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Table 3 CN ratio of bulk soil and soil fractions (cPOM; fPOM and OMF) and mass of fractions along rotations from the end of the first 7-year-rotation (R1Y7), to year 2 of the second rotation (R2Y2) and 5 of the second rotation (R2Y5)

From: Soil organic matter quality along rotations in acacia and eucalypt plantations in the Congolese coastal plains

  R1Y7 R2Y2 R2Y5
Soil/fractions 100A 50A50E 100E 100A 50A50E 100E 100A 50A50E 100E
CN bulk soil 16.9 (± 0.054) a 17.8 (± 0.48) a 17.1 (± 0.51) a 20.2 (± 0.43) a 22.7 (± 0.19) b 25.0 (± 0.27) a 11.3 (± 0.90) b 10.4 (± 0.66) b 9.7 (± 0.95) a
CN cPOM 19.4 (± 0.056) a 23.9 (± 0.68) b 26.5 (± 0.91) c 18.6 (± 0.16) a 22.2 (± 0.19) b 25.0 (± 0.27) a 18.8 (± 0.36) b 21.5 (±0.27) b 25.9 (± 0.88) a
CN fPOM 24.1 (± 1.68) a 27.1 (± 0.72) ab 25.4 (± 0.81) a 20.2 (± 0.32) a 24.7 (± 0.37) b 25.7 (± 0.41) a 20.8 (± 0.60) b 20.3 (± 0.77) b 22.8 (± 0.79) a
CN OMF 13.6 (± 0.034) a 15.3 (± 0.27) b 14.9 (± 0.43) b 14.3 (± 0.17) a 15.3 (± 0.18) b 16.2 (± 0.30) a 14.1 (± 0.33) b 14.9 (± 0.32) b 14.2 (± 0.31) a
cPOM (fraction per g) 0.11 (± 0.001) a 0.15 (±0.02) b 0.10 (± 0.01) a 0.41 (± 0.03) a 0.49 (± 0.03) b 0.34 (± 0.03) a 0.14 (± 0.01) b 0.18 (± 0.01) b 0.19 (± 0.03) a
fPOM (fraction per g) 0.20 (± 0.002) b 0.19 (± 0.02) b 0.17 (± 0.02) a 0.23 (± 0.01) a 0.30 (± 0.01) b 0.28 (± 0.02) a 0.35 (± 0.02) b 0.39 (± 0.02) b 0.40 (± 0.03) a
OMF (fraction per g) 1.91 (± 0.005) b 1.86 (± 0.04) a 1.83 (± 0.07) a 1.47 (± 0.03) a 1.64 (± 0.03) b 1.56 (± 0.05) a 2.01 (± 0.06) b 1.77 (± 0.03) b 1.81 (± 0.07) a
  1. 100A and 100E = pure acacia and eucalypt, respectively, while 50A50E = mixed-species (50% acacia and 50% eucalypt) stands. cPOM = coarse POM (4000–250 μm), fPOM = fine POM (250–50 μm) and OMF = organo-mineral fractions (< 50 μm). Different letters indicate significant differences at P = 0.05 between stand types at each rotation stage and along rotations