Print PageCheatgrass (Bromus tectorum L.) is a highly invasive winter annual grass in the sagebrush steppe of North America. Here, arbuscular mycorrhizal fungi (AMF) are an important driver of plant community assembly. Cheatgrass is a facultative AMF host that receives little benefit from AMF, reduces AMF density in invaded soils, and alters AMF infecting neighboring grasses. The goal of our research is to better understand how cheatgrass interacts with AMF by investigating temporal association with AMF, how coexisting cheatgrass and big sagebrush (Artemisia tridentata Nutt.) differ in their associations with AMF, and how native ruderal plant species interact with AMF associated with cheatgrass. Cheatgrass root samples were collected every three weeks from an invaded steppe community, from germination to senescence. Cheatgrass and big sagebrush root and soil samples were collected from three sites where both species coexist, and soils were used to establish trap cultures to identify sporulating AMF species. Soil was collected from a cheatgrass-invaded site, and fifteen native ruderal species were grown in sterile and non-sterile soil to compare plant responsiveness to the AMF community. AMF responses to the plant hosts were also compared by measuring AMF density changes in soils compared to the initial field soil.
Results/Conclusions
Cheatgrass roots were colonized by AMF during its entire life, but colonization was low during most sampling intervals. Colonization rapidly peaked near the end of the life cycle when cheatgrass was reproducing. Diversity of AMF species associated with cheatgrass differed from those associated with big sagebrush. Alpha diversity of AMF species was lower in association with cheatgrass than big sagebrush, beta diversity was higher, and gamma diversity was similar. Thus, big sagebrush individuals produce AMF diversity hotspots that are similar between individuals in a population, while cheatgrass individuals associate with fewer AMF species and communities are dissimilar between individual plants. Native ruderal plant species were highly variable in their interactions with the AMF community from an invaded soil. Plant species responses ranged from highly positive to highly negative, while AMF density responses ranged from no change to large increases. In conclusion, cheatgrass associates with AMF throughout its life, but differs in its species associations compared to big sagebrush, and some native ruderal plant species are able to rapidly increase AMF density in invaded soils, regardless of whether they benefitted or were parasitized. These findings could improve restoration of invaded soils through improved utilization of AMF.
