Table 2.

Relative humidity and microbial respiration at surface-air interfaces.

Control/inoculated paired microcosm matrix	U	p
Clay 30%	12	0.458
Clay 75%	8	0.008*
PEG 30%	1	0.174
PEG 75%	2	0.014*
Sand 30%	1	0.063
Sand 75%	3	0.256
Plastic 30%	4	0.414
Plastic 75%	2	0.138

Differences between inoculated matrices and un-inoculated controls were assessed with a Mann–Whitney U test of independent means for non-parametric data. The u values (U) and probability values (p) are compared, with significance indicated* at a confidence interval of 95%.