Investigations of Bromus tectorum: restoration strategies and interactions with arbuscular mycorrhizal fungi
Citation
Helen Ivy Rowe, Investigations of Bromus tectorum: restoration strategies and interactions with arbuscular mycorrhizal fungi: .
Summary
Bromus tectorum (L) (cheatgrass, downy brome), one of the most pervasive weeds in the United States, reduces native species diversity and transforms habitats. I conducted four experiments designed to better understand B. tectorum ecology and evaluate control and restoration strategies. I measured the responsiveness of six native plants and B. tectorum to field and commercial sources of arbuscular mycorrizal fungi (AMF) inoculum. Bromus tectorum and early successional plant species were negatively responsive and late successional species were positively responsive to field AMF inoculum, while commercial inoculum was ineffective. I compared mycorrhizal inoculum potential of field soils from beneath native plants surrounded by B. tectorum [...]
Summary
Bromus tectorum (L) (cheatgrass, downy brome), one of the most pervasive weeds in the United States, reduces native species diversity and transforms habitats. I conducted four experiments designed to better understand B. tectorum ecology and evaluate control and restoration strategies. I measured the responsiveness of six native plants and B. tectorum to field and commercial sources of arbuscular mycorrizal fungi (AMF) inoculum. Bromus tectorum and early successional plant species were negatively responsive and late successional species were positively responsive to field AMF inoculum, while commercial inoculum was ineffective. I compared mycorrhizal inoculum potential of field soils from beneath native plants surrounded by B. tectorum and the same species surrounded by native vegetation. I found that B. tectorum was associated with diminished AMF. Next I tested responses of two native plant species when grown in soils 'trained' by B. tectorum in a greenhouse. Spore counts, percent root colonized, and final biomass of the native plants were not different amongst B. tectorum and native plant trained soils, indicating that B. tectorum did not directly affect the AMF community compared with other native plants. To address decreased AMF found associated with B. tectorum soils, I conducted a field experiment that included soil community and sucrose additions with native seed applications to improve native species growth and establishment. Sucrose reduced both B. tectorum and other annual plant species abundance and richness. Although soil community addition reduced B. tectorum, it did not appear to increase native perennial species. In a second field experiment, I reduced B. tectorum cover to less than 5% with glyphosate and added different seed mixtures based on successional models of tolerance and facilitation. This tested an 'ecological bridge' approach in which early successional species replace invasive species and allow succession to proceed. There were no seed treatment differences amongst late successional plant species establishment. The native plant species included may have been marginally effective at forming an 'ecological bridge' for other late successional species, but none of the seeding treatments inhibited B. tectorum re-invasion.