The growing season lasts 240 days in the south and 100 days in the north. Most of Sweden has a relatively even topography and is less than 300 m above sea level. These mountain peaks are not forest-covered. The timberline varies from 700 m above sea level in the southern portion of the chain to 400 m in its northerly portion. The country's forest soils chiefly consist of moraines which were deposited when the inland ice cap melted 10,000 years ago.
Most Swedish forests are part of the Boreal coniferous belt.
Leaching of mineral nutrients has thus reduced their level by half in recent decades. Critical loads are being exceeded, both in terms of sulfur dioxide and nitrogen dioxide deposits. Air pollution poses a serious threat to the forest eco system and to the growth of forests. Only in the northern interior are the forests less affected by humans. Today these virgin-like forests are largely protected, either as nature reserves or by other means.