Peat pipes were measured at two different frequencies using Ground Penetrating Radar (GPR), either in continuous (all terrain vehicle; DMS) or local (manual; Birkbeck) mode across recorded transects using GPS.
Although peat pipes appear to be only infrequent at our sites (based on initial visual observations), they do provide a mostly hidden underground export route for water and dissolved or particulate carbon (DOC, POC).
In August 2012 we surveyed all control and treatment sub-catchments with automated GPR equipment with both 100 and 250 MHz antenna, criss-crossing over the sub-catchments and alongside one side of the monitoring plots.
Although these surveys did not provide peat pipes at a high enough resolution to be useful, they did provided large scale peat depth information to enable peat carbon stock estimates.
We also manually surveyed the individual plots at control and treatment sites with GPR (Charles Bristow; Birkbeck, London). For this we used a 200 MHz antenna to survey the entire plot perimeters at 10-20 cm steps, to capture peat pipes as well as a detailed peat depth profile.
The same locations will were re-surveyed in 2016 using the same equipment. Both peat pipes and peat depth could be recorded at high enough resolution.
Peat pipe (partly collapsed) with some gully erosion at the Forest of Bowland
Automated peat depth and pipe survey by DMS at the Forest of Bowland
Manual Peat depth and pipe survey by Charles Bristow at the Forest of Bowland
Sample output for GPR survey at Mossdale (C. Bristow)
Above graphs: Peat depth (left) and peat carbon stock (right) results from the GPR survey (GIS predictions)
Above table: Peat depth and soil carbon stock estimates based on catchment scale GPR surveys
Above table: Peat pipe survey results from the manual GPR survey (at monitoring plots)