At Stillberg, we study the growth of trees at the treeline and the interaction between the trees, snowpack and avalanches. The field site is situated on the left, northeast-facing and highly topographically structured slope of the Dischmatal in Davos at an altitude of 2,000 to 2,230 metres above sea level.
The slope gradient in the upper section of the site is 100%, while in the lower section it is 60%. The field site lies directly above the present treeline in the transitional area between the larch/Swiss stone pine forest and the inner-Alpine dwarf shrub communities. An area of approximately 10.4 ha was set aside and fenced off for the actual field site. In 1975, an area of 5 ha was afforested. The entire afforestation area was divided into a grid of units measuring 3.5 x 3.5 m and planted extensively in a systematic pattern of Swiss stone pine, larch and mountain pine (totalling around 92,000 trees). There is a large amount of information for each unit, both with regard to the site conditions and the success of afforestation. Two smaller comparative afforestation areas in different aspects complete the field site.
The field site is accessible via the following facilities:
- "Hof Dischma" car park on Dischmastrasse
- Hof Dischma cable car – Stillbergalp; capacity: four people in manual mode or two people in automatic mode
- Cable car from Stillbergalp -> Mittelgrat field site (one person, can be lowered)
- Goods cableway Stillbergalp – Hüttiboden
- Hüttiboden helipad
- Path network: access to the field site via Jakobshorn-Teufi path; additional network of paths within the field site
Two huts (cabins) were built in the immediate vicinity of the field site:
The lower hut is situated on the Stillbergalp at an altitude of 2,000 metres above sea level, directly next to the summit station of the cable car and the Alpine buildings of the Stillbergalp. Inside, there is a large multipurpose room (workroom, living room, kitchen), two additional rooms with four beds, a telephone/modem connection, hot water, a toilet and a shower.
The upper hut (Hüttiboden) is situated at approximately 2,350 metres above sea level, immediately above the highest trees of the afforestation study, and is accessible by helipad and a goods cableway. The hut has a bedroom (four beds), kitchen and bathroom, as well as a large seminar and workroom with telephone and modem connection.
The automatic climate station at Stillberg (2,090 m) has been in operation since 1975. The climate of the field site as a whole and microclimate distribution have been discussed in Turner (1988a, 1988b). The virtually uninterrupted data series incorporates the following parameters:
- global radiation (horizontal and parallel to the slope), refl. radiation parallel to the slope (albedo).
- Sunshine duration (measurement height 2.0 m, winter 4.0 m)
- Precipitation (measurement height 2.0 m, winter 4.0 m)
- Humidity (measurement height 2.0 m, winter 4.0 m)
- Wind speed and direction (measurement height 10 m)
- Vertical air temperature profile 10, 50, 100, 200 cm (200 cm aspirated)
- Air and dew point temperature (measurement height 2.0 m, winter 4.0 m; from 1987)
- Soil temperatures 0, -10, - 50 cm, (from 1975) - 100 cm (1975 - 1991)
- Snow depth
- Air pressure (at Stillberg hut, 1,970 metres above sea level, from 1980)
- Ozone (at Stillberg hut, 1,970 metres above sea level, from 1989)
At the four main locations of the Stillberg field site (large hollow), satellite stations for additional microclimatic measurements were equipped with the following sensors:
- Soil temperatures - 5, -10, -30, -50 cm (1975 - 1991)
- Air and snow temperatures +10, 30, 60, 100 cm (1980 - 1991)
- Global radiation and albedo parallel to the slope (1980 -1983)
- Total radiation balance (1980 -1983)
Archiving the data:
- 1975 - 1996: mean and extremal 5-minute values every hour
- from 1997: 10-minute values