Aren't some articles missing in the following sentence?
... when traditional pattern of landscape became established.
Or is it something else that is wrong with this sentence?
When you write "the traditional patterns", you're referring to specific patterns. There was no article in that case because the author meant traditional patterns in general. But I think I would have written "traditional patterns" (plural) instead of "traditional pattern".
Compare the following:
(I like cats in general.)