A survey of vegetation and wildland fire hazards on the Nevada Test Site

In the springs of 2004, 2005, and 2006, surveys were conducted on the Nevada Test Site (NTS) to characterize vegetation resources and climatic components of the environment that contribute to wildland fires. The NTS includes both Great Basin Desert and Mojave Desert ecosystems and a transitional zone between these two deserts. The field surveys assessed 211 sites along major NTS corridors for the abundance of native perennial and annual species and invasive weeds. The abundance of fine‑textured (grasses and herbs) and coarse‑textured (woody) biomass was visually estimated on numerical scales ranging from zero to five. Distribution of biomass is shown in Geographic Information System maps by NTS operational area. Precipitation on the NTS from January through April of 2004, 2005, and 2006 was above average. There has been an average of 11 wildland fires per year on the NTS over the past 28 years with an average of about 239 acres (97 hectares) per fire. A map showing the location and description of historic fires is presented. The three most commonly observed invasive annual plants to colonize burned areas are Arabian schizmus (Schizmus arabicus) at low elevations, red brome (Bromus rubens) at lower to middle elevations, and cheatgrass (Bromus tectorum) at middle to higher elevations. Colonization by invasive species increases the likelihood of future wildland fires because they provide abundant fine fuels that are more closely spaced than native vegetation. Blackbrush (Coleogyne rammosissima) vegetation types appear to be the most vulnerable plant communities to fire followed by pinyon juniper/ sagebrush vegetation types. Wildland fires are costly to control and to mitigate once they occur. Recovery of burned areas is very slow without reseeding or transplanting with native species and other rehabilitation efforts. Untreated areas become much more vulnerable to future fires once invasive species, rather than native species, colonize a burned area.