Best way to go about planting under trees
Hello! I have a slightly sloped north facing front yard with two 40 year old trees- one birch and one choke cherry in it. In my ideal world, I would convert the whole yard into a wildlife oasis through creating lasagna beds and planting mostly native species underneath the canopy. However I'm concerned about a few things, one is suffocating the roots. Would covering my yard in cardboard and layers of organic material do this? Another is I've heard that the trees will just absorb most of the water and nutrients from said lasagna beds after they break down into rich soil. Any thoughts on this?
I'm in Anchorage, Alaska and was wanting to fill the understory with plants that we see commonly growing in birch forests such as fireweed, wild geraniums, ferns, rose, lupin, yarrow, etc. Of course I don't want to hurt the trees, but I also want to convert the lawn haha. Not sure how to go about this in the best way!