Novel interactions between wildfire and sudden oak death influence sexual and asexual regeneration in coast redwood forests
| Authors: | Allison B. Simler, Margaret R. Metz, Ross K. Meentemeyer, Kerri M. Frangioso, David M. Rizzo |
| Year: | 2017 |
| Type: | General Technical Report |
| Station: | Pacific Southwest Research Station |
| Source: | Proceedings of the sudden oak death sixth science symposium. Gen. Tech. Rep. GTR-PSW-255. Albany, CA: U.S. Department of Agriculture, Forest Service, Pacific Southwest Research Station: 27-28. |
Abstract
Novel interactions between compounded disturbances can leave lasting ecological legacies on communities and alter regeneration trajectories. Sudden oak death (SOD), caused by Phytophthora ramorum, is a biotic disturbance, an emerging disease causing widespread oak and tanoak mortality in California’s coastal forests. In these redwood-tanoak forests, wildfire is a keystone process, shaping stand structure and composition. Dominant tree species can resprout rapidly after being “top-killed” by fire, in addition to regenerating via seed. Yet, in SOD-impacted areas, fuels generated by disease-related tree mortality may alter fire behavior and consequent stand recovery. In this system, tree species differ in resprouting capacity, patterns of seedling regeneration, effectiveness as hosts for P. ramorum, and susceptibility to fire and SOD.
In 2006 and 2007, we established 280 forest plots to monitor the impacts of SOD in the Big Sur region. The 2008 Basin Complex fires burned across infested and disease-free plots in this area, generating an opportunity to investigate impacts of a novel disturbance interaction on forest regeneration. Following the fire, burned and unburned forest plots were repeatedly sampled to assess tree mortality, pathogen presence, microclimate, and regeneration, including resprout and seedling recruitment across a gradient of SOD impacts. We investigated how interactions between fire and disease influence forest regeneration trajectories, and in turn, how regeneration in host tree species impacts post-fire disease dynamics and prevalence of P. ramorum.