; if no intervention has been carried out, it is based on the type of operation that the district forester thinks would have been carried out at the time of the current Inventory. Reference: Forest Service Survey (MID 351: Ausführung der Holzernte)

Areas in higher and lower altitude zones classified according to the system used for altitudinal vegetation belts in the guidelines for monitoring the sustainability and performance of protection forests (NaiS; Frehner et al. 2005). The boundary between the higher and lower altitudes runs between the «upper montane» and «lower montane» levels on the Northern Alps and between the «high montane» and «upper/lower montane» levels to the Southern Alps. 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).

Sample plots with/without signs on the interpretation plot (50 × 50 m) that the forest stand or forest site is subject to very intense (excessive) recreational use or other strong human influence (e.g. landfill, land drainage, construction). Where there are such signs, indication of the type of overuse or disturbance. Reference: Field Survey (MID 219: Spuren von Überbelastungen und Störungen)

Located in/outside a groundwater protection zone. The cantons demarcate groundwater protection zones around groundwater wells and groundwater recharging facilities to protect drinking water where this is in the public interest. The indicator variable combines the various protection zone categories in force since 2016 in accordance with Art. 121 of the Waters Protection Ordinance (SR 814.201) into one class. Data status: 8 July 2022 (download from geodienste.ch).

Sample plots without/with a distinct vertical stand edge («inner forest edge») on the interpretation area (50 × 50 m). If an inner edge is present, what the lower of the two stands consists of is also indicated. Reference: Field Survey (MID 281: Innenränder)

Sample plots with/without current recreational use within a radius of 100 m around the sample plot centre, classified according to visitor frequency as a measure of the intensity of recreational use. No recreational use: <10 persons/year; very low intensity: <1 person/day; low: 1-10 persons/day; moderate: 11-100 persons/day; high: 101-500 persons/day; very high: >500 persons/day based on the entire year or the relevant season, taking into account all types of recreational use. Reference: Forest Service Survey (MID 330: Intensität der aktuellen Erholungsnutzung)

Classification of trees and shrubs ≥12 cm in diameter at breast height (dbh) into the three classes: «introduced tree species», «native tree species» and «indeterminable and/or shrub species». Introduced tree species are tree species that have been intentionally or unintentionally introduced by humans into habitats outside their natural range. With this classification attribute, which is used in all inventories, the Japanese larch (L. kaempferi) and introduced arboreal willow species are not counted as introduced tree species, because they are recorded together with related native species in certain inventories. The Japanese larch (Larix kaempferi), for example, is grouped together with the European larch (L. decidua). Reference: Field Survey (MID 50: Baumart)

Introduced tree species ≥12 cm in diameter at breast height (dbh), recorded in all the Inventories, classified into the eight classes: Austrian pine (Pinus nigra), Weymouth pine (Pinus strobus), Douglas fir (Pseudotsuga menziesii), red oak (Quercus robur), non-native poplars (Populus [other introduced]), black locust (Robinia pseudoacacia), other introduced tree species (including sequoia, redwood, thuja, cedar, tree-of-heaven, horse-chestnut, tulip-tree). The remaining woody species (native tree species and all shrub species) are summarised in one class.

Length of lying dead trees and shrubs ≥12 cm in diameter at breast height (dbh) up to the limit for merchantable wood (7 cm in diameter) – in six classes. If an individual tree is broken, the lengths of all the parts are added together. Reference: Field Survey (MID 415: Stücklänge liegender Probebäume)

Sample plots with/without tracks of timber-harvesting vehicles such as tractors, forwarders and harvesters on the forest floor within the 200 m² circle, classified according to where the tracks occur. Reference: Field Survey (MID 545: Schadenumgebung)

Location of the tracks of timber harvesting vehicles such as tractors, forwarders and harvesters – in four classes. Reference: Field Survey (MID 955: Bodenschadenumgebung)

Machines or tools used for felling and processing the trees. If an intervention has taken place since the last Inventory, the data is based on the means actually used. If no intervention has taken place, it is based on the means that would have been used in the case of an intervention at the time of the current Inventory, according to the district forester's assessment. Reference: Forest Service Survey (MID 352: Art der Holzernte)

Type of trees and shrubs ≥12 cm in diameter at breast height (dbh) with the ten most common species or species groups in Switzerland ('main tree species') categorised, and the classes 'other conifers' and 'other broadleaves' for the remaining species. The main tree species are: spruce (Picea spp.), fir (Abies spp.), pine (Pinus sylvestris, P. nigra, P. strobus, P. mugo subsp. uncinata), larch (Larix spp.), Arolla pine (Pinus cembra), beech (Fagus sylvatica), maple (Acer spp.), ash (Fraxinus spp.), oak (Quercus spp.) and chestnut (Castanea sativa). Reference: Field Survey (MID 50: Baumart)

Species of young forest plants ≥10 cm in height and ≤11.9 cm in diameter at breast height (dbh) with individual classes for the ten most important species or species groups in Switzerland («main tree species»), as well as the classes «other conifers», «other broadleaves» and «species not assessed in all inventories». The main tree species are spruce (Picea spp.), fir (Abies spp.), pine (Pinus sylvestris, P. nigra, P. strobus, P. mugo subsp. uncinata), larch (Larix spp. ), Arolla pine (Pinus cembra), beech (Fagus sylvatica), maple (Acer spp.), ash (Fraxinus spp.), oak (Quercus spp.) and chestnut (Castanea sativa). Reference: Field Survey (MID 1051: Jungwaldpflanzenart - Zählung)

Species of young forest plants ≥10 cm in height and ≤11.9 cm in diameter at breast height (dbh) with individual classes for the ten most important species or species groups in Switzerland («main tree species»), as well as the classes «other conifers», «other broadleaves» and «species not assessed in all inventories». The main tree species are spruce (Picea spp.), fir (Abies spp.), pine (Pinus sylvestris, P. nigra, P. strobus, P. mugo subsp. uncinata), larch (Larix spp. ), Arolla pine (Pinus cembra), beech (Fagus sylvatica), maple (Acer spp.), ash (Fraxinus spp.), oak (Quercus spp.) and chestnut (Castanea sativa). Reference: Field Survey (MID 1050: Jungwaldpflanzenart - nächste Pflanze)

Type of microhabitat that occurs at least once on a tree or shrub ≥12 cm in diameter at breast height (dbh). Reference: Field Survey (MID 819: Bemerkung zu Ex-LFI-Probebaum, MID1027: Baumschadenart, MID 1035-1049: Baummikrohabitate)

Natural hazard processes that can occur in forests designated as protection forests by the cantons according to the harmonised criteria of SilvaProtect. Reference: Losey & Wehrli (2013)

Correspondence between the actual proportion of conifers in a stand and the postulated natural proportion of conifers in the corresponding potential natural vegetation (PNV). Reference: NaiS site types, aggregated into groups with similar mixing and regeneration objectives («Gfein») according to the NaiS-NFI project (Arge Frehner et al. 2020) for the PNV; classification of the proportion of conifers according to the Kienast method; Field Survey (MID 50: Baumart, MID 60: Brusthöhendurchmesser, MID 62: Umfang)

Classification of trees and shrubs ≥12 cm in diameter at breast height (dbh) into four classes according to the number of visible cases of damage or the condition of the tree (living/dead, standing/lying). Reference: Field Survey (MID 1018: Baumzustand, MID 1027: Baumschadenart)

Number of natural hazard processes that can occur simultaneously in forest designated «protection forest» by the cantons (as of 2022) according to the harmonised criteria of SilvaProtect-CH (as of 2022). The following four natural hazard processes can be considered: rockfall, avalanches, hillslope debris flows/landslides, channel processes. Reference: GIS data from the FOEN, 2022

Number of standing living trees and shrubs ≥24 cm in diameter at breast height (dbh) – in classes of 100. Reference: Field Survey (MID 60: Brusthöhendurchmesser, MID 62: Umfang, MID 1018: Baumzustand)

Number of standing living trees and shrubs ≥36 cm in diameter at breast height (dbh) – in classes of 100. Reference: Field Survey (MID 60: Brusthöhendurchmesser, MID 62: Umfang, MID 1018: Baumzustand)

Number of standing living trees and shrubs ≥12 cm in diameter at breast height (dbh) per hectare – in classes of 100. Reference: Field Survey (MID 60: Brusthöhendurchmesser, MID 62: Umfang, MID 1018: Baumzustand)

Number of tree and shrub species in the upper stand layer – in six classes. The information refers to the relevant stand on the interpretation area (50 × 50 m) and only takes into account species with a cover ≥5%. Reference: Field Survey (MID 242: Baumart in der Oberschicht)

Number of tree and shrub species present along the forest edge – in five classes. The data is for a distance of 50 m along the edge of the forest. Reference: Field Survey (MID 568: Pflanzenarten am Waldrand)

Classification of forest stands according to the dominant diameter at breast height (dbhdom), i.e. the 100 largest (thickest) standing living trees per hectare, as: «old timber stand» (dbhdom >50 cm) or «not old timber stand». Reference: Field Survey (MID 60: Brusthöhendurchmesser, MID 62: Umfang)

Forest ownership, classified according to the two categories: 'public' and 'private'. Reference: Forest Service Survey (MID 365: Eigentum)

Forest ownership at the time of NFI5, classified into the two classes: «public» and «private». The attribute is used in analyses of change to ensure that changes in ownership do not influence the results. Reference: Forest Service Survey (MID 365: Eigentum)

Ownership of the forest, categorised according to the 7 types 'federal government', 'canton', 'municipality', 'citizens' community', 'corporation', 'individual private ownership' and 'company'. Reference: Forest Service Survey (MID 365: Eigentum)

Sample plots with/without traces of grazing by livestock pasturing in the relevant stand on the interpretation area (50 × 50 m), as well as intensity and recency of pasturing based on the occurrence and freshness of pasturing signs, especially tracks and droppings. Reference: Field Survey (MID 205: Beweidungsintensität)

Sample plots with either no wood pile or with at least one compact wood pile ≥30 cm in height and 3 m² in area on the interpretation area (50 × 50 m) left in the stand after harvesting. Reference: Field Survey (MID 209: Asthaufen)

Level of potential demand for local recreation, classified into five classes according to a model that estimates the number of permanently occupied and temporarily occupied/unoccupied dwellings within a radius of two kilometres. The variable is only available for NFI2 and NFI3.

Tree species group (conifers or broadleaves) with the larger basal area. For the calculation, the standing living trees and shrubs ≥12 cm in diameter at breast height (dbh) were taken into account. Reference: Field Survey (MID 1018: Baumzustand, MID 50: Baumart, MID 60: Brusthöhendurchmesser, MID 62: Umfang)

Main tree species with the largest basal area. For the calculation, the standing living trees and shrubs ≥12 cm in diameter at breast height (dbh) were taken into account. Reference: Field Survey (MID 1018: Baumzustand, MID 50: Baumart, MID 60: Brusthöhendurchmesser, MID 62: Umfang)

Sample plots with/without at least one still clearly recognisable root plate that protrudes at least 30 cm above the terrain. Reference: Field Survey (MID 227: Wurzeltellerklasse)

Sample plots with/without at least one pile of soil or mulch, created by the decay of a root plate and protruding at least 30 cm above the terrain. Reference: Field Survey (MID 227: Wurzeltellerklasse)

Sample plots with/without tracks of timber-harvesting vehicles such as tractors, forwarders and harvesters on the forest floor within the 200 m² circle. If there are tracks, indication of the track type. In the case of track type 3 (severe disturbance), it can be assumed that the damage to the soil fertility will be significant and long term (Lüscher et al. 2016). Reference: Field Survey (MID 544: Fahrzeugspuren, MID 496: Bodenschadentyp)

Type of the most important forest function relevant for managing the forest according to forest plans or an assessment by the local forest service during NFI4 (2009-2017). Reference: Forest Service Survey (MID 911: Vorrangfunktion 2)

Type of the most important forest function relevant for management according to forest plans or an assessment by the local forest service during NFI5 (2018-2026). Reference: Forest Service Survey (MID 911: Vorrangfunktion 2)

Presence of the primary function «nature and landscape conservation», classified into the four classes: «landscape protection», «nature conservation», «game protection» or «other» according to forest plans or an assessment by the local forest service during NFI5 (2018-2026). Reference: Forest Service Survey (MID 911: Vorrangfunktion 2)

Presence of the primary function: «nature conservation» according to forest plans or an assessment by the local forest service during NFI5 (2018-2026). Reference: Forest Service Survey (MID 911: Vorrangfunktion 2)

Proportion of conifers in the basal area of standing living trees and shrubs ≥12 cm in diameter at breast height (dbh) – in four classes. Reference: Field Survey (MID 60: Brusthöhendurchmesser, MID 62: Umfang)

Percentage of sanitary/salvage fellings in total fellings - in three classes. Reference: Forest Service Survey (MID 344: Anteil Zwangsnutzung)

Area in/outside a forest that provides protection against avalanches which the cantons designated «protection forest» according to the harmonised criteria of SilvaProtect-CH in 2022. Reference: GIS data from FOEN, 2024

Area in/outside a forest that provides protection against channel processes which the cantons designated «protection forest» according to the harmonised criteria of SilvaProtect-CH in 2022. Reference: GIS data from FOEN, 2022

Area in/outside a forest that provides protection against hillslope debris flows/landslides which the cantons designated «protection forest» according to the harmonised criteria of SilvaProtect-CH in 2022. Reference: GIS data from FOEN, 2023

Area in/outside a forest that provides protection against rockfall processes which the cantons designated «protection forest» according to the harmonised criteria of SilvaProtect-CH in 2022. Reference: GIS data from FOEN, 2025

Area inside/outside the protection forest that the cantons had designated in 2022 according to the harmonised criteria of SilvaProtect-CH (Losey & Wehrli 2013). In 2022, Canton Aargau had not yet designated its protection forest. Reference: GIS data from FOEN, 2022

Main reason for sanitary/salvage felling. Reference: Forest Service Survey (MID 345: Ursache der Zwangsnutzung)

Main reason for sanitary/salvage felling. Reference: Forest Service Survey (MID 345: Ursache der Zwangsnutzung)

Sample plots without/with recreation infrastructure (paths and specific recreation facilities) on the interpretation area (50 × 50 m). Reference: Field Survey (MID 220: Erholungseinrichtungen)

Sample plots with/without current recreational use 'camping' within a radius of 100 m around the sample plot centre. The type of recreation is recorded with a visitor frequency ≥10 persons per year. Reference: Forest Service Survey (MID 329: Art der aktuellen Erholungsnutzung)

Sample plots with/without current recreational use 'cross-country skiing' within a radius of 100 m around the sample plot centre. The type of recreation is recorded with a visitor frequency ≥10 persons per year. Reference: Forest Service Survey (MID 329: Art der aktuellen Erholungsnutzung)

Sample plots with/without current recreational use 'cycling' within a radius of 100 m around the sample plot centre. The type of recreation is recorded with a visitor frequency ≥10 persons per year. Reference: Forest Service Survey (MID 329: Art der aktuellen Erholungsnutzung)

Sample plots with/without current recreational use 'hiking' within a radius of 100 m around the sample plot centre. The type of recreation is recorded with a visitor frequency ≥10 persons per year. Reference: Forest Service Survey (MID 329: Art der aktuellen Erholungsnutzung)

Sample plots with/without current recreational use 'horse-riding' within a radius of 100 m around the sample plot centre. The type of recreation is recorded with a visitor frequency ≥10 persons per year. Reference: Forest Service Survey (MID 329: Art der aktuellen Erholungsnutzung)

Sample plots with/without current recreational use 'jogging' within a radius of 100 m around the sample plot centre. The type of recreation is recorded with a visitor frequency ≥10 persons per year. Reference: Forest Service Survey (MID 329: Art der aktuellen Erholungsnutzung)

Sample plots with/without current recreational use 'mountain biking' within a radius of 100 m around the sample plot centre. The type of recreation is recorded with a visitor frequency ≥10 persons per year. Reference: Forest Service Survey (MID 329: Art der aktuellen Erholungsnutzung)

Sample plots with/without current recreational use 'other activities' within a radius of 100 m around the sample plot centre. The type of recreation is recorded with a visitor frequency ≥10 persons per year. Reference: Forest Service Survey (MID 329: Art der aktuellen Erholungsnutzung)

Sample plots with/without current recreational use 'ski- and snowboarding' within a radius of 100 m around the sample plot centre. The type of recreation is recorded with a visitor frequency ≥10 persons per year. Reference: Forest Service Survey (MID 329: Art der aktuellen Erholungsnutzung)

Sample plots with/without current recreational use 'snowshoeing' within a radius of 100 m around the sample plot centre. The type of recreation is recorded with a visitor frequency ≥10 persons per year. Reference: Forest Service Survey (MID 329: Art der aktuellen Erholungsnutzung)

Sample plots with/without current recreational use 'walking' within a radius of 100 m around the sample plot centre. The type of recreation is recorded with a visitor frequency ≥10 persons per year. Reference: Forest Service Survey (MID 329: Art der aktuellen Erholungsnutzung)

Sample plots with/without recreational use within a radius of 100 m around the sample plot centre, with details about the recreational activity (e.g. walking, jogging or biking). Recreational activities are recorded if the visitor frequency is ≥10 people per year. Reference: Forest Service Survey (MID 329: Art der aktuellen Erholungsnutzung)

Proportion of the area covered by regeneration, i.e. broadleaved and coniferous trees ≥10 cm in height and ≤11.9 cm in diameter at breast height (dbh), in six classes. The feature is available as of NFI2 (1993-1995). Reference: Field Survey (MID 270: Verjüngungs-Deckungsgrad)

Terrain topography - in five classes. Reference: Field Survey (MID 192: Relief)

Type of forest reserve («natural forest reserve», «special forest reserve“ or «other forest»), based on the forest reserves as designated by the cantons (as of 2023) and the forest/non-forest decision of the respective Inventory. Reference: GIS data from FOEN, 2023, and Field Survey (MID 816) or – if the forest is inaccessible – aerial photo interpretation

Presence of non-forestry buildings and facilities, such as railway lines, main roads, power- and pipelines or residential areas, which potentially impede logging, i.e. tree felling and processing. Reference: Field Survey (MID 207: Einschränkungen für die Holzhauerei)

Sample plots with/without current recreational use within a radius of 100 m around the sample plot centre, classified according to seasonality of recreational use (all year round, almost only during the growing season, almost only in winter). Reference: Forest Service Survey (MID 403: Saisonalität der aktuellen Erholungsnutzung)

Type of transition line between the forest and the open land along the forest edge - in five classes. Reference: Field Survey (MID 42: Waldrandverlauf)

Indication as to whether a silvicultural treatment took place since the last inventory. Reference: Forest Service Survey (MID 611: Art alle Eingriffe seit Referenzdatum)

Production capacity of the site in kilograms per hectare and year based on the total mean increment (TMI) according to Keller (1978) - in four classes. Low: TMI ≤1500 kg/(ha/year), moderate: TMI 1501-3000 kg/(ha/year), good: TMI 3001-4500 kg/(ha/year), very good: TMI >4500 kg/(ha/year).

Size of young forest plants ≥10 cm in height and ≤11.9 cm in diameter at breast height (dbh) – in three classes (two height classes and one dbh class). Reference: Field Survey (MID 507: Jungwaldklasse)

Size of young forest plants ≥10 cm in height and ≤11.9 cm in diameter at breast height (dbh) – in five size classes (two height and three dbh classes). Reference: Field Survey (MID 507: Jungwaldklasse)

Forest area under the same management – in eight classes. Several forest owners form a management unit («enterprise») if they have joined forces to manage their forests permanently (and not just for one logging operation). Reference: Forest Service Survey (MID 410: Grösse der Bewirtschaftungseinheit)

Slope in classes of 20%. Reference: Digital height model DHM 25 from Swisstopo

Slope in classes of 40%. Reference: Digital height model DHM 25 from Swisstopo

Sample plots with/without standing dead trees («snags») ≥20 cm in diameter at breast height (dbh) on the interpretation area (50 × 50 m), which together reach a volume of at least 1 m³. Reference: Field Survey (MID 211: Dürrständer)

Presence of a forest function that is locally very important according to forest plans or an assessment by the local forest service – in two classes (present/absent). Forest functions include e.g. timber production, protection against natural hazards, nature conservation and drinking water protection. Reference: Forest Service Survey (MID 327: Spezielle Waldfunktionen)

Age of the stand – in classes of 20 years. Reference: Field Survey (MID 264: Bestandesalter)

Age of the stand – in classes of 40 years. Reference: Field Survey (MID 264: Bestandesalter)

Density of a stand – in four classes. The Stand Density Index (SDI) is calculated on the basis of the number of stems per hectare of trees and shrubs ≥12 cm in diameter at breast height (dbh) and the mean diameter. Reference: Field Survey (MID 60: Brusthöhendurchmesser, MID 62: Umfang, MID 1018: Baumzustand)

Stand in which the existing regeneration is very important because it is most likely to form the future main stand. In NFI, this is understood to mean the development stage young growth/thicket, regeneration under shelterwood and selection-type high forest. Reference: Field Survey (MID 261: Entwicklungsstufe, MID 433: Waldbauliche Beurteilung, MID 267: Bestandesstruktur); Forstdienstbefragung (MID 611: Art alle Eingriffe seit Referenzdatum)

Classification of tree collectives into three classes in order to distinguish small collectives (group [500-900 m²] and groves [1000-4900 m²]) from stands in the sense of silvicultural theory (≥5000 m²). Reference: Field Survey (MID 259: Bestandesgrösse)

Mechanical resistence of a stand to abiotic and biotic stresses within the next 10 to 20 years – in three classes. Reference: Field Survey (MID 310: Gesamtstabilität)

Vertical structure (stratification) of a stand, defined on the basis of the degrees of cover of the upper, middle and lower layers. Reference: Field Survey (MID 267: Bestandesstruktur)

Indication as to whether the current main stand (i.e. the trees of the upper layer) originated from natural regeneration (100% natural regeneration), artificial regeneration (<20% natural regeneration) or mixed regeneration (20-99% natural regeneration). Reference: Forest Service Survey (MID 404: Art der Bestandesentstehung)

Type and intensity of direct or indirect human interventions in the forest edge - in eight classes. Reference: Field Survey (MID 44: Waldrandzustand)

Status and type of certification. Reference: Forest Service Survey (MID 319: Art der Zertifizierung)

Status of the forest development plan or a comparable cantonal forest planning document. Reference: Forest Service Survey (MID 803: Stand der Waldentwicklungspläne)

Information on whether the forest road network has been completed or whether an improvment is in progress (construction, project planning) or planned according to the current transportation system plan. Reference: Forest Service Survey (MID 614: Erschliessungsabsichten)

Height of the still standing stem section of broken snags, i.e. of standing dead trees and shrubs ≥12 cm in diameter at breast height (dbh) – in six classes. Reference: Field Survey (MID 829: Schafthöhe gebrochener Probebaum)

Value of the forest edge with respect to its vertical and horizontal structure, without taking the herbaceaous fringe into account - in three classes. Reference: Field Survey (MID 37: Waldrandaufbau, MID 42: Waldrandverlauf, MID 43: Waldranddichte, MID 38: Waldmantelbreite, MID 39: Strauchgürtelbreite)

Value of the forest stand as a habitat – in three classes, derived from the attributes: development stage, crown closure, stand structure, proportion of old timber, degree of damage to the stand, presence of forest or stand edge, occurrence and type of gaps in the stand, degree of cover of the herb layer, degree of cover of berry bushes as well as the occurrence of stumps, lying deadwood, snags and piles of branches. Reference: Field Survey (various attributes)

Formation of the transition from forest to open land - in seven classes. Reference: Field Survey (MID 37: Waldrandaufbau)

Species group (conifers or broadleaves) of stumps ≥7 cm in diameter. Reference: Field Survey (MID 970: Stocktotholz - Baumart)

Stage of wood decomposition of stumps ≥7 cm in diameter – in five classes. Reference: Field Survey (MID 971: Stocktotholz - Festigkeit)

Sample plots with/without stumps and lying deadwood on the interpretation area. «With» applies if there are at least five tree stumps ≥30 cm in diameter and 20 cm in height or a lying tree ≥30 cm in diameter at breast height (dbh) on the interpretation area. Reference: Field Survey (MID 210: Stöcke)

Classification of the open land adjacent to the forest edge - in eleven classes. Reference: Field Survey (MID 46: Waldrandumgebung)

Sorting of roundwood into four diameter classes on the basis of the 2010 and 2021 editions of the Swiss Trading Customs for Raw Timber (HG 2010, Waldwirtschaft Schweiz et al. 2010). Classes 1 and 2, 3 and 4, as well as 5 and 6 of the HG 2010 are each combined into one class.

Techniques used in timber harvesting, i.e. for felling, processing and extracting trees – in twelve classes. If timber has been harvested since the last Inventory, the information is based on the procedures actually used. If, on the other hand, no harvesting has taken place, it is based on the procedures which, according to the district forester's assessment, would have been used in the case of an intervention at the time of the current Inventory. Abbreviations: LO: logging, EX: extraction, PS: pre-skidding, FE: felling, PRO: processing, CH: chopping, AS: assortment, FT: full tree. Reference: Forest Service Survey (MID 352: Art der Holzhauerei, MID: 3001: Rückemittel)

Number of years since the last silvicultural treatment – in classes of ten years. Silvicultural treatments include harvesting and tending interventions, planting and afforestation, as well as sanitary and safety interventions. Reference: Forest Service Survey (MID: 607: Anzahl Jahre seit dem letzten Eingriff)

Number of years since the last silvicultural treatment in classes of five or ten years. Silvicultural treatments include harvesting and tending interventions, planting and afforestation, as well as sanitary and safety interventions. Reference: Forest Service Survey (MID: 607: Anzahl Jahre seit dem letzten Eingriff)

Number of years since the last silvicultural treatment – in classes of 50 years. Silvicultural treatments include harvesting and tending interventions, planting and afforestation, as well as sanitary and safety interventions. Reference: Forest Service Survey (MID: 607: Anzahl Jahre seit dem letzten Eingriff)

Number of years until the next silvicultural treatment according to the forest planning schedule. Silvicultural treatments include harvesting and tending interventions, planting and afforestation, as well as sanitary and safety interventions. Reference: Forest Service Survey (MID 337: Zeitpunkt des nächsten Eingriffs)

Sample plots with/without traces of erosion due to water on at least 100 m² (sum of eroded parts) of the interpretation area (50 × 50 m). Reference: Field Survey (MID 194: Erosion durch Wasser) or – if the forest is inaccessible – aerial photo interpretation

Sample plots with/without extensive traces of forest fire (e.g. burnt ground vegetation, charred parts of tree or soil layers) on the interpretation plot (50 × 50 m). Reference: Field Survey (MID 203: Spuren von Waldbrand)

Sample plots with/without traces of landslides (e.g. a toe or crack, and trees leaning uphill) on at least 100 m² of the interpretation area (50 × 50 m). Reference: Field Survey (MID 193: Rutschung)

Sample plots with/without traces of livestock pasturing in the relevant stand on the interpretation area (50 × 50 m). Traces could be: presence of pasturing livestock, faeces, fresh tracks, resting places, torn hairs and traces of browsing or fraying, and indication of the livestock class in the case of pasturing. Reference: Field Survey (MID 204: Beweidungsart)

Sample plots with/without current traces of rockfall on the interpretation plot (50 × 50 m). Reference: Field Survey (MID 195: Steinschlag)

Sample plots with/without traces of snow movement, i.e. snow creep, snow sliding or avalanches on the interpretation area (50 × 50 m). Reference: Field Survey (MID 202: langsame Schneebewegung und MID 400: Lawinenspuren)

Type of tracks of timber harvesting vehicles such as tractors, forwarders and harvesters on the forest floor – in three classes. For track type 3 (severe disturbance), it can be assumed that the soil fertility is significantly and permanently damaged (Lüscher et al. 2016). Reference: Field Survey (MID 954: Bodenschadentyp LIS)

STRBEFAHR gibt an, mit welchem Lastwagentyp eine Strasse befahren werden kann. Dabei sind Achsenzahl und Gesamtgewicht des LKW für die Klassierung ausschlaggebend. Lastwagenstrassen im Schweizer Wald müssen, um in der Erschliessungserhebung erfasst zu werden, eine Mindestbreite von 2.50 m aufweisen, wobei der Strassenoberbau mindestens für eine Achslast von 10 t ausgelegt sein muss. Im Rahmen der Försterumfrage des LFI4 wurden zusätzliche Informationen erhoben. Dabei steht nicht die lastwagenbefahrbare Strasse nach LFI mit 10 t Achslast und einer Mindestbreite von 2.50 m im Fokus, sondern die für die Holzabfuhr relevante Strasse mit mindestens 3 m Fahrbahnbreite und genügender Tragfähigkeit für Fahrzeuge mit 3 Achsen und einem Gesamtgewicht ab 26 t.

Information about the large- and small-scale infrastructure used for the extraction and transport of timber. Reference: Forest Service survey (MID 326: Erschliessungskonzept)

Estimated age of living trees and shrubs (standing and lying) ≥12 cm in diameter at breast height (dbh) – in classes of 40 years. Reference: Field Survey (MID 826: Baumalter)

Classification of trees and shrubs ≥12 cm in diameter at breast height (dbh) as standing or lying, and as living or dead. Reference: Field Survey (MID 58: Bemerkungen, MID 1018: Baumzustand)

Type of trees and shrubs ≥12 cm in diameter at breast height (dbh). The three most common species or species groups in Switzerland (spruce - Picea spp.; fir - Abies spp.; beech - Fagus sylvatica) are in individual classes, while the remaining species are classified as «other conifers» or «other broadleaves». Reference: Field Survey (MID 50: Baumart)

Type of trees and shrubs ≥12 cm in diameter at breast height (dbh) – in 56 classes. The species (or species groups) not explicitly listed are subsumed in the classes «other conifers», «other broadleaved trees» and «other shrubs». Reference: Field Survey (MID 50: Baumart)

Classification of trees and shrubs ≥12 cm in diameter at breast height (dbh) as living or dead. Reference: Field Survey (MID 58: Bemerkungen, MID 1018: Baumzustand)

Classification of trees and shrubs ≥12 cm in diameter at breast height (dbh) into standing or lying. Reference: Field Survey (MID 58: Bemerkungen, MID 1018: Baumzustand)

Sorting of roundwood into five length classes (4 for conifers, 1 for broadleaves) on the basis of the 2010 and 2021 editions of the Swiss Trading Customs for Raw Timber (HG 2010, Waldwirtschaft Schweiz et al. 2010). Reference: Forest Service Survey (MID 2020: Längensortierung des Nadelrundholzes)

Type of damage to trees and shrubs ≥12 cm in diameter at breast height (dbh) – in thirteen classes. Eleven of these classes focus exclusively on standing living trees and shrubs with dbh ≥12 cm, while one class applies to lying living trees and shrubs with dbh ≥12 cm , and one to dead trees and shrubs with dbh ≥12 cm. Reference: Field Survey (MID 1027: Baumschadenart, MID 1018: Baumzustand)

Sample plots with/without gaps ≥10 × 10 m from crown edge to crown edge and cover with woody plants of maximum 20% that intersect with the interpretation area. Classified into different gap types according to the predominant surface of the largest gap. Reference: Field Survey (MID 221: Lückentyp)

Indication of how the stand was treated during the last intervention. Reference: Forest Service Survey (MID 610: Kalenderjahr alle Eingriffe seit Referenzdatum, MID 611: Art alle Eingriffe seit Referenzdatum)

Indication of how the stand is likely to be treated in the next intervention, taking into account local forest functions and planning. Reference: Forest Service Survey (MID 335: Art des nächsten Eingriffs)

Type of stand establishment, with natural and artificial regeneration distinguished. Reference: Field Survey (MID 275: Verjüngungsart)

Type of shrub forest, i.e. «pure shrub forest» or «shrub forest with trees» according to the interpretation of aerial photos. Reference: Aerial photo interpretation

Sample plots with/without tracks of timber-harvesting vehicles such as tractors, forwarders and harvesters on the forest floor within the 200 m² circle. Reference: Field Survey (MID 544: Fahrzeugspuren)

Sample plots without/with water bodies on the interpretation area (50 × 50 m), classified according to the type of the largest water body. Pond: 1-200 m², small lake: >200 m², creek: channel width <2 m, stream: 2-5 m, river: > 5 m. Reference: Field Survey (MID 401: Gewässer)

Width of the shelterbelt (forest mantle), i.e. the part of the forest edge consisting of single individuals or graded rows of typical edge trees, i.e. trees with crowns that are one-sided and rather long – in four classes. Reference: Field Survey (MID 38: Waldmantelbreite)

Width of the shrub belt, i.e. that part of the forest edge which lies between the forest mantle and the herbaceous fringe and consists of woody plants (in NFI such plants ≤12 cm in diameter at breast height (dbh), excluding dwarf shrubs). Reference: Field Survey (MID 39: Strauchgürtelbreite)

Presence of woodpecker cavities on dead trees and shrubs (standing and lying) ≥12 cm in diameter at breast height (dbh). In NFI5, information on woodpecker breeding cavities can be found via the topic (target variable): «Number of stems (standing-living) with microhabitat». However, this refers to the standing living trees and not, as here, to the standing or lying dead trees. Reference: Field Survey (MID 490: Totholz Spechtloch)

Year in which the forest was (re)afforested during past centuries – in classes of ten years. Reference: Forest Service Survey (MID 332: Jahr der Aufforstung)

Year in which the forest was (re)afforested in the past – in five classes: «before 1851», «1851-1900», «1901-1950», «1951-2006», or «no afforestation/afforestation unknown.». Reference: Forest Service Survey (MID 332: Jahr der Aufforstung)

Year in which the forest was (re)afforested in earlier periods in six classes: before 1851; 1851-1900; 1901-1950; 1951-2000; 2001-2020; oe «no afforestation/afforestation unknown». Reference: Forest Service Survey (MID 332: Jahr der Aufforstung)

Year in which the forest development plan or a comparable cantonal planning document was put into effect – in six classes. Reference: Forest Service Survey (MID 804: Kalenderjahr der Inkraftsetzung des Waldentwicklungsplans WEP)

Sample plots without/with grazing and year when last grazed on by livestock. Reference: Forest Service Survey (MID 341: Jahr der letzten Beweidung)

Division of Switzerland into 14 regions (2 in the Jura, 3 on the Plateau, 3 in the Pre-Alps, 5 in the Alps and 1 in the Southern Alps). The economic regions are a subdivision of the production regions according to economic-geographical criteria.

Demarcation of Switzerland used in NFI for protection forest analyses. The six protection forest regions were derived from the economic regions by combining individual regions according to natural and statistical criteria.

Regional demarcation with the cantons as a unit, with the two half-cantons, Basel-Land and Basel-Stadt, combined into one canton for statistical reasons.

Demarcation of Switzerland into six regions with similar flora and fauna. The six regions correspond to the basic categories in the publication «The Biogeographical Regions of Switzerland», which was published by FOEN in 2022.

Regional demarcation with the forest districts as a unit. This variable is based on a survey of the cantonal forest services in winter 2022/2023.