Variations in nitrogen, phosphorus, and delta N-15 in Sphagnum mosses along a climatic and atmospheric deposition gradient in eastern Canada

摘要

We examined concentrations of nitrogen (N) and phosphorus (P) and delta N-15 value in Sphagnum sections Acutifolia and Cuspidata inhabiting hummocks and hollows from eight bogs along a transect from similar to 45 to similar to 55 degrees N in Ontario and Quebec. The N concentration in Sphagnum declined from south to north, correlating with a decrease in atmospheric N deposition. Although the overall N concentration was larger in hollows than hummocks, the pattern was inconsistent across the sites. There was a proportionally larger decline in P concentration from south to north and an overall larger P concentration in hollows than hummocks, but there were inconsistent differences across the sites. The N:P ratio ranged from 12:1 to 29:1, driven primarily by the variation in P concentration. Ratios of N and P concentration in Sphagnum capitulum: stem averaged 1.2:1, suggesting nutrient resorption from stem to capitulum during growth; the ratio rose with increasing N and P concentration in the capitulum. The delta N-15 value of Sphagnum rose from similar to-6% in the south to similar to-1% in the north, correlated with the decrease in Sphagnum N concentration and with a rise in the water table. We interpret this to indicate a greater dependence on N-2-fixation for N acquisition in the northern and wetter sites.