Old-growth Fosters Seedling Root Fungi

Douglas-fir seedlings growing near old-growth patches benefit by acquiring more ectomycorrhizal fungi.

The fungi are essential for tree growth; they attach to tree roots and enable their hosts to take up soil nutrients.

One research study concludes that retaining trees within cutblocks contributes to maintaining the site's diversity of ectomycorrhizal fungi.

The study sites, situated in Coastal Douglas-fir and Coastal Western Hemlock biogeoclimatic zones on southern Vancouver Island, were all logged using variable retention. Two years after planting, the greatest number and diversity of root fungi were found on seedlings growing 5 m or 15 m away from retained patches of mature trees, compared with seedlings at 25 m or 45 m distance. Fungal inoculation appears to decline with distance away from source trees.

The previous forest's history is also important. The research compared seedlings planted on sites recently harvested of old-growth forest with areas harvested of second-growth forest. Seedlings in cutblocks that previously held old-growth forest had a higher proportion of root tips covered in ectomycorrhizae. As well, a greater diversity of fungi occur in seedlings on old-growth cutblocks. Of the 41 distinct looking fungi found on seedling roots, 20 are common to both types of stands, while 14 are unique to harvested old-growth and 7 are unique to harvested second-growth sites.