Cutting trees in Blender

Hi folks, I'm starting using Blender and I have a doubt. I created a 3d model landscape from a drone mapping. Now I would like to remove the objects such as trees quickly but I don't find the way. I send you a screenshot where you can see the 3d shapes corresponding to the trees... I want to remove these trees easily to get a flat area. is there any way to do it without pain? Thanks a lot!