Contrasting nitrogen use efficiency of Antarctic vascular plants may explain their population expansion in Antarctica

摘要

Regional warming in Antarctic ecosystem profoundly influences soil nutrient processes, such as nitrogen mineralization, and potentially plant growth. This work evaluates the physiological responses to incremental dosage of inorganic nitrogen (ammonium or nitrate) in Deschampsia antarctica and Colobanthus quitensis, two Antarctic vascular plants. Nitrogen fertilization increased shoot biomass, specially leaf number and leaf area in both species, however, D. antarctica biomass increased 6.5 fold with ammonium and 4.0 fold with nitrate; meanwhile C. quitensis biomass increased 1.6 and 1.8 fold with each nitrogen source, respectively, in both cases respect to control plants with only basal nitrogen supply. Apparent recovery efficiency of nitrogen or uptake efficiency exhibited strong differences among the two species. D. antarctica showed a 12% recovery for ammonium and 5% for nitrate, while C. quitensis was less efficient (4% and 3%, respectively). These results are also consistent with higher nitrogen use efficiency (higher biomass production and carbon assimilation by unit of nitrogen) in D. antarctica than in C. quitensis. This study contributes additional evidence about how interspecific differences between nitrogen use efficiencies of these vascular Antarctic plants may explain the faster population spread experienced by D. antarctica than C. quitensis in Antarctica.