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Effects of disturbance on Kochia prostrata spread in native and exotic Great Basin communities.
Sullivan, Amy1, Anderson, Val2, 1 2
ABSTRACT- The ability of forage kochia (Kochia prostrata), a Eurasian half-shrub, to establish in stands of invasive weeds and effectively compete for resources has generated concern that it may spread into and dominate native communities. We seeded kochia into 2m2 plots in 3 communities (native sagebrush, exotic wheatgrass, exotic annual) treated with disturbances (fire, grazing, off-road vehicle use, rodent mounding) to test for potential kochia spread using establishment and growth as indicators. The experiment was established in 1998 and repeated in 1999. A mixed model ANOVA was used to test the effects of disturbance, community, and planting year on kochia emergence, survival, and growth. Emergence was highest in the wheatgrass community both years, lowest in the sagebrush community in 1998 and the annual community in 1999. Disturbance had no effect on emergence in 1998, though emergence was higher in rodent treatments in 1999. Survival was highest in the annual community and lowest in the wheatgrass community both years. Kochia growth was greatest in the annual community in 1998 while in 1999 there was little growth in any community. Differences in precipitation between years (high in 1998, low in 1999) probably affected results. Data indicate that kochia can establish in these three communities regardless of disturbance, and may spread most quickly through the annual community. Favorable microclimate created by rodent mounds may be important in kochia establishment if precipitation is low.
KEY WORDS: Kochia prostrata, invasive/exotic species, Great Basin