I surveyed tree regeneration in part of Ryvoan in 1989 (for my own interest), just as the RSPB purchased much of its present reserve. At that time, although Scots pine seedlings were present, very few survived above heather height and grazing damage was almost universal. The RSPB then started a programme of reducing deer numbers, and 25 years later the wealth of young, naturally regenerated pine trees growing in Ryvoan and elsewhere testify to the success of that policy.
What is missing is almost any regeneration of birch, alder or willow and the most likely explanation appears to be a lack of seed source. Abernethy is not a pristine woodland: it has experienced centuries of human intervention, including selective removal of these broadleaved species, by felling and by human-caused high grazing pressure. So the existing woodland is unable to supply sufficient seeds of these trees.
Planting clumps of broadleaved trees in the woodland expansion area (and pines in areas distant from present stands), to act as future seed sources to enable future natural regeneration, seems to me to be an appropriate response considering the present nature of the parent woodland, and the treeless areas distant from it.
We have our inheritance, and it is one of degraded hills and modified woodlands. Should we now sit back and merely watch the halting, incomplete process towards recovery? Or should we recognise that as human actions were responsible for what is now regarded as damage, then sensitive and careful human assistance towards restoration is appropriate and necessary?