Before winter fades . . . Firewood and food; Splitting Firewood, by David Tresemer. Brattleboro, Vt.: Hand & Foot Ltd. 142 pp. $6.50 (paperback). Warm & Tasty: The Wood Heat Stove Cookbook, by Margaret Byrd Adams. Seattle: Pacific Search Press. $6.95. (paperback).

''Splitting Firewood'' ought to be read in summer, the one season when the wood supply demands little of our attention. In winter we are too busy felling trees. In spring we haul the four-foot lengths out of the woods between mud-time and blackfly season. In autumn we are sawing and stacking dry stove lengths for the coming winter. Perhaps in July, overwhelmed by heat and garden work, it will be refreshing to reread David Tresemer's ''Splitting Firewood.''

Mr. Tresemer has written what amounts to a PhD thesis on firewood. He tells beginners just what makes up a tree, and many old hands, too, will learn from his discussion of woodcutting tools, ancient, traditional and modern. He has taken no old woodsman's tales for granted, but has expended enormous energy, both mental and muscular, to test both tools and theories.

The book contains valuable graphs and charts which will save newcomers to wood heat much fumbling and not a few cold, smoke-filled winter nights. There is also a valuable chapter on ''poise,'' or how best to use our bones and muscles in working wood, important advice for those who haven't a skilled old grandfather to learn from.

A chapter on the mythology and folklore of cutting wood, enhances our enjoyment of this way of keeping warm.

Margaret Byrd Adams has done her readers a small disservice in making cooking on a wood heating stove sound more romantic than it often turns out to be.

Even on one of the new air-tight stoves, wood heat cooking is a very tricky and time-consuming salad of skills, and we advise people with several children or busy schedules to stick with a modern gas range.

That said, she has collected an impressive array of recipes that are well suited to heat-stove cooking. We decided not to risk burning the author's polenta recipe on our old Ashly, but our griddle scones were a great success.

Especially useful is a mail-order shopping guide for wood-stove paraphernalia. ''Warm & Tasty'' ought to come equipped with a husky 12-year-old who enjoys spittling firewood as much as Mr. Tresemer, but it does not.