Which type of tree fiber is typically shorter and helps make paper smoother?

The correct choice refers to hardwood fibers, which are typically shorter and play a significant role in producing smoother paper products. This is because hardwoods, which come from broadleaf trees, have fibers that are generally more variable in length and provide better fiber-to-fiber bonding when they are processed into pulp. This enhanced bonding is key to creating a smoother surface on the paper, making it ideal for printing and writing applications.

In the context of paper production, the characteristics of fiber length and the nature of bonding significantly influence the quality of the final product. Hardwoods are often preferred for fine papers due to their unique fibrous structure that captures ink better and produces a smoother texture.

Softwood fibers, on the other hand, are typically longer and provide strength, but they can lead to a rougher texture in paper. While specific types of trees like pine and spruce are softwoods, the question focuses on the broader category of hardwoods which is more relevant to the context of achieving smooth paper surfaces.