Softwood Regeneration: The Green Shadow

By Maxwell McCormack

Since conifer seeds do not accumulate and remain viable in the forest duff layer, what is the origin of the green carpets of needleleafed seedlings that appear a few years after harvesting of a softwood stand? After many observers suspect that there is no natural regeneration established, they seem to suddenly materialize. “See? There were some viable seeds in the duff.” I often have been challenged. “No,” I respond, “You didn’t notice all those tiny seedlings in the shadows of the stumps, slash, logs, boulders and other sheltering structures.”

For example, Figure 1 shows a typical spruce seedling, previously unnoticed, that is poised to emerge as viable reproduction when given a post-harvesting opportunity. Such miniature trees are usually presumed to have originated from seeds in the duff at the time of harvest.

But let’s take a closer look at that same seedling by viewing a microscopic cross-section (Figure 2) of the root collar (diameter: 1.5 millimeter). Careful examination of the growth rings indicates that the stem is approximately seven years old. Such established miniature, advanced regeneration, albeit fragile and difficult to discern within the complex structure of the forest duff layer, eventually reveals itself as a potential component of a developing young stand.

In the first years after harvest, these small trees can be difficult to see. Sometimes, when in doubt, I must crawl and meticulously pick through the litter and slash to find them. In the process it’s good to begin distinguishing between the villains such as raspberry seedlings and sprouts, and the jewels among the spruces, such as yellow birch and sugar maple seedlings. From that point on woodlot managers can begin to extract the weeds and thin out the potential crop tree seedlings.

Co-author, and photos: Patrick Strauch, Executive Director, Maine Forest Products Council. The early stand development of red spruce (Picea rubens Sarg.) and balsam fir (Abies balsamea (L.) Mill.) natural regeneration in Maine. MS (Forestry) Thesis, University of Maine, 1991