Fig. 2

A Relative abundances of nifH from the treatment ¹⁴ N and ¹⁵ N after incubation. The abundance of the nifH gene in each fraction was converted to the proportion of total nifH gene abundance throughout the gradient fractions. B Relative abundances of 14 most abundant microbial genera in light, ¹⁴ N treatment, and heavy ¹⁵ N DNA fractions at days 28 and 35. Each bubble stands for one DNA fraction. Triplicate fractions were sequenced for each treatment