Plant interactions with soils conditioned by different vegetation: A potential explanation of Bromus tectorum L. invasion into salt-deserts?

Invasion by Bromus tectorum L. may condition the soil and increase nutrient availability. We hypothesized that nutrient poor soils of the arid Honey Lake Valley of northeastern California U.S.A., similar in physical and chemical properties, but conditioned by either B. tectorum, Krascheninnikovia lanata, or Artemisia tridentata, would differ as a rooting medium. These soil/vegetation types were placed in equal volumes in replicate 5400 cm3 cylindrical containers, the template removed, and sown to B. tectorum or Leymus triticoides; controls were left unplanted. At harvest, root mass, root nutrient concentrations, and selected soil nutrients were quantified for each soil/vegetation type. Root mass was statistically similar among soil/vegetation types and seeded plants. After harvest, and relative to unplanted controls, B. tectorum invaded soil lost a greater proportion of several nutrients than the other soil/vegetation types suggesting greater nutrient uptake from that soil. Soil/vegetation types planted to B. tectorum had significantly greater depletion of soil nutrients compared to soils planted to L. triticoides. Soil invaded by B. tectorum had greater nutrient availability than similar soil conditioned by A. tridentata or K. lanata and offers a plausible explanation of why this exotic annual grass has been able to invade nutrient poor salt-desert ecosystems.