Document: ANT-3-68-41

Reconstructing attributes of pre-Euroamerican settlement fire at a watershed scale, Sequoia and Kings Canyon National Parks.

CAPRIO, A.C.*

Sequoia and Kings Canyon National Parks, Three Rivers, CA 93271, USA ¹

Abstract:
Fire history studies utilizing fire scarred material have typically involved sampling one to a few sites in particular locations or vegetation types. However, sampling at such a local scale limits our ability to resolve attributes and variation in pre-Euroamerican settlement fire regimes at a landscape scale. 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 about three times longer than on south aspects (31.8 yr and 9.1 yr respectively). In contrast, at higher elevations differences did not appear to be as significant. Additionally, the network of sites allowed GIS techniques to be used to create maps from which coarse annual estimates of area burned were determined. The maps showed considerable annual variability and indicated that in most years area burned was small (<300 ha) although uncommon years occurred when large fires burned through much of the conifer forest in the drainage. Reconstructed burn area size was also related to aspect and elevation with frequent small fires occurring on lower south aspects while less frequent but larger fires occurred across all aspects but dominated north and upper elevation south aspects. Average area burned annually was greatest on low elevation south aspects (320 ha or 11.5% of the area) and lowest on upper elevation north aspects (37 ha or 1.2% of the area). Larger fires on all aspects appeared 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.

Keywords: fire history, landscape, aspect, elevation, GIS

This abstract is being presented at: 1:00 PM in session:
Oral Session #35: Fire Ecology.