Seeds Stored Above the Ground

Some lodgepole pines store seeds in cones that remain closed after the seeds mature. This trait is called serotiny. A resinous bond holds the cone scales together, sometimes for many years. When a fire heats the cones, the bond weakens and the scales can open, releasing seeds onto the newly exposed ground. Because fire may also reduce competing vegetation, the released seeds can encounter conditions that favor germination. This strategy does not guarantee successful regeneration. An extremely intense fire may damage seeds before they are released, while a mild fire may not produce enough heat to open many cones. The distance between a burned area and surviving seed sources also matters. Thus, the number of seedlings that appear after a fire depends on the fire's severity as well as the supply and condition of seeds. Not every lodgepole pine bears the same kind of cone. Some trees have cones that open without fire and scatter seeds over time. A forest containing both open and closed cones can therefore retain seeds for a major disturbance while also producing seedlings during years without fire. The mixture provides more than one path to regeneration in an environment where disturbances differ in timing and intensity.