Masters Thesis

Reburn severity interactions over 30 years in the Klamath Mountains ecoregion, California, USA

Over the past few decades, the frequency and number of large fires has increased in the western United States. The objective of this study was to evaluate the patterns and drivers of reburn severity in the Klamath Mountains ecoregion over a 30 year chronosequence. Research in the Klamath Mountains and elsewhere in California has indicated occurrence of high-severity fire may be related to prior fire severity, time since fire, topography, vegetation structure and type, and average monthly fire weather conditions. Given the forest health concerns related to the paucity of fires in many forests during most of the 20th century, reburn areas are of particular interest for understanding where there may be qualitative shifts in fire severity and the ecological consequences in context of ecosystem resilience and climate changes. There were three important findings from this study: 1) prior and reburn fire areas were dominated by moderate-severity fire, with a tendency towards higher severity in reburn areas; 2) subsequent fires tended to burn at similar severities as prior fires in the same locations, especially at fire intervals of 19 years; and 3) reburn fires tended to be more severe at mid-slope positions and ridge tops, in forests with low canopy cover and smaller diameter trees, in shrub cover types, and under hotter and drier than average fire weather conditions. Better understanding the patterns and factors of reburning will provide managers with information to anticipate effects of reburning over different time intervals.

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