Prominent scientists, including E.O. Wilson, consider invasive species to be one of the greatest threats to biodiversity, second only to habitat destruction. Over 20 non-native invasive species have been documented in Lassen Volcanic National Park. Invasive seeds make their way into the park on socks, shoelaces, pack animals, fire management equipment, tires, and even pet fur. Keeping Lassen pristine is a continuous challenge that requires a comprehensive understanding of invasive plant biology, threats, and effective treatments.
Priority SpeciesNot all non-native plants impair the natural landscape through aggressive colonization. Lassen prioritizes the treatment of non-native invasive species according to the size of the infestation as well as the species' capacity to displace native vegetation and alter ecosystem functionality. Resource managers also factor in their ability to effectively eradicate or control a particular problem area given limited resources. Lassen's invasive species, listed in order of priority, include:
Mapping Lassen's Top Priority Invasive Plants
Invasives and Fire
Many non-native invasive plants are well adapted to establish and expand their populations after fires. The abundance of some invasives will alter local fire regimes and therefore are among the most influential agents in changing ecosystem structure and function. These species not only compete with native species, but they “alter the fundamental rules of existence for all organisms in the area.” For example, the highly invasive annual cheatgrass (Bromus tectorum) shortens the fire return interval and alters both the intensity and seasonality of fires by producing a dense mat of fine, highly flammable fuels.
Low elevation communities are more vulnerable to invasion than high elevation communities in part due to a much longer history of anthropogenic disturbance at lower elevation. Changes in regional processes also play a role. Elevation along the west slope of the Sierra Nevada/ Southern Cascades is strongly correlated with the distance to nitrogen emissions in the Central Valley resulting in greater total nitrogen deposition at lower elevations. Additionally, as a result of advancing climate change, the physiological correlates of elevation (e.g. solar radiation, mean annual minimum temperature) that were once a barrier to many invasives are beginning to break down. Nitrogen deposition alone has been shown to increase the rate of invasion from annual grasses, annual grass biomass, fuel continuity and hence total fuel loading.
These processes further increase the competitive ability of cheatgrass and its ability to penetrate higher elevation communities previously resistant to invasion. Recently burned areas are even more vulnerable to invasion either from locally established invasive plant populations or by propagules introduced by fire management operations. While disturbances from firebreaks, temporary roads, handlines, and spike camps are usually mitigated immediately after suppression activity, some impacts cannot be readily addressed in post-fire rehabilitation. Invasive plant propagules accidentally introduced with contaminated fire-fighting equipment and personnel (as seen above) require subsequent attention to protect natural and cultural resources.
2012 Reading Fire Specifics
Last updated: January 27, 2018