Growth and nutrition of combinations of native and introduced plants and mycorrhizal fungi in a semiarid range

Abstract

The symbiotic responses of native and introduced plant-fungus combinations were determined Indian ricegrass ( Oryzopsis hymenoides (R.&S.) Ricker) and crested wheatgrass ( Agropyron desertorum (Fisch.) Schult.) were pre-inoculated with an introduced fungus, three native fungi, or a mixed native inoculum (VAM plants), and transplanted to fumigated field plots on a semiarid range in western Nevada. Non-fumigated and fumigated plots with non-VAM plants were used as controls. No treatment produced significant plant growth responses relative to controls. Crested wheatgrass generally had the lowest levels of VAM fungal colonization, yet the highest levels of nutrient uptake when compared with Indian ricegrass. Differences in nutrient concentrations, but not contents, were significant among fungal inoculum treatments. Glomus pallidum increased N shoot concentrations above the fumigated control levels for both Indian ricegrass and crested wheatgrass, and the native Glomus mosseae increased N concentration for Indian ricegrass only. For Indian ricegrass, G. pallidum increased P shoot concentrations above controls. G. mosseae and G. pallidum enhanced the uptake of P when compared with the introduced isolate. The introduced G. mosseae and the native Glomus etunicatum enhanced Mn uptake for Indian ricegrass only. The uptake of N and P were reduced in plants colonized by a mixture of three native isolates when compared with uptake by single native isolates for Indian ricegrass. The lack of a shoot growth effect for Indian ricegrass and crested wheatgrass in the presence of introduced or native VAM fungi suggests that these plants are facultative mycotrophs. Mycorrhizae appear to facilitate luxury consumption of nutrients by these grasses, which may be an important adaptation in nutrient-poor desert environments. Further knowledge of effects by native and introduced VAM fungi, and of host effects on the symbiotic association will contribute to more effective establishment of plants in new areas.