HOLOCENE PATTERN OF FIRES AND FORESTS ACROSS THE BIODIVERSE KLAMATH MOUNTAINS, NORTHERN CALIFORNIA, USA

The Klamath Mountains of northern California support an amazing array of species including thirty-nine conifer species. As a biodiversity hotspot, the influence of past climate change and fire activity is a significant concern for the region. Extensive fires have burned Klamath forests in the last couple decades leaving ecologists, managers and locals speculating if the fires are a common occurrence or something needed to maintain the diversity. However, examining questions related to the historical range of variability has been difficult due to the temporal resolution of historical documents and proxy records from tree rings.

The Klamath’s has a large network of paleoenvironmental records from lake sediments (pollen and macro charcoal) in the western US, many extending back to the last glacial period (~16,000 years ago). A spatial analysis of eleven pollen and charcoal records along a coastal-to-inland precipitation gradient was conducted to examine fire regimes and vegetation patterns in mid-to-high elevation forests during significant periods of climate change during the Holocene. Fire activity was infrequent and more variable at wetter western sites at higher elevations, while it was more frequent and consistent at drier eastern locations at lower elevations. Most sites experienced higher fire activity than today during warm, dry periods (Medieval Climate Anomaly and early Holocene), and fewer fires than today during the Little Ice Age. The wet northwestern forests with closed –canopy fir and Douglas fir burned more severely than more open sites to the southeast. Large, severe burns, while fairly uncommon, did occur in the historical past, especially in the northwestern Klamath’s. The forests that occur in the Klamath’s today are a result of Little Ice Age conditions and are uncharacteristic of the late Holocene; therefore, it is important to examine these longer records when examining questions related to changing fire regimes and forests in the diverse Klamath region.