The importance of considering origin in effects of nitrogen deposition on plant performance and competitive ability

Background and Aims Differential capacity of species/genotypes to respond to increased atmospheric N deposition may be an important long-term driver of species composition change. In this study, differences in response to atmospheric N deposition were analysed for different accessions of Prunella vulgaris. Methods P. vulgaris plants deriving from different N deposition accessions (0–15, 15–25 and 25–35 kg N ha−1 yr−1) were exposed to different N
treatments (10 or 30 kg N ha−1 yr−1), with and without competition with the grass Bromus erectus. After 8 months, plant performance and differences
in competitive ability were determined. Results Strong effects of accession were found, often in interaction with N treatment: P. vulgaris plants from
populations with low N deposition backgrounds often outperformed plants from medium to high N backgrounds, illustrated by greater biomass at high N treatment and higher chlorophyll and leaf N concentrations at low N treatments. When grown in competition, however, a strong decrease in biomass was observed for plants from all accessions. Conclusion All accessions of P. vulgaris showed a low competitive ability. Plants from low N accessions proved to be most sensitive to competition in terms of root biomass. However, in the absence of competition, low N accessions showed a greater plasticity in nitrogen
use efficiency. These results illustrate the importance of including accession when considering effects of N deposition.