Farming is concentrated in the flatlands of the four west coast provinces, where a longer growing season, level land, adequate rainfall, and good irrigated soil permit the most intensive cultivation of crops. A narrow strip of similarly fertile land runs through the eastern seaboard Hamgyŏng provinces and Kangwŏn Province, but the interior provinces of Chagang and Ryanggang are too mountainous, cold, and dry to allow much farming. The mountains contain the bulk of North Korea's forest reserves while the foothills within and between the major agricultural regions provide lands for livestock grazing and fruit tree cultivation.