Competitive interactions between an exotic annual, Halogeton glomeratus, and 10 North American native species

Abstract

Invasive plant species diminish ecosystem integrity and limit restoration success when they compete with reintroduced native species. The invasive annual forb halogeton ( Halogeton glomeratus (M. Bieb.) C.A. Mey. [Chenopodiaceae]) is increasing in abundance on disturbed lands and energy extraction sites in the Intermountain West. Successful seedings in the presence of halogeton in the past relied on competitive nonnative forage species. Because disturbance increases nutrient availability in otherwise stressful environments, we hypothesized that annual native species may be more competitive at the seedling stage than are perennial natives. We hypothesized that annuals would increase aboveground growth in the presence of the exotic while perennials would increase allocation to root growth. We documented growth and survival of halogeton in the presence of 10 species native to the western North American basin shrublands and in monocultures. Sporobolus cryptandrus (Torr.) A. Gray (Poaceae), Gaillardia aristata Pursh (Asteraceae), and Helianthus annuus L. (Asteraceae) reduced survival of halogeton ( Sporobolus and Gaillardia had greater biomass while Helianthus grew taller in the presence of halogeton than when grown with conspecifics. Halogeton aboveground growth was less when grown with H. annuus and Cleome serrulata Pursh (Capparaceae) (2 annual forbs). Annuals that demonstrated rapid biomass production also limited survival of halogeton. In general, perennials did not differ in aboveground tissue allocation in competition with halogeton. We suggest reclamation seedling establishment may be improved by including native annuals with the potential for rapid aboveground growth on arid land restoration sites where halogeton seedbanks persist.