Shredded conifers are not toxic, feel free to use them. Much of what is written about conifers (especially pines) toxicity is urban myths and old wives tales. I compost mine first. Dry half-dead christmas trees will probably compost best with a little extra green material. Pine "straw" (dead needles) can make a very effective mulch and weeds will have a hard time growing on it, but that isn't because they are toxic.

Coniferous woods don't support much plant life at ground level because it is dark and dry all year round, and also because there is a constant rain of needles which bury small plants and form an extremely free-draining surface layer with almost no nutrients. Even deciduous woods can be pretty dead in late summer but usually support a good population of spring ephemerals in spring when there is good light and water.

More than half of the country of Sweden is coniferous forests, consisting mostly of Norway spruce and, in drier areas, pines which I believe are called Scots pine in Britain. This may be a poor environment but it is not barren. The ground is covered with bilberries, considered the most common species of all in Sweden and Scandinavia in general. In spring one doesn't notice them for all the windflowers and hepaticas that carpet the ground.

Thankyou.
I am reassured and off to spread the shreddings. I may even volunteer to take my neighbours xmas trees off their hands.

Yay for Bilberries! Nobody in America ever seems to have heard of them but they thrive in the peaty uplands of northern England. Strangely enough they grow out in the open and I've not seen them in wooded areas, but then most coniferous woodland in northern England is dense monoculture timber forestry and it really is pretty dead under there.

"pines which I believe are called Scots pine in Britain"

Correct!

"Yay for Bilberries! Nobody in America ever seems to have heard of them"

Bilberry (Vaccinium myrtillus) does not occur in the Americas. But it is fairly similar to blueberries (same genus).

"Strangely enough they grow out in the open and I've not seen them in wooded areas"

That's because most of the woodland has been destroyed by centuries of cutting and overgrazing. I've often seen Bilberry growing in remnant woodlands (and also anywhere in conifer plantations where some light does reach the ground, such as where a tree has blown down).

Most of the native Scots Pine forests in Scotland have a very dense ground cover of Bilberry up to a metre high.

Resin