Abstract:
Peatlands contain a significant proportion of the worlds’ total soil carbon, and are
commonly assumed to serve as carbon sinks. There is however increasing evidence of
carbon loss from peat soils, and DOC concentrations in UK rivers have increased
markedly over the past three decades. Numerous drivers for increasing DOC release
have been proposed but to date the potential role of land management has not been fully
explored.
This study examines the potential effects of land management on DOC production and
release from upland peat for a series of catchments in the South Pennines and North
Yorkshire Moors. Spatial variability in drainage DOC concentration was examined in
50 small headwater catchments (<3 km
2
) and nine reservoir catchments (1.5-21 km
2
). A
subset of the reservoir catchments was further examined through time to establish any
relationship between land management and DOC.
Of the factors assessed, representing all combinations of soil type and land use, the
proportion of new vegetation burn on blanket peat was consistently identified as the
most significant predictor of spatial variation in DOC concentration. Significant
relationships were identified between both temperature and sulphate deposition and
longer-term DOC concentrations, but no interaction or cumulative effect of these two
factors was shown. In contrast, the area of new burn on blanket peat explains more than
twice the degree of variance in DOC over the same period. For catchments where no
change in the area of new burn was determined, drainage DOC increases were minimal.
This study demonstrates that land management activities are important landscape-scale
drivers of DOC concentration. Exposed peat surface following burning may be altering
peat hydrology and improving conditions for microbial activity and enhanced DOC
production. Land management therefore has significant consequence for water utilities
facing increased costs of treatment and also for the conservation of blanket bog and
blanket peat ecosystems currently managed by fire.
