The Ecological Effects of Fire on Stand Structure and Fuel Dynamics in Red Fir Forests of Mineral King, Sequoia National Park, California

MASTERS THESIS: Fire is an infrequent but vital factor in red fir forests. In order to study the structure and fire history of red fir forests, 3 large permanent plots were established in the Mineral King area of Sequoia National Park, California. All trees greater than 10 cm in height were mapped. Species, height, crown area, diameter at breast height, and crown class were recorded for each tree. Increment cores were obtained from 402 trees and fire scar sections were taken from 16 trees. Fuels were intensively sampled using the planer intersect method. Correction factors for the planer intersect method were developed that significantly improved the accuracy of measurement for ground fuel weights in the red fir forests. There is little evidence for secondary plant succession in red fir forests following disturbance because species composition is dominated by red fir at every growth stage. A pictorial model of red fir forest regeneration is presented. Stand regeneration takes place in relatively small openings created by fires or other disturbance factors. The quantity and composition of fuel in these openings is significantly different from that of mature forests. Red fir age structure is dominated by 1 to several age classes arranged in a complex mosaic of overlapping tree groups. Small-scale patterns average 10m across, and the large-scale patterns average approximately 30m in width. There is no evidence for progressive changes over time in the size of the age groups. Fire scar analysis of the study area showed that fires have been infrequent. Most fires may have been ignited by lightning during the relatively infrequent summer cyclonic storms. Indian burning was probably not a major factor affecting red fir forests. Historical fire behavior varied greatly due to differing weather conditions, stand structure, and fuel weight, and distribution. Evidence does not conclusively support the idea that the fire-free interval has been altered in this century. No fires have occurred in the study area since 1886, and this is in part due to fire suppression actions.