Do nitrogen inputs stimulate dissolved organic carbon production in upland peat bogs?

Abstract

This study uses a 10-year record of precipitation, soil, and stream concentration of nutrient and carbon species from an upland peat catchment to examine whether or not changes in nutrient inputs can explain long-term increases in DOC flux from peat. The study uses time series analysis and particularly the derivation of impulse response functions to provide an alternative approach to environmental manipulations and experimental additions of nitrogen. The study shows that (1) the catchment has a fixed capacity for nitrogen uptake and as such nitrogen flux from the catchment is controlled by precipitation inputs; (2) the DOC flux from the catchment shows no relationship with precipitation inputs and flux from the peat itself continues to increase over the period; (3) impulse response functions suggest that high DOC concentrations suppress nutrient flux from the catchment and not the other way around; and (4) no significant correlation could be found between nutrient time series and the residual of the DOC concentrations after removing the effects of both temperature and changes in water table. The study can find no evidence of a link between nutrient inputs and the release of DOC from the peat profile. The DOC flux corrected for rainfall inputs and the residual time series of regression all show sharp step changes in the DOC release after severe drought.