Beechwoods – Hollow

The Wildlife Trust’s description of the Beechwoods claims that ‘Medieval plough terraces are still visible beneath the trees’.  I think they are very difficult to pick out.  Another, more obvious feature is the hollow, clear of trees, at the heart of the wood.  It is now a shallow bowl with smoothed sides; I remember visiting as a child when the edges were ragged and the shallow roots of the beech trees formed inviting caves.  What is the origin of this trace, this shadow of some past activity or event?