Bromus tectorum (cheatgrass) has replaced native Artemisia (sagebrush)/bunchgrass communities throughout the Intermountain West. Using the framework of Jenny (1941), we hypothesized that invasion by B. tectorum could alter pedogenic trajectories. Hypothesis testing involvedmonitoring the invasion of a Krascheninnikovia lanata (winterfat) community by B. tectorum. In 1999, 13 points were established, 50 m apart, extending from the invasion front to noninvaded areas. For more than 11 years, soils were sampled randomly near each point, 0 to 20 cm, and analyzed for various soil attributes. Using autoregression, trends with time between invaded and noninvaded soils differed significantly (P <= 0.05) in solution-phase ortho-P and Ca+2, phosphatase activities, and net 30-day N mineralization potentials. Notable trends with time, regardless of invasion status, included a decline in solution-phase Mg+2 and K+ and an increase in soil pH and the molar proportion of NH4+ in the mineral N fraction. Relative to noninvaded soils, B. tectorum soils had greater mineral N and greater molar proportion of NH4+ in that fraction; greater amidase and phosphatase activities; greater solution-phase ortho-P and molar proportion of NO2- in the NO2--N + NO3--N pool; greater micronutrient availability of Fe and Cu; and higher soil pH. The decline in solution-phase Ca+2 and ortho-P and the increase in soil pH are likely caused by an invasion-fostered increase in bioturbation from rodents, which mixes carbonate-bearing soil from lower horizons to the soil surface. Changes in surface soil properties induced by both B. tectorum invasion and elevated bioturbation have potential long-term ramifications to soil pedogenesis and plant successional trajectories.
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