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Section 4.4

Status of Wetland-associated Mosses

Summary of the effects of human disturbance on moss species associated with wetlands in the boreal forest as measured by the Biodiversity Intactness Index.

Updated January 2025

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Banner credit: Kirstan Tereschyn
Circle photo credit: R Caners

The average intactness of wetland-associated mosses in the forested region was 94%. Intactness by wetland category was:

Bogs & Poor Fens

98%

intact

Rich Fens

96%

intact

Swamps & Marshes

92%

intact

Generalists

90%

intact

This section was updated in January 2025 to reflect additional moss data, updated species models, and new human footprint results. The number of moss species reported on increased from 45 to 56. Overall, habitat suitability for most wetland-associated moss species remained largely unchanged.

Introduction

Mosses—technically classified as bryophytes, a group that includes mosses, liverworts, and hornworts—are among the most important indicators used to classify certain wetland types, playing a key role in defining their ecological characteristics, functions, and overall condition[1,2].

  • In peat-forming wetlands, such as bogs and fens, mosses often dominate the ground cover and play a vital role in ecosystem processes. They are essential to organic matter accumulation (commonly known as peat), while also influencing nutrient cycling, water retention, decomposition, and acidification, all of which contribute to the distinct characteristics of these ecosystems[3].
  • In swamps and marshes, the moss layer is typically less developed but remains ecologically important[4,5]. Mosses in these wetlands provide critical habitat for microorganisms and contribute to essential functions such as nitrogen fixation. Wet depressions within swamps, in particular, serve as rich habitats for diverse moss species, including leafy mosses such as Rhizomnium and Plagiomnium species, as well as spear mosses like Calliergon species.
  • Due to their sensitivity to variations in water levels and chemical composition (e.g., nutrients, pH), individual moss species are valuable indicators for identifying microhabitats within different wetland types[1]. For example, Warnstorf’s Peat Moss (Sphagnum warnstorfii) thrives in nutrient-rich fens with a pH range of 5 to 7, and is typically found in lawns and low hummocks. Meanwhile, Marsh Leafy Moss (Plagiomnium ellipticum) commonly grows in wet depressions within wooded fens and forested swamps.
Oskar Gran

Warnstorf’s Peat Moss (Sphagnum warnstorfii)

 

Marsh Leafy Moss (Plagiomnium ellipticum)

In this section, we report on the status of wetland-associated moss species classified into four wetland types (bogs & nutrient-poor fens, rich fens, swamps & marshes, generalists) in the forested region of Alberta, using the Biodiversity Intactness Index. These results have been updated incorporating more data, updated species models, and human footprint as of 2021.

Foundation of Peatland Ecosystems

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Mosses are keystone species of peatland ecosystems.

  • Peatlands are wetlands where plant production is greater than decomposition, resulting in an accumulation of peat (partially decomposed plant material).
  • Peatlands are the dominant category of wetland in Alberta, comprising 90% of our wetlands. 
  • Peatlands exist along a continuum from bogs that are acidic and nutrient poor, typically dominated by Sphagnum mosses, to rich fens that are neutral to alkaline and nutrient rich. Fens are characterized by different moss species depending on their nutrient status; poor fens feature Sphagnum species, while rich fens are dominated by brown mosses. 
  • Peatland communities occur along a gradient from hummocks (elevated mounds) to hollows (flatter and wetter habitat). The height of hummocks can range from a few centimetres to a metre.
  • Peatlands are sensitive to changes in water chemistry, hydrology, and climate, making moss species good indicators of ecosystem health.
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Intactness for moss species associated with wetlands. This graph shows the predicted deviation in species abundance from intact reference conditions (100%) for moss species associated with four wetland types: bogs/poor fens, rich fens, swamps/marshes, and generalists. Solid line indicates no change in habitat suitability between the current landscape with human footprint and the modelled reference landscape without human footprint. Both positive (predicted increases) and negative (predicted decreases) deviations from reference result in lower intactness. Each dot represents an individual species; hover over a dot to view individual species intactness values.


Status of wetland-associated mosses in the forested region. The status of moss species associated with wetlands in Alberta's forested region is assessed using the Biodiversity Intactness Index. Moss species are classified into four wetland categories: bog/poor fens, rich fens, swamps/marshes, and generalists. Three species—Blunt Pincerwort (Cephalozia pleniceps), Polygamous Hook Moss (Drepanocladus polygamus), and Common Green Bryum Moss (Ptychostomum pseudotriquetrum)—are associated with two wetland types and are therefore included in both categories. Species are ranked from lowest to highest intactness, and the Habitat Suitability column indicates whether habitat suitability has increased or decreased due to human footprint. Click on a species to view its profile for Alberta in the ABMI's Biodiversity Browser.

Conclusion

  • Habitat suitability of moss species with general habitat preferences as measured by intactness is largely driven by their ability to inhabit both upland and a range of lowland habitats.
  • Ground-covering mosses restricted to wetlands in the forested region (e.g., Sphagnum species, brown mosses) vary slightly in response to human footprint as a group, but individual species’ responses are important in explaining how habitat suitability changes with human footprint.
  • The ABMI continues to collect moss data, working to improve our understanding of species' distributions in Alberta, as well as habitat associations and impacts of human footprint on these often overlooked species.
image R Caners

Rusty Peat Moss (Sphagnum fuscum) is very common in bogs in the boreal forest.

References

1.

Vitt, D.H. 2014. A key and review of bryophytes common in North American peatlands. Evansia 31(4):121-158.

2.

Vitt, D.H. and M. House. 2021. Bryophytes as key indicators of ecosystem function and structure of northern peatlands. Bryophyte Diversity and Evolution 043 (1):253–264. Available at: https://doi.org/10.11646/bde.43.1.18

3.

Wieder R.K., D.H. Vitt, and B. Benscoter. 2006. Peatlands and the boreal forest. Pp. 1-8 in: Wieder, R.K. and D.H. Vitt (eds.). Boreal Peatland Ecosystems. Springer-Verlag, Berlin-Heidelburg-New York. Available at: https://doi.org/10.1007/978-3-540-31913-9_1

4.

Zoltai, S.C. and D.H. Vitt. 1995. Canadian wetlands: environmental gradients and classification. Vegetation 118:131-137.

5.

Turetsky, M.R. 2003. The role of bryophytes in carbon and nitrogen cycling. The Bryologist 106(3):395-409.

6.

Alberta Biodiversity Monitoring Institute. 2023. Wall-to-wall human footprint inventory—year 2021. Dataset. Last modified August 16, 2023. Available at: https://abmi.ca/data-portal/46

7.

Alberta Biodiversity Monitoring Institute. 2021. Terrestrial field data collection protocols (abridged version). Available at: https://abmi.ca/publication/601

8.

Alberta Biodiversity Monitoring Institute. 2010. Laboratory protocols for processing bryophytes. Available at: https://abmi.ca/publication/330

9.

Alberta Biodiversity Monitoring Institute. 2017. ABMI species website manual, version: 2017-10-06. Available at: https://abmi.ca/publication/505

10.

Sólymos, P., E.T. Azeria, D.J. Huggard, M-C. Roy, and J. Schieck. 2019. Chapter 4. Predicting species status and relationships. In ABMI 10-year science and program review. Available at: https://abmi10years.ca/10-year-review/resources/

Contributors

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Krista Williams, Lead Scientist, Bryophytes, Alberta Biodiversity Monitoring Institute (ABMI)

Krista has been exploring the world of bryophytes since 2007, and with the ABMI since 2014. She can usually be found scouring the woods for bryophytes or with eyes glued to a microscope assigning names to these miniature plants.

If you have questions about the ABMI's bryophyte monitoring program, please get in touch: krista.williams@ualberta.ca

We are grateful for the support of the ABMI's delivery partners.

We would like to acknowledge the organizations and sponsors highlighted below who financially supported the development of this report.