Let's say I am talking to a friend of mine:
I had a walk in the forest yesterday. (the?) Trees had scratch marks on them. They must have been left by bears.
Note that both the speaker and listener had NOT discussed or mentioned any trees or scratch marks prior to this conversation.
Despite "trees" being quite definite, (i.e. it is rather obvious to the listener that I'm talking about the trees growing in the forest that I went to yesterday) I believe that the zero article is, however, a better choice here with the definite article still being acceptable, though.
Zero article would be mean something like: "some trees I was passing by had marks on them"
while "the" would be closer in meaning to "the whole group of trees I saw in the forest mostly had marks on them"
Are my assumptions correct? If not, please kindly provide your opinions and the reasoning behind it. NB: I would really appreciate some in-depth answers.