 Yosemite National Park has documented more than 130 non @-@ native plant species within park boundaries . These non @-@ native plants were introduced into Yosemite following the migration of early Euro @-@ American settlers in the late 1850s . Natural and human @-@ caused disturbances , such as wildland fires and construction activities , have contributed to a rapid increase in the spread of non @-@ native plants . A number of these species aggressively invade and displace the native plant communities , resulting in impacts on the park 's resources . Non @-@ native plants can bring about significant changes in park ecosystems by altering the native plant communities and the processes that support them . Some non @-@ native species may cause an increase in the fire frequency of an area or increase the available nitrogen in the soil that may allow more non @-@ native plants to become established . Many non @-@ native species , such as yellow star thistle ( Centaurea solstitialis ) , are able to produce a long tap root that allows them to out @-@ compete the native plants for available water . 
