Ponderosa pine ecosystems

Abstract

Ponderosa pine is a wide-ranging conifer occurring throughout the United States, southern Canada, and northern Mexico. Since the 1800s, ponderosa pine forests have fueled the economies of the West. In western North America, ponderosa pine grows predominantly in the moist and dry forests. In the Black Hills of South Dakota and the southern portion of its range, the species primarily occupies ponderosa pine potential vegetation types (PVTs) but, in the northern portion of its range, it grows on Douglas-fir, grand fir and/or white fir and western redcedar PVTs. Within this wide range of biophysical settings it is often associated with complex vegetation mixes. Non-lethal, mixed, and lethal wildfires historically burned through most ponderosa pine forests leaving in their wake a wide variety of species compositions and vegetative structures arranged in a variety of mosaics. Since the 1800s, fire exclusion, animal grazing, timber harvest, and climate cycles have contributed to changing these forests. As a result, succession accelerated, plant compositions shifted, trees and other biomass accumulated, soil chemical and physical properties changed, non-native plants were introduced, and epidemics of insects and diseases are more common. Together these changes altered fire regimes, displaced native species, and disrupted other ecological processes. Although the extent of wildfires that now burn in these altered forests is not noteworthy, their severity is. Canopy treatments and surface fuel treatments in combination are most likely to reduce the risk of severe and intense wildfires in these forests that mean a great deal to individuals and society.