Turnover of labile and recalcitrant soil carbon differ in response to nitrate and ammonium deposition in an ombrotrophic peatland

• Published in: Global change biology Vol. 16; no. 8; pp. 2307 - 2321
• Main Authors: CURREY, PAULINE M, JOHNSON, DAVID, SHEPPARD, LUCY J, LEITH, IAN D, TOBERMAN, HANNAH, van derWAL, RENÉ, DAWSON, LORNA A, ARTZ, REBEKKA R.E
• Format: Journal Article
• Language: English
• Published: Oxford, UK Oxford, UK : Blackwell Publishing Ltd 01.08.2010; Blackwell Publishing Ltd; Wiley-Blackwell
• Subjects: acid phosphatase; Ammonium; ammonium nitrate; Animal and plant ecology; Animal, plant and microbial ecology; Biological and medical sciences; Carbon; carbon turnover; cellulose 1,4-beta-cellobiosidase; Decomposition; Enzymatic activity; enzyme activity; Fundamental and applied biological sciences. Psychology; General aspects; Geochemistry; Mineralization; monophenol monooxygenase; Nitrates; Nitrogen; nitrogen deposition; Nutrients; peatland; peatlands; Phenols; Respiration; Simulation; soil; soil enzymes; Soil sciences; Soils; substrate-induced respiration; Wetlands; Ammonium; Atmospheric fallout; nitrogen deposition; peatland; Nitrates; carbon turnover; Nitrogen; Carbon; Peat bog; Substrate; Soils; Enzymatic activity; enzyme activity; Turnover; Respiration; substrate-induced respiration
• ISSN: 1354-1013; 1365-2486
• DOI: 10.1111/j.1365-2486.2009.02082.x

The effects of 4 years of simulated nitrogen deposition, as nitrate (NO₃⁻) and ammonium (NH₄⁺), on microbial carbon turnover were studied in an ombrotrophic peatland. We investigated the mineralization of simple forms of carbon using MicroResp[trade mark sign] measurements (a multiple substrate induced respiration technique) and the activities of four soil enzymes involved in the decomposition of more complex forms of carbon or in nutrient acquisition: N-acetyl-glucosaminidase (NAG), cellobiohydrolase (CBH), acid phosphatase (AP), and phenol oxidase (PO). The potential mineralization of labile forms of carbon was significantly enhanced at the higher N additions, especially with NH₄⁺ amendments, while potential enzyme activities involved in breakdown of more complex forms of carbon or nutrient acquisition decreased slightly (NAG and CBH) or remained unchanged (AP and PO) with N amendments. This study also showed the importance of distinguishing between NO₃⁻ and NH₄⁺ amendments, as their impact often differed. It is possible that the limited response on potential extracellular enzyme activity is due to other factors, such as limited exposure to the added N in the deeper soil or continued suboptimal functioning of the enzymes due to the low pH, possibly via the inhibitory effect of low phenol oxidase activity.