Tree grafting, rootstock possibilities

I have just gotten into gardening and permaculture. There are several very large old trees on or near my property a lot of cypress trees in the slew and a pine tree in the front yard. I am trying to incorporate fruit trees into my landscape, but space is limited and the existing trees are on the south side of my house (great for Air Conditioning bill, but shades a good deal of yard as well). Right now I have 2 apple trees (granny smith and pink lady) in the shade and a cherry tree in pretty much full sun (I think Bing is the cultivar).

I have been reading up on grafting as a way to maximize the available space that I have. What are the requirements for something to be a "rootstock"? Does the tree need to be cut down or topped and then the scion grafted to the area that has been topped? Does the rootstock need to be from another fruit tree or will any tree work? For example, is there some way to graft a scion to the existing pine or cypress trees? Could scions from apple trees be grafted onto the cherry tree?

I would appreciate any feedback related to grafting, or home fruit trees in general.

Any number of books or other sources can help you out. Basically the trees need to be close relatives....usually the same species or closely related species. So, different varieties of apples can be grafted onto each other, onto seedlings, and onto many crabapples. Many of the stone fruits (plums, peaches, apricots, etc.) can graft onto each other and several of their wild relatives. But you can't graft apple onto peach, and even apple onto pear or vice versa doesn't usually work. Sometimes a graft will work one way with one as the rootstock, but not the other way, with the other one as the stock.... Some families are a little more promiscuous...like the nightshades....just about any of them will graft onto any other and survive. But whether a graft survives long enough to fruit is another question. With most common fruits, there are lists of recommended compatible rootstocks, some of them adapted to various soils and resistant to different problems, and some capable of influencing the size and hardiness of the top part of the tree.....
Grafting and budding themselves take a bit of skill....a workshop or demonstration might be the best way to start, and if you have some existing trees around the place to play with, that's a good way to practice....I'm still sort of a beginner at it, so I usually graft profligately when I can....i.e. graft ten trees and only count on one or two to grow....

Welcome to permies Will
Pruning the big trees to increase light isn't an option? It's certainly an expensive, complicated business!
Alder's got the grafting thing covered; and I very much agree with grafting much more than you expect to 'take'.
I've got a couple of random thoughts...
Most plants really struggle to fruit in shade, but some actually prefer it or at least cope.
Maybe check if mountain pawpaw will grow in your climate.
I've seen lemons fruit in dappled shade.
And not graft-y or tree-y, but many berries prefer light shade.
Some apple varieties do much better than others in low light, so I recommend doing plenty of research before getting scions.

Cutting the trees back are an option, I suppose; but I would prefer to alter the existing vegetation as little as possible (except the grass). All three fruit trees were put in this year (with 3 cultivars of blueberry and 2 navajo blackberry bushes, plus wild blackberry brambles I found in the same are after planting). The apple trees growing fast, but the cherry tree hasn't grown much at all, and the leaves are yellowing and wilting. The apples were from a local nursery, but the cherry was from Walmart. Any advice for the cherry tree? Any ideas for rejuvenating it?

Not sure how much effect this has, but there is a streetlight in close proximity to the cherry tree; so it never gets a dark period.

Alder Burns wrote:.... Some families are a little more promiscuous...like the nightshades....just about any of them will graft onto any other and survive. But whether a graft survives long enough to fruit is another question. ....

How far is this true? The April Fools possibilities are fabulous! This year we got our students (at 11,500 high in the Himalayas) to go out and dig to plant coconut "seeds" before dawn because everybody knows they won't grow if the sun hits them. My mind is boggling at the potato-tomato possibilities for next year!