| Popis: |
Following decades of fire suppression, fire is slowly being reintroduced into the North Cascades National Park (NOCA) through prescription burning and wildland fire use in the attempt to restore native fire adapted ecosystem. The presence of cheatgrass (Bromus tectorum), a fire-adapted invasive grass, has been documented in NOCA within the past few decades. Although other studies have shown that fire increases the extent of cheatgrass, little work has been done to document its response after fire in NOCA. A field survey in 2006 documented the location of cheatgrass patches, as well as size and percent cover of each patch. Late in the season, a wildfire burned a portion of the study area, providing the opportunity to analyze the effects of fire on cheatgrass patches. In 2008, the burned area and an unburned control were revisited and the patches from the 2006 survey were again measured for size and percent cover. Analysis of field data indicates two years post-fire, Bromus tectorum has expanded its range more in burned areas than unburned areas. Although mean patch size increased in both the burned and unburned areas, mean patch size nearly doubled between 2006 and 2008 in the burn. Results suggest that very low, low and moderate severity fire encourages cheatgrass expansion more than high and very high severity fire. Additionally, this research found that when combined with fire, certain landscape characteristics such as southwest aspects, slopes of 24-43 degrees, low canopy cover, and elevations between 625-667 meters, are more conducive to increases in cheatgrass patch size. The effects of fire on cheatgrass in NOCA must be better understood prior to prescription burning so further expansion does not offset ecological benefits of fire. This thesis provides information about the effects of fire on established cheatgrass patches, and increases the ability of managers to mitigate for these effects following prescription burning. |
