That could be any type of saddle. I ride a dressage saddle for trails - or a close contact depending on the horse, whereas of of my best friends will ride in either a syd hill borey poley or a roping saddle.
What type of saddle for trails are you looking for?
I agree with the previous suggestions. One question is what discipline you want to ride? A fork tree western saddles and gaited saddles are designed to have extra clearance in the front. Australian saddles can be a cross between western and english saddles and be very comfortable for trail riding.
Another option would be to look for a pad that will also take pressure off your horse's withers such as a cut out and built up pad.
Aussi, english, western, saddles all come with different trees. Any one that says an aussi is good for a high withered horse while a western isnt doesnt have a clue. I have an Aussi saddle made for a QH and one made for a TWH, Western saddles are the same way. You can get them for any type horse.