13 October 2013

It is autumn again and the leaves are changing colour. Autumn is happening a bit earlier this year due to the very dry spring which induced drought stress in many soils. Early loss of leaves may be one consequence of that.
Early autumn is a good time for picking out and identifying some of our minor tree and shrub species as different trees have different autumn colours and show them at different times. Hazel is showing up well just now, and adds to the amenity value of many woodland areas at this time of year.
As previously noted, hazel (pictured) becomes more common the further west you go in Scotland, forming very extensive stands on the west coast. These ‘Atlantic hazelwoods’ are older than the oakwoods, and older than many of our Caledonian pinewoods.
Pollen evidence suggests that vast areas of pure hazel scrub dominated much of western Scotland for perhaps a thousand years. Remnant stands still exist today, habitat that has been there continuously for 10,000 years. This pollen evidence also suggests that after the last ice-age that hazel moved in to the British Isles from SW Ireland (which escaped the ice flows) and gradually moved northwards up the west coast of England, Wales and then Scotland, as well as the east coast of Ireland. From these locations, there was secondary movement inland, so we have hazel in Highland Perthshire, but not as much as in the west.
There is a very strong suspicion that hazel came to Scotland via hazelnuts floating on sea currents, getting washed in to sheltered inlets from which it would spread inland. The pollen record suggests that the more exposed shores and islands where flotsam was not deposited by currents did not get hazel until much later*.
This hypotheses that hazel came here by floating up the Irish Sea is becoming more accepted. It is really quite intriguing.
If you take some hazelnuts and put them in a bucket of water, they do indeed float, seemingly without any harm coming to them. It is not known however if they can remain viable after an extended period in sea water.
Scottish Native Woods are working with a West Coast school to test whether hazelnuts remain viable after periods floating in sea water. We will report back when we have an answer from these trials.
The hypothesis above is detailed in a book “Atlantic Hazelwoods” by Sandy Coppins. The book will be published this autumn, as an important output of the Atlantic Hazelwoods Action Group (AHAG) of which SNW are also a member.
* Birks, H.J.B. 1989.  Holocene isochrone maps and patterns of tree-spreading in the British Isles.  Journal of Biogeography 16: 503–540.

Victor Clements - Scottish Native Woods

 

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