The Effect of Nitrogen on the Growth Rate of the Invasive Species Brassica nigra

Abstract

Brassica nigra is an invasive species of mustard that is growing in California. Recent studies have shown that B. nigra is invading nitrogen (N) rich plots1 displacing native shrubs. Similar studies have shown N addition increases plant productivity2 and N uptake3 of alien plants. Brassica nigra exposed to high levels of N had higher biomass production than plants growing in low N (control) plots. The increase in biomass production was due to shoot growth and reproductive output in plants exposed to N. Plants exposed to N had higher tissue N concentration than control plants during the growth phase, but N resources became diluted at the end of the season by the higher shoot production. These data indicate that the invasive species, Brassica nigra, can become invasive in high N environments because of high shoot and reproductive biomass production. These results have important implications for species diversity in chaparral ecosystems exposed to high levels of N deposition.