Fire and the persistence and decline of montane chaparral in mixed conifer forests in the southern Cascades, Lassen Volcanic National Park, CA

Open Access
Author:
Airey, Catherine T
Graduate Program:
Ecology
Degree:
Master of Science
Document Type:
Master Thesis
Date of Defense:
May 18, 2012
Committee Members:
  • Alan H Taylor, Thesis Advisor
Keywords:
  • forest dynamics
  • mixed conifer forests
  • fire exclusion
  • vegetation heterogeneity
Abstract:
Stands of montane chaparral are an integral component of the mixed conifer forest in the Cascade Mountains of northern California. In this region, chaparral stands found on sites that could support trees are thought to have established following high severity fire. The exclusion of fire for over a century may have allowed trees to invade chaparral. The conversion of chaparral to forest has reduced chaparral in the mixed conifer landscape. This study investigated the timing and spatial dynamics of chaparral and tree establishment in six chaparral stands in Lassen Volcanic National Park, California. Findings include that the oldest chaparral established after a fire event and were older than most trees in the stand. The chaparral were multi-aged, indicating continued resprouting in the absence of fire. Tree density (trees hectare-1) was higher closer to the forest edge than further into the chaparral, suggesting gradual tree invasion from the forest. Pinus jeffreyi were older at the forest edge than further into the chaparral while Abies concolor and Abies magnifica showed no relationship between age and distance from forest edge. Fir density was higher in invaded chaparral than in the surrounding forest. In three recent wildfires in the Park, historically chaparral dominated areas burned with more high severity compared to forest vegetation. Characterization of the dynamics of montane chaparral can contribute to our understanding of the historic importance of high severity fire to forest landscape heterogeneity. This study demonstrates that most trees in the chaparral have established since fire suppression was implemented and that wildfires have the potential to restore tree-invaded chaparral.