Quantifying moss moisture stresses in undrained, afforested and rewetted peatlands located in Republic of Ireland using laboratory measurements and computer modelling

This study utilized site-specific peat hydrophysical properties (inverse of air-entry pressure, α; pore size distribution index, n; saturated hydraulic conductivity, Ks; and pore tortuosity, L) as inputs into the HYDRUS 1-D computer model for quantifying moss moisture stresses on Irish peatlands. The site-specific peat hydrophysical properties computed using pedotransfer functions obtained from laboratory measured bulk density (BD) and % organic matter (OM). The peat samples obtained from undrained sites (Scohaboy, Pollagoona and Lough Ghe), three afforested sites (S18, S28 and S44) and rewetted sites (Scohaboy and Pollagoona). The moss moisture stresses quantified using a known ecohydrological threshold of −100 cm. The site-specific peat hydrophysical properties, four initial WTDs (3, 8, 20 and 30 cm) and two distinct precipitation regimes (single and consecutive 4 years having severely dry [SD], extremely dry [ED], near normal [NN], very wet [VW] and extremely wet [EW] periods) were inputs into HYDRUS 1-D model. The modelling results showed that none of the peatland sites ever reached −100 cm threshold in single year simulations at all initial WTDs. However, in the consecutive 4-year simulations, Scohaboy, Pollagoona and Lough Ghe undrained, S28 afforested and Pollagoona rewetted sites first reached −100 cm threshold on 516, 508, 624, 1329 and 517 day, respectively. In the consecutive 4-year simulations, undrained Scohaboy, Pollagoona, Lough Ghe, S28 afforested and Pollagoona rewetted reached −100 cm threshold in ED and SD years. We concluded that moss recolonization is likely to be successfully on peatlands having minimal to no −100 cm threshold days.