I did these scenes in UE 4.27.1 with this first Quixel Megascans Tree Pack. What astounding work from our vegetation colleagues!
I had a lot of fun playing with the Season & Health function.
Nils Arenz explains that nice feature here: https://www.artstation.com/artwork/3dRrXg
You can download the pack from the UNREAL ENGINE MARKETPLACE: https://www.unrealengine.com/marketplace/en-US/product/megascans-trees-european-black-alder-early-access?sessionInvalidated=true
I recommend you to give it a try. You'll be amazed to create exciting landscapes in no time.
To better understand how it works, please visit this tutorial: https://www.youtube.com/watch?v=-QK5gaeEAig