Alexis A. Suazo
The expansion of invasive exotic plant species into natural habitats is a major concern for land managers because invasive plants can potentially alter ecosystem processes. Sahara mustard (Brassica tournefortii) is an exotic invader in the Mojave Desert, but its potential effects on native species and habitats are not well known. To better understand the ecology of Sahara mustard, we established experimental plots in large washes, road shoulders, and disturbed areas and documented responses of this exotic species to water additions and soil disturbance. Water additions (7 liters/plot/application) were applied from November 2007 through January 2008 at a two week interval. We performed the soil disturbance treatment by dragging a metal rake to break up the top 5 cm of mineral soil and this treatment was applied once. We collected data on Sahara mustard seedling density, phenology, plant height, and number of fruits, and tested for treatment effects. At our study sites seedling emergence was patchy; we recorded low densities in large washes (Mean ± SE, 1.58 ± 0.68) and high densities (47. 42 ± 14.98) in disturbed road sides. Seedling density was influenced by site (P<0.001) while experimental treatments had a marginal effect (P = 0.052) on seedling density. Plant height and the number of fruits produced did not differ between treatments, but plant phenology was associated with treatments. Our results suggest that habitats with disturbed soils are conducive for the establishment of Sahara mustard, and we recommend that land managers monitor disturbed areas for sign of infestations.
Keywords: NULLBRASSICA TOURNEFORTII, INVASIVE SPECIES, MOJAVE DESERT, HABITAT DISTURBANCE
