Disturbed peatlands may undergo a dramatic alteration in ecohydrological conditions, potentially limiting the recolonisation of peat-forming species like Sphagnum. A poor fen was experimentally drained in 1984, both the drained and undrained portion of the peatland burned in 2001, providing an unique opportunity to examine the ecohydrological response to ‘double disturbance’. The undrained site was characterized by a healthy recovery of peatland microform Sphagnum species, low soil water pressure (Ψ), high volumetric soil moisture (θ) content and high and stable water table position. However, the drained site showed no recolonization of Sphagnum with Brome grasses representing the dominant surface cover nine years post-wildfire. While the study period was generally wet and as such Ψ did not exceed thresholds limiting Sphagnum growth (≥ -100 mb) during the study period, a series of ecohydrological influences were found to be operating, limiting Sphagnum recolonisation at the drained site. The physical peat structure following drainage and wildfire has been considerably altered, changing the moisture retention and water storage properties of the peat, largely through substantive increases in bulk density (ρb). Moreover, specific yield (Sy) has also decreased the drained peat having become more humified, increasing unstable water table fluctuations. As such, this has lowered the resilience to drought. Only smaller decreases in θ are required to reach Ψ ≥ -100 mb at the drained and impose ecophysiological stress on Sphagnum growth. Dense canopy cover (Betula and Salix) has limited available radiation at the surface to recolonisation, shading out the surface, further limiting Sphagnum recolonisation.

Master of Science (MSc)