Category: Ecological Research
Title: Chapter 2: The Evolutionary and Historical Context
Author: * Covington, W.W.
Subject: Ecological Restoration, Pre-settlement, Ponderosa pine (Pinus ponderosa)
Abstract: Forests composed of ponderosa pine and closely related species such as Apache pine (Pinus engelmannii), Arizona pine (P. arizonica), and Durango pine (P. durangensis) cover more than 7 million acres (2.8 million hectares) in the Southwest and some 30 million acres (12.1 million hectares) in other western states, Canada, and northern Mexico. Throughout this range, pine ecosystems occur in a belt of varying width that ranges from a high of approximately 9,500 feet (2,900 meters) in the southern portion of its range to a low of 1,000 feet (300 meters) in the northern portion and that typically occurs above woodland, grassland, and chaparral ecosystems and below montane mixed conifer and spruce-fir forests. Most of these forests have changed dramatically in structure and function in the 120 to more than 300 years since the onset of Euro-American settlement. Forests that were characterized by open stands with widely scattered, large pines now support dense thickets of thin doghair pines. Where historical photographs depict an understory of varied grasses and forbs, todays forests often support little herbaceous growth. The secondary changes brought about by these shifts in forest structure have significant implications for ecosystem functioning and for human welfare, and they make up much of the material in this volume. Cumulatively, they make clear the need for ecological restoration of these forests. But we cannot hope to implement restoration responsibly without understanding how the Southwests ponderosa pine forests were shaped. Specifically, we need to understand both the long-term evolutionary environment of these forests-why did they come to occur in the places and forms that they do?-as well as their recent history-what forces have degraded ecosystem structure and function and have thereby caused the ecosystem to depart from its previous evolutionary trajectory?
Source: Ecological Restoration of Southwestern Ponderosa Pine Forests
Publisher: Arizona Board of Regents