Table 1 Summary of the Generalized Linear Mixed Models (GLMM) testing for main and 2^nd order interactive effects of litter species (random effect) and age (fixed effect, either 0 or 180 days of decomposition) on bioassay results (i.e. growth of plants, fungi and bacteria, expressed as percentage of the untreated control).

	Effect type	SS	df	MS	F	p
*All data pooled*
Litter species (L)	Random	766411	17	45083	3.24	0.0058
Litter age (A)	Fixed	212583	1	212583	26.09	0.0001
Target organism group (O)	Fixed	4789183	2	2394591	190.77	<0.0001
L × A	Random	207740	17	12220	2.00	0.0412
L × O	Random	426784	34	12552	1.95	0.0273
A × O	Fixed	2488776	2	1244388	193.81	<0.0001
*Bacteria*
Litter species (L)	Random	219385	17	12905	2.33	0.0459
Litter age (A)	Fixed	236545	1	236545	15.60	0.0049
Target species (T)	Random	329809	5	65962	5.38	0.0425
L × A	Random	91187	17	5364	2.33	0.0057
L × T	Random	209600	85	2466	1.07	0.3723
A × T	Random	60483	5	12097	5.27	0.0003
*Fungi*
Litter species (L)	Random	358819	17	21107	2.40	0.0353
Litter age (A)	Fixed	962182	1	962182	44.51	0.0001
Target species (T)	Random	412704	5	82541	5.33	0.0406
L × A	Random	141914	17	8348	4.77	<0.0001
L × T	Random	188262	85	2215	1.27	0.1397
A × T	Random	75104	5	15021	8.58	<0.0001
*Plants*
Litter species (L)	Random	821469	17	48322	9.22	<0.0001
Litter age (A)	Fixed	1308116	1	1308116	16.95	0.0012
Target species (T)	Random	2604705	13	200362	2.57	0.0492
L × A	Random	150299	17	8841	2.00	0.0123
L × T	Random	1153846	221	5221	1.19	0.1019
A × T	Random	1003151	13	77165	17.54	<0.0001
*Plant functional types*
Litter species (L)	Random	853545	17	50209	6.74	0.0003
Litter age (A)	Fixed	1204105	1	1204105	252.35	<0.0001
Target functional type (F)	Fixed	1008085	2	504042	65.84	<0.0001
L × A	Random	162235	17	9543	1.93	0.0490
L × F	Random	260288	34	7656	1.54	0.1060
A × F	Fixed	721938	2	360969	72.69	<0.0001

GLMMs were tested for all data pooled, including a fixed effect of the group of organisms (3 levels), and separately for plants, fungi and bacteria, including a random effect of target species. In the case of plants, a further GLMM was tested, including the effect of target functional type (3 levels: annual, perennial and woody).

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