haven't you ever heard of the mapple/pine trees ?
when they grow so close together they eventualy join,
it's common for two trees of the same species to ( join) in that fashon , altho the diffrent ssp of trees can do it aswell , my addvice is just to go down to a garden center Bonni and ask the Gardener in charge for some addvice you are in a diffrent part of the county than alot of other people alaska right ?
i know when i lived in Washington we had two Ceder trees that did that they werre over a century old tho , so that does play a part .
and like trees get all of the water from the roots through the bark to the branches if you cut down a tree and see " rings " those rings are dead cambrium layers , think of it like your makeing a rose bush graft , you have to peirce the cambrium just enough not to the center were you have "wood that is dead" but to that liveing layer of live bark that supplys the nutrients to the bud that will be come the grafted fineshed product.
pine trees swell removeing old bark , reveiling new young bark every year.