Frost and new enemies stress Douglas firs in Swiss forests
Published: Tuesday, Oct 31st 2023, 17:11
Updated At: Wednesday, Nov 1st 2023, 00:55
Back to Live Feed
Douglas firs suffered in Switzerland last year. The needles of the trees, which originate from North America, turned red in many places from mid-April. The reason for this was frost damage, as a new study by Forest Protection Switzerland shows.
Douglas firs are considered the tree species of the future for the Swiss forest, as the Swiss Federal Institute for Forest, Snow and Landscape Research (WSL) announced on its website on Tuesday. This is because, compared to local coniferous species, they tolerate drought better, which gives them advantages under climate change.
However, the new study in the journal "Waldschutz Aktuell" shows that frost in spring could become a problem for the Douglas firs. The researchers from Forest Protection Switzerland examined reddened Douglas fir shoots. They were able to rule out pathogenic fungi as the cause of the damage.
March cold snap
Thus, frost in February and March was the most likely cause of needle reddening, WSL said. In particular, the second half of February 2023 was exceptionally warm, but there was a sudden cold snap at the end of the month.
This could have caused so-called alternating frost damage, according to the study. However, previous experience with pronounced frost damage to conifers suggests that the damaged Douglas firs will recover in the coming years, the researchers said.
New pest emerged
Whether the Douglas fir passes the suitability test as a future tree for Switzerland depends on other factors, according to the WSL. The tree species is also under stress due to a new invasive mosquito species.
In 2022, Waldschutz Schweiz first discovered Douglas fir gall midges of the genus Contarinia in the canton of Basel-Landschaft. According to WSL, subsequent monitoring programs showed that the invasive gall midges from North America are already widespread in northern Switzerland.
©Keystone/SDA
English 
German 
French 
Spanish 
Arabic