Keeping trails open like that is a never ending battle. Count your blessings it's not all tag alder. I've got places where that stuff reaches 25' sideways 2' off the ground to get into the openings. When I fight that by hand, I learned to cut the segment at the edge of the trail and throw that off, and then go deeper and cut the rest off at the stump. Then It'll be a couple years to make 25' back to the trail where I've got to do it again.
Through rage I discovered a compact track loader and a bucket make a great 'push it back and smash it' implement. You lose some lights and windshield wipers doing work like that, but it's gotta be done. I've spent days sawing down and throwing tag alder segments back into the woods.