Effects of neighbor species and distance on 2- and 4-year survival of Lehmann lovegrass and native grasses

Abstract

The relationship between Lehmann lovegrass, an invasive African grass, and native Southwestern grasses has not been fully determined. The first purpose of this study was to compare the survival of Lehmann lovegrass with two native grasses (plains lovegrass and Arizona cottontop) seeded on the Santa Rita Experimental Range in southeast Arizona in 1994. One year after establishment, survival was 92 percent for plains lovegrass, 90 percent for Arizona cottontop, and 92 percent for Lehmann lovegrass. High survival was maintained until the second summer of the study, when many plants that were alive in June 1996 suffered mortality by September 1996. At that time, survival was 10 percent for plains lovegrass, 30 percent for Arizona cottontop, and 76 percent for Lehmann lovegrass. Four years after establishment, survival was zero for plains lovegrass, 16 percent for Arizona cottontop, and 60 percent for Lehmann lovegrass. The second purpose of the study was to determine if Lehmann lovegrass, as a same-aged neighbor, affected the two native grasses differently than same-species neighbors. After 2 years, plains lovegrass mortality was higher with same-species neighbors than no neighbors or Lehmann lovegrass neighbors; cottontop mortality was highest with Lehmann neighbors; and Lehmann mortality was highest with plains lovegrass neighbors. By the end of 4 years, all plains lovegrass seedlings perished regardless of neighbor density (one or two within 40 by 40 cm), spacing (1 to 2 cm or 5 to 6 cm), or species. After 4 years, Arizona cottontop seedlings had 60-percent survival with no neighbors, 10-percent survival across both densities and spacings with same-species neighbors, and no survival with Lehmann lovegrass neighbors. Lehmann lovegrass had 80- percent survival with no neighbors, 60-percent survival with same-species neighbors, and 50- percent survival with native neighbors. These results suggest that the intensity of competition between Lehmann lovegrass and the native grasses increased over the first 4 years.

Parent Publication

• Santa Rita Experimental Range: 100 years (1903 to 2003) of accomplishments and contributions; conference proceedings; 2003 October 30-November 1; Tucson, AZ

Citation

Biedenbender, Sharon H.; McClaran, Mitchel P.; Roundy, Bruce A. 2003. Effects of neighbor species and distance on 2- and 4-year survival of Lehmann lovegrass and native grasses. In: McClaran, Mitchel P.; Ffolliott, Peter F.; Edminster, Carleton B., tech. coords. Santa Rita Experimental Range: 100 years (1903 to 2003) of accomplishments and contributions; conference proceedings; 2003 October 30-November 1; Tucson, AZ. Proc. RMRS-P-30. Ogden, UT: U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station. p. 149-153.