As the climate gets warmer and winters less severe, deciduous forest replaces the conifers. Oak, beech, maple and hickory are the main species in America. Soil rich in humus supports many plants and fungi. Survival is not difficult except at very high altitudes where tundra or snow-field conditions appear. Many of these areas have been cleared by man.
Water can be a problem in summer a shelter in winter.
The lands bordering on the Mediterranean are semi-arid areas with long hot summers and short dry winters. There is sunshine most of the year and drying winds. At one time this region was forested with oaks. When these were cut down, the soil erodes, much of the area became covered with evergreen shrub. The Chaparral of California is very similar.