Table 1.
Microbial responses summarized for forest floor (Oe/Oa)a
| Response to chronic N deposition | % change | Reference(s) |
|---|---|---|
| Plant | ||
| NPP | +10 | 7 |
| Leaf litter production | 0 | 7 |
| Leaf litter N concn | +25 | 3 |
| Fine root litter | 0 | 4 |
| Fine root N concn | 0 | 4 |
| Biogeochemical | ||
| Forest floor mass | +51 | 3 |
| Forest floor turnover | −60 | 3 |
| Soil organic matter content | +18 | 3 |
| Soil solution NO3− concn | +288 | 3 |
| NO3− leaching | +680 | 5 |
| Dissolved organic matter leaching | +26 | 5 |
| Microbial | ||
| Soil respiration | −15 | 4 |
| Active microbial biomass (PLFAb) | +23 | 36, 59 |
| Phenol oxidase activity | −33 | 36, 59 |
| Peroxidase activity | −30 | 36, 59 |
| Basidiomycete laccase copy no. | −5 to −8 | 16 |
a
Eighteen years of experimental N deposition have increased the storage and slowed the cycling of C in forest floor and surface mineral soil. With the exception of the laccase copy number, all of these responses are statistically significant.
b
PLFA, phospholipid fatty acid analysis.