The interaction of disturbance and climate change is expected to play a critical role in the dynamics of plant community change in coming decades. Canopy disturbance and mortality resulting from drought and wildfire create windows of opportunity for establishment and community turnover. In addition, species' ability to survive or recover following disturbance may be associated with climate tolerances, so direct effects of disturbance on community composition could make communities more or less resilient to future climate change. The Tubbs Fire (Oct, 2017; Sonoma Co., California), burned large areas of oak woodlands and mixed hardwood forests, with a range of low to very high severity. In 2018 a complete demographic resurvey of a pre-existing set of forest plots was conducted in order to gain deeper insight into the post-fire recovery strategies of each woody species present. The plot network, established in 2013, is located at the Pepperwood Preserve in NE Santa Rosa, Ca (38.57_N, _122.68_W), and consists of fifty four 20 x 20m plots which are stratified across the varying topographic gradients present on the preserve and evenly represented by evergreen and deciduous oak woodland sites (Oldfather 2016). Over thirty woody plant species are represented in the network, including ten species of Quercus. All trees (dbh >1cm) and all saplings (> 50cm tall and <1cm dbh) were tagged and measured, and all seedlings (<10cm) and juveniles 11-50cm) were tallied by species, both pre and post fire.
Results/Conclusions
We quantified fire severity across different vegetation types, and post-fire mortality and regeneration of tree species in all plots. The fire burned 14,895 ha, with >25% in both medium and high severity. Chaparral and knobcone pine stands mostly burned at high severity, while other vegetation types experienced a fairly even distribution of fire severity. The fire killed 50% of saplings (dbh <1cm) and 27% of trees (dbh ≥1cm), with higher mortality in high severity patches. Coast live oak, black oak, madrone, and California bay exhibited very high levels of topkill combined with basal resprouting. Douglas-fir, which lacks resprouting ability, exhibited high mortality, especially in saplings at high severity. The results provide a baseline to examine potential vegetation change due to high-severity fire, especially in high-severity stands of Douglas-fir. The surveys also provide critical baseline data for long-term studies of forest recovery and help to advance basic knowledge about the impacts of wildfire on mixed hardwood forests of coastal California.