Nitrogen accumulation and acetylene reduction activity of native lupines on disturbed mountain sites in Colorado

Abstract

Lupines are pioneering plants in many disturbed mountain habitats in Colorado. The purpose of this work was to determine if Lupinus argenteus, L. caudatus, and L. alpestris could be useful revegetation plants in a reclamation program. Paired soil samples from 33 disturbed sites supporting native lupines were used to determine if lupines increased the nitrogen content of the soil. Soil samples collected 10 cm from lupine tap roots averaged 13.8 mg kg-1 more exchangeable ammonium and 2.7 mg kg-1 more nitrate than soil samples collected 3 m from lupine plants. Field measured acetylene reduction rates of detached lupine nodules averaged 10.0 micromol ethylene g-1 nodule dry weight h-1 for L. argenteus and 17.3 micromol ethylene g-1 nodule dry weight h-1 for L. alpestris. Soil adjacent to lupines had higher levels of inorganic nitrogen than soils 3 m from lupine plants and lupines had the ability for biological nitrogen fixation as shown by the acetylene reduction assay, suggesting that native lupines are potentially useful revegetation plants in a reclamation program.