TABLE 2.
Numbers of organisms in the rhizosphere in relation to plant species and soil depth (November)
| Microorganisms | Plant species | No. of subsamples
|
Mean no. of colonies/g (dry wt) of roots (SD)
|
||||
|---|---|---|---|---|---|---|---|
| 0-20 cm | 20-40 cm | 40-60 cm | 0-20 cm | 20-40 cm | 40-60 cm | ||
| PCB degraders (106) | Ash | 4 | 6 | 4 | 1.6 (0.9) Aaa | 1.0 (0.9) ABa | 0.3 (0.2) Aa |
| Birch | 0 | 4 | 0 | NDb | 2.0 (1.5) AB | ND | |
| Black locust | 4 | 3 | 4 | 5.2 (5.1) Aa | 0.1 (0.1) Aa | 0.7 (0.4) Aa | |
| Pine | 6 | 6 | 0 | 2.4 (1.8) Aa | 3.0 (1.8) Ba | ND | |
| Willow | 4 | 4 | 3 | 0.95 (0.9) Aa | 1.4 (0.3) ABa | 5.3 (3.1) Bb | |
| Grass | 8 | 0 | 0 | 160.0 (210.0) A | ND | ND | |
| Total heterotrophs (109) | Ash | 4 | 6 | 4 | 2.8 (1.3) Dd | 2.6 (2.1) DEd | 4.0 (1.3) Dd |
| Birch | 0 | 4 | 0 | ND | 1.0 (0.5) D | ND | |
| Black locust | 4 | 3 | 4 | 8.6 (7.2) DEd | 0.4 (0.3) Dd | 1.4 (0.6) Ed | |
| Pine | 6 | 6 | 0 | 3.1 (3.5) Dd | 5.8 (3.1) Ee | ND | |
| Willow | 4 | 4 | 3 | 2.2 (1.3) Dd | 2.8 (1.2) DEde | 2.9 (0.3) DEe | |
| Grass | 8 | 0 | 0 | 17.0 (7.5) E | ND | ND | |
a
Uppercase letters indicate significant differences in the same column, and lowercase letters indicate differences in the same row (P < 0.05, as determined by ANOVA).
b
ND, not determined because a sample was not available.