Moisture dynamics and hydrophysical properties of a transplanted acrotelm on a cutover peatland

Abstract

Abstract:The natural carbon storage function of peatland ecosystems can be severely affected by the abandonment of peat extraction, influencing peatland drainage, leading to large and persistent sources of atmospheric CO 2 . Moreover, these cutover peatlands have a low and variable water table position and high tension at the surface, creating harsh ecohydrological conditions for vegetation re-establishment, particularly peat forming Sphagnum moss. Standard restoration techniques aim to restore the peatland to a carbon accumulating system through various water management techniques to improve hydrological conditions and by reintroducing Sphagnum at the surface. However, restoring the hydrology of peatlands can be expensive due to the cost of implementing the various restoration techniques. This study examines a peat extraction-restoration technique where the acrotelm is preserved and replaced directly on the cutover peat surface. An experimental peatland adopting this acrotelm transplant technique had both a high water table and peat moisture conditions providing sufficient water at the surface for Sphagnum moss. Average water table conditions were higher at the experimental site ( 8Ð4 š 4Ð2 cm) compared to an adjacent natural site ( 12Ð7 š 6Ð0 cm) suggesting adequate moisture conditions at the restored surface. However, the experimental site experienced high variability in volumetric moisture content (VMC) in the capitula zone (upper 2 cm) where large diurnal changes in VMC (¾30%) were observed, suggesting possible disturbance to the peat matrix structure during the extraction-restoration process. However, soil-water retention analysis and physical peat properties (porosity and bulk density) suggest that no significant differences existed between the natural and experimental sites. Any structural changes within the peat matrix were therefore minimal. Moreover, low soil-water tensions were maintained well above the laboratory measured critical Sphagnum threshold of 33% ( 100 mb) VMC, further indicating favourable conditions for Sphagnum moss survival and growth.

Response of hydrology and CO<sub>2</sub> flux to experimentally-altered rainfall frequency in a temperate poor fen, southern Ontario, Canada

“…In our study -100 cm of tension was reached at a VMC of 37 %, similar to thresholds found in other peatlands (Price and Whitehead, 2004;Cagampan and Waddington, 2008). The high-and medium-frequency treatments for all vegetation communities maintained soil moisture above this value for at least 92 % of the experiment; however, deviations below this threshold increased considerably in the low-frequency rain treatment (Fig.…”

Moisture controls on CO2 exchange in a Sphagnum‐dominated peatland: results from an extreme drought field experiment

“…Using 40-50% VWC as a threshold, equivalent to when pressure heads fall below 100 cm water and hyaline cell drainage occurs (Price and Whitehead, 2004;Cagampan and Waddington, 2008), it is clear that all plots within 15 m of the ditch never exceeded this threshold. In contrast, the natural plots exceeded the threshold 100% of the time and D-25 exceeded the upper bound ¾70% of the season.…”

“…Hayward and Clymo (1982) indicate that hyaline cell drainage occurs at pressure heads below 100 cm water. Studies relating pressure head and volumetric water content (VWC) for peat suggest that this threshold pressure is equivalent to a VWC of 40-50% (Price and Whitehead, 2004;Cagampan and Waddington, 2008). Beyond this threshold Sphagnum moss water content and hence productivity will likely be greatly reduced.…”

Advances in Canadian Peatland Hydrology, 2003-2007

“…Drained and cutover peatlands have an erratic water table regime caused by degraded peat hydraulic properties (Price and Whitehead, 2004). New peat extraction where the acrotelm is preserved shows great promise (Cagampan and Waddington, 2007; but nevertheless, degraded peat properties result in lower soil-water pressures that are detrimental to recolonization of peat-forming Sphagnum mosses (McNeil and Waddington, 2003). Where mosses have recolonized they modulate water table and soil-water pressures (Price and Whitehead, 2004).…”

“…Asada et al (2005) demonstrated that shallow flooding of a peatland caused an initial net decrease in carbon stores but the development of vegetation on floating peat mats offset this decrease in carbon storage. In cutover peatlands a stable moisture supply is most beneficial to Sphagnum growth (Petrone et al, 2003;2004b;Cagampan and Waddington, 2007) compared with repeated wetting and drying events (McNeil and Waddington, 2003). CO 2 exchange in these ecosystems has been correlated to DOC concentration (Glatzel et al, 2003).…”