Is there a way to get an email notification that a post you have made in other forums has been responded to?

No, you can only set that up for private message notifications. I would be absolutely swamped with emails if I got one every time someone responded to a thread I am watching or had participated in!
The only way to know if there is a reply to a watched thread is to visit the Home page. All new posts to threads would be at the top of the page.

Sounds like a good idea though.

If you have too many threads that you have commented, all you would have to do is turn off the email notifications. But if you have few or you have few active at any one time, the emails would be very helpful.

I am not sure if there is a feature that can also turn off any and all notifications regarding a specific post? Is there? Like when you are no longer interested in the topic of the post because the persons are discussing something else.

Or.... is there a way for the originator to "close" a post to more comments? ... because the issue has been resolved to their satisfaction and you do not want any more comments?

Just wondering...

Often, people posting for the first time in the Plant ID Forum mark a thread closed after the first wild guess. Or, they ask a question in this forum and the first person who responds doesn't answer correctly but the OP closes it to future comments. If OPs could close a post, they may not come away with the right info.

Its a problem for crowd sourced websites but, bigger problems could be caused by allowing the closing of threads by OPs. It would be best if we just remembered to stay on topic unless the OP joins the weird direction of the conversation.

The Admins can close a thread to future comments at the request of the OP.

I don't believe the OP can close his own threads to future comments, only admin can. In the Plant ID forum he may mark his thread as 'Solved/identified' but it remains open to comments.

To stop getting notifications for thread, go to the top of the thread and on the left side above the first post, click the 'Unwatch'.

Members can propose that threads are locked/closed, but only the admin can actually implement that.

I didn't want to turn off comments. I was wondering about getting email notifications like Houzz does. On there, you can turn it off if you are getting too many.