In my garden, the snow has compressed my leaf-mulch into a flat, wet, mat. So about this time of year, I de-limb the Christmas tree and chop the branches up into tiny pieces. Then I spread them in a thin layer around the base of my acid-loving plants. This mid-winter mulch protects the soil around my blueberries and native evergreen huckleberries.

Then I saw the Christmas tree trunk into 12 inch lengths and pile it up in an inconspicuous corner of the perennial garden. Come next year, this area will provide winter homes for beneficial insects. It also provides slug habitat, but my chickens will take care of those.
Someday it'll be expensive to ship in soil improvements. For that reason, anything you can add to your soil for free is money in the bank. I feel a bit guilty when I carry off my neighbor's fallen leaves every year.