Front page (part) of Rit Mógilsár, volume 50
Front page (part) of Rit Mógilsár, volume 50

An article in the latest volume of the Icelandic Forest Research' science bulletin Rit Mógilsár shows interesting results from recent measurements of the so called Rarik-experiment, set out 25 years ago with 50 provenances of downy birch. It appears that birch from Southeast Iceland produces the highest amount of seeds and shows highest resistance to rust fungus. Authors recommend further work on the already fruitful breeding work that has been carried out in Iceland to enhance the development of birch reproduction material suited for Icelandic lowlands in the future.

In English, the title of the article is Cultivation dependability, growth, seed formation and health of Icelandic birch provenances. Authors are Brynjar Skúlason and Brynja Hrafnkelsdóttir, researchers at the Icelandic Forest Research – Mógilsá, together with Aðalsteinn Sigurgeirsson, Deputy Director of the Icelandic Forest Service – Skógræktin. Aðalsteinn actually worked on the initial phase of the experiment managing , among other things, seed collection from the provenances used.

The Icelandic downy birch woodlands show substantial variation in both height and growth habit (straightness, shrubbiness) at maturity. However, it can be difficult to distinguish which is more dominant, hereditary characteristics or local environmental conditions on the particular site.

Seed production on test sites Varmadalur, Hjaltastaður, Fagurhólsmýri and Lækur. Birch from Southeast Iceland ranking top five. Good seed production is an important trait for projects where birch trees planted on intermittent patches of land are supposed to seed itself out and finish the reforestation work.In the spring of 1998, a seed experiment was set up with 50 provenances of Icelandic downy birch (Betula pubescens), planted on 9 different test locations. Measurements were made in five of those locations in 2020 and 2021. The height and diameter of the plants were measured, as well as survival, rust formation and seed quantity. There was a positive correlation for all traits in the scores between experimental sites and differences were significant in the majority of cases, which indicates that the traits are determined by genotype rather than environment.

Birch from South Iceland showing advantage

A very good correlation was found between the southern test locations in terms of survival, where the ­Steinadalur provenance is decisively the best and the provenances from the Southeastern and Southwestern parts of the country are almost all ranked above those from the Northeast and Northwest.

The ranking of provenances in terms of survival is more variable at experimental sites in North Iceland and in the Westfjords. The birch from Bæjarstaður Forest in Southeast Iceland and nearby populations generally show the highest biomass figures, and the birches from the Southeast and Northeast are least likely to develop multiple stems.

Further breeding work important

The clearest results are for seed yield and rust resistance, where the birch from the Southeast has an advantage in abundant seed production and the highest resistance to birch rust. When using birch for woodland creation in the lowlands of Iceland, it seems viable to take advantage of the breeding benefits shown by the cultivar 'Embla', as well as promoting increased genetic variation by adding clones to the population from provenances that have shown positive results in the experiment such as birch from Steinadalur, Þingvellir, Þórsmörk and Bæjarstaður.

The article is published in Icelandic with an English abstract.


Text: Pétur Halldórsson