To write about the Dark Ages it was essential I carried out a lot of research into forests - they were the life blood for the Anglo-Saxon folks in England. It was no great hardship.
During the Roman reign of England, from about 43 to 410, forests, like everything else, were managed and structured. Woodland was cleared for agriculture and timber to support the building of settlements and developing industry. After they departed these shores, however, some forest land was reclaimed but nowhere near pre-Roman levels. It is thought that about a quarter of England was covered by woodland, according to the Forestry Commission.
While the Romans built many of their buildings from stone, the Anglo-Saxons preferred wood. The people of the Dark Ages were great carpenters and many of their woodlands were managed for this purpose with specific types of trees grown for their individual purpose. No longer were forests left to the wilderness but were given names and boundaries and therefore given ownership. When William the Conqueror took over in 1066 he declared all forests as belonging to the crown so he and other nobles could go hunting the rich wildlife in peace. The consequences of taking a deer to eat were dire. A nice article from The Guardian explains further. Although these days the words forest and woodland are used interchangeably, traditionally forests had to be big enough to home deer and boar for hunting purposes. Woodlands were more open and smaller. And to the people of the Dark Ages, safer.
Besides the practical aspects forests also served the spiritual and were the subject of fear and folklore. See Gulfyrian, Teon, Crushed and The Dark Garden for more about the types of folklore surrounding trees.
The king of trees and woodlands, the oak, represented strength and endurance. It was the sacred tree of Thunor and the acorns were placed in people's homes to protect against lightning strikes. The Oak is an excellent fuel and the Yule log at the winter solstice was always made from Oak.
The powdered bark was used to treat fever and the crushed leaves treated stings. Being a very strong wood, structural beams were made from Oak.