Fig. 3

Nitrate production and isotopic ratios (δ¹⁸O and δ¹⁵N) of nitrate in throughfall samples from Cj1 passed through 0.2-, 0.4-, 2-, and 10-µm-pore filters after 4 weeks of incubation (a δ¹⁸O, c δ¹⁵N), and those in the unfiltered samples after different incubation periods (b δ¹⁸O, d δ¹⁵N). Unfiltered samples incubated for 1 week were not analyzed. The data points of “before incubation (a, c)” and “0 weeks (b, d)”, and those of “unfiltered (a, c)” and “4 weeks (b, d)” are same meaning