Researchers test cedars as alternatives to vulnerable spruce forests

Researchers in Austria are testing Lebanon and Atlas cedar varieties as possible alternatives for spruce forests increasingly affected by drought, pests and wind damage, ORF reported.

At a 2.5-hectare trial site run by the Birnleitner forestry administration in Aistersheim, Upper Austria, eight ecotypes of Lebanon cedar and two of Atlas cedar have been planted in a precisely measured experimental layout. The roughly 3,000 young trees, most planted in 2023 as part of a Forest Fund project, are about two metres tall and are still partly hidden by tall grass.

The site was previously covered by spruce and oak trees and had to be replanted after damage, said Joachim Pennetzdorfer, a forestry adviser at the Upper Austria Chamber of Agriculture. Without human intervention, oak would grow there, he said.

Similar trials are under way in Lower Austria and Burgenland. The sites form an east west gradient, said project leader Raphael Thomas Klumpp of the University of Natural Resources and Life Sciences in Vienna. Burgenland has a Mediterranean continental climate, Upper Austria is more Atlantic, meaning milder and wetter, while Lower Austria lies between the two. The researchers want to determine which ecotypes develop best in each region.

Other plots are being used to produce seed. Once researchers know which varieties perform well, they could harvest seed from them, said Stephan Rechberger of the Upper Austria Chamber of Agriculture, a project partner in the Cedrus4Clim project.

Lebanon cedar is mainly found in Turkey and also grows in Lebanon, where it appears on the national flag. Atlas cedar comes from mountain regions in North Africa. Rechberger said neither should be confused with the North American giant thuja often called red cedar, which has also played a role in Austrian forestry since the middle of the 20th century.

Klumpp, who has researched Lebanon cedar for more than 20 years, has greater hopes for it than for Atlas cedar. Atlas cedar is much more sensitive and suffers during dry periods, he said, while Lebanon cedar does not. However, frost is a challenge for almost all Mediterranean tree species, and the trials will examine how well the different ecotypes withstand it.

Klumpp does not expect cedars to replace spruce forests, partly because cedar saplings cost significantly more than native conifers. Austria will not have thousands of hectares of cedar forest “overnight”, he said.

Spruce remains the key timber

Spruce remains the most important timber for forestry and the wood industry, Klumpp said. Its wood is light and stable and, like fir, is suitable for construction, while beech and oak are heavier. Large natural spruce ranges remain in the Alps, he said.

The problem is spruce forests planted by people at lower elevations, where increasingly long dry periods are creating difficulties. Douglas fir from North America or cedars could offer alternatives. Cedar produces valuable wood similar to Swiss stone pine and suitable for construction.

Klumpp said he would recommend cedar on south-facing slopes, combined with silver fir and beech in groups. Austria currently has only a few cedar stands, all still young, while older trees are mainly found in parks. Until about 40 years ago, Lebanon cedar was considered too slow-growing for Austrian forestry. Climate warming has changed that assessment, Klumpp said.

Older trees are more vulnerable to bark beetles, which is why the rotation period for spruce has been shortened from 100 to 80 years for production security. It remains unclear how long cedar stands can be left standing.

Cedar suited to south-facing slopes

Lebanon cedar needs well-aerated soil and does not tolerate waterlogging or sites with alternating wet and dry conditions. In Austria, it could be combined with black pine and fir, Klumpp said. He sees it mainly on south-facing slopes, while native tree species would be preferable on north-facing slopes. Cedar is less resistant to fire than larch or Douglas fir.

The researchers say cedar could therefore become one element of climate-suitable forestry. Before forest owners begin planting larger cedar areas, however, the different ecotypes must first be studied to determine which are best suited to Austrian conditions.