Table 1.

Results of general linear models (selected based on the Akaike information criterion, AIC, following a stepwise search in backward and forward directions) examining the influence of key predictors (mean annual temperature, T; mean specific leaf area, SLA, and litter phylogenetic diversity, PD, as litter variables; and pH and wetted width, SW, as stream environmental variables) on total litter breakdown rates of litter mixtures and alder in coarse-mesh bags (k_c), microbial breakdown rates in fine-mesh bags (k_f) and detritivore-mediated breakdown rates (k_d). The AIC, adjusted r², F-test and p-value are shown for each model, and the mean estimate and standard error, t-statistic and p-value for each factor (italic entries indicate significant results at the p < 0.05 level).

litter breakdown	selected model	factor	estimate	s.e.	t	p
litter mixtures
total	kc ∼ T + SLA + PD + pH + T × SLA + T × PD + T × pH
	AIC =−175	intercept	0.081160	−0.714000	0.49	0.489
	adjusted r2 = 0.41	T	0.001409	0.004210	0.34	0.744
	F7,12 = 2.92	SLA	−0.000321	0.000110	−2.92	0.013
	p = 0.0499	PD	−0.135900	0.088550	−1.54	0.151
		pH	0.023480	0.010510	2.24	0.045
		T × SLA	0.000019	0.000006	2.95	0.012
		T × PD	0.009196	0.006253	1.47	0.167
		T × pH	−0.000975	0.000559	−1.75	0.106
microbial	kf ∼ T + SLA + pH + T × SLA
	AIC =−18	intercept	−6.650175	1.632409	−4.07	0.001
	adjusted r2 = 0.32	T	−0.058414	0.049330	−1.18	0.255
	F4,15 = 3.25	SLA	−0.010108	0.005675	−1.78	0.095
	p = 0.042	pH	0.422662	0.166398	2.54	0.023
		T × SLA	0.000629	0.000325	1.94	0.072
detritivore-mediated	kd ∼ T + PD + pH + SW + T × PD + T × pH + T × SW
	AIC =−208	intercept	−0.009987	0.024860	−0.40	0.693
	adjusted r2 = 0.25	T	0.000562	0.001266	0.44	0.663
	F7,16 = 2.08	PD	−0.077460	0.028080	−2.76	0.014
	p = 0.107	pH	0.004855	0.003296	1.47	0.160
		SW	0.000021	0.000011	1.88	0.078
		T × PD	0.005619	0.001892	2.97	0.009
		T × pH	−0.000305	0.000173	−1.76	0.098
		T × SW	−0.000001	0.000001	−1.60	0.129
alder
total	kc ∼ T + pH + SW + T × pH
	AIC =−22	intercept	3.578300	3.945612	0.91	0.376
	adjusted r2 = 0.27	T	−0.475873	0.209678	−2.27	0.036
	F4,18 = 3.00	pH	−1.029913	0.541762	−1.90	0.073
	p = 0.046	SW	0.000984	0.000525	1.87	0.077
		T × pH	0.068805	0.028986	2.37	0.029
microbial	Kf ∼ T
	AIC =−16	intercept	−4.963240	0.372650	−13.32	0.000
	adjusted r2 = 0.17	T	0.046910	0.019960	2.35	0.029
	F1,21 = 5.52
	p = 0.029
detritivore-mediated	kd ∼ T + pH + SW + T × pH + T × SW
	AIC =−223	intercept	0.029220	0.051040	0.572	0.574
	adjusted r2=−0.19	T	−0.001610	0.002725	−0.591	0.562
	F5,17 = 0.31	pH	−0.003204	0.006897	−0.465	0.648
	p = 0.899	SW	0.000015	0.000022	0.665	0.515
		T × pH	0.000247	0.000369	0.667	0.514
		T × SW	−0.000001	0.000001	−0.663	0.516