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.
The average intactness of wetland-associated mosses in the forested region was 94.2%.
Bogs & Poor Fens
97.0%
intact
Rich Fens
95.5%
intact
Swamps & Marshes
92.8%
intact
Generalists
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90.0%
intact
Introduction
Mosses are small, non-vascular plants that reproduce by means of spores. In the boreal forest, mosses can be a major component of the vegetation forming the ground cover in peatlands (bogs and fens).
Mosses—technically known as bryophytes which includes species of mosses, liverworts and hornworts—are among the most significant indicators used to classify wetlands as well as guide our understanding of wetland structure, function and overall health.
- Bogs are nutrient poor, acidic ecosystems and are typically dominated by Rusty Peat Moss (Sphagnum fuscum).
- Fens are characterized by either Sphagnum species (poor fens) or brown mosses (rich fens).
- Moss communities can be used as an indicator of overall health, nutrient status, and hydrological conditions of bogs and fens
- Individual moss species can also be reliable indicators of microhabitat within wetland types because they are limited by small-scale chemical and hydrological gradients[1]. For example, Warnstorf’s Peat Moss (Sphagnum warnstorfii) occurs in lawns and on low hummocks in rich fens (pH 5–7) of the boreal forest. Marsh Leafy Moss (Plagiomnium ellipticum) is typical in the wet depressions in wooded fens and forested swamps.
Mosses are prevalent in many types of wetland ecosystems and provide several important ecological roles and services[2]:
- In peat-forming wetlands, such as bogs and fens, a moss-dominated ground layer significantly influences nutrient cycling, water-holding capacity, decomposition, organic matter accumulation, and acidification[3].
- Liverworts are typically present in lower abundances but remain a major component of wetland biodiversity.
- In swamps and marshes, the moss ground layer is poorly developed but still provides essential ecosystem services such as habitat for microorganisms and nitrogen fixation[4,5]. Wet depressions are one of the richest habitats for moss species including the leafy mosses (Rhizomnium species, Plagiomnium species) and spear mosses (Calliergon species).
In this section, we report on the status of wetland-associated moss species in the forested region of Alberta using the Biodiversity Intactness Index.
Foundation of Peatland Ecosystems
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 exist along a continuum from bogs that are acidic and nutrient poor to rich fens that are neutral to alkaline and nutrient-rich.
- Peatlands are the dominant wetland class in Alberta, comprising 90% of our wetlands.
- Peatland communities occur along a hummock (elevated mounds) and hollow (flatter and wetter) gradient. The height of hummocks can range from a few centimetres to a metre.
- Mosses—including Sphagnum species (e.g., Rusty Bog Moss) and brown mosses (e.g., Varnished Hook Moss [Hamatocaulis vernicosus])—are keystone species and the foundation of peatland ecosystems.
Methods
The ABMI collects data on moss species and builds statistical models to identify how the relative abundance of species varies in relation to native land cover, human footprints, and spatial/climate variables. For species with sufficient data, we determine cumulative effects of human footprint on species by comparing predictions under current landscape conditions to predictions in reference landscapes where all human footprints have been removed (backfilled). We convert the difference in relative abundance between predicted current and reference abundances to a scaled Biodiversity Intactness Index (BII).
Here we calculate intactness for moss species associated with three wetland types—bogs/poor fens, rich fens and swamps/marshes—and generalists. Mosses were classified into these four groups using a two-step process:
- Wetland-associated species were first associated with upland vs lowland (wetland) habitats based on habitat coefficients.
- Those species associated with lowland habitats were then further classified into the four wetland types based on literature and expert knowledge.
Please note that these habitat associations may change for some species as more data are collected.
For field sampling protocols see ABMI 2015[6], for lab processing protocols see ABMI 2010[7], and for analysis methods see ABMI 2017[8].
Krista Williams
Collection of moss samples to be identified in the lab.
- Some explanatory variables may be confounded with each other. The ABMI collects observation data—we do not manipulate levels of habitat and human footprint types at our sites. This means that some variables may be confounded, such as the effects of latitude and agricultural footprint on occurrence.
- Our species distribution models are created through batch processing by taxonomic group. This means that all species within a given taxonomic group (e.g., amphibians, mosses) are modeled using the same combination of environmental variables (e.g., habitat types, human footprint types, climate), even though there may be a more appropriate combination for specific species.
- The vegetation and soil layers we use in our models are based on GIS analysis. No GIS product has 100% accuracy. Errors in classification could lead to inaccuracies in our predictions of species’ distributions.
- We currently don't include effects outside of direct habitat loss in our models. We know that many species respond to impacts such as edge effects, grazing, pollution, or alteration in groundwater flows. We are continuing to improve our species–habitat models to include additional effects, but our models are unable to include all possible impacts on species abundance.
Results
Status of Mosses Associated with Wetlands
The status of 45 wetland-associated moss species in the forested region as measured by the Biodiversity Intactness Index: 94.5%
Intactness for four moss groups defined by their ecological affinity (primarily water and nutrient levels) for different wetland types averaged:
Bogs & Poor Fens
97.0%
Intact
Rich Fens
95.5%
Intact
Swamps & Marshes
92.8%
Intact
Generalists
90.0%
Intact
Highlights
- At 90.0% intact, habitat suitability was lowest for generalist wetland moss species that are not restricted to wetland habitats—these are species that while common in lowlands, can also be found in a variety of upland forested habitats.
- Some human development activities (e.g., forestry) occur more often in upland habitats resulting in greater impacts to generalist species such as Stair Step Moss (Hylocomium splendens; 83.5% intact), Common Broom Moss (Dicranum scoparium; 84.4% intact) and Wavy-leaved Broom Moss (Dicranum polysetum; 84.9% intact).
- Intactness for species associated with swamps and marshes was 92.8%; habitat suitability is reduced for all but one species in this group. Three of the species with intactness of less than 90% were Heart-leaved Spear Moss (Calliergon cordifolium: 85.5% intact), Slender Leafy Moss (Rhizomnium gracile: 89.1% intact) and Swamp Thread Moss (Meesia uliglinosa: 89.6% intact). These mosses are typical of nutrient-rich and moist microhabitats. Insufficient moisture conditions could lead to lower habitat suitability and these species are negatively impacted by human footprint.
- Intactness for mosses associated with bogs and poor fens—mainly Sphagnum moss species and brown mosses—was highest at 97.0% intact, on average.
- Intactness for mosses associated with rich fens was 95.5% with intactness greater than 90% for all species.
- Human footprint is lower in fens and bogs compared to other habitat types resulting in higher intactness for species associated with these wetland types.
Habitat suitability for moss species associated with bogs and poor fens was high.
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.
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.
R Caners
Rusty Peat Moss (Sphagnum fuscum) is very common in bogs in the boreal forest.
References
Vitt, D.H. 2014. A key and review of bryophytes common in North American peatlands. Evansia 31(4):121-158.
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
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
Zoltai, S.C. and D.H. Vitt. 1995. Canadian wetlands: environmental gradients and classification. Vegetation 118:131-137.
Turetsky, M.R. 2003. The role of bryophytes in carbon and nitrogen cycling. The Bryologist 106(3):395-409.
Alberta Biodiversity Monitoring Institute. 2015. Terrestrial field data collection protocols (abridged version), Version 20210411. Alberta Biodiversity Monitoring Institute, Alberta, Canada. Report available at: https://www.abmi.ca/home/publications/1-50/46.html
Alberta Biodiversity Monitoring Institute. 2010. Laboratory protocols for processing bryophytes (10009), version 2010-05-31. Alberta Biodiversity Monitoring Institute, Alberta, Canada. Report available at: https://abmi.ca/home/publications/301-350/330
Alberta Biodiversity Monitoring Institute. 2017. ABMI Species Website Manual, Version: 2017-10-06. Alberta Biodiversity Monitoring Institute, Alberta, Canada. Report available at: https://www.abmi.ca/home/publications/501-550/505
Contributors
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.
