When I mowed our yard with the BIG tractor, I would notice marks in some spots where I turned, or had to use 4 wheel drive (I mowed in 2 wheel drive mostly). The tractor is heavier, so it has to compact more than the B series, but I've only used the L3010, so it's hard to compare. I still bush hog by the small sapplings and they are growing okay. I really can't say for sure whether or not I'm impacting them with the weight of the tractor. Actually, I never thought about it before. To me, the weight is such a huge advantage on my hills that I couldn't really consider going lighter. I do have my tires loaded, that alone adds 1300 pounds. But, I only bush hog the area two or three times a year. I have noticed the big tree farms around here have bigger tractors than mine.
Sorry I can't be of more help for your compaction question.
Moon of Ohio