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

Forest Ecosystems

Table 4 Decrease (in percentages) in N and C concentrations in soil fractions along rotations from the end of the first 7-year-rotation (R1Y7), to year 2 of the second rotation (R2Y2, values used as references) and 5 of the second rotation (R2Y5)

Fractions	cPOM (4000–250 μm)						fPOM(250–50 μm)						OMF (0–50 μm)
Stands	Reference (R2Y2)		R1Y7		R2Y5		Reference (R2Y2)		R1Y7		R2Y5		Reference (R2Y2)		R1Y7		R2Y5
N&C	N%	C%	N decrease (%)	C decrease (%)	N decrease (%)	C decrease (%)	N%	C%	N decrease (%)	C decrease (%)	N decrease (%)	C decrease (%)	N%	C%	N decrease (%)	C decrease (%)	N decrease (%)	C decrease (%)
100A	2.2	40	9	7	21	21	1.9	37	25	13	27	26	0.7	10	18	21	31	33
50A50E	1.9	41	18	13.9	24	26	1.6	40	14	7	11	35	0.7	11	21	21	31	35
100E	1.7	42	17	13.2	22	21	1.6	41	9	12	25	34	0.7	11	20	26	24	35

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