Sotherton dates from the 16th century, when parks were landscaped in a very formal style with geometric layouts and ruler-straight avenues of trees being planted. The feeling was of nature kept firmly under control and the wilderness rigorously excluded.

Through the 18th century the fashion changed, and formality was superseded by a much more naturalistic style, of which 'Capability Brown' was the most famous exponent. In the late 18th-early 19th century the work of Repton and others developed this naturalism further. Ideas of the 'Picturesque' were also influential, and the wildness of nature was increasingly appreciated rather than shunned.

I wonder if this sort of dichotomy was part of what JA had in mind. Fanny loves those old trees; her preference is for old established ways and the security of places where nature is kept under control. Henry Crawford has no respect for formality and the established order, and is associated with a potentially dangerous fashion for the wildness of nature.

I may be quite wrong - this is just an idea.