How is the berries of a mountain ash, the helicopter seeds of maples and linden trees, the parachute seeds of the cottonwood tree, and the acorn seed of the oak tree each the tree in its habitat?

Well you see each of the seeds have developed a special technique that allows their individual seeds to travel further and lower the probability of landing close to the tree and not getting the sunlight it needs

For the berries birds and various animals eat them carrying them away so hopefully they can get more sunlight

Helicopter seeds do the same thing except the sides themselves float away from the tree to get  a further distance.

Finally the acorn seeds of the oak tree use the same concept of the berries. Various squirrels do eat these kinds of nuts and bury them in the ground in hopes of finding them later. But due to squirrels not remembering where they buried their acorn seeds the acorns are well away from the tree and start growing. 

So you see all of these tree seeds are specially developed to help it get away from the trees. Especially so that they can grow in a much better environment than the one provided to them initially.