Microbial biomass measured in the root zone of bare root tree seedlings 33 months after transplant into field soil amended with three organic amendments. For each species × amendment combination, n = 8 (standard error in parentheses). Within a column, lowercase letters denote significant differences (P < 0.05) in amendments. Pooled values are marginal means (and standard error) for treatment factors. Uppercase letters denote significant differences in marginal means.
| Soil microbial biomass carbon (mg kg−1) | ||||
|---|---|---|---|---|
| Chestnut oak | Red maple | Pin oak | Pooled value | |
| Control | 289.8 (23.8) ab | 344.2 (13.1) ab | 489.6 (23.4) a | 380.6 (19.6) A |
| Peat moss | 252.5 (19.9) b | 250.9 (37.2) b | 269.4 (21.2) b | 258.9 (11.6) B |
| Leaf-based compost | 371.9 (38.7) a | 389.5 (18.0) a | 501.3 (47.9) a | 427.2 (22.0) A |
| Biosolids-based compost | 370.0 (30.8) a | 382.1 (35.7) a | 463.3 (68.5) a | 408.9 (24.8) A |
| Pooled value | 319.5 (16.6) B | 341.6 (16.1) B | 429.8 (26.9) A | |