TABLE 1

Soil physicochemical parameters and process rates measured in soil microcosmsa

VariablebPoplar monocultureFarmlandLarch monoculture
eH2-PaH2-PeH2-FaH2-FeH2-LaH2-L
pH5.11 (0.02)c5.21 (0.02)c5.25 (0.02)5.20 (0.05)4.81 (0.01)4.77 (0.01)
% C7.6 (0.4)7.9 (0.1)2.4 (0.1)2.5 (0.3)4.3 (0.4)4.7 (0.2)
% N0.64 (0.03)0.66 (0.01)0.24 (0.01)0.24 (0.03)0.36 (0.02)0.37 (0.01)
C/N ratio11.8 (0.1)11.8 (0.1)10.1 (0.2)10.3 (0.1)11.9 (0.2)c12.7 (0.31)c
% H2O0.46 (0.01)0.51 (0.01)0.19 (0.01)c0.25 (0.01)c0.34 (0.02)0.31 (0.01)
High-affinity H2 oxidatione59 (0)c1003 (45)c22 (2)c361 (87)c47 (18)c1045 (250)c
Low-affinity H2 oxidationf264 (32)c43 (2)c61 (1)c19 (3)c59 (18)c29 (2)c
CH4 oxidatione45 (12)c198 (2)c29 (7)c59 (0)c16 (0)c45 (9)c
Net CO2 productionf82 (6)c178 (20)c9 (1)c37 (1)c18 (2)c58 (3)c
EcoPlatesg3.20 (0.01)c3.06 (0.01)c3.22 (0.04)c3.05 (0.02)c3.11 (0.01)c3.00 (0.02)c
Bacterial species richnessg6.39 (0.02)c5.85 (0.08)c,d5.83 (0.09)c6.26 (0.03)c6.02 (0.06)6.16 (0.01)
Fungal species richnessg4.11 (0.05)NA4.33 (0.03)d4.50 (0.05)4.23 (0.04)3.98 (0.18)
Bacterial species evennessh0.85 (0.00)c0.78 (0.01)c,d0.78 (0.01)c0.84 (0.00)c0.81 (0.01)0.82 (0.00)
Fungal species evennessh0.66 (0.01)NA0.72 (0.01)d0.73 (0.01)0.69 (0.01)0.65 (0.03)
  • a Shown are the mean (standard deviation) for triplicate microcosms exposed to aH2 and eH2 treatments. NA, not available.

  • b The variables water content, EcoPlates, bacterial species richness (Shannon index), fungal species richness (Shannon index), bacterial species evenness (Pielou index), and fungal species evenness (Pielou index) followed a normal distribution (Shapiro-Wilk test). Transformations were applied to obtain normal distribution of the other variables. The variable net CO2 production was square root transformed, low-affinity H2 oxidation was log transformed, C was cosine transformed, and C/N was Box-Cox transformed. The variables pH, CH4 oxidation, and high-affinity H2 oxidation could not be transformed to obtain normal distribution. dw, dry weight.

  • c Significant difference (α = 0.05) between the two H2 treatments (one-way analysis of variance for normally distributed variables and Wilcoxon-Mann-Whitney test for nonnormally distributed variables).

  • d Calculated from duplicate instead of triplicate results.

  • e Expressed in picomoles per gram of soil (dry weight) per hour.

  • f Expressed in nanomoles per gram of soil (dry weight) per hour.

  • g Shannon index.

  • h Pielou index.