Category: Theses and Dissertations
Title: Comparing Methods of Reconstructing Fire History Using Fire Scars in a Southwestern Ponderosa Pine Forest
Author: * Van Horne, M.L.
Subject: Fire history, Fire scars, Ponderosa pine (Pinus ponderosa)
Abstract: Fire scars have been used extensively to understand the historical role of fire in ponderosa pine (Pinus ponderosa Dougl. ex Laws.) ecosystems. However, the sampling methods and interpretation of fire scar data have been criticized as statistically invalid, biased, and leading to exaggerated estimates of fire frequency. We tested alternative sampling schemes by comparing targeted sampling, random sampling, and grid-based sampling to a complete census of all 1,479 fire-scarred trees in a one square kilometer study site in northern Arizona. The effects of sample size and area sampled on fire frequency estimates were also tested. Given a sufficient sample size, we concluded that all tested sampling methods result in reliable estimates of the true fire frequency, with mean fire intervals very similar to the census. We also investigated the usefulness of three techniques developed to compensate for spatial uncertainties: 1) fire intervals from individual trees, 2) the interval between the tree origin and the first scar, and 3) filtering, a technique used to classify large fires. The seasonality distributions of the census and targeted sample were also compared. Quantification of the differences in sampling approaches cannot resolve all the limitations of fire scar methods, since scarred trees are inherently point-sources of data. But measurement of sampling uncertainty did reduce the scope of uncertainty in interpretation of fire regime statistics.
Source: Masters Thesis
Publisher: NAU School of Forestry, http://www.for.nau.edu