Expectations for birch forest regeneration by soil scarification

Contemporary significance of soil Scarification for promoting tree regeneration in Hokkaido, northern Japan

Eriko Ito (a), Toru Hashimoto (a), Shuhei Aizawa (b), Satoshi Ishibashi (a)

(a) Hokkaido Research Center, FFPRI, Sapporo, Hokkaido, Japan.
(b) Department of Forest Soils, FFPRI, Tsukuba, Ibaraki, Japan.

Japanese Journal of Forest Environment Vol.60 No.2:71-82, December 2018

In Hokkaido, a large area of Abies sachalinensis plantation has entered the main logging stage. In terms of human resources, it would be challenging to re-plant this whole area. Therefore, a method of re-afforestation that would serve as an alternative to the regeneration of A. sachalinensis has been sought. Presently, there is interest in birch forest regeneration by “soil scarification.” Soil scarification is a natural regeneration practice wherein both understory dwarf bamboo and surface soil are removed using civil engineering machinery. Soil scarification has been widely employed since the 1960s in areas without standing trees in Hokkaido, resulting in the establishment of secondary forest dominated mainly by birch trees. For assessing the potential of soil scarification for sites cleared of A. sachalinensis plantation forest, we examined past soil scarification cases from the viewpoint of soil disturbance and analyzed the factors that distinguished success or failure. Results indicate that the following three factors are important: (1) Do not scrape off all the surface soil, otherwise nutrient levels fall too severely; (2) Avoid compacting the surface soil so that breathability and water permeability are maintained; (3) Remove dwarf bamboo completely, since dwarf bamboo can dominate birch. The price of birch wood has been on the rise due to a recent increase in demand. We aim to combine suitable operating technologies to create high quality birch forest using carefully executed soil scarification.
 

Picture: 31-year-old Erman’s birch (Betula ermanii) forest created by soil scarification (National forest in Ishikari)