Hello and welcome,
Does this avenue of trees have a sign with info about it, such as the fact that the reserve has been around since 1750? Natural features typically are hard to get approved, unless there is a sign marking them as such. Many nature preserves have signs, and many use them as a place marker for them, since ML, the AI system, doesn’t really like a lot of plants in photos.
Beig you’re in a rural area, you may want to check out the tips for nominating in rural areas. I nominage in both rural and urban areas, and this list has helped me. Tips for Rural Nominators