Check at area parks or ask your neighbors who have pines to share their needles. Layer a two-inch covering of pine needles out to the drip line of the tree. The mulch should be at least a half-foot away from the trunk. Next week, when you cut again, spread another one-inch layer. I spread the leaves two or three inches thick, and it's a wonderful mulch that breaks down over the winter months.
Soil amendment is a finer material than mulch and is incorporated into the soil to enrich it.
Mulch is left on top of the soil as a covering or insulation. Some mulches do double duty. Organic compost, redwood soil conditioner, or leaf mold, for instance, become soil amendments when they are tilled into the soil. A sawdust mulch is never worked into the soil, however, because sawdust causes a nitrogen deficiency in the soil. A coarse bark mulch would take three or four years to break down in the soil.