Well, a few reasons for tilling.
1) the field had "tire ruts" in it (you can sort of see them going from left, to right (and slightly up) that mound in the background is our drainfield, so there are ruts from a big truck. They are old, but the ground is so dense (peat) that it doesn't relax. Tilling it was easier than "filling" it
2) the strawberry paint is in training. He is 4. I'm not worried of coming off, but I wanted a well worked surface anyway.
3) I used to board at a barn where the owners did barrels & other games (at very high levels) and they ripped their arena often, so i'm used to working in fluffy ground.
4) I've noticed that the fluffy ground works really well for muscle tone. They have to work harder & pick up their feet more. Haskell is lazy by nature, and will drag himself all over the place if allowed to (he's the reason I own a pair of spurs!)
Now my work space is level, fluffy, and free of food. We plan to add sand to build it up & aid in the drainage of it, but that won't be happening this year. It will be over time, and worked in.
You can see that there are trees in the picture. They are small, but will get very large. I'm not worried about them. If you build a quality fence, you would have to have some huge branches come down on it to destroy it. Generally a wood rail (build right) will hold up way better to a tree fall than poly wire or even high tension wire. The only thing I slightly worry about is that our baby trees will grow into the fence. But I think they'll be fine.