Trees in deciduous forests

have needlelike leaves

shed their leaves during one season

grow in a warm mediterranean climate

grow in a climate that is cold year-round

Trees in "deciduous forests" shed their leaves during 'one season'.

Explanation:

After the major climate change that occurred around 12000 years ago, the trees in the deciduous forests gradually adapted to the cycle that caused four major seasons in the "temperate regions" of the world. These regions are characterized by "both cold and warm weathers" depending on what period of the year it is. The deciduous trees shed their leaves in winters for there is no photosynthesis taking place during the winter. These trees grow new leaves in the spring season.

Nation of conflicting ethnic groups