Wildfire Effects On A Ponderosa Pine Ecosystem

A wildfire of variable severity swept through 717 acres (290 ha) of ponderosa pine forest in north-central Arizona in May 1972. Where the fire was intense it killed 90% of the small trees and 50% of the sawtimber, burned 2.6 in (6.5 cm) of forest floor to the mineral soil, and induced a water-repellent layer in the sandier soils. The reduced infiltration rates, which greatly increased water yield from severely burned areas during unusually heavy fall rains, caused soils to erode and removed some nutrients which had been mineralized by the fire. Water yields have declined each year toward prefire levels.

Excerpt from Wildfire Effects on a Ponderosa Pine Ecosystem: An Arizona Case Study The effects of a wildfire which burned in a north-central Arizona ponderosa pine forest in May 1972 were evaluated on watersheds with three burn conditions: unburned, moderately burned, and severely burned. Approximately 50% of the pulpwood-size trees and 7% of the sawtimber were killed on the moderately burned watershed. On the severely burned watershed, 90% of the pulpwood and 50% of the sawtimber trees were killed. N 0 natural tree regeneration is evident after 4 yr. About the Publisher Forgotten Books publishes hundreds of thousands of rare and classic books. Find more at www.forgottenbooks.com This book is a reproduction of an important historical work. Forgotten Books uses state-of-the-art technology to digitally reconstruct the work, preserving the original format whilst repairing imperfections present in the aged copy. In rare cases, an imperfection in the original, such as a blemish or missing page, may be replicated in our edition. We do, however, repair the vast majority of imperfections successfully; any imperfections that remain are intentionally left to preserve the state of such historical works.

The Rodeo-Chediski Wildfire--the largest in Arizona's history--damaged or destroyed ecosystem resources and disrupted ecosystem functioning in a largely mosaic pattern throughout the ponderosa pine (Pinus ponderosa) forests exposed to the burn. Impacts of this wildfire on tree overstories were studied for 5 years (2002 to 2007) on two watersheds in the area burned. One watershed was burned by a high severity (stand-replacing) fire, while the other watershed was burned by a low severity (stand-modifying) fire. In this paper, we focus on the effects of the wildfire on stand structures, post-fire mortality of fire-damaged trees, and stocking of tree reproduction. We also present a fire severity classification system based on the fire-damaged tree crowns and a retrospective description of fire behavior on the two burned watersheds.

This synthesis provides an ecological foundation for management of the diverse ecosystems and fire regimes of North America, based on scientific principles of fire interactions with vegetation, fuels, and biophysical processes. Although a large amount of scientific data on fire exists, most of those data have been collected at small spatial and temporal scales. Thus, it is challenging to develop consistent science-based plans for large spatial and temporal scales where most fire management and planning occur. Understanding the regional geographic context of fire regimes is critical for developing appropriate and sustainable management strategies and policy. The degree to which human intervention has modified fire frequency, intensity, and severity varies greatly among different ecosystems, and must be considered when planning to alter fuel loads or implement restorative treatments. Detailed discussion of six ecosystems--ponderosa pine forest (western North America), chaparral (California), boreal forest (Alaska and Canada), Great Basin sagebrush (intermountain West), pine and pine-hardwood forests (Southern Appalachian Mountains), and longleaf pine (Southeastern United States)--illustrates the complexity of fire regimes and that fire management requires a clear regional focus that recognizes where conflicts might exist between fire hazard reduction and resource needs. In some systems, such as ponderosa pine, treatments are usually compatible with both fuel reduction and resource needs, whereas in others, such as chaparral, the potential exists for conflicts that need to be closely evaluated. Managing fire regimes in a changing climate and social environment requires a strong scientific basis for developing fire management and policy. --