Brändli, U. B. (1993). The national forest inventory .. a window on the Swiss forest. Verified knowledge thanks to systematic observation. Birmensdorf: Federal Institute of Forest, Snow and Landscape Research.

This pamphlet was published for the exhibition The National Forest Inventory ... a Window on the Swiss Forest

Editor:

Prof. Rodolphe Schlaepfer, Oirector, WSL Text by:

Urs-Beat Brandli Layout:

Ruth Walder, Oas Grafik Werk, Zurich Reproduction:

Jacqueline Gilgien English translation:

Margaret Joyce Sieber Photos:

Bildagentur Baumann, Federal Ottice of Topography, Photographic Sevlce WSL, Urs-Beat Brandli, Paul Rienth, Urs Waldvogel, Andreas Zingg

Reference:

Brandli, U.-B.,1993: The National Forest Inventory ... a Window on the Swiss Forest. Verified Knowledge thanks to Systematic Observation. Birmensdorf, Federal Institute of Forest, Snow and Landscape Research. 16 pp.

Available In German, French, Italian and English from:

WSL Library

The

National Forest Inventory ...

... a Window

on the Swiss Forest

Verified Knowledge thanks to Systematic Observation

Urs-Beat Brandli

Federal Institute of

Forest, Snow and Landscape Research (WSL) CH-8903 Birmensdorf

1993

Why a National Forest Inventory?

Forest covers 29% of Switzerland and provides wood, protection and recreation.

Politicians, ecologists and foresters need reliable information on its extent, condi- tion and development. The National Forest Inventory (NF/) provides such informa- tion, the empbasis being on changes in the forest. Together with other inventories, the NF/ forms part of a national forest information system.

Information has been gathered over decades, even centuries, but without the necessary uni·

formity and completeness, particularly as regards the state of the forest. The surveys made for silvicultural planning were often non- uniform and not comparable for the whole country. Little was known about privately owned forest or abandoned forest in the moun- tains.

On 12 August 1981 the Federal Government therefore decided to institute the National Forest Inventory (NFI), ideally with surveys every 10 years. The first ran from 1983-85, the second started in 1993.

The NFI provides reliable data for Switzer- land as a whole, the larger cantons, and the main geographic regions, the data being stored in a database at the WSL and available to users any time. The major results of the first NFI were published in 1988.

The first survey was oriented toward timber production. The second will also provide data on other forest functions, which will be investi- gated in more detail in the third.

Land Use in Switzerland

■ forest

D

D

D unproductive areas (lakes, cliffs etc.)

Percentage Forest in the Main Regions

■ Jura

D Mittelland

□ Pre-Alps

□ Alps

■ Southern Alps (Ticino)

Forest Monitoring in Switzerland The NFI is a main pillar of the forest survey programme being conducted by the Federal Institute of Forest, Snow and Landscape Re- search (WSL) in association with the Federal Office of Environment, Forests and Landscapes/

Federal Forest Directorate (F+D).

The programme has 4 long-term projects:

• the NFI, which provides a general picture of the Swiss forests, information on its func- tions and long-term changes;

An Instrument for Forest and Environmental Policy

• the Forest Damage Inventory, which reports annually on crown thinning as a measure of vitality;

• the Long-Term Monitoring project, studying the state of health, stresses and develop- ment of various forest ecosystems;

• the Phytosanitary Service, which, on the basis of monthly questionnaires to District Officers, records acute damage by insects and fungi.

forest policy

environmental policy ~teering measures Laws

interests

...-i---~

systematic monitoring

Information forestry

forest users pollution sources Information

ecosystem forest

various influences pollution

The forest ecosystem is exposed to many kinds of exploitation by man, and also to pollu- tion stress. The large game population hinders natural regeneration.

Sustained yield and the preservation of natu- ral habitats require objective information.

Systematic monitoring forms a basis for politi- cal decisions, public relations and further research.

3

The Legal Basis

The first NFI survey was approved by a special decree of the Federal Council in 1981.

The new Forest Bill, in force since 1 Jan. 1993 embrances the forest in all its functions. This bill is the legal basis for further NFI surveys.

Art. 33 stipulates systematic monitoring: "The Federal Government is responsible for periodic surveys of the site conditions, the functions and the state of the forest..."

Personnel and Costs of the NFI

The NFI comprises 10-17 permanent staff, with 8-15 two-man teams for the field surveys, all forest engineers, chief foresters or forest wardens.The field teams attend an introductory course and refresher courses.

The first NFI survey consumed 100 man- years for collecting and checking the data alone. The total cost for surveying each sample area was SFr. 550. The overall cost of the project from the first survey in 1983 to the publication of the results in 1988 was some 10 mio. SFr.

8.1 mio. SFr. have been granted for the second survey, 1993-1995. In view of inflation this is much less than the amount allotted for the ·first survey. In the second survey more data will be gathered from air-photos and only half of the plots will be surveyed in the field.

Applications

To date, the NFI service has completed well over a hundred major commissions, e.g.:

• detailed study of potential timber utilization in the various cantons (BUWAL);

• assessment of the protective capacits of mountain forests (EISLF Davos);

• distribution and frequency of particular tree species (Forest Protection, WSL);

• structure and distribution of coppice forest and selection-type high forest (FITZ);

• potential use of large harvesting machines (forest enterprises);

• basic information for planning and public relations ( cantonal Forest Offices);

• frequency of old stands and deadwood (Nature Protection);

• data for international projects and statistics (ECE/FAO)

How the NFI Data Are Collected

There are about 500 mio. trees in Switzerland - far too many to be individually observed. Sufficient information can be obtained from sample plots. For the first survey a 1 x 1 km grid was laid over the whole of Switzerland, the some 12 000 sample plots being located at its intersection points. Each of the plots represents a square kilometre of forest. With this system the standing reserve can be estimated to within 2% accuracy.

Forest or non-forest? This question is settled by specialists with the help of air-photos.

Except for shrub stands and inaccessible areas, each forest plot is assessed in the field. The field crews inspect 13 trees per plot on average and record the stand and site condi- tions.

Questionnaires to local forest officers and ordnance survey maps provide information on ownership, harvest, roads and paths.

The data from the first NFI survey were recorded in the field on preprinted forms.

Those for the second survey will be registered in handheld computers and checked on the spot for completeness. To ensure a high degree of data quality, 8% of the sample plots will be checked by independent field crews.

NFI Definition of Forest

Whether an area counts as forest or not depends on its width and the top height of the vegetation; also, to qualify as forest, the crown cover must be at least 20%.

Analytical Plotter for Air-Photo Interpretation Many data are more easily obtained from air- photos than through fieldwork. Therefore the 2nd NF/ survey will collect more data from air- photos over a 500 m grid, and only half of the sample plots from the first survey will be checked in the field. Air-photos and special sta- tistical methods provide the same degree of precision as the first survey.

- - - width - - - , 50 m 40 m 30 m 25 m O m 0%-.---+-+--+--+--+--+---, 20% -r---+=t---t---t--t--t---j 40% -l---+-+--+----+--1---i 60% -1---+t-+--+--+-~-+---+---i 80% +--+t-+--+--+--+-tt---+---i 100% .,____._I--'---'--'--'---'----+---'

no

non-forest

5

Information from air-photos

Here a sample plot near Moutier: the 50 x 50 m grid delimits the stand in question. Starting from the reference points (circled) the field crew locates the plot centre using a measuring tape, telescopic staff compass and handheld computer.

By kind permission of the Federal Offite of Topography given on 14. 9. 93.

Field work

A metal tube buried in the soil marks the plot centre. In the first survey some 130000 trees were measured and marked so that they could easily be found in subsequent inventories.

Circular sample plots and sample trees Within the smaller circle covering 200 m², all trees with a diameter of 12 cm or more at breast height (1.3 m, abbr. DBH) are assessed;

within the larger circle of 500 m² all those with a DBH of 36 cm or more.

On flat ground the radii are r, = 7.98 m

r2 = 12.62 m

What does the NFI monitor?

At first the NF/ was strongly oriented to questions concerning wood production.

The second survey will, for the first time, register changes in the structure and state of the forest, and also more information on its ability to provide recreational areas for Man and near-to-nature habitats for the flora and fauna. It is foreseen that the third survey will also assess its capacity for protection.

The NFI database contains information on 450 parameters registered in the first survey (1983-85):

• area of forest and forest ownership;

• standing volume: assortments and quality;

• site conditions: altitude, inclination, aspect, site quality, soil;

• structure: species, forest type, stand age;

• natural regeneration and game damage;

• condition: priorities for tending, stability, damage;

• opening up;

• harvesting: potential exploitation, accessibi- lity, harvesting techniques.

The second survey (1993-95) will provide important landwide data on changes in the forest, especially as regards standing volume:

• volume increment;

• timber harvests;

• trees which have died since the last survey. It will also register data on new topics:

• recreational functions: infrastructure, resul- ting damage;

• forest as a near-to-nature habitat: special sites, brushwood layer, micro-biotopes, forest margins, etc.

The long-term aim of the NFI is to furnish detailed knowledge on the functions of the forest and its ability to fulfil them. An important aim of the third survey will be to assess its protective capacity.

7

Results from the first NFI survey

The following excerpts from the results of the first NF/ survey (1988) provide a brief overview of the structure and condition of Swiss forests.

The results of each survey are estimates. Their precision depends on the number of plots in- spected. The NFI furnishes reliable data for the Jura, the Mittelland, the Pre-Alps, the Alps and

Forested Area

Unit of estimation: total forest area

Jura Forested area in 1000 ha 195,0

% distribution 16,4

% forest in the total area 39,7

m² forest per capita 2100

According to the NFI 29% of Switzerland or 37% of the stockable area actually bear forest - a total of some 12 000 km², mostly on land poorly suited to agriculture, two thirds in the alpine regions.

Ownership

Unit of estimation: total forest area

Ownership Jura

%

Citizens corporations 31

Political communes 34

Public corporations 1

Canton 9

Confederation 0

Total of publicly owned forest 75

Privately owned 23

Corperations 2

Total of privately owned forest 25

Total forest in% 100

Total forest In 1000 ha 195,0

their southern slopes (Ticino), with an estima- tion error for standing reserve, stem counts and forest area of only ±1 %, for Ticino ±2%.

Mittelland Pre-Alps Alps Ticino Switzerland

228,2 217.0 381,6 164.5 1186,3

19,2 18.3 32,3 13,9 100,0

24,2 32,8 22.7 46.4 28,7

600 2600 6300 6200 1900

The mean area of forest per capita is similar to that in neighbouring countries. In the densely populated Mittelland it is 600 m² per capita - about as big as two tennis courts.

Mittelland Pre-Alps Alps Ticlno Switzerland

% % % % %

25 13 39 66 34

19 10 26 8 21

5 20 10 2 8

7 6 2 1 5

1 1 1 1 1

57 50 78 78 69

40 43 17 21 28

3 7 5 1 3

43 50 22 22 31

100 100 100 100 100

228,2 217,0 381,6 164,5 1186,3

Standing Volume

Standing Volume per ha. forest area

D

Standing volume:

D

• over 500 m1/ha

The Swiss forests contain some 365 mio. m³ wood; the privately owned forests in the Mittel- land have the largest standing volume, with

Percentage Conifers and Broadleaves

some 444 m1/ha. The standing volume of 333 m1 per ha. gives Switzerland one of the largest timber reserves within Europe.

Unit of estimation: accessible forests excluding brushwood

Switzerland

Ticino Alps Pre-Alps Mittelland Jura

•• ••

0% 50%

In Swiss forests, conifers are dominant. The mainly coniferous mountain forests (Alps, Pre- Alps) have a near-to-nature species composi- tion. Left to nature, the Mittelland would bear

■

■

□

□

only broadleaves, but because of man's inter- vention, spruce dominates on 39% of the area;

10% of the Mittelland forest comprises pure

spruce stands. 9

Forest Type and Stage of Development Unit of estimation: total forest area

Forest type Jura

%

Uniform high forest 67

them: young growth/thicket 6

pole wood 11

young timber 18

medium timber 21

old timber 11

Nau-uniform high forest 9

Selection-type high forest 7

Coppice with standards 6

Coppice forest 1

Divers 0

Loosened stand 6

Unstocked forest areas 4

Inaccessible forest D

Brushwood D

% total forest 100

Total forest per 1 ODO ha 195,0

Over the centuries, different types of exploita- lion have led to different types of forest. The most frequent (19%) is the "medium timber

Uniform High Forest

In contrast to tropical rain forest, ours tends to form uniform, single-storeyed stands. Even in the managed forests of today uniform forest with various stages of development dominates.

Mlttelland Pre-Alps Alps Ticino Switzerland

% % % % %

82 63 47 32 58

9 5 6 4 6

13 7 8 11 10

15 15 9 5 12

31 24 14 7 19

14 12 10 5 11

5 11 10 8 9

2 11 13 6 8

5 1 2 11 4

1 0 1 11 2

1 0 1 1 1

D 5 9 8 6

4 6 5 3 4

D 2 4 6 3

D 1 8 14 5

100 100 100 100 100

228,2 217,0 381,6 164,5 1186,3

stand" - uniform high forest with trees of 40-50 cm diameter at DBH (1.3 m).

Selection-type High Forest

Selection-type high forests, a mixture of trees of all ages, may sometimes occur naturally but can usually only be established through human intervention. Selection forest management aims at sustaining protection forests. "Non-

Loosened Stand

Large loosened stands result from earlier intensive pasturage in mountain forests. Forest grazing is allowed only in exceptional cases.

The NF/ found that 12% of the forest is still used for grazing. On steep slopes with inade- quate regeneration, grazing can endanger the protective function of the forest. NF/ results show that this is true for 1/7 of pastured forest.

Coppice Forest with Standards The present coppices with standards are remnants of traditional usage near settlements.

Certain levels were periodically clear-cut for fuelwood, as in coppice forest. The large- crowned dominant trees were left to grow and later felled for timber.

Brushwood

Centuries of alpine exploitation have driven the conifers far back. Alpine alders are of little interest to farmers or cattle. This fact has favoured the development of brushwood. Alpine alder and prostrate pine not only provide no protection against avalanches but may even promote them.

Coppice Forest

Earlier coppice forests served for the produc- tion of fuelwood and stakes. They were clear- cut every 10-30 years and the stumps then produced new suckers. Patches of low forest with poor quality wood are still common in Ticino.

11

Species Composition (stem count)

Unit of estimation: accessible forest, trees with a DBH of 12 cm or more, excluding brushwood

Species Jura Mittelland Pre-Alps Alps Ticino Switzerland

% % % % % %

Spruce 23 35 50 52 19 39

Silver fir 19 14 19 5 2 12

Pine 3 3 1 9 1 4

Larch 0 1 0 10 9 4

Cembran pine 1 0 3 0 1

other conifers 0 1 0 0 0 0

Total conifers 45 54 70 79 31 60

Beech 34 24 17 9 19 19

Maple 5 4 4 3 1 4

Ash 4 6 4 1 3 4

Oak 4 5 1 1 4 3

Chestnut 0 0 21 2

other breadleaves 8 7 4 7 21 8

Total breadleaves 55 46 30 21 69 40

Total in% 100 100 100 100 100 100

Total per 1000 trees 91269 103350 107765 148858 55914 507157

Spruces constitute about 40% of all trees with forest, producing its typical appearance. Exotic a DBH above 12 cm. Together with silver fir species are rare. NFI results record that 99.6%

and beech they comprise 70% of the Swiss of the trees are indigenous.

Species Composition (Standing Volume)

Unit of estimation: accesible forest, trees with a DBH of 12 cm or more, excluding brushwood

Species Jura Mittelland Pre-Alps Alps Ticino Switzerland

% % % % % %

Spruce 31 43 58 63 35 49

Silver fir 22 15 22 6 6 15

Pine 4 5 1 5 2 4

Larch 0 1 0 13 15 5

Cembran pine 0 2 0 1

other conifers 0 1 0 0 0 0

Total conifers 57 65 81 89 58 74

Beech 30 20 13 7 13 16

Ash 4 2 2 1 0 2

Esche 3 5 2 1 2 2

Oak 3 5 1 0 3 2

Chestnut 0 14 1

other breadleaves 3 3 2 10 3

Total breadleaves 43 35 19 11 42 26

Total in% 100 100 100 100 100 100

Total per 1000 m³ 63 574 92785 88139 97 481 23148 365128

Stand Age (Forested Area)

Unit of estimation: acessible forest, excluding brushwood

Stand age Jura

%

uneven-aged 20

up to 40 years 13

41-80 years 20

81-120 years 30

121-160 years 13

over 160 years 4

Total in% 100

Total in 1000 ha 186,4

The high timber reserve arises from the past treatment of the forest: for centuries our forests were ruthlessly exploited. With the first Forest Bill, a hundred years ago, measures for re-establishment began. Alpine meadows were afforested and coppices with standards were changed into high forests. Until recently, the major goal in many places was to increase the standing volume, while regeneration was neglected. Today, the results are reflected in a high proportion of timber-rich stands 80-120 years old and a lack of young forests.

Last Exploitation or Tending (Forested Area)

Mittelland Pre-Alps Alps Ticino Switzerland

% % % % %

12 25 36 31 25

22 12 11 31 16

26 19 10 16 18

33 28 14 8 23

6 11 15 8 11

1 5 14 6 7

100 100 100 100 100

218,7 197,5 313,9 127,4 1043,9

To maintain a sufficient sustained yield, for- estry in Switzerland must aim at establishing a balanced age distribution. It would be wrong to say that the Swiss forests are over-aged, for hardly any tree reaches its natural life-span of several hundred years; in economic terms, however, there is a trend towards over-aging.

Unit of estimation: acessible forest, excluding brushwood

Last intervention before: Jura

%

1-1 o years 66

11-20 years 19

21-30 years 6

31-50 years 3

over 50 years 6

Total in% 100

Total in 1000 ha 194,0

In many places, the lasting unfavourable situa- tion resulted in decreased tending. In the past 20 years nearly a third of the Swiss forest has

Mittelland Pre-Alps Alps Ticmo Switzerland

% % % % %

79 60 36 16 52

14 19 18 12 17

3 7 12 12 8

1 6 13 27 9

3 8 21 34 14

100 100 100 100 100

227,0 211,4 333,7 131,4 1097,5

not been exploited at all. The timber reserve continues to climb.

13

Distance to nearest forest road (Forested Area) Unit of estimation: accessible forest excluding brushwood

Hauling distance Jura

¾

up to 50 m 36

51-100 m 16

101-200 m 17

201-500 m 20

501-1000 m 9

over 1000 m 2

Total in% 100

Total m 1 ODO ha 194,0

Proper exploitation and tending require an appropriate network of forest roads. The Forest Directorate finds that accessibility to the for- ests in the Alps, where they exercise important protective functions, is inadequate. According to the NFI some 7% of the mountain forests are

Common Types of Damage (Stem Count)

Mittelland Pre-Alps Alps T1cino Switzerland

% % ¾

. , , .

45 14 13 9 23

18 10 7 6 11

17 16 11 9 14

15 28 22 18 21

4 19 21 20 15

1 13 26 38 16

100 100 100 100 100

227,0 211,4 333,7 131,4 1097,5

in a critical, unstable state; silvicultural oper- ations are urgently needed for 30 000 ha of such stands. On the other hand, the noise and disturbance involved in the construction and use of new forest road would disrupt the hith- erto undisturbed habitats of the alpine fauna.

Unit of estimation: accessible forest, trees with a DBH of 12 cm or more, excluding brushwood.

Jura Total no-of trees in 1 OOOs 91269

Damage due to: %

Harvesting 9

Wind, snow, frost, sun 4

Rockfall 3

Fire 0

The NFI records all types of damage and dis- ease recognisable with the naked eye, but not those whose cause is not obvious. Over a quarter of the trees show such classic injuries.

In the Mittelland and the Jura one tree in ten has been damaged through harvesting; in the Alps most damage is due to rockfalls, wind and avalanches and much more perilous.

Mittelland Pre-Alps Alps Ticino Swllzerland 103 350 107 765 148 858 55914 507157

% % % % %

9 8 4 6 7

5 7 6 2 6

0 4 6 15 4

0 0 0 3 0

Harvesting damage Storm damage

Degree of Damage to Stands (Forested Area)

Unit of estimation: accessible forest, excluding brushwood

The NFI weights all types of damage of known cause in terms of type, extent and position in the tree according their influence on tree vitali- ty. Stands with small bark injuries on the stem are classed as slightly damaged; those with damage at the stem base or broken tips at the very top as moderately damaged; and those with large bark wounds, massive injury to the crown or numerous moderate injuries as severely to very severely damaged.

D

D

■ moderate damage

■ severe - very severe damage

NFI observations on classic damage: in the Mittelland only 1 % of the forest is severely or very severely damaged, but in the Alps 7%.

Altogether, 50 000 ha of forest - an area as large as that of the canton of Obwalden - are severely or very severely damaged.

15

Information for You Too?

The NF! database is open to all those with individual questions or problems. The WSL in Birmensdorf offers consultancy and statistical evaluation services.

A summary of the results of the first NFI sur- vey was published as a WSL Report in 1988 in German and French. It covers the main needs for information and gives a picture of possibili- ties for evaluation. So far the data and results of the first NFI survey have most often been applied in public relations work, staff training, and the fields of ecology, nature conservation, forest sciences, administration, politics and forest and timber economy.

For special cases the NFI Report often has too few details, but all the data are stored in the database and can be retrieved for individual evaluations. To date the Section NFI has ful- filled numerous commissions, large and small.

The "Data Catalogue", a detailed description of the available data is obtainable free of charge from the Section NFI, WSL, Birp,ensdorf.

Telephone main switchboard: Telephone Section NFI: Fax:

Address:

01/739 2111 01/739 23 53 01/739 2215

Schweizerisches Landesforstinventar Eidg. Forschungsansalt fur Wald, Schnee und Landschaft

ZOrcherstrasse 111 CH-8903 Birmensdorf Switzerland

How to Reach the WSL Urdorf-Sud

Birmensdorf

Birmensdorf- Sternen

PTT-Bus Triemli

Motorway N20

Railway station, line S9 Airport ZOrich-Kloten

Publications

Schweizerisches Landesforstinventar, Ergebnisse der Erstaufnahme 1982-1986 Eidg. Anstalt tor das forstliche Versuchswesen.

Report No. 305: 375 pp.1988. German or French.

In colour, richly illustrated, including maps.

Obtainable from: F. Fluck-Wirth, Internationale Buchhandlung fur Botanik und Naturwissen- schatt, CH-9053 Teufen, Switzerland, Price: SFr. 90.00

ISSN 0259-3092

Der Schweizer Wald heute

Eine forstpolitische Interpretation zum Schwei- zerischen Landesforstinventar (LFI).

Berne, Federal Office of Environment, Forests and Landscapes (BUWAL), Federal Forest Directorate (F+D). 1989. 46 pp., illustrated.

German, French, Italian.

Obtainable from: Eidg. Drucksachen- und Materialzentrale, CH-3003 Bern, Switzerland Form 310.345 German; 310.345 French;

310.345 Italian

A detailed list of all publications regarding the NFI is obtainable from the Section NFI, WSL, Birmensdorf.

Eidgentissische lnstitut federal de lstituto federale Swiss Federal

~

Forschungsanstalt recherches sur di ricerca per Institute for Forest, fur Wald, Schnee la fore!, la neige la foresta, la neve Snow and und Landschaft et le paysage e 11 paesaggio Landscape Research CH-8903 Birmensdorf