Soil Ecology Restoration Group

last update December 05, 2000

Responses of Hedysarum boreale Nutt. to mycorrhizas and Rhizobium: plant and soil nutrient changes in a disturbed shrub-steppe



Effects of inoculation of Hedysarum boreale ssp. boreale Nutt. (Fabaceae) with mycorrhizal fungi (topsoil inoculum) and Rhizobium (pure inoculum) were studied in the field in southwestern Wyoming, USA. After 3 years, plants recieving both inocula had greater total aboveground biomass and leaflet biomass, more leaves, higher aboveground nitrogen and phosphorus contents and greater survival than plants which recieved single or no inoculum. Soil 20-40 cm deep (where roots were concentrated) beneath Hedysarum individuals from all treatments had a lower concentration of total nitrogen than did soil between plants. Hedysarum plants, inoculated or not, apperently extracted sufficient nitrogen from the soil, as they had similar leaflet nitrogen concentrations. Hedysarum decreased the size of the pool of soil nitrogen even with Rhizobium inoculation on disturbed land in a semi-arid environment during the first 3 years of growth.