Reconstructing Attributes of Pre-Euroamerican Settlement Fire - Abstract

Smoke curls up from a prescribed burn in a sequoia grove.
Smoke curls up from a prescribed burn in a sequoia grove.

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Fire history studies utilizing fire scarred material have typically involved sampling one to a few sites in particular locations or vegetation types. As a result reconstructions of pre-Euroamerican settlement fire regimes fail to capture variation at a landscape level due to influences such as topography and variable vegetation patterns. The objective of this study was to reconstruct attributes of past fires regimes at a large scale by collecting a network of sites from throughout the conifer belt of a 24,591 ha watershed in the southern Sierra Nevada. The network of sites, located across aspects, vegetation types and elevations, permitted a spatial and temporal reconstruction of the drainage's fire history for the period from 1700 to 1920 when written fire records begin. Analysis showed strong differences between north and south aspects, particularly at low-to-mid elevations <2286 m, with fire return intervals on north aspects averaging approximately three times longer than on south aspects (31.8 yr and 9.1 yr respectively). At higher elevations differences do not appear to be as significant. Additionally, the network of sites allowed GIS techniques to be used to create course burn maps with estimates of area burned annually determined. These showed considerable annual variability and indicate most burns were small (<300 ha) but that in some years burns extended through much of the conifer forest in the drainage (burning at least 4,300 ha). Area burned was also related to aspect and elevation with small burns generally located on lower south aspects while less frequent but larger burns were reconstructed across all aspects but dominated north and upper elevation south aspects. Average area burned annually was greatest on low elevation south aspects (320 ha) and lowest on upper elevation north aspects (37 ha). Larger burns on all aspects appear to be closely linked to annual climatic conditions. Within this complex landscape the characteristics of pre-Euroamerican fire undoubtedly had significant influences on ecosystem dynamics that varied spatially and temporally.

Last updated: March 1, 2015

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