Rocky mountain tree species in the Tyrolean Alps

by Petra Meisel This email address is being protected from spambots. You need JavaScript enabled to view it.  Austrian Research Centre for Forests

The idea of experimenting with non-native tree species in the Alpine Space is not a millennial thing. In Jörg Heumader’s career, the method of trial and error with foreign seed material goes far back to the 1970s. Climate change was not yet the driver to immerse oneself into the topic of using foreign tree species, but the worrisome lack of tree diversity in high elevations of the Alpine Space in Tyrol was. Eager to find solutions, the Vienna-born student of forestry focussed his interest on the high elevations of the Alpine Space in Tyrol, which should later become his professional and private home.  

In the 1970s you could find Swiss stone pine (Pinus cembra), larch (Larix decidua) and spruce (Picea abies) as the dominant tree species at high altitudes of the Western Alps. But what if one species were to fail – which indeed happened decades later to the Swiss pine due to shoot dieback (Scleroderris disease) – then there would be only one more dominant species left. Which species could help to increase tree diversity and where to find them? Still under the auspices of his professors, the academically trained forester Jörg Heumader was introduced to subalpine tree species from the Rocky Mountains area.

Why the Rockies?

It was cold and hostile at the heights of the last ice age 115.000 –10.000 years ago. Massive ice sheets covered big parts of the northern hemisphere. Due to the east-west extension of the European Alps, tree migration beyond the mountain ranges was hindered while the retreating ice released space for life to spread in a roughly east-west direction on the exposed soil in lower areas. The Rocky Mountains extend in straight-line distance, north-south from the northernmost part of Western Canada, to New Mexico in the Southwestern United States. During the interglacial periods, tree species could migrate unhindered from South to North here and thus had time to adapt to a wider range of climatic conditions. That is why in the Rocky Mountains’ subalpine areas, tree species diversity is much higher than in the European Alpine Space.

Laboratories in high altitudes

After his graduation, Jörg Heumader started working in the district office “Oberes Inntal” for the Federal Forest Engineering Service in Torrent and Avalanche Control in Imst in Tyrol, in 1968, before he later was promoted as head of the unit, till his retirement in 2006. In the course of implementing protection measures for torrents, avalanches and rockfalls, he represented the forestry side in the western regions of Tyrol from 1980 to 2010 and his approach took particular action in the reforestation for high elevations.

Jörg Heumader’s objective was to increase the number of tree species in the subalpine area to have a wider range of diversity as buffer for future developments. His previous studies with northern American tree species came in handy and led to his vision to provide tree diversity with non-native seeds from the golden west of the United States.

Heumader contacted U.S. foresters of the Rocky Mountain Region and was generously provided with literature and contacts of local seed companies from the Rocky Mountain area.

Since the reforestation area in the Oberland of Tyrol has continental climate, he had to select the U.S. material according to the distinctive climate and soil data of both regions. The data concluded that only those non-native tree species were suitable for his working area, that thrive on the side facing away from the Pacific in the rain shadow of the Rockies where there is low precipitation. So for example the North American Sitka spruce was out of discussion, because it requires much more rainfall than the Alps provide. 

You’ve got Mail!

After receiving seeds via Airmail, Heumader’s team could successfully plant 10.000 samples of Engelmann Spruce (Picea engelmannii) that brought the advantage of not being browsed by game due to its bitter taste, in comparison to the “delicious” native spruce. Moreover, Engelmann spruce grows at the same rate as the native alpine spruce. So it exhibits slow and squat growth when young, to gather strength for growth and after 7- 10 years it starts to grow rapidly. To the team’s amazement, the roots showed fungal growth like their native relatives and thrived similarly well with our native Mycorrhiza.

Seeds of Mountain Lodgepole Pine (Pinus contorta subsp. latifolia) thrived successfully on dry areas in the Inner Alps and grew very fast only on acid soils, but not on lime. The Alpine test area includes parts of the Central Alps, crystalline, acidic soils and parts of the Northern Limestone Alps, limestone and alkaline soils – so forest managers can't mix all non-native species due to different soil specifications and requirements of tree species.

Also 10.000 seeds of Mountain Pine (Pinus uncinata) from the French Alps and the Pyrenees were successfully planted and support high-elevation forests of Jörg Heumader’s Upper Inn Region/Tyrol to this day.

Chances for a next generation of potent U.S. seedlings  

“The trees that we planted back then in the 70s and 80s are still thriving well today”, Jörg Heumader laughs, “sometimes I come to visit the area, but since we are in the subalpine area, close to the tree line, everything grows extremely slow. My oldest babies are 40 years old, but they are only 4 meters high. They won’t produce any seedlings in the near future!”