Succession of vegetation in the glacier forefield
Comparing photos from (top) and 2002 (bottom) shows the growth of larches (Larix decidua) and swiss stone pines (Pinus cembra), as well as in some photos, willows (Salix sp.) and alders (Alnus viridis).
Frontal position of 1900
The tall larch in the foreground has not only grown in height, but also become much wider!
Frontal position of 1920
17 years in the life of a pine (left of path) and larches (right)!
Frontal position of 1940
A «moraine landscape with larches» transforms into «an open larch forest with some moraine».
Frontal position of 1950
Due to growth of larches the glacier tongue becomes invisible from this location.
Frontal position of 1960
The tallest bushes here are mountain willow.
Frontal position of 1970
Note the massive shrinking of the glacier tongue!
Maximum tree highest in front of the glacier
At the respective frontal positions (years mean that the glacier then left this position) of previous years the height of the tallest larches (Larix decidua) and swiss stone pines (Pinus cembra) was estimated. Several estimations were averaged and used to draw the diagram on the left. This clearly shows: Pines take much longer to establish themselves on the nee, ice-free ground. They require approximately 40 years to properly establish themselves. In contrast larchescan be found on terrain which has emerged only 10 years ago from the ice. However, after 100 years both kinds of trees reach similar heights.
Ground covered by vegetation
The percentage of ground covered by vegetation was estimated, again averaging several observations at each location. Locations with large boulders (>0.4m) were avoided. After one century (frontal position of the glacier in 1900) 85% is reached. Even outside the moraines from the Little Ice Age (before 1850) it is not much higher. As expected the values decrease as one gets nearer to the glacier, but remarkably pioneer plants can be found even in terrain which has been ice free for two years only.
Morteratsch and Mount St. Helens
The idea to document vegetation changes in front of Vadret da Morteratsch was born, not near a glacier, but at Mount St. Helens volcano. Its eruption in 1980 destroyed large areas of forest. In 1988 J. Alean documented the starting re-colonization of the terrain by plants, and in 2001 the photos were repeated. The material is on STROMBOLI ON-LINE in the section on Mt. St. Helens in the chapter «Life returns». The treeline is considerably lower at Mount St. Helens (1500m.a.s.l. vs. 2200m at Vadret da Morteratsch). See also the virtual climb of Mount St. Helens.
|Image quality: Photos from 1985 were exposed on inferior film. Therefore, intensive processing had to be applied in order to show detail in the vegetation. This led to somewhat strange colours but has the advantage of clearly showing detail in the image foreground.|