Effect of increasing N limitation on leaf-level variables.
Figures are generally photos, graphs and static images that would be represented in traditional pdf publications.
Relationship between leaf-level variables and experimental N limitation, where maximum N limitation (i.e., N limitation = 100%) means zero nitrogen addition in the N limitation treatment. Line shows modelled response (linear, except for NL per unit mass, panel d, that also includes a quadratic term) and the shaded area indicates the 95% confidence interval. Each point represents one experiment. The individual panels show (a) photosynthesis (studies = 50, experiments = 182), (b) leaf area (21, 80), (c) NL per unit area (23, 120), (d) NL per unit mass (17, 95), (e) chlorophyll content (32, 116), and (f) Rubisco content (13, 50). See Table 3 for more details on model fit. We modelled a quadratic relationship for NL per unit mass, as this model provided a better and more sensible fit to the data and was supported statistically (P<0.01, Table 3). A quadratic relationship was also weakly statistically supported for other variables (photosynthesis, leaf area, NL per unit area; Table 3) but showed non-sensible fits driven by some data points at low N limitation and a linear fit was therefore preferred.