Abstract
The effects of 7 years simulated pollutant nitrogen (N) deposition on soil microbial biomass C (C-mic), soil phosphomonoesterase (PME) activity and utilisation of carbon (C) and organic N and phosphorus (P) sources by soil bacteria are reported for a heathland, an acidic grassland and a calcareous grassland. N additions increased C-mic, in the heathland, decreased it in the acid grassland, and had no effect in the calcareous grassland. These effects mirrored the changes in plant cover, indicating close-coupling of plant and microbial responses to chronic N additions. In the heathland, PME activity generally rose with each increment of N addition while in the acid grassland, PME activity significantly increased only in the 14 g N m(-2) y(-1) (ammonium nitrate) treatment. In the calcareous grassland, PME activity was highly correlated with KCl extractable N (R-2 = 0.71), indicating increased PME activity in response to increasing N saturation. At all three sites, PME activity per mg C-mic,was greater in plots receiving N inputs, reflecting greater P limitation. In the heathland, N treatments caused a 3-foId increase in the utilisation rate of C and organic N substrates in BIOLOG plates, whereas utilisation of organic P substrates rose 10-fold in response to 8 g N m(-2) y(-1) and 18-fold in response to 12 g N m(-2) y(-1). In the acid grassland, utilisation of the C sources decreased in response to the N treatments. The results demonstrate that long-term chronic inputs of pollutant N can significantly increase microbial biomass and activity in N-limited heathland ecosystems, but may reduce microbial biomass and microbial activity in P-limited grasslands. (C) 1998 Elsevier Science Ltd. All rights reserved.
Original language | English |
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Pages (from-to) | 239-250 |
Number of pages | 12 |
Journal | Environmental Pollution |
Volume | 103 |
Issue number | 2-3 |
DOIs | |
Publication status | Published - 1 Nov 1998 |
Keywords
- nitrogen
- nitrogen saturation
- phosphase activity
- soil microbial biomass
- BIOLOG plates
- acid-phosphatase-activity
- diversicolor F Muell
- forest soils
- nutrient availability
- organic phosphorus
- calluna-vulgaris
- ecosystems
- litter
- carbon
- plant