Response of phosphomonoesterase activity in the lichen Cladonia portentosa to nitrogen and phosphorus enrichment in a field manipulation experiment

• Published in: The New phytologist Vol. 186; no. 4; pp. 926 - 933
• Main Authors: Hogan, E.J, Minnullina, G, Sheppard, L.J, Leith, I.D, Crittenden, P.D
• Format: Journal Article
• Language: English
• Published: Oxford, UK Oxford, UK : Blackwell Publishing Ltd 01-06-2010; Blackwell Publishing Ltd; Wiley Subscription Services, Inc
• Subjects: ammonium; Analysis of Variance; Biomarkers; Cladonia; Cladonia portentosa; Deposition; Enrichment; Environmental effects; lichens; Lichens - enzymology; N : P ratio; nitrate; nitrates; Nitrogen; Nitrogen - metabolism; nitrogen deposition; Nitrogen enrichment; Peatlands; phosphatase; Phosphoric Monoester Hydrolases - metabolism; Phosphorus; Phosphorus - metabolism; Plant Leaves - metabolism; Pollution levels; Thallus
• ISSN: 0028-646X; 1469-8137
• DOI: 10.1111/j.1469-8137.2010.03221.x

Effects of nitrogen (N) enrichment on the heathland lichen Cladonia portentosa were quantified to test the hypothesis that modified N : phosphorus (P) relationships observed in this species in N-polluted natural environments are a direct effect of increased N deposition, and to evaluate potential confounding effects of N form and P availability. Cladonia portentosa was harvested from experimental plots in lichen-rich peatland vegetation (background total N deposition of 8 kg N ha⁻¹ yr⁻¹) treated for 4 yr with additional wet N deposition at 0, 8, 24 and 56 kg N ha⁻¹ yr⁻¹ as either NH₄⁺ or NO₃⁻, and with or without P added at either 0.6 or 4 kg P ha⁻¹ yr⁻¹. Nitrogen enrichment increased thallus N concentration, N : P mass ratio and phosphomonoesterase (PME) activity by factors of up to 1.3, 1.4 and 1.7, respectively, effects being independent of N form. Phosphomonoesterase activity was tightly related to thallus N : P ratio with additions of P at 4 kg ha⁻¹ yr⁻¹ depressing PME activity by a factor of 0.4. Nitrogen enrichment induces P-limitation in C. portentosa with attendant changes in chemical and physiological characteristics that could be used as sensitive biomarkers with which to detect low levels of N pollution.