The Bavarian Alps belong to the northern border of the Alps and have an oceanic origin which formed the dolomite and limestone rocks as well as a narrow band of flysch. The highest elevation of 2.962 meters is found on the summit of the Zugspitze in the Wetterstein mountain chain and the lowest point of 473 meters lies in Saalachtal nearby Bad Reichenhall. Since the vegetation period decreases with increasing elevation there is a diversity of forest types in the Alps which range from submontane deciduous forest communities to the high elevation larch and Swiss pine forests. Today about fifty-two percent of  the Bavarian Alps are forested which sums to about 250.000 Hectares of woodland. Before humans influenced the landscape over eighty percent was forested. 

Human influence

The human influence on natural forests, which has lasted for almost 2.000 years, has changed the composition of tree species in favor of spruce at the expense of beech (Table 1).  The "industrialized" use of wood served large scale harvesting practices and was interested primarily on conifers rather than beech. On the other hand, forest usage from peasant communities utilized single stems which resulted in the preservation of various structured uneven ages forests in private woodlands.

The reduction of species diversity and the emergence of pure spruce stands have diverse anthropogenic causes such as a high demand for timber, clear cutting practices, excessive grazing or the exorbitantly high population of wild game. The largest contributor to the promotion of spruce in recent decades may have been made by hoofed game which significantly hindered the development of spruce competitors.

Natural range

In table 1 the average tree species composition for the entire forested area of the Bavarian Alps was calculated but it doesn't show the actual mixing proportions. There are, to a greater degree, significant areas with practically pure spruce stands in the mountain forests. Results of the second federal forest inventory shows that on almost three quarters of the forest area in the Bavarian Alps practically pure stands of spruce are to be found and are predominately in the age classes 2 to 4. This corresponds to five times  the proportion of naturally occurring forest types composed primarily of spruce, especially at altitudes of 1.200 meters above sea level (table 2). In lowland areas the spruce can be found naturally, however it rarely takes a dominating stance.

Future distribution

The Alps are particularly susceptible to climate change and  the warming there in the recent past was about three times as strong as the world average. According to a regional climate model a temperature increase of around two degrees Celsius is to be expected. The optimal climate for the spruce lies between 5°C and 7.5 °C. This means that the spruce could hold its dominant position in the subalpine and alpine zones (Table 2). However, it will be subjected to increasing competition through classical mixed mountain forest species such as silver fir and beech.

Algorithms from the forest information system for the northern Alps calculated habitat models for the most frequent tree species using regionalized climate scenarios (temperature increases during the growing season from 1.5°C and 3,2°C) for the year 2100. From these models it can be deduced how climate change will affect the vitality of the spruce in various forest types (Table 3). In the entire montane area (this means half of the mountain forest area) the spruce will lose vitality and presence in forest stands. In subalpine areas the vitality of the spruce could increase.

This is supported by the analysis of tree-rings which examined the reactions in growth in dry years within  the various altitudinal zones in the mountain forest. Thus it can be found that the spruce has the relatively strongest losses in growth after dry periods in the lower elevations (<1.000 m above sea level). On the other hand, spruce shows a predominately positive effect on growth in elevations over 1.4000 meters above sea level. This means that the high mountain areas can become a place of retreat for the spruce. 

The proportion of spruce will not only decline in the future due to climate change but also because of silvicultural operations. This arises since the forests in the Alps fulfill an important protective function on many sites. Additionally, pure stands of spruce are very susceptible for calamities. The highest commandment of the hour is therefore the cultivation of mixed stands of spruce, silver fir and beech.

It won't be easy for the spruce in the future

If spruces from high elevations are planted in lowlands, then they will usually break their buds and sprout in the spring earlier than the lowland spruce trees. With a rapid warming in  the higher elevations this effect could possibly also occur there. As a result, the spruce in the higher elevations could be exposed to an increased risk of late frost - at least until they have become adapted to the new climatic conditions.

Parallel to the decreasing vitality of the spruce in  the montane areas, the vitality of the eight-toothed spruce bark beetle (i.e. typographer beetle) is strengthened. It can create more than one generation a year in  the high mountain ranges and can become a primary pest. A visual witness to this are the bark beetle "nests" which can now occur in all elevations (Figure 2).

Shallow, humus poor sites are found in the montane, moderately dry, carbonate dominant mixed mountain forest. This affects a significant five percent of the Bavarian Alps. On these sites the spruce regeneration has difficulties to establish itself and clear cutting has led to a degradation of the soil. On these sites clear cutting caused a massive mineralization of the humus layer and thus the loss of the nutritionally favorable acidic organic layer. The availability of the elements phosphorous, potassium and manganese decreased. A deficient supply of these elements can lead to severe damage in spruce monocultures. Stable protection forests with the climax tree species spruce can only work out in the long run if  the humus layer is regenerated. Degraded sites can be reforested with the pioneer species larch and pine. The natural regeneration of spruce has to occur by itself. This can, however, take between thirty to forty years.

The nutrients nitrogen and phosphorus limit the growth of the spruce. However, particularly in the middle areas of the Bavarian carbonate Alps, these elements are commonly deficient. In order to avoid a further reduction in yield the humus layer should be regenerated so that nitrogen and phosphorus can be mineralized in the future. The protection of the humus layer on productively weak calcareous soils has to be prioritized over whole tree harvesting. The protection of the humus layer is of fundamental importance for the whole Alpine region since humus loss is probably also a result of climate change and occurs on sites which are not used for forestry.

Even on sites with better nutrient availability the spruce also has a problem to establish regeneration. Spruce regeneration can be out competed by that of beech, maple and silver fir where these mixed tree species are not disparaged by excessive browsing from wild game. The spruce can be helped on such sites through appropriate silvicultural measures.

The spruce in an avalanche protection forest

The gradual retreat of the spruce from  the montane areas of the Bavarian Alps has a long term influence on the protective function of the mountain forests regarding avalanches. Evergreen coniferous trees accomplish avalanche protection better than winter-bare deciduous and larch forests since snow interception is higher with conifers: snow falling from the crowns prevents the creation of a homogeneous snow layer and the probability that a slab of snow begins to slide is reduced. As a result, the proportion of deciduous or larch trees in avalanche protection forests should not exceed thirty percent.

In order to maintain the avalanche protection function of the mountain forests it makes sense to implement the use of the climate tolerant silver fir as an evergreen conifer species more often on sites where the spruce is retreating due to climate changes. Due to the warming it is to be expected that the precipitation will take the form of rain more often in the future. However, this doesn't mean that the danger of avalanches is over. Extreme precipitation events with respective avalanches will surely continue to exist.


Of all the tree species of the mixed mountain forest the spruce will be the most affected. In the montane areas it will diminish the most; on these sites one should already start to think about alternatives. The most suitable species to take over the role of the spruce is the silver fir. In higher elevation the spruce will be able to hold onto its high proportion.

A consequent abatement of the bark beetle is necessary in order to strengthen the vitality of the spruce in the Bavarian Alps. It is urgently required to counteract the loss of the humus layer and to increase the reserves of humus in order to preserve and encourage the natrual regenration of the spruce. Harvesting residues (i.e. slash) should remain in the stand where the guidlines of forest protection thus allows.

The forests - and primarily those with low stocking rates on shallow soils - must be quickly restocked with site appropriate tree species. Therefore, regeneration should always be found over a wide spread area and with site appropriate species to its full stocking potential. This only seems to be possible as long as a framework for such conditions exist (e.g. adjusted and appropriate wild game populations for the sites).