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NFI4
forest area
ownership · harvest of timber
unit of reference: economic region
unit: 1000 ha
unit of evaluation: accessible forest without shrub forest NFI3/NFI4
grid: 1.4 x 1.4 km grid
state2009/17
		ownership
		public		private		total
economic region	harvest of timber	1000 ha	± %	1000 ha	± %	1000 ha	± %
Western Jura	in-house harvesting	15.3	11	11.6	13	26.9	8
	harvest by contractor	74.7	4	25.0	8	99.7	3
	felling by contractor	0.0	.	0.2	100	0.2	100
	processing by contractor	0.2	100	0.0	.	0.2	100
	felling and processing by contractor	0.6	58	0.0	.	0.6	58
	skidding by contractor	20.5	9	2.0	32	22.5	9
	sale of standing timber by contractor	0.2	100	0.2	100	0.4	71
	total	111.5	2	39.0	6	150.5	1
Eastern Jura	in-house harvesting	17.0	9	3.1	25	20.1	8
	harvest by contractor	15.2	10	5.9	17	21.1	8
	felling by contractor	0.0	.	0.2	100	0.2	100
	processing by contractor	1.1	45	0.2	100	1.3	41
	felling and processing by contractor	0.8	50	0.0	.	0.8	50
	skidding by contractor	2.9	27	0.0	.	2.9	27
	sale of standing timber by contractor	0.3	100	0.0	.	0.3	100
	total	37.2	4	9.4	13	46.6	2
Western Plateau	in-house harvesting	12.1	12	3.8	22	15.9	10
	harvest by contractor	16.6	9	11.0	12	27.5	6
	felling by contractor	0.0	.	0.0	.	0.0	.
	processing by contractor	0.0	.	0.0	.	0.0	.
	felling and processing by contractor	0.4	71	0.0	.	0.4	71
	skidding by contractor	4.2	21	0.6	58	4.8	20
	sale of standing timber by contractor	0.2	100	0.2	100	0.4	71
	total	33.4	5	15.6	10	49.1	2
Central Plateau	in-house harvesting	7.0	16	14.4	10	21.5	8
	harvest by contractor	23.4	7	17.1	9	40.5	5
	felling by contractor	0.0	.	0.2	100	0.2	100
	processing by contractor	2.1	30	0.0	.	2.1	30
	felling and processing by contractor	0.8	50	0.0	.	0.8	50
	skidding by contractor	3.5	23	0.4	71	3.9	22
	sale of standing timber by contractor	0.2	100	0.0	.	0.2	100
	total	37.0	5	32.1	6	69.1	1
Eastern Plateau	in-house harvesting	30.5	7	17.3	10	47.9	5
	harvest by contractor	24.1	8	24.6	8	48.8	5
	felling by contractor	0.2	100	0.4	71	0.6	58
	processing by contractor	3.8	22	0.2	100	4.0	22
	felling and processing by contractor	2.7	26	0.0	.	2.7	26
	skidding by contractor	2.5	28	1.1	41	3.6	23
	sale of standing timber by contractor	0.0	.	0.0	.	0.0	.
	total	63.9	4	43.7	5	107.6	1
Western Pre-Alps	in-house harvesting	7.9	15	3.8	24	11.7	12
	harvest by contractor	7.8	15	11.8	12	19.6	8
	felling by contractor	0.0	.	0.0	.	0.0	.
	processing by contractor	0.0	.	0.0	.	0.0	.
	felling and processing by contractor	0.3	100	0.0	.	0.3	100
	skidding by contractor	6.2	17	3.2	25	9.4	14
	sale of standing timber by contractor	0.0	.	2.3	29	2.3	29
	total	22.1	7	21.2	8	43.3	3
Central Pre-Alps	in-house harvesting	22.6	8	23.2	8	45.7	5
	harvest by contractor	13.4	11	27.1	8	40.5	6
	felling by contractor	0.0	.	0.0	.	0.0	.
	processing by contractor	0.0	.	0.0	.	0.0	.
	felling and processing by contractor	0.0	.	0.0	.	0.0	.
	skidding by contractor	8.6	15	3.9	22	12.5	12
	sale of standing timber by contractor	0.0	.	0.7	58	0.7	58
	total	44.5	5	54.9	4	99.4	2
Eastern Pre-Alps	in-house harvesting	13.6	11	12.0	12	25.6	8
	harvest by contractor	14.0	11	16.1	10	30.1	7
	felling by contractor	0.0	.	0.2	100	0.2	100
	processing by contractor	0.0	.	0.0	.	0.0	.
	felling and processing by contractor	0.4	71	0.0	.	0.4	71
	skidding by contractor	8.1	15	2.8	26	10.9	13
	sale of standing timber by contractor	2.9	26	2.2	28	5.1	19
	total	39.0	5	33.4	6	72.3	2
Northwestern Alps	in-house harvesting	4.4	21	5.1	20	9.5	14
	harvest by contractor	12.9	11	29.9	7	42.8	5
	felling by contractor	0.0	.	0.0	.	0.0	.
	processing by contractor	0.0	.	0.0	.	0.0	.
	felling and processing by contractor	0.0	.	0.2	100	0.2	100
	skidding by contractor	5.1	19	0.4	71	5.5	19
	sale of standing timber by contractor	0.6	58	0.2	100	0.8	50
	total	23.1	8	35.8	6	58.9	3
Central Alps	in-house harvesting	6.8	15	1.9	31	8.8	13
	harvest by contractor	2.5	27	4.8	19	7.4	14
	felling by contractor	0.0	.	0.0	.	0.0	.
	processing by contractor	0.0	.	0.0	.	0.0	.
	felling and processing by contractor	0.0	.	0.0	.	0.0	.
	skidding by contractor	7.8	14	0.4	71	8.2	14
	sale of standing timber by contractor	1.0	44	0.0	.	1.0	44
	total	18.2	7	7.2	14	25.4	4
Northeastern Alps	in-house harvesting	7.5	15	1.7	33	9.1	13
	harvest by contractor	11.0	12	4.2	20	15.2	9
	felling by contractor	0.0	.	0.0	.	0.0	.
	processing by contractor	0.2	100	0.0	.	0.2	100
	felling and processing by contractor	0.0	.	0.0	.	0.0	.
	skidding by contractor	4.7	19	0.4	71	5.1	19
	sale of standing timber by contractor	0.2	100	0.0	.	0.2	100
	total	23.6	6	6.2	16	29.8	5
Southwestern Alps	in-house harvesting	22.3	9	6.7	17	29.0	7
	harvest by contractor	6.2	17	9.7	14	16.0	10
	felling by contractor	0.0	.	0.0	.	0.0	.
	processing by contractor	0.2	100	0.0	.	0.2	100
	felling and processing by contractor	0.0	.	0.0	.	0.0	.
	skidding by contractor	58.5	4	9.8	14	68.3	4
	sale of standing timber by contractor	0.4	71	0.0	.	0.4	71
	total	87.6	3	26.3	8	113.8	2
Southeastern Alps	in-house harvesting	46.3	6	2.9	26	49.2	5
	harvest by contractor	49.1	5	16.1	11	65.1	4
	felling by contractor	0.2	100	0.0	.	0.2	100
	processing by contractor	2.2	30	0.0	.	2.2	30
	felling and processing by contractor	0.2	100	0.0	.	0.2	100
	skidding by contractor	21.2	9	1.7	35	22.9	9
	sale of standing timber by contractor	2.2	30	0.8	50	3.0	26
	total	121.4	2	21.4	9	142.8	2
Southern Alps	in-house harvesting	9.7	14	10.4	13	20.1	9
	harvest by contractor	104.7	3	22.3	9	127.0	2
	felling by contractor	0.0	.	0.0	.	0.0	.
	processing by contractor	0.0	.	0.0	.	0.0	.
	felling and processing by contractor	0.0	.	0.0	.	0.0	.
	skidding by contractor	1.5	35	0.0	.	1.5	35
	sale of standing timber by contractor	1.3	38	0.0	.	1.3	38
	total	117.2	3	32.7	7	150.0	2
Switzerland	in-house harvesting	222.9	3	118.0	4	340.9	2
	harvest by contractor	375.6	2	225.7	3	601.3	1
	felling by contractor	0.4	71	1.2	41	1.6	35
	processing by contractor	9.8	14	0.4	71	10.1	14
	felling and processing by contractor	6.2	18	0.2	100	6.4	17
	skidding by contractor	155.4	3	26.6	8	182.1	3
	sale of standing timber by contractor	9.5	15	6.7	17	16.1	11
	total	779.7	1	378.8	2	1158.5	1

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.

Table citation

Abegg, M.; Brändli, U.-B.; Cioldi, F.; Fischer, C.; Herold, A.; Meile, R.; Rösler, E.; Speich, S.; Traub, B., 2020: Swiss national forest inventory - Result table No. 797447. Birmensdorf, Swiss Federal Research Institute WSL
https://doi.org/10.21258/1758590

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Selection from the list of topics

Estimates and standard error of the estimates

Confidence interval of the estimate

Significance of the estimate

Dealing with missing values

Changes

Table citation