A comparison of the hydrology, hydrochemistry and aquatic carbon flux from intact, afforested and restored raised and blanket bogs

Peatlands store more carbon than any other terrestrial ecosystem and deliver important water regulatory ecosystem services. The loss of formerly accumulating peatlands to forestry and potential effects on the global climate have led to increased restoration initiatives. Forest-to-bog restoration, where coniferous forestry on bogs is clear-felled and other re-wetting measures implemented, is becoming more widespread. However, while the intention is to restore the pre-afforestation ecosystem function, little is known about the impacts on peat properties, hydrology and hydrochemistry. This thesis sought to improve the understanding by comparing intact, afforested and restored bogs at raised and blanket bog locations in Scotland. Monitoring over 18 months revealed that mean water-table depth in the afforested bogs (28.1 cm) was significantly deeper than intact bogs (9.7 cm) but shallower than the afforested bogs in the oldest restoration sites (12.4 cm). Peat bulk densities were significantly higher in the afforested bogs, and moisture and carbon content were slightly lower than intact bogs. Lower bulk density and greater moisture content in the restored peat than the afforested peat indicated peat swelling might occur as pores reopen after restoration. Higher total solutes in the porewater and streamwater of afforested bogs were evidence of aerosol scavenging from the trees. In contrast, elevated dissolved organic carbon (DOC) and phosphate (PO4-P) in the restored bogs were from the felled waste (brash). Water yield was 18% lower in the afforested than the intact systems, reflecting the influence of evapotranspiration from growing tree stands. However, there were fewer differences in the peat properties, hydrological functioning and hydrochemistry between the intact bogs and the oldest restoration sites (10 - 17 years) than between the intact, afforested and most recent restoration sites (5 - 6 years), particularly where drain and furrow blocking had taken place.