Original Paper

Biological Invasions

, Volume 15, Issue 5, pp 1113-1123

First online:

Fire promotes downy brome (Bromus tectorum L.) seed dispersal

  • Arnaud MontyAffiliated withBiodiversity and Landscape Unit, Gembloux Agro-Bio Tech, University of Liège Email author 
  • , Cynthia S. BrownAffiliated withDepartment of Bioagricultural Sciences and Pest Management, Graduate Degree Program in Ecology, Colorado State University
  • , Danielle B. JohnstonAffiliated withColorado Division of Parks and WildlifeGraduate Degree Program in Ecology, Colorado State University

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Particularly well-known among the many impacts of the invasive annual grass downy brome (Bromus tectorum, Poaceae) is its ability to alter fire cycles and increase in abundance after fire. However, little is known about how fire influences B. tectorum dispersal. We quantified fire effects on B. tectorum dispersal using three recently burned areas in the western region of the Colorado Rocky Mountains by marking diaspores (seeds) with fluorescent powder, and then recovering them at night using ultraviolet lights. Diaspores were of two types: with and without sterile florets attached. We also characterized vegetation cover and near-surface wind speed in burned and unburned areas. Diaspores travelled much farther in burned areas than in nearby unburned areas (mean ± standard error at the end of the experiment: 209 ± 16 cm and 38 ± 1 cm, respectively; maximal distance at the end of the experiment: 2,274 cm and 150 cm, respectively), indicating an increase in dispersal distance after fire. Diaspores with sterile florets attached dispersed longer distances than those without sterile florets (mean ± standard error at the end of the experiment: 141 ± 14 cm and 88 ± 7 cm, respectively). Vegetation cover was lower and wind speeds were higher in the burned areas. Our results indicate that at least one of the mechanisms by which the spread of B. tectorum is promoted by fire is through increased seed dispersal distance. Preventing movement of seeds from nearby infestations into burned areas may help avoid the rapid population expansion often observed.


Diaspore Secondary dispersal Wind dispersal Seed dimorphism Seed tracking Cheatgrass