Tolerance of fen mosses to submergence, and the influence on moss community composition and ecosystem resilience

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.

Disturbing to restore? Effects of mounding on understory communities on seismic lines in treed peatlands

“…The recovery of bryophyte cover on unmounded seismic lines reflects their tolerance for the flooded conditions of seismic lines and their faster growth in wet conditions, as mound height in unmounded seismic lines was comparable with those in the reference sites. In their submergence experiments, Borkenhagen and Cooper (2018) found that after submergence, bryophytes species tolerant to flooding compensated in growth for the loss of bryophytes that were more sensitive to flooding; thus, total bryophyte cover was resilient to flooding. Experimental studies also show that growth of some Sphagnum spp.…”

Spatial Habitat Structure Assembles Willow-Dependent Communities across the Primary Successional Watersheds of Mount St. Helens

“…These findings enlighten our previous species richness results as the absences of other community members such as chrysomelid beetles and chewing guild herbivores also drive comparisons in which weevils are dominant, meaning that these community members are disassociated with the presence of weevils. In a species-poor community such as this, the lack of certain community members can have a powerful effect on the services and resilience of the resulting ecosystem [124][125][126][127]. Leaf area is a much finer metric of habitat structure given its role in potential food availability, but can also be important in a willow's ability to house different types of species.…”

Spring water table depth mediates within‐site variation of soil temperature in groundwater‐fed mires

“…Even a small decline of a few centimetres in the WTD due to ongoing summer warming may trigger a chain of processes, starting with an elevated decomposition of organic matter and associated nutrient release and availability (Bridgham et al, 1998; Zak et al, 2010). This may cause, in combination with the changes in temperature conditions, substantial changes in species and functional composition of the moss layer (Borkenhagen & Cooper, 2018; Peterka et al, 2018; Vicherová et al, 2017). The patches where the groundwater thermal buffering is the strongest, as in our plots of type A, can disappear completely.…”