Fig. 1. Differences in (a) ¹³C and (b) ¹⁵N values () among physical fractions and whole soil (WS) samples at the oak and pine lysimeters. Zero refers to WS and a positive difference corresponds to the given physical fraction being enriched in the heavier isotope as compared with WS; SA = sand + coarse and medium silt (5–2000 µm), FL = floatables (50–2000 µm), FS = fine silt (2–5 µm), and CL = clay (<2 µm). *indicates significance between physical fraction and WS at p = 0.10 and **at p = 0.05. Error bars represent standard errors.