Why do aspens grow so close together?

So Nathan and I decided to make it an early day and ski up and down the highest point in Colorado. I said all along that the hardest part of the 12 mile round trip would be the first couple miles, and they were. 4 miles in, due to injury, painfully slow progress, numerous navigating errors and overall poor route finding as there was no established trail in the snow, we had to give it up, but the hardest part was yet to come. We had to try and "ski" down through an aspen grove that was literally the size of a town with trees never further then 2 feet apart - most of the time it was impossible to pass through our intended route. Once surpassing this seemingly insurmountable obstacle (2 hours to go 1/2 mile) we then had to contend with waist deep snow (with our skis on) in the flats, oppressing heat, and thin ice covering the 100 feet of pond we had to cross (again, due to a route finding error) we finally regained the established trail and the easy ski out to the car 2 more miles away. It was a long, slow, mentally painful day. But on the other hand, it was a beautiful day, and we were lucky to be in a place so beautiful, although we might not have realized it at the time...

Enjoy.