Final answer:
Oak timbers have a dense structure with varying growth rings that contribute to their bending strength. Douglas fir, while also strong, has different wood grain patterns that affect its strength. Dendroprovenance studies emphasize the importance of wood strength in significant constructions.
Step-by-step explanation:
Wooden structures' strength depends largely on the type of wood used. Oak timbers, for example, have a dense structure with hard fibers, indicated by growth rings that demonstrate periods of slow and fast growth, leading to significant density differences within the timber. In a cross section of red oak (Fig. 9), the production of large diameter vessels in springtime contrasts with the denser, vessel-free wood produced later. These growth patterns contribute to the wood's bending strength.
Douglas fir, although strong with a straight grain, may have a different proportion of earlywood and latewood as shown in the photomicrograph (Figure 11.5). These proportions affect the wood's overall strength. Furthermore, dendroprovenance studies have revealed that historical structures utilizing vast amounts of timber rely on woods with superior strength for durability and load-bearing capacity.