Appendix 3—table 3. Results of mediation tests from structural equation modeling (SEM) analysis based on data excluding extreme values of effect sizes.

C statistic and associated p-value for SEM without the path from biodiversity or abundance to decomposition for the four datasets: Stressors - Diversity, Stressors - Abundance, Nutrients - Diversity and Nutrients - Abundance. ΔAIC is the difference in AIC score between models with and without biodiversity- or abundance-mediated effects.

Dataset	C statistic	Df	p-value	$\mathrm{\Delta }$AIC	No. of studies	N
Stressors, Biodiv	10.18	6	0.117	−6.71	22	94
Stressors, Abdc	7.39	4	0.117	−4.23	27	254
Nutrient, Biodiv	14.80	6	0.022	−4.85	26	93
Nutrient, Abdc	2.74	4	0.603	0.15	35	159