Nitrogen and phosphorus availability at early stages of soil development in the Damma glacier forefield, Switzerland; implications for establishment of N2-fixing plants

Background and aims Di-nitrogen (N-2)-fixing plants are absent in the pioneer stages of glacial forefields in the European Alps despite low amounts of nitrogen (N) in the soil. We aimed to evaluate whether symbiotic N-2-fixation is needed to meet the N demand of plants during the early stages of soil formation, and how phosphorus (P) availability affects plant establishment. Methods We measured total and available N and P in soil and N and P in the vegetation along the 137 year chronosequence in front of the Damma glacier (Switzerland). Results Available N as determined by in situ resin N decreased from the pioneer stage (<16 years since deglaciation) to the intermediate (5780 years), likely resulting from increased plant N uptake and reduced funnelling of N by rocks. N concentrations in the vegetation were positively correlated to in situ resin N, and the N: P-ratio of the vegetation was negatively correlated with P concentrations in the vegetation. Conclusions The N requirement of plants in the pioneer stage of soil development in the forefield is fulfilled by atmospheric N deposition being funnelled between rocks. N-2-fixation is not needed as the vegetation is often limited by P, or co-limited by N and P.