C/N ratios of SOM fractions also differed considering plot age
and SOM fraction at both soil depths (plot age x SOM fraction
interaction; P < 0.001; Table A.1 (v). The mineral-associated OM
had the lowest C/N ratios of all SOM fractions at both depths,
except in SC-43 plot at 0–10 cm (Fig. 2). C/N ratios of fPOM and
iPOMc differed among plots but were similar in iPOMf and
mineral-associated OM fractions at both depths (Fig. 2). At
0–10 cm, fPOM C/N ratios were higher in the SC-50 plot than in
forest, SC-20 and SC-25 plots, while iPOMc C/N ratios were higher
in SC-25 than in forest, SC-43 and SC-50 plots. At 10–20 cm depth,
C/N ratios differed among plots only in the iPOMc fraction, with a
lower ratio in forest and SC-50 than in SC-20, SC-25 and SC-43 plots
(Fig. 2).
iPOM C concentrations were affected by plot age and iPOM
fraction at both soil depths(plot age x iPOM fraction interaction;
P < 0.001; Table A.1 (vi). In all plots, the concentration of iPOMf C in
microaggregates (53f) was higher than of iPOMc C in large
macroaggregates (2000c) at both depths (Fig. 3). Also, the
concentration of iPOMf C in microaggregates was higher than of
all other iPOM C fractions in forest and SC-50 plots at 0–10 cm
depth. Most iPOM C fractions showed differences among plots,
except iPOMf C concentration in large macroaggregates at 0–10 cm
depth and iPOMf C concentration in microaggregates at 10–20 cm
depth (Fig. 3). At 0–10 cm depth, iPOMf C in microaggregates (53f)
and iPOMc C in both large- and small macroaggregates (2000c and
250c, respectively) were higher in forest and SC-50 plots than in
SC-20 and SC25 plots, and intermediate in SC-43 plot. At 10–20 cm
depth, iPOMc C in large macroaggregates (2000c) was higher in
SC-50 than in all other plots; iPOMf C in large macroaggregates
(2000f) was higher in forest than in SC-20 and SC-25 plots; iPOMc