Redwood/tanoak stand development and response to tanoak mortality caused by Phytophthora ramorum

Abstract

Coast redwood ( Sequoia sempervirens) and tanoak ( Lithocarpus densiflorus) form mixed-evergreen forests along the northern California coast. In the mid-1990s, an introduced pathogen ( Phytophthora ramorum) began causing extensive mortality of tanoak in these forests. This research reconstructed stand development patterns occurring in stands with and without the pathogen, measured stand responses to tanoak mortality, and developed projections of future stand development and structure in the presence of P. ramorum. Redwood forms an upper canopy layer while tanoak forms a multicohort lower canopy, resulting in distinct vertical stratification patterns. Individual redwood tree response patterns to tanoak mortality included crown expansion, increased basal sprouting, and increased basal area growth. Future stand structures will likely have greater proportions of redwood relative to tanoak.