Seasonal Indicators as Key Descriptors of Water Deficit in <i>Sphagnum</i> Farming Systems

Paludiculture, in the form of Sphagnum farming, is a renewable and cyclical way to produce Sphagnum moss fibres. The duration and frequency of water deficit due to the positioning of the water table level in the peat profile is a key driver for biomass accumulation rates in Sphagnum farming. For optimal outcomes, it is necessary to establish the threshold water table depth beyond which Sphagnum productivity decreases. In this article the daily water deficit (WD), the sum of daily water deficit (SWD) and the seasonal average water table ( ħ ) are examined to quantify water deficit. The compilation of data from five years of experimental Sphagnum farming, in both managed peatlands and greenhouse mesocosms, was used to build a dataset covering a wide variation of water table levels. This study strengthens the idea that the higher the water deficit, the lower the productivity of the Sphagnum species. Among the water deficit indicators analysed, WD and SWD have stronger correlation with Sphagnum productivity than ħ . The threshold water table depth determined for each subgenus is as follows: Acutifolia at 13.8 ± 1.9 cm, Sphagnum at 12.5 ± 1.4 cm, and Cuspidata at 3.1 ± 1.8 cm. These values correspond to a water table closer to the surface than reported in the literature for Sphagnum peatland recolonisation, which is 40 cm, and this is because the aim in Sphagnum farming is to maximise productivity.