Climatic extremes, such as severe drought, are expected to increase in frequency and magnitude with climate change. Thus, identifying mechanisms of resilience is critical to predicting the vulnerability of ecosystems. An exceptional drought (

1.Reclaiming peatland ecosystems is challenging our understanding of how to rebuild functioning landscapes. Assisted succession may provide a practical approach to guide the reestablishment of peatlands in denuded landscapes. In Alberta, the majority of peatlands began as fens during the paludification process. This research focuses on creating fen initiation conditions to establish fen moss species on mineral sediment as an approach for peatland reclamation in the oil sands region. 2. In a field mesocosm experiment, we evaluated the establishment of five common fen mosses (Drepanocladus aduncus, Ptychostomum (Bryum) pseudotriquetrum, Campylium stellatum, Tomentypnum nitens and Aulacomnium palustre) introduced in equal proportions to clay loam. To determine the optimal hydrologic conditions for the establishment of each species, we tested four water levels (0, À10, À20 and À30 cm). We created vegetation types similar to those identified at the peat-mineral interface in peat profiles to determine the effect of herbaceous plant, low shrub and wood-strand mulch cover treatments on moss establishment. 3. Three seasons after introduction, total moss cover averaged 40% and was greatest under all cover treatments and at the 0 cm water level. Total moss biomass averaged 95Á5 g m À2 in moss introduction mesocosms and was greatest under low shrubs and herbaceous plants and at the 0 and À30 cm water levels. Fen moss species distribution was significantly influenced by water-table depth. Drepanocladus aduncus and Ptychostomum pseudotriquetrum were most common at 0 cm and Aulacomnium palustre and Tomentypnum nitens at À30 cm. 4. In this approach, we created vegetation types similar to those found on mineral sediments at the base of Alberta peat cores and successfully established distinct fen moss communities along a water-table gradient and under shade cover. Introducing a suite of fen moss species that inhabit a range of hydrologic niches under low shrubs or herbaceous plants improves moss establishment. 5. Synthesis and applications. Our research shows that it is possible to create fen initiation conditions on clay loam sediment by introducing foundation moss and vascular plant species at optimal water levels. Restoring the community structure and biomass accumulation that occurs in the initial stages of fen development appears to be a suitable target for peatland reclamation. These methods introduce a practical strategy to reclaim peatlands in the heavily impacted oil sands region of Alberta.

No abstract

No abstract

Question Flood disturbance in peatlands can create temporary or permanently submerged areas where tolerant species may persist and replace intolerant species over time. Fen moss species and communities occur along a hummock–hollow gradient in natural ecosystems, but their resistance and resilience to different durations of submergence has yet to be tested. We asked what are the short‐ and long‐term effects of submergence duration on four common boreal fen moss species and the implications for ecosystem resilience? Location Rich fen near Fort McMurray, Alberta, Canada. Methods To examine the effect of submergence duration on fen moss species and communities, we harvested and submerged monoculture plugs dominated by Hamatocaulis vernicosus, Sphagnum warnstorfii, Tomentypnum nitens and Aulacomnium palustre in the field under rich fen water for 1–8 weeks. After submergence, we planted the plugs in bare peat at the same site to evaluate the short‐ and long‐term responses of each species and changes in moss community composition over time. Results We found that moss species response to duration of submergence is not strictly related to their occurrence along a hummock–hollow gradient and that tolerant species maintain or restore moss cover. H. vernicosus was most tolerant to submergence of all durations, whereas S. warnstorfii was nearly eliminated by submergence. Over the long term, more tolerant species replaced less tolerant species, increasing diversity and moss community resilience. Overall, moss communities without S. warnstorfii were resilient to 4 weeks of submergence because T. nitens and H. vernicosus maintained dominance or established where the cover of less resilient species was limited. Conclusions We show that moss species varied in their responses to submergence duration, resulting in shifts in community composition and long‐term effects on community resilience with longer durations of submergence. This provides insight into how moss communities provide stability to peatlands in response to disturbance through shifts in community composition that support tolerant dominant species.