Table 2.

Effects of altered wolf spider densities and warming on belowground litter decomposition and litter N

Response	Fixed effects terms	Estimate	SE	df	t	P
Mass remaining, %	Intercept	98.03	5.74	19	17.07	0.000
	Litter moisture content, %	−0.36	0.08	19	−4.84	0.0001
	Control SD	3.58	2.54	19	1.41	0.175
	High SD	−6.34	2.57	19	−2.47	0.0232
	Warming	−8.14	2.52	19	−3.23	0.0044
	Control SD × warming	4.82	3.51	19	1.37	0.186
	High SD × warming	15.01	3.54	19	4.24	0.0004
N remaining, %	Intercept	111.81	13.95	19	8.02	0.000
	Litter moisture content, %	−0.35	0.18	19	−1.90	0.073
	Control SD	1.30	5.98	19	0.22	0.830
	High SD	8.20	6.06	19	1.35	0.192
	Warming	10.27	5.935	19	1.73	0.0997
	Control SD × warming	−8.66	8.28	19	−1.05	0.309
	High SD × warming	−16.14	8.34	19	−1.94	0.068

Mixed effects model results of belowground ecosystem function response variables, as predicted by wolf spider density (SD; reference category: low SD), warming (reference category: ambient temperature), and average litter moisture content. The decomposition rate is expressed as percent litter mass remaining in proportion to initial mass. Litter N is percent N remaining in litter in relation to initial N content of litter. Litter bags were buried below the tundra litter layer and underwent 14 mo of experimental treatment. Model results with control SD as the reference category for the wolf spider treatment are shown in SI Appendix, Table S5.