Ponderosas love the sun and hate the shade. In order to compete with trees that are shade-tolerant for sunlight and nutrients, and to assert their dominance in the forest, Ponderosas have evolved to develop thick, fire-resistant bark. In the past, low-intensity fires (caused by various factors like lightning or natural ignition) that occur every five to ten years would kill competing species that shaded out young Ponderosa pines. The frequent burning triggers pitch flows in the base of the Ponderosa, which produces its durable trunk. Ponderosas actually provide their own light fuel (needles and cones) that ensures frequent burning. 

Starting in the late 1800s, these low-intensity fires have been suppressed by management practices such as logging, livestock grazing, and fire suppression and exclusion. Because of this there has been significant ecosystem disturbance in Ponderosa pine forests. Fire suppression has increased the risk of wildfire and insect outbreaks in these forests. Furthermore, young “second-growth” Ponderosas (“old-growth” being the older generation of trees who have experienced the fires) are developing weaker bark and are being crowded in forests by shade-tolerant trees. As a result the Ponderosa pine, once a major source of lumber, is no longer used for wood because the “second-growth” pines create boards that warp and split. Additionally, the snags of “old-growth pines,” because of their thick bark, remain standing for 50-150 years and provide habitat for woodpeckers and other small animals while “second-growth” pines rot and fall within a few years of dying, preventing the development of wildlife habitats. One last effect on the wildlife is the impact on black bears who like to use the Ponderosa’s fire scars for climbing exercises!

The need for the ecological restoration of Ponderosa pine forests is now being recognized and foresters and landowners are trying to recreate historic conditions. Practices such as the reintroduction of low-severity fires and the reduction of stand densities by thinning and burning are being employed. This will reduce the growth of smaller, shade-tolerant trees and strengthen the “second-growth” Ponderosa’s bark.