»Invasive Plants
Vital Signs Included in Protocol
- Distribution & abundance of invasive/non-native plants
Parks Where Protocol Will Be Implemented
- All park units
Justification/Issues Being Addressed
The invasion of non-native and exotic plant species is challenging protection and management of resources in National Parks throughout the United States (Welch 2007a). Colonization and spread of some species of invaders is a direct consequence of disturbance, while other plants are able to colonize into undisturbed communities (Welch 2007b). Roadways and river banks are common conduits for dispersal by invasive non-native plants. Examples in CHDN include salt cedar (Tamarix spp.), giant reed (Arundo donax), bufflegrass (Cenchrus ciliaris), and Lehmann lovegrass (Eragrostis lehmanniana). Ecological and system effects depend on the rate and amount of spread, site characteristics, and the biology of organisms in infected areas (Hupy et al. 2004, Welch 2007b). Although initial establishment of non-native plants species can result in increased bio-diversity, prolonged occupancy by non-native species can disrupt user interactions and communities, and ultimately lead to a less diverse biota. For example, salt cedar has spread rapidly throughout the western US in riparian areas, stock tanks, roadsides, and drainage canals. This species is non-palatible and can prevent native riparian vegetation from establishing and can alter local hydrology of riparian zones. In turn, alteration of riparian zones that result in changes of floristic structure can inhibit use by bird species for breeding, over-wintering, or for migration stops (Fleishman et al. 2003). Some species of invasive non-native plants can become prevalent enough to alter fire regimes (D'Antonio and Vitousek 1992).
Early warning of approaching invasive species or early detection before extensive spread is critical when managing the effects of non-native invasive plants. Restoration once an aggressive non-native species has spread over large areas is often improbable in National Parks due to poor access and limited funds. Monitoring efforts that provide early warning of approaching non-native plant species will help prevent costly restoration and spread of new invasive species into CHDN park units. Monitoring of distribution of existing non-natives can also aid in assessing the success of attempted restoration projects.