Field Nodulation and Acetylene Reduction Activity of High-Altitude Legumes in the Western United States
D. A. Johnson, M. D. Rumbaugh
Soil disturbances in high-altitude areas frequently require rehabilitation to minimize erosion and reduce further environmental degradation. However, factors such as an abbreviated growing season, cool summer temperatures, high winds, and frost action dictate that only adapted plant materials be used to revegetate these areas. Because of their ability to biologically fix nitrogen and thereby possibly enhance soil nitrogen levels without regular applications of fertilizers, legumes native to high-altitude areas may be particularly beneficial in revegetating such sites. To obtain field estimates of nitrogen fixation activity, plants of Astragalus alpinus, Trifolium parryi, Trifolium nanum, Lupinus caudatus, and Lupinus argenteus growing at high altitudes in Utah and Montana were sampled for acetylene reduction activity. Astragalus alpinus and Trifolium nanum exhibited the highest rates of acetylene reduction on a specific nodule activity basis (101 and 73 μmol ethylene g−1 h−1 nodule dry weight, respectively). However, the lupine species had a greater nodule mass (0.05 to 2.0 g dry weight per plant) and whole plant estimates of nitrogen fixation were 5 to 15 times greater for lupines than for the other legumes. Acetylene reduction measurements from disturbed sites in Montana indicated that plants of Lupinus argenteus were nodulated and fixing nitrogen on these high-altitude disturbances. The results from this study indicated that legumes from high-altitude areas are capable of fixing nitrogen even on disturbed sites and appear promising for rehabilitation of these areas. The results are discussed with particular reference to adaptation of the nitrogen fixation process to cold temperatures and the possible presence of perennial nodules in these legumes.
Citation Note: This article was published when our journal had an earlier shorter name: "Arctic and Alpine Research."