title: Direct and indirect effects of ammonia, ammonium and nitrate on phosphatase activity and carbon fluxes from decomposing litter in peatland.
abstract: Here we investigate the response of soils and litter to 5 years of experimental additions of ammonium (NH4), nitrate (NO3), and ammonia (NH3) to an ombrotrophic peatland. We test the importance of direct (via soil) and indirect (via litter) effects on phosphatase activity and efflux of CO2. We also determined how species representing different functional types responded to the nitrogen treatments. Our results demonstrate that additions of NO3, NH4 and NH3 all stimulated phosphatase activity but the effects were dependent on species of litter and mechanism (direct or indirect). Deposition of NH3 had no effect on efflux of CO2 from Calluna vulgaris litter, despite it showing signs of stress in the field, whereas both NO3 and NH4 reduced CO2 fluxes. Our results show that the collective impacts on peatlands of the three principal forms of nitrogen in atmospheric deposition are a result of differential effects and mechanisms on individual components.
authors.affiliation: Institute of Biological and Environmental Sciences, University of Aberdeen AB24 3UU, UK. d.johnson@abdn.ac.uk
authors.forename: David
authors.initials: D
authors.lastname: Johnson
authors.forename: Lucy
authors.initials: L
authors.lastname: Moore
authors.forename: Samuel
authors.initials: S
authors.lastname: Green
authors.forename: Ian D
authors.initials: ID
authors.lastname: Leith
authors.forename: Lucy J
authors.initials: LJ
authors.lastname: Sheppard
mesh_terms: D000641:Ammonia / Q000737:chemistry* / Q000378:metabolism / Q000633:toxicity; D029795:Calluna / Q000187:drug effects / Q000201:enzymology / Q000378:metabolism; D002244:Carbon / Q000032:analysis* / Q000737:chemistry / Q000378:metabolism; D057486:Carbon Cycle; D029785:Cyperaceae / Q000187:drug effects / Q000201:enzymology / Q000378:metabolism; D017753:Ecosystem; D004784:Environmental Monitoring; D009566:Nitrates / Q000737:chemistry* / Q000378:metabolism / Q000633:toxicity*; D010744:Phosphoric Monoester Hydrolases / Q000737:chemistry / Q000378:metabolism*; D000644:Quaternary Ammonium Compounds / Q000737:chemistry* / Q000378:metabolism / Q000633:toxicity; D012989:Soil Pollutants / Q000737:chemistry / Q000378:metabolism / Q000633:toxicity; D044003:Sphagnopsida / Q000187:drug effects / Q000378:metabolism
chemical_list: D009566:Nitrates; D000644:Quaternary Ammonium Compounds; D012989:Soil Pollutants; D002244:Carbon; D000641:Ammonia; D010744:Phosphoric Monoester Hydrolases