Survey of the Data available for the Elaboration of the Val Bavona's Forest Management Plan

This is probably the most interesting aspect for the participants of the meeting "Forest Survey Designs". We will thus deal with it in detail. It should be stated from the outset that the survey (phase II, see chap. 3.7.3) has taken into consideration the following demands:

- of having the possibility of using a sufficient quantity of up-to-date information

- of documenting the present forest situation for "future recollection", as requested by the

"Bavona Foundation".

3. 7.4.1 Organisation of the Surveys

Initial information concerning the forests of Val Bavona was scarce and out-of-date.

Moreover, no forest management is practised on any of the valley's forest properties.

The planning therefore required a survey of the entire forest area of the valley, clearly distinguishing, in terms of execution's means and related costs, between the valley-floor and the mountain-sides. The information regarding the mountain-sides' forests has been collected purely to record the distribution and present state of the forest, and not for any practical management purposes.

In order to get an up-to-date view of the study-area, and to reduce the difficulties associated with plot assessment, an infra-red aerial photo survey was made in 1991 of the whole Bavona Valley. This was followed by the identification of the boundaries of forest stands and their measurement and plotting on a topographic map at a scale of 1:10'000. The characteristics of the valley-side stands were thus deduced from the interpretation of the aerial photos, while the stands located on the valley-floor were subject to ground survey (fig.1).

Since in the Bavona Valley there is scarce timber production, no assessments were made of timber production.

Particular attention was paid instead to the ecological and wildlife characteristics of the valley-floor's forest. A stand map was drawn up, together with a forest station map. The survey for both plans was performed together. The station map was based on a classification of forest environments purposely elaborated for this area by H. U. Frey, forest engineer, who is a specialist in phytosociology.

3. 7.4.2 Collection of the Data

The unit chosen for the collection of the information is the forest stand.

The characteristics of every stand have been recorded on survey cards specially designed for this project (see Appendix card 1 and 2). Except for the use of a stereoscope for the interpretation of the aerial photographs of the mountain-sides, the collection of the data has made no use of instruments.The technicians' examination of the forest and of the appropriate air photographs was considered to be sufficient for the purposes of the assessment of non-timber resources.

Val Bavona

Entire surface: I l '853 ha Forest area: 3'004 ha (24%)

Mountain-sides

Entire surface: 1 1 '263 ha (95%) Forest area: 2'447 ha (22%)

Valley-floor

Entire surface: 590 ha (5%) Forest area: 4 1 7 ha (71 %)

Fig. 1 . Organisation of the survey for the Val Bavona forest management plan.

Strategy used for the mountain-sides:

- aerial photo coverage scale about 1:10'000

- identification of stand limits on the aerial photographs - aerial photograph interpretation (see Appendix. card 1) -transfer to a topographic map (l:10'000)

-no ground survey.

Strategy used for the valley-floor:

-aerial photo coverage: scale about 1:10'000

-identification of stand limits on the aerial photographs -transfer to a topographic map (l:10'000)

-ground survey (see Appendix, card 2).

The record of the characteristics of the mountain-side stands is shown on card 1. Through the interpretation of the aerial photographs, we were able to designate the most important features for the evaluation of the forest's capacity to fulfil its protective function for the valley-floor. They are the following:

forest canopy cover

mixture of conifers and broadleaved trees - structure (even-aged forest or not).

Card 2 was used to determine the characteristics of the valley-floor stands. It can be divided into two parts. The first part describes the present forest situation. The information takes into account the principal structural components of the ecosystem:

- uppermost layer

- underwood (ground/bush cover and regeneration) - grass cover

- pedogenic substrate (soil and geology).

The second part evaluates the following characteristics:

- actual forest situation (viability and stability) - hazards threatening the stand

- presence of forest utilisation (stumps) - present and potential forest function

- need for silvicultural intervention and, if necessary, specific intervention suggestions.

In addition to the valley-floor survey, an estimate on the ecological and wildlife value of the forest has been carried out. About twenty different forest environments have been singled out as reference points for this estimate (see chap. 3.7.4.1).

An expert on mammals and an ornithologist have evaluated the degree of suitability that the various forest types have as potential wildlife habitat. Meanwhile, a survey of the flora was carried out in representative areas of the various forest types following traditional phytosociological methods. The cooperation with the ornithologist R. Lardelli has proved to be particularly effective for our aims (see chap. 3.7.5.3).

The forest stations map was then used to generalize the collected information on the flora and fauna.

In the alluvial forests, the protection of which is very important in Switzerland, the study of the vegetation was the subject of an even closer examination which has resulted in the production of a special map financed by the Nature Protection Office.

3. 7.4.3 Data Processing

A Geographic Information System (PC ARC/Info) was used for the management of the data. The various mapped areas have been digitized and the survey cards entered into a relational database.

The possibility of using an electronic database has made the analysis easier. Moreover, thanks to the possibilities for producing maps, much information has been emphasized and exploited to the advantage of the planning work.

As far as the Bavona's forest is concerned, the most important analysis were (they are grounded also on data of which we haven't dealt with in chap. 3.7.4.1 and 3.7.4.2):

For the valley-floor:

- analysis of the development of the forest area over the last 20 years (see chap. 3.7.5.2);

analysis of the present situation of the forest stands (for instance: the distribution of three species, of development stages, underwood presence, varieties of species);

analysis of the forest stands' evolutional tendencies (stability, viability, hazards, existence and quantity of regeneration);

analysis of silvicultural intervention needs or of other types of intervention;

analysis of wildlife aspects (thanks to the statiom map and to the vegetation map of the alluvial forest);

location of the areas exposed to natural hazards (see chap. 3.7.5.1).

For the mountain-sides:

- analysis of the distribution and present state of the forest;

- evaluation of its capacity to fulfil its protective functions.

3.7.5 Some Aspects and Problems dealt with while preparing the Forest Management Plan