Gymnosperms account for approximately 75 percent of the world’s timber and a large amount of the wood pulp used to make paper. In North America the white spruce, Picea glauca, is the main source of pulp wood used for newsprint and other paper. Other spruce wood is used to manufacture violins and similar string instruments because the wood produces a desired resonance. The Douglas fir, Pseudotsuga menziesii, provides more timber than any other North American tree species and produces some of the most desirable lumber in the world. The wood is strong and relatively free of knots. Uses for the wood include house framing, plywood production, structural beams, pulp wood, railroad ties, boxes, and crates. Since most naturally occurring areas of growth have been harvested, the Douglas fir is being grown in managed forests. The wood from the redwood Sequoia sempervirens is used for furniture, fences, posts, some construction, and has various garden uses.