Articles | Volume 8, issue 3
Biogeosciences, 8, 585–595, 2011
Biogeosciences, 8, 585–595, 2011

Research article 07 Mar 2011

Research article | 07 Mar 2011

Experimental nitrogen, phosphorus, and potassium deposition decreases summer soil temperatures, water contents, and soil CO2 concentrations in a northern bog

S. Wendel1, T. Moore2, J. Bubier3, and C. Blodau1,2,* S. Wendel et al.
  • 1Limnological Research Station and Department of Hydrology, University of Bayreuth, 95440 Bayreuth, Germany
  • 2Department of Geography and Global Environmental and Climate Change Centre, McGill University, 805 Sherbrooke Street W, Montreal, Quebec, H3A2K6, Canada
  • 3Environmental Studies Program, Mount Holyoke College, 50 College Street, South Hadley, MA 01075, USA
  • *now at: School of Environmental Sciences, University of Guelph, ON, Canada

Abstract. Ombrotrophic peatlands depend on airborne nitrogen (N), whose deposition has increased in the past and lead to disappearance of mosses and increased shrub biomass in fertilization experiments. The response of soil water content, temperature, and carbon gas concentrations to increased nutrient loading is poorly known and we thus determined these data at the long-term N fertilization site Mer Bleue bog, Ontario, during a two month period in summer. Soil temperatures decreased with NPK addition in shallow peat soil primarily during the daytime (t-test, p < 0.05) owing to increased shading, whereas they increased in deeper peat soil (t-test, p < 0.05), probably by enhanced thermal conductivity. These effects were confirmed by RMANOVA, which also suggested an influence of volumetric water contents as co-variable on soil temperature and vice versa (p < 0.05). Averaged over all fertilized treatments, the mean soil temperatures at 5 cm depth decreased by 1.3 °C and by 4.7 °C (standard deviation 0.9 °C) at noon. Water content was most strongly affected by within-plot spatial heterogeneity but also responded to both N and PK load according to RMANOVA (p < 0.05). Overall, water content and CO2 concentrations in the near-surface peat (t-test, p < 0.05) were lower with increasing N load, suggesting more rapid soil gas exchange. The results thus suggest that changes in bog ecosystem structure with N deposition have significant ramifications for physical parameters that in turn control biogeochemical processes.

Final-revised paper