Am I waisting my time growing trees?

Hi,
My wife and I bought a piece of land that we are currently developing (slowly) into our little slice of permaculture heaven. The land is fairly far north, zone 4a, Canadian zone, and small, 3 acres. There are mostly balsam fir, maple and poplar trees with beaked hazelnuts and chokecherry bushes in the few breaks of sun. I love trees and I want more of a variety on it so, I planted some white pine seedlings, two four year old Korean pines and some seedlings of those as well, along with pin oaks and black locust. My neighbour says I am probably wasting my time as oak and pine will not likely grow there. I did my research and found that the soil conditions were favourable to those trees. Still, I am wondering if maybe he is right and I am wasting my time and the trees will not do well.
Any thoughts?

I planted in ground several things people told me won't grow here.  Including a supposedly not hardy fig tree.   It's on year four and doing great.  Will it survive a particularly hard winter?  I don't know, but it's age and established status can't hurt.   I figure if I plant 100 things (at good prices) and only 30-40 survive and thrive,  that's a good turn out.   And look what I'll have learned.   Not that I don't "listen" to advice and local wisdom, but it won't stop me from trialing and experimenting.  Especially if I find conflicting information, like you have.   Report back when you see what happens!  

Donald Smith wrote:My neighbour says I am probably wasting my time as oak and pine will not likely grow there. I did my research and found that the soil conditions were favourable to those trees. Still, I am wondering if maybe he is right and I am wasting my time and the trees will not do well.

Pfft, I think your neighbour is a negative nelly naysayer with limited knowledge. I'm in a much harsher climate. I have white pine growing here, and somebody planted an oak tree many years ago that keeps growing (very slowly) as long as I keep the snowshoe hares from chewing off all the new growth. Plant away, I say!

According to pfaf.org all those trees are hardy to zone 4, although only one is hardy to zone 3, so you are at the extreme of their range by the sound of it. All else being equal I don't see why the trees shouldn't survive for you. They may grow a bit slower than a warmer area, I suppose, and an exceptional cold spell could be a problem for a young tree, that an older tree would survive.
Trees are good - I hope all yours do well and you can prove your neighbour wrong.