Source : Webster's Revised Unabridged Dictionary (1913)

Reforest \Re*for"est\, v. t. [imp. & p. p. {Reforested}; p. pr.
   & vb. n. {Reforesting}.]
   To replant with trees; to reafforest; to reforestize.

Source : WordNet®

reforest
     v : forest anew; "After the fire, they reforested the mountain"