A forest can quickly reclaim its own after a disturbance. A decade ago, much of Mt. Lemmon was burned in a fire that destroyed nearly all the understorey and much of the canopy. Today, the scar of the fire remains, but evidence of regrowth is easy to find. Here you can see the broken remains of many pines, but also a riot of new growth – the forest floor is full of new seedlings: Ponderosa pines, box elders, aspens, elderberries, and Gambel oaks. Competition for resources is strong, and nearly all of these seedlings will die before reaching maturity. The process of succession is not always orderly, and the forest may not ever return to its earlier pine-dominated state. Changing climate conditions may select for a new assemblage of species with properties not seen before.

Regrowth is slower in more exposed, south-facing slopes. The dryness of these sites means dehydration or overheating (when water is not available for evapotranspiration-based cooling) can easily lead to plant death. Nevertheless you can still see the beginnings of a new forest coming in.

In some areas, large pine trees survived the fire intact, thanks to favorable locations in deep ravines where fire did not reach. Many trees have burn scars around their base but their large size and thick bark enabled them to avoid more permanent harm. These large trees play a key role in forest regrowth, because they contribute disproportionately to the seed bank and thus the identities of new seedlings.

Regrowth begins to erase human artifacts too. We found the wreckage of a jet engine, remains of a fighter that crashed in the mountains last century. The metal body is crumpled and rusting, and is beginning to be buried by a steady rain of pine needles and leaves.

It is also tent caterpillar season – dozens were walking on the frame and conduits of the wreck. Strange that this artifact, appearing suddenly from out of the sky, should become habitat for so diminutive a creature for a few years!