Data calculation and statistical analysis
The 15N atomic percentage was calculated as the
percentage difference between the 15N-treated sample
and the control sample. 15N uptake (mg15N per quadrat) and root uptake efficiency (mg15N g−1 root) were calculated using
aboveground and root biomass (g m−2) and the15N atomic percentage and N concentrations (mg N
g−1 DW).
The relative contributions of different N forms
(NO3-,
NH4+, and glycine) were estimated as
the percentage uptake of a single N form of the total uptake of all
three N forms.
Community species richness was expressed by the number of species per
quadrat. The community similarity coefficient was modified by referring
to the method of Jackson et al. (1989):