ASSISTED MIGRATION OF TREES – PART 2

 

In Ontario, there are 35 static seed zones. These were established to ensure that planting stock was climatically adapted to the region of planting. This supported the approach of ‘ local is best ‘ where locally adapted seeds would be more acclimatized to the site. Recommended distances were no more than 50 kilometers from the parent stand and, if possible, less than 30 kilometers.

What is strikingly clear is that static provenances are no longer valid with a changing climate. Climatic envelopes, areas of suitable climatic habitat for tree species, are shifting north. This change will be ongoing and unrelenting. It is this unrelenting change that has us paralyzed.

So what are some issues concerning assisted migration? It is the intent of assisted migration to push seed provenances north or even introduce new species north and accomplish climatic adaptation in 1 generation in what would have taken nature several generations to achieve. One of the biggest risks of planting stock north of its current zone, is freezing damage. Natural selection has resulted in species aligning their growing cycles to avoid damage from late spring and early fall frosts. Events such as breaking dormancy, bud burst and flowering are carefully timed for tree species adapted to a local environment.

On an even larger scale, we could be mismatching tree species to photo period. By moving seed sources north, species are no longer matched to local day length. Longer photo periods experienced at more northerly latitudes may cause trees to be more susceptible to all frosts. By mid century, it is estimated that most of Ontario’s tree species will have to move 400 to 600 kilometers north to keep withing their climatic envelopes. This will, indeed, cause mismatching of tree species to photo period.

We have decided, at Puslinch Naturally Native Trees nursery, to take the plunge. We will be launching an assisted migration program. A huge undertaking but we have always been committed to a sustainable environment and forests. Now the hard work begins where we build the program and try to introduce it to our clients and general public.