The Collaborative International Dictionary of English v.0.48:

Afforestation \Af*for`es*ta"tion\, n.
   The act of converting into forest or woodland. --Blackstone.
   [1913 Webster]

WordNet (r) 3.0 (2006):

afforestation
    n 1: the conversion of bare or cultivated land into forest
         (originally for the purpose of hunting)

Moby Thesaurus II by Grady Ward, 1.0:

52 Moby Thesaurus words for "afforestation":
   Christmas tree farming, arboretum, arboriculture, boondocks, bush,
   bushveld, chase, climax forest, cloud forest, dendrology, forest,
   forest land, forest management, forest preserve, forestation,
   forestry, fringing forest, gallery forest, greenwood, hanger,
   index forest, jungle, jungles, logging, lumbering, national forest,
   palmetto barrens, park, park forest, pine barrens, primeval forest,
   protection forest, rain forest, reforestation, scrub, scrubland,
   selection forest, shrubland, silviculture, sprout forest,
   stand of timber, state forest, timber, timberland, tree farming,
   tree veld, virgin forest, wildwood, wood, woodcraft, woodland,
   woods