The competitive ability of a serpentine nickel hyperaccumulator, Alyssum murale, under varying nutrient conditions

Background/Question/Methods

The role of edaphic factors in influencing the competitive ability of serpentine species has long been of interest to plant ecologists.  Alyssum murale (Brassicaceae) is a nickel-hyperaccumulating species found in serpentine areas throughout the Mediterranean. It is not restricted to serpentine soils, however.  Little is known about the competitive ability of metal hyperaccumulators on serpentine and nonserpentine soils.  Understanding the competitive ability of Alyssum murale is particularly important because Alyssum murale is under development for phytoremediation and phytomining of nickeliferous soils in North America. Thus, it is important to explore the potential for this species to spread inadvertently to non-nickeliferous soils adjacent to target sites. This study focuses on the effect of varying nutrient conditions on the competitive ability of two populations of A. murale from Albania and Bulgaria in non-serpentine soils.  The objective of this study was to determine how well Alyssum murale would grow in competition with perennial ryegrass (Lolium perenne) on a non-metalliferous soil with varying soil nutrients.  For each population, 288 pots were set up as pure treatments (20 Alyssum seeds/ 2.5 inch pot) or mixed treatments (10 Alyssum seeds + 10 Lolium seeds/pot). Pure and mixed pots were fertilized with three nutrient treatments (0mg/L, 62 mg/L, 113 mg/L 24:8:16 NPK plus micronutrients) at three week intervals. Germination and growth was monitored; after 11 weeks plants were harvested, dried and weighed. Results were analyzed by 2-way ANOVA for effects of planting treatment and nutrient level. 

Results/Conclusions

Alyssum from both populations showed a significant negative effect of competition with Lolium.  Plant height and shoot biomass of Alyssum from both populations were significantly lower in mixed pots compared to pure pots (p <0.000).  Soil nutrients had a significant positive effect on shoot biomass of Lolium grown with both populations of Alyssum (p=0.009; p=0.000).  Shoot biomass of Alyssum from both populations did not show a significant response to increased nutrients. This may reflect the fact that A. murale generally grows on nutrient-poor soils. The results of this study suggest that Alyssum murale has low competitive ability on non-nickeliferous soil, and its competitive ability does not change with soil nutrient availability.  Low competitive ability on non-nickeliferous soil decreases the likelihood that Alyssum murale will show the strongly invasive characteristics seen in some other members of the Brassicacae such as Alliaria petiolata (garlic mustard) and Brassica tournefortii (sahara mustard).