copse vs understory

copse

noun
  • Any thicket of small trees or shrubs, coppiced or not. 

  • A coppice: an area of woodland managed by coppicing (periodic cutting near stump level). 

  • Any woodland or woodlot. 

verb
  • To trim or cut. 

  • To plant and preserve. 

understory

noun
  • The layer of plants that grow in the shade of the canopy of a forest. 

How often have the words copse and understory occurred in a corpus of books? (source: Google Ngram Viewer )