Category: Theses and Dissertations
Title: Snags and Partial Snags in Managed, Relict, and Restored Ponderosa Pine Forests of the Southwest
Author: Waskiewicz, J.D.
Subject: Snags, Ponderosa pine (Pinus ponderosa), Management
Abstract: Snags form an important habitat resource in ponderosa pine forests, but are susceptible to destruction in wildfires. Partial snags -live trees bearing dead parts -have been suggested as a more fire-resistant alternative to snags that may have played an important role in pre-settlement forests and may become important following treatments designed to emulate pre-settlement forest structure and function. I studied snags and partial snags in a managed forest receiving restoration treatments at Mt. Trumbull, Arizona to learn how restoration treatments affect the densities, characteristics, and use of snags by wildlife. I studied partial snags at four unmanaged relict sites in Arizona and New Mexico to estimate their quantity, quality, and use in relatively undisturbed forests, and to establish a protocol for their future measurement and description. At Mt. Trumbull, snag loss was five times higher in treated than in control plots Newly recruited snags outnumbered losses in both treatment and control plots, leading to net snag density increases 10 times higher in treatment than control plots. Partial snags were destroyed at the same rate in both treatment and control plots, but were more likely to remain standing than snags in treatment plots. Cavity-bearing snags decreased slightly in both control and treatment plots . Trees bearing evidence of woodpecker foraging increased slightly in control plots and by almost four times in treatment plots. Trees bearing ant colonies increased by half in control plots and decreased slightly in treatment plots. Partial snag densities at relict sites ranged from 2.13 to 3.18 per ha and spiketopped trees were the most common type at all four. The managed site had 1.70 partial snags per ha and lightning scars were the most common type. At relict sites, 19% of partial snags contained excavated cavities, while at the managed site, 42% did. Partial snags with greater-than-median surface area of dead wood, distance to nearest neighboring snag and dbh, and less than median crown-base height were disproportionately selected from partial snags at relict sites. I developed models for estimating dead wood surface areas in spike-topped and in lightning-scarred trees that do not require time-consuming measurements or heavy equipment.
Publisher: NAU School of Forestry, http://www.for.nau.edu