Gleann Giubhasachain is a quiet glen in the central Cairngorms running between Bod an Deamhain, and Beinn Bhrotain.
As a place name Gleann Giubhasachain – means glen of little fir wood.
The floor of the glen is almost level – you can walk westward from the Dé for 2-miles without crossing the 2,000 ft. contour.
Ironically - there are no trees in Gleann Giubhasachain within the reach of deer, nor have there been within living memory. That fact suggests that the derivation of the place name disappears into the mist of time.
There were certainly trees growing in the glen at some time in the past – the evidence sticks out of the peat everywhere.
In Gordon (1925) – the author describes finding the remains of trees in the glen under many feet of peat - writing :
the peat, down to 8 feet below the surface, contains many well-reserved roots. In once instance the entire trunk of a tree has been exposed by the action of the waters. These ancient roots are not entirely of pine - there is birch bark in places, as silvery as on the far-off day when the trees swayed gracefully upon the wind
- Gordon (1925) (p126)
The significance of the 8 ft. depth is obvious ; the deposition rate of peat must be fairly constant. It's not something I know anything about, but I'd bet an expert could say how many years it would take for 8 ft. of peat to form, and by implication, how long ago the trees died off.
Also in Gordon (1925) – the author tells us the upper limits of the ancient forest - writing :
As one climbs one expects momentarily to leave the traces of the early forest behind, but always in the peat one sees the tree stumps. To-day I noted carefully the upward limit of their growth and, so far as could be determined by a reliable aneroid, this was 2,300 feet above sea level
- Gordon (1925) (p127)