Does invasion by Eupatorium adenophorum increase forest fire severity?
Eupatorium adenophorum (Ageratina adenophora: Asteraceae) is a widespread invasive alien species in China which was first introduced in 1940. In the Sichuan Province, A. adenophora can increase understory plant density from 3 to 8 stems per m2 in a single year. An established invasion can result in 85 – 90 % cover which reduces native plant occurrence. The structural change in the understory as a result of the invasion can have significant impacts on the intensity and duration of fires (due to natural events) in the region. In the current study, five forest sites were selected where each differed in the dominant plant species. In each site, invaded and uninvaded plots were selected and the number of species, percentage cover of each species and height was recorded. Litter was harvested from 5, 1 x 1 m quadrats in each plot at each site and wet and dry biomass was recorded along with heat content values and ignition points. Using computer models to simulate fire intensity, the fuel chemistry (moisture, ash, heat value and ignition point) and fire severity (flame length and fire intensity) was compared under three burning scenarios (low, moderate and extreme) for invaded and uninvaded plots at each site. At each site, fire severity and fuel loads were forecast to be significantly higher in invaded plots compared to uninvaded plots indicating the presence of A. adenophora may increase fire surface severity through increased fuel loads while reducing the moisture, ash and ignition point of understory herbaceous species.
Sources
Wang S, Niu S (2016) Do biological invasions by Eupatorium adenophorum increase forest fire severity? Biological Invasions 18, 717-729.