C stocks

We are measuring both vegetation and soil C stocks from samples taken at the beginning and end of the project. We will also up-scale plot measurements to the landscape scale based on Ground Penetrating Radar (GPR) derived peat depth transects. Care will be taken to not affect bulk density during sampling of peat sections, bulk density is a crucial parameter for not only for measurement (see Garnett et al. 1998) but also when modelling C dynamics (see Kennedy et al., 2008). We will also install permanent peat plates to determine long-term peat growth and short-term shrinkage/expansion due to environmental changes. This will include the total peat depth, which is quite often not considered as measurements are limited to a certain depth such as 1 m, but total peatland C stocks and models should consider the total peat depth (see Heinemeyer et al., 2010). This has become particularly evident in global C stock estimates (Tarnocai et al., 2009).

In August 2012 we took one manual peat depth sample down to the bedrock with a combination of a 1 m box corer and a D-shaped peat corer for depth below 1 m. This was done at 50 cm distance from the individual temperature and water table plots for all monitoring plots. We sampled 5 cm slices with minimal bulk density impact at the following depth intervales if depth allowed: 0-5; 10-15; 20-25; 40-45; 80-85; 120-125; 150-155 cm. If peat depth was deeper we also sampled at the very bottom of the peat column. We also recorded the main vegetation coverage percentages at the time of coring (i.e. % calluna, sedge, rush, grass, moss, sphagnum and bare ground). The same locations will be re-surveyd in 2016.

We further monitored manually the peat depth along the same paths of the DMS automated GPR survey (see section on peat pipes). At ~25 locations in each sub-catchment peat depth was also assessed manually using peat depth rods pushed to the bedrock and heather coverage was recorded at those loations from around 5 m2. The same locations will be re-surveyed in 2016. We also inserted peat (steel) rods into the bedrock to create fixed data peat depth positions, also allowing peat shrinkage and expansion rates to be determined in situ (i.e. due to water table and thus peat moisture changes).

After mowing, although there was visual compaction of about 20 cm during mowing, we could not detect any compaction effects after a few months using peat rods (see peat depth comparison before vs. after mowing) at either site. This has also been confirmed by measuring bulk density across the surface peat layers (0-5; 10-15; 20-25; 40-45 cm).

Peat profile sample for SOC determination

Assessing Peat depth before vs. after mowing at Nidderdale

Marking a 20 cm mark
Marking a 20 cm marker position on the steel rod

Bulk density values per depth layer across all sites

Assessing Peat depth before vs. after mowing at Mossdale

Hammering peat rod into place
Hammering the rod into place to the 20 cm marker

Manual peat sampling alongside GPR surveys

Preliminary peat depths across all sites

Assessing Peat depth before vs. after mowing at Whitendale

Ready-to-go steel rod with marker position visible and marker disk for protection