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number of stems of young forest plants with browsing damage #404
Number of stems of conifers and broadleaves 10 to 129 cm in height on which browsing on the shoot from the previous year was detected. Since a different method was used for assessing browsing traces in NFI2, the browsing intensity was overestimated in comparison with in the inventories from NFI4 on. Thus, only increases in browsing intensity can be clearly determined in comparisons with NFI2. For a reliable estimate, at least 30 individuals per estimated value (table cell) should have been assessed for browsing. Therefore, the corresponding tables with the target variable "Number of trees assessed for browsing (no extrapolation)" should also be consulted.

number of stems of young forest plants assessed for browsing #405
Number of stems of conifers and broadleaves 10 to 129 cm in height for which the condition of the previous year's shoot was assessed with regard to browsing. Since a different method was used for assessing browsing traces in NFI2, the browsing intensity was overestimated in comparison with in the inventories from NFI4 on. Thus, only increases in browsing intensity can be clearly determined in comparisons with NFI2. For a reliable estimate, at least 30 individuals per estimated value (table cell) should have been assessed for browsing. Therefore, the corresponding tables with the target variable "Number of trees assessed for browsing (no extrapolation)" should also be consulted.

protection forest against avalanches (2022) #2645
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

size classe (young forest; 5 classes) #2623
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)

main tree species in young forest (counting) #2625
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)

production region #49
Demarcation of Switzerland into five regions (Jura, Plateau, Pre-Alps, Alps and Southern Alps) with relatively uniform growth and timber production conditions. The production regions were established by the Federal Office of Forestry long before the first National Forest Inventory (NFI1, 1983-1985). With a small exception along Lake Geneva, the boundaries of the production regions still follow the municipal boundaries of the time. Unlike the NFI, the Forestry Statistics of the Federal Statistical Office don't use the production regions as demarcation but rather the forestry zones, whose boundaries are somewhat different.

stockable and accessible forest without shrub forest #1876
Stockable part of the accessible forest without shrub forest, i.e. accessible forest without shrub forest excluding the area of forest roads, recreational facilities, streams, avalanche paths, etc.

1.4-km grid #410
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.

Estimates and standard error of the estimates

The results published in the NFI tables are estimates for variables in the Swiss forest (population parameters) whose true values are not known and must therefore be extrapolated (estimated) from the NFI sample data.

The extrapolations carry uncertainties. However, the accuracy of the extrapolations can be reliably estimated from the NFI sample, which is designed to be a random sample. To this end, all NFI tables include a second figure in addition to the estimate itself, namely the standard error of the estimate.

In most tables the percent standard error is reported (±%), but the absolute standard error (±) is also reported occasionally, especially for estimated percentages. The relationship between absolute and percent standard error is as follows:

percent standard error = absolute standard error / estimate × 100

absolute standard error = percent standard error × estimate / 100

Information on the forest road network is based on a full survey of all forest roads. In this case, there is no need to specify a standard error because there is no uncertainty caused by sampling.

Confidence interval of the estimate

With the estimate and the standard error of the estimate, the limits of the so-called confidence interval of the estimate can be calculated as:

lower limit = estimate – tQ × absolute standard error

upper limit = estimate + tQ × absolute standard error

If the simple standard error is used for the calculation (tQ = 1), then the 68% confidence interval is formed. In this case, the true value of the population parameter has a 68% probability of lying within this confidence interval of the estimate. If the double standard error is used (tQ = 2), then there is a 95% probability that the true value lies within this 95% confidence interval.

Significance of the estimate

The confidence interval can be used to statistically test whether the estimated population parameter is larger or smaller than a specific reference or target value, or whether two estimated population parameters truly differ (in the real population). For practical applications, proceed as follows: if a reference value lies outside the confidence interval, the estimated population value can be interpreted as being significantly different from it; if it lies within the confidence interval, the difference between the estimated population parameter and the reference value can be interpreted as random or not significant. When two population parameters are compared, they can be interpreted as differing significantly if their confidence intervals do not overlap.

Dealing with missing values

When calculating a results table, data are not always available for all combinations of characteristics^* of the classification variables and regional demarcation applied. In most cases, this indicates that the attribute estimated with the respective target variable does not occur or occurs only very rarely. Usually, the value 0 is used (imputed). However, as this value is not based on direct measurements, the associated standard error is represented with a full stop [.]. If the imputed value of 0 is referred to in the calculation, e.g. in the case of percentages or certain change estimates, no value can be entered. In this case, the estimated value and standard error are both represented with a full stop [.].

For example, no Arolla pines have been found and measured in the Swiss Plateau to date (growing stock of Arolla pines by production region). The values can be assumed to be missing because Arolla pine does not occur in the Swiss Plateau and therefore the growing stock there must be 0.

^* e.g. ‘Arolla pine’ characteristic of the classification variable ‘tree species’ and ‘Swiss plateau’ characteristic of the ‘regional demarcation’

Changes

There are two types of changes in the NFI:

The first type involves specific target variables relating to components of change, such as increment, fellings, mortality and losses. These target variables are only available for two consecutive inventory cycles, e.g. NFI3–NFI4. In the evaluation of components of change, the classification variable characteristic of the second inventory cycle is assigned to the first inventory cycle. These evaluations therefore do not take into account potential changes in a classification variable characteristic from the earlier to the later inventory (e.g. from private to public ownership).

With the second type of change, the difference in target variables, such as number of stems, growing stock or forest area, is used to assess the change between two inventory cycles. Target variables are generally used to represent states, such as that in NFI4, but can also indicate the net change between any two inventory cycles, e.g. NFI1–NFI4. In evaluations of change using these target variables, the change in a classification variable characteristic is considered in the analysis. Consequently, one can detect, for example, that the forest area without shrub forest increased between the two inventory cycles. This only has an effect on classification variables whose characteristic (class) can actually change, e.g. the affiliation with a forest area or the tree condition.

NFI4
number of stems of young forest plants with browsing damage divided by number of stems of young forest plants assessed for browsing
protection forest against avalanches (2022) · size classe (young forest; 5 classes) · main tree species in young forest (counting)
regional demarcation: production region
unit: %, cell total
evaluation area: stockable and accessible forest without shrub forest
grid: 1.4-km grid
state 2009/17
		protection forest against avalanches (2022)
		inside		outside		total
size classe (young forest; 5 classes)	main tree species in young forest (counting)	%	±	%	±	%	±
n/a	n/a	0.0	.	0.0	.	0.0	.
	spruce	0.0	.	0.0	.	0.0	.
	fir	0.0	.	0.0	.	0.0	.
	pine	0.0	.	0.0	.	0.0	.
	larch	0.0	.	0.0	.	0.0	.
	Arolla pine	0.0	.	0.0	.	0.0	.
	other conifers	0.0	.	0.0	.	0.0	.
	beech	0.0	.	0.0	.	0.0	.
	maple	0.0	.	0.0	.	0.0	.
	ash	0.0	.	0.0	.	0.0	.
	oak	0.0	.	0.0	.	0.0	.
	sweet chestnut	0.0	.	0.0	.	0.0	.
	other broadleaves	0.0	.	0.0	.	0.0	.
	species not assessed in all inventories	0.0	.	0.0	.	0.0	.
	total	0.0	.	0.0	.	0.0	.
height 10-39 cm	n/a	0.0	.	0.0	.	0.0	.
	spruce	1.4	1.4	2.7	0.7	2.6	0.7
	fir	4.8	4.8	19.7	2.2	19.4	2.2
	pine	0.0	.	3.4	3.0	3.0	2.7
	larch	0.0	.	11.3	3.2	10.2	3.0
	Arolla pine	0.0	.	0.0	.	0.0	.
	other conifers	0.0	.	0.0	.	0.0	.
	beech	3.1	2.1	3.0	0.5	3.0	0.4
	maple	33.5	7.1	16.9	1.9	17.0	1.8
	ash	27.1	6.5	12.5	1.1	12.8	1.1
	oak	0.0	.	31.7	9.0	31.7	9.0
	sweet chestnut	0.0	.	23.1	4.8	23.1	4.8
	other broadleaves	40.4	8.7	25.1	1.8	25.9	1.7
	species not assessed in all inventories	0.0	.	0.0	.	0.0	.
	total	19.8	3.3	12.1	0.8	12.2	0.8
height 40-129 cm	n/a	0.0	.	0.0	.	0.0	.
	spruce	1.1	0.8	2.2	0.5	2.1	0.5
	fir	0.0	.	25.2	4.0	24.6	3.9
	pine	0.0	.	4.2	2.9	4.1	2.9
	larch	0.0	.	8.5	2.9	6.7	2.2
	Arolla pine	0.0	.	0.0	.	0.0	.
	other conifers	0.0	.	0.0	.	0.0	.
	beech	8.0	5.0	4.5	0.6	4.6	0.6
	maple	54.0	10.9	30.9	2.5	31.4	2.4
	ash	48.9	14.4	24.7	2.0	25.2	2.0
	oak	0.0	.	27.7	5.8	27.7	5.8
	sweet chestnut	0.0	.	25.3	10.5	25.3	10.5
	other broadleaves	45.3	10.8	27.7	2.1	28.7	2.1
	species not assessed in all inventories	0.0	.	0.0	.	0.0	.
	total	17.9	3.9	14.9	0.8	15.0	0.8
DBH 0-3.9 cm	n/a	0.0	.	0.0	.	0.0	.
	spruce	0.0	.	0.0	.	0.0	.
	fir	0.0	.	0.0	.	0.0	.
	pine	0.0	.	0.0	.	0.0	.
	larch	0.0	.	0.0	.	0.0	.
	Arolla pine	0.0	.	0.0	.	0.0	.
	other conifers	0.0	.	0.0	.	0.0	.
	beech	0.0	.	0.0	.	0.0	.
	maple	0.0	.	0.0	.	0.0	.
	ash	0.0	.	0.0	.	0.0	.
	oak	0.0	.	0.0	.	0.0	.
	sweet chestnut	0.0	.	0.0	.	0.0	.
	other broadleaves	0.0	.	0.0	.	0.0	.
	species not assessed in all inventories	0.0	.	0.0	.	0.0	.
	total	0.0	.	0.0	.	0.0	.
DBH 4-7.9 cm	n/a	0.0	.	0.0	.	0.0	.
	spruce	0.0	.	0.0	.	0.0	.
	fir	0.0	.	0.0	.	0.0	.
	pine	0.0	.	0.0	.	0.0	.
	larch	0.0	.	0.0	.	0.0	.
	Arolla pine	0.0	.	0.0	.	0.0	.
	other conifers	0.0	.	0.0	.	0.0	.
	beech	0.0	.	0.0	.	0.0	.
	maple	0.0	.	0.0	.	0.0	.
	ash	0.0	.	0.0	.	0.0	.
	oak	0.0	.	0.0	.	0.0	.
	sweet chestnut	0.0	.	0.0	.	0.0	.
	other broadleaves	0.0	.	0.0	.	0.0	.
	species not assessed in all inventories	0.0	.	0.0	.	0.0	.
	total	0.0	.	0.0	.	0.0	.
DBH 8-11.9 cm	n/a	0.0	.	0.0	.	0.0	.
	spruce	0.0	.	0.0	.	0.0	.
	fir	0.0	.	0.0	.	0.0	.
	pine	0.0	.	0.0	.	0.0	.
	larch	0.0	.	0.0	.	0.0	.
	Arolla pine	0.0	.	0.0	.	0.0	.
	other conifers	0.0	.	0.0	.	0.0	.
	beech	0.0	.	0.0	.	0.0	.
	maple	0.0	.	0.0	.	0.0	.
	ash	0.0	.	0.0	.	0.0	.
	oak	0.0	.	0.0	.	0.0	.
	sweet chestnut	0.0	.	0.0	.	0.0	.
	other broadleaves	0.0	.	0.0	.	0.0	.
	species not assessed in all inventories	0.0	.	0.0	.	0.0	.
	total	0.0	.	0.0	.	0.0	.
total	n/a	0.0	.	0.0	.	0.0	.
	spruce	1.3	0.9	2.5	0.5	2.4	0.5
	fir	3.8	3.8	20.7	2.1	20.4	2.0
	pine	0.0	.	3.8	1.9	3.5	1.8
	larch	0.0	.	10.1	2.3	8.6	2.1
	Arolla pine	0.0	.	0.0	.	0.0	.
	other conifers	0.0	.	0.0	.	0.0	.
	beech	5.3	2.8	3.4	0.4	3.5	0.4
	maple	38.0	6.4	18.7	1.7	18.9	1.7
	ash	29.7	6.8	14.0	1.1	14.4	1.1
	oak	0.0	.	31.6	8.7	31.6	8.7
	sweet chestnut	0.0	.	23.4	4.5	23.4	4.5
	other broadleaves	41.8	7.7	25.9	1.5	26.7	1.5
	species not assessed in all inventories	0.0	.	0.0	.	0.0	.
	total	19.2	2.9	12.6	0.7	12.8	0.7

Table citation

Abegg, M.; Ahles, P.; Allgaier Leuch, B.; Cioldi, F.; Didion, M.; Düggelin, C.; Fischer, C.; Herold, A.; Meile, R.; Rohner, B.; Rösler, E.; Speich, S.; Temperli, C.; Traub, B.,
2023: Swiss national forest inventory - Result table No. 1260850. Birmensdorf, Swiss Federal Research Institute WSL

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