I can't say much about the top seedlings, but the bottom one looks like a maple. The red petiole on the leaf makes me think red maple, Acer rubrum. However, I'm not very familiar with the various ornamental maple species that are planted in landscapes, which it could be a seedling of. I'd recommend identifying any tree of seed bearing age around your yard and your neighbors' yards to see what could have dropped seed in the fall.

Thank you treeguy. Those seedlings grow in my flower beds, which i don't intend them to. I just would like to know whether or they are some kinds of trees I can plant them somewhere else. I definitely don't want the kind that is not attractive and invasive or something poison.

By the way, I have read a lot posts. I read many of your replies. You are a very knowledgeble tree guy. Thank you

The ones in the top picture appear to be just getting their true leaves and need a bit more time before you can identify them. When you pulled them out, was there any particular seed or nut remains attached to the roots? For example, oaks often still have their acorn and cherry tree seedlings (which I have a lot of) usually have the small round seed attached.

Maple trees. Ask again later when they are more developed.

Esh, no, there was nothing attached to the roots. And bboy, I will ask later when they grow bigger. I left a few unpulled. Thank you all

Don't know what they are in the first pic, but not maples, as they only have a single true leaf, indicating alternate leaf arrangement. Maples always start with an opposite pair.

There would be a chance with a single seedling that one extra opposite leaf might have been browsed, but for that to happen exactly the same to four seedling seems a bit improbable!

Agree with Red Maple for the second photo.

Resin