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Abstract
Fire and Invasive Plants in the Mixed Coniferous Forest
Jon E. Keeley, U.S. Geological Survey, Sequoia-Kings Canyon Field Station, Three Rivers, CA 93271; ph: (559) 565-3170; email: jon_keeley@usgs.gov.
In the coniferous forests of Sequoia and Kings Canyon national parks, species diversity is a function of fire severity and time since fire. High intensity fires create gaps that decrease canopy coverage and increase light levels and nutrients for an ephemeral successional flora. Few species have persistent seed banks so time since fire is an important determinant of colonization success. Complicating the picture of postfire response is the fact that there was a highly significant interaction between fire severity and time since fire for understory cover, species richness and alien richness and cover. Time was consistently a significant factor for these parameters, whereas fire severity was a significant factor only for species richness parameters. In general, understory was sparse the first year after fire, particularly in low severity burns and increased substantially several years after fire, particularly on high severity burns. Both fire severity and time since fire affected alien species richness and dominance. Coniferous forests had about a third as many alien species as the foothill oak savannas and fewer than half of the species were shared between these communities. Some sites were largely free of alien species whereas others had a significant alien presence that presents a challenge for fire restoration of these forests.
