"He trod a path" This sentence seems to have two different meanings: 1. He walked (through the grass, for example) and his heavy steps shaped a path. 2. He walked along a path. I would like to know if it is possible to add a preposition after "trod" to remove the ambiguity. For example, is it correct to write: "he trod upon a path" or "he trod along a path". Thank you for your advice.
I always recommend looking up to a dictionary when you encounter this kind of "word usage issue".
According to Merriam-Webster,
tread is a transitive verb when you shape a path. Therefore, you should not use a preposition.
Also, when you use "tread" to mean "walk along", it is also a transitive verb. So, you should not use a preposition.
Hope it helps.
Transitive verbs have intransitive uses. That is, even when a verb may take an object, it needn't necessarily have to take one. Thus it is with "tread." The Ngram viewer finds numerous instances of the intransitive use of this verb, and I present one below from Along the Road: A Parabolic Appalachian Journey by J. T. Elder:
Paul's pulse quickened as he considered this possibility. He had sought the career path he had long trod along for one primary reason: security!