Characterizing current and predicting future variability of organic matter in runoff from upland peat catchments

Abstract

Peatlands are a global carbon store that is predicted to be adversely affected by global warming, in which the amount of organic carbon they release may increase. Indirect carbon dioxide fluxes from run-off are likely to be larger and harder to quantify than direct fluxes. This study simulated future climate conditions by monitoring a damaged (eroded) catchment paired with an intact (vegetated) catchment. Bulk carbon fluxes for the vegetated and eroded catchment were; 17.57 t km-2 yr-1 and 108.30 t km-2 yr-1 calculated via interpolation, and 31.57 t km-2 yr-1 and 65.48 t km-2 yr-1 calculated via rating relationships. Attempts were made to identify differences in hydrology between the vegetated and eroded catchments, particularly before and after remediation of the eroded catchment, attempted in 2007. The pH and hydrogen ion concentration did not differ between the two catchments. Prior to restoration, time to peak and run-off coefficients appeared to be unaltered; although, there is a suggestion that conditions may have improved at the eroded catchment in 2019. There were also differences between organic carbon fluxes subdivided into sub-micron size classes (0.2 µm, 50 kDa, 10 kDa and 3 kDa). Fluxes at the vegetated catchment were larger than the eroded; 48.64 43 t km-2 yr-1 and 34.92 43 t km-2 yr-1. The distrubution of the flux remained relatively similar, the two smallest fractions remaining dominant. Carbon dioxide production from samples of organic carbon classifications showed smaller sizes to have greater lability. Inorganic carbon, only dissolved carbon dioxide considered, was consistently supersaturated on average by 545 ppm at the vegetated catchment and 214 ppm at the eroded. Carbon dioxide concentrations decreased at both sites during an event. In a global warming scenario where peat is likely to become similar to the eroded catchment; the organic carbon flux is likely to increase and the sub-micron flux will potentially be smaller, but the distribution of this will remain the same.

Date of Award	1 Aug 2020
Original language	English
Awarding Institution	The University of Manchester
Supervisor	Stephen Boult (Supervisor)