Enhanced fire-related traits may contribute to the invasiveness of Downy Brome (Bromus tectorum)

Authors: FENISI, ANNAMARIA - University Of Agricultural Sciences And Veterinary Medicine - Romania; SAURA-MAS, SANDRA - Autonomous University Of Barcelona; Blank, Robert - Bob; KOZMA, ANITA - University Of Agricultural Sciences And Veterinary Medicine - Romania; LOZER, BEATA-MAGDOLNA - University Of Agricultural Sciences And Veterinary Medicine - Romania; ESZTER, RUPRECHT - University Of Agricultural Sciences And Veterinary Medicine - Romania

Submitted to: Invasive Plant Science and Management
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/2/2016
Publication Date: 9/1/2016
Citation: Fenisi, A., Saura-Mas, S., Blank, R.R., Kozma, A., Lozer, B., Eszter, R. 2016. Enhanced fire-related traits may contribute to the invasiveness of Downy Brome (Bromus tectorum). Invasive Plant Science and Management. 9(3):182-194.

Interpretive Summary: We hypothesized that traits related to enhanced flammability of the invasive annual grass cheatgrass might be under selection. A series of experiments was undertaken on six populations of B. tectorum collected from frequently burned areas (Great Basin of North America) and rarely burned areas (Central-Europe). Frequently burnt populations had enhanced flammability in almost all measured parameters. Moreover, we found significantly increased seedlings biomass after four weeks of growth under post-fire conditions in those populations, which originated from the most frequently burnt populations. In summary, enhanced flammability might promote frequent and low intensity fires, which might help this invasive grass species to gain and then sustain dominance.

Technical Abstract: Although several invasive species have induced changes to the fire regime of invaded ecosystems, potential intraspecific shifts in fire-related traits that might enhance their invasion success, have never been addressed. We assumed that traits conferring persistence and competitiveness in post-fire conditions to Downy brome, a quintessential invasive species of the Great Basin (North America), might be under selection in areas with recurrent fires. Therefore, we hypothesized that populations from frequently burned regions of the Great Basin would have (1) greater tolerance to fire at seed level, (2) higher relative seedling performance in post-fire environments, and (3) greater flammability than unburned Central-European populations that evolved without fire. Seeds were collected from three introduced populations from frequently burned regions in North America, and three introduced populations of rarely or never burned sites from Central Europe. We performed (1) germination experiments with seeds subjected to the effect of different fire components (heat shocks, smoke, flame, ash), (2) pot experiments analyzing the effect of post-fire conditions on the early growth of the seedlings from different continents, and (3) a series of flammability tests on dry biomass of plants reared in a common garden. All seeds tolerated the low temperature treatments (40 – 100°C), but were destroyed at high heat shocks (140 and 160°C for 5 minutes). Only the 120°C heat treatment for 5 minutes caused a difference in reaction of seeds from different continents, as the European seeds were less tolerant to this heat shock. We found significantly increased seedling height and biomass after four weeks of growth under post-fire conditions in American populations, but not in European ones. American populations had enhanced flammability in three out of five measured parameters compared to European populations. In summary, these intraspecific differences in fire-related traits might contribute to the persistence and perhaps invasibility of the frequently burned North-American Downy brome populations.