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Non-native plant presence and prevalence in Illinois: The Critical Trends Assessment Program.
Ellis, James1, Carroll, Connie1, Spyreas, Greg1, Molano-Flores, Brenda1, 1
ABSTRACT- The Critical Trends Assessment Program (CTAP) is a long-term endeavor to monitor the condition of forests, wetlands, and grasslands across Illinois. A total of 450 sites representing these three systems (150 of each) have been randomly selected from across the state. Monitoring has been established in 103 forest, 108 wetland, and 98 grassland sites to-date. In each site data on herbaceous and woody vegetation have been collected to measure species richness, diversity, and dominance; coverage of native, non-native, threatened and endangered species; and FQI (Floristic Quality Index). These sites (30 per year per habitat) will be revisited every five years to assess changes. Preliminary results show that forest sites have the highest species richness and FQI compared to wetland and grassland sites, and non-native species are the least dominant in forest sites and most dominant in grassland sites. Non-native species are more abundant in northern Illinois sites compared to central and southern Illinois. Across all sites, as non-natives become more dominant total site diversity declines. Of the 309 sites monitored, only two threatened or endangered species have been found. Overall CTAP data show that non-native species are present in every system, are sometimes specific to a system, and may be distributed unequally within vegetation strata and regions of the state. The long-term monitoring being undertaken by CTAP will help determine the full impact of non-native plant species in Illinois.
KEY WORDS: non-native, invasive, Illinois, monitoring