Table S3.

Fractional and average valence states of Mn obtained from a linear combination fit of Mn XANES spectra as described in ref. 50

		Relative contribution, %
Figure	Location	Mn2+	Mn3+	Mn4+	Avg Mn valence	Sum	NSS × 10−3
Fig. 1	Fresh litter	93	7	0	2.07	1.08	0.9
	Layer 1	85	15	0	2.14	1.06	0.9
	Layer 2	78	22	0	2.22	1.01	0.7
	Layer 3	74	20	6	2.31	1.04	0.3
	Layer 4	67	17	16	2.49	1.01	0.4
	Layer 5	59	22	18	2.59	1.00	0.3
	Layer 6	49	28	23	2.74	0.99	0.4
	O horizon	46	24	30	2.83	0.97	0.5
	A horizon	29	28	43	3.14	0.93	0.2
	A/B horizon	33	31	36	3.02	1.00	0.2
Fig. S1	Mesophyll	99	0	1	2.02	0.95	0.2
	Mesophyll	88	12	0	2.12	0.98	0.3
	Fungi	99	0	1	2.02	0.99	0.2
	Diffuse spot	72	0	28	2.57	1.00	1.3
	Diffuse spot	83	4	13	2.30	0.96	0.9
	Particle 1	45	21	35	2.90	1.11	2.4
	Particle 1	49	0	51	3.01	1.05	0.5
	Particle 1	27	20	53	3.26	1.01	0.2
Fig. 4D	Spot 1	85	15	0	2.15	1.05	4.7
	Spot 2	88	12	0	2.12	1.00	3.6
	Spot 3	43	57	0	2.57	1.10	9.2
	Spot 4	48	48	4	2.57	1.03	1.3
	Spot 5	27	73	0	2.73	1.04	6.4

NSS, the normalized sum-squared residual = ∑n(data – fit)/∑n(data).