Douglas fir dries out the forest soil less than Norway spruce

Douglas fir, this is one of the promising tree species on which scientists are focusing their research. It could partially replace the withering spruce during the restoration of forests after the bark beetle disaster, at least. Therefore, information about the water regime of Douglas fir and Norway spruce is of extraordinary importance, also due to climatic fluctuations following by possible floods and droughts. In addition, Douglas fir is described as a tree species with higher requirements for nutrients and more favourable soil amelioration effects compared to Norway spruce.

Scientists from the Research Station in Opočno, FGRMI, v. v. i., have been engaged in research on Douglas fir for a long time, and they published their latest findings in the article Douglaska využívá vodu z hlubší vrstvy půdy než smrk (Douglas fir uses water from a deeper layer of soil than Norway spruce), which was published in the journal Reports of Forest Research 2/2022.

In their research work, they compared the moisture content of the upper soil layers in young Douglas fir stand with admixture of European beech (BK) and a young Norway spruce stand with admixture of European larch and Scots pine. They made the comparison for the upper soil layer at a depth of 0–35 cm. Information from the top soil layer is important, because about three quarters of the loss of water content from the entire soil profile comes from this top soil layer.

Scientists realized their research on two experimental trials in the Natural Forest Region (PLO) No. 26 (Foothills of the Orlické hory Mts.).

Among the main findings of the research, there can be mentioned these ones:

Mature Norway spruce, as the main tree species, consumes more water from the top layer of the soil during the growing season and dries it more than adult Douglas fir.

Compared to Norway spruce, Douglas fir has more favourable effects on soil acidification and improvement of humus forms.

These findings and other results were published in the paper “Douglas fir uses water from a deeper soil layer than Norway spruce,” which is available for download here.

Authors of paper: František Šach, Vladimír Černohous, Jan Bartoš, Research Station in Opočno, FGRMI, v. v. i., e-mail: frantisek.sach@tiscali.cz

Prepared by Ing. Jan Řezáč, FGRMI, v. v. i., e-mail: rezac@vulhm.cz

Illustrative photos: Douglas fir in mixture with Norway spruce and other tree species, FGMRI archive.