Mosses and the Restoration
of Disturbed Sites
Suzanne Campeau, Bryophyta Technologies inc.
A
wide array of vascular plants – grasses,
forbs, legumes, shrubs and trees - are
traditionally used to revegetate disturbed
areas in various habitats. Bryophytes and
lichens, on the other hand, are often
overlooked and seldom considered when
it comes to restoration. One notable
exception is peatland restoration, where
efficient techniques have been developed
by the Peatland Ecology Research Group
(www.gret-perg.ulaval.ca) to successfully
establish Sphagnum mosses and other
peatland plants on the bare peat surfaces
remaining after peat extraction (Quinty
and Rochefort, 2003).
The oversight of mosses and lichens
in restoration may be in part due to a lack
of knowledge about these plant groups,
A
significantly to the flora as well as the
functioning of many ecosystems. A number of species are pioneers of poor, dry
and disturbed soils. In peatlands, in alvars
and in boreal, alpine or arctic environments, these plants make up a significant
portion of the ground cover. They inhabit
rock outcrops, colonize nutrient-poor,
disturbed areas of sand and gravel and
establish spontaneously on stone walls,
pavement edges - even sidewalk cracks
in cities! Frost hardy, desiccation tolerant,
and requiring little in terms of nutrients,
pioneer mosses form colonies that retain
water, trap seeds and open the way to soil
development and to the establishment of
plants of higher stature.
This article presents two research
southern Ontario.
Use of Pioneer Mosses in
Revegetation
In July 2004, an experiment was initiated near the town of Mary’s Harbour,
at the southeastern tip of Labrador (latitude: 52o 18’ N, longitude 55 o 49’ W).
The objective was to see if, by introducing
pioneer mosses and other native plants
propagules1, we could accelerate the colonization of bare mineral substrates by
native vegetation. The project was undertaken in collaboration with Intervale
Associates Inc., a non-profit organization
specializing in environmental conservation and rural development. Project partners included the Conservation Corps
of Newfoundland and Labrador, and
B
Figure 1. Collecting plant propagules at the donor site (A) and spreading them on one of the experimental plots (B) in
Mary’s Harbour, Labrador.
as their taxonomy and identification are
not as widely taught as those of vascular
plants and are considered difficult by
many. Another reason, and maybe not
the least, is that when hearing the term
“mosses” the first image that often comes
to mind is that of tiny, delicate and
fragile plants found in shaded and cool
understory or wet areas. Not your typical
“reclamation candidates”!
Yet, mosses and lichens contribute
projects that were conducted by
Bryophyta Technologies, a small Québecbased company, on the use of mosses in
restoration. One project in southeastern
Labrador examined how pioneer mosses
can be established on bare mineral substrates in order to facilitate native vegetation development. The second project
looked at how colonies of mosses characteristic of alvars can be established on the
floor of depleted limestone quarries in
Environment Canada through its EcoAction and Science Horizons programs.
The experiment took place at four
sites located on road embankments along
the Trans-Labrador highway. At each site,
two 50 m2 experimental plots received
plant fragments, mulch and a low dose
of fertilizer. An adjacent, comparable
plot was left untreated and used as a control. The approach we tested is derived
from the one used to successfully re-
1 Propagules are any portion of a plant (e.g. a seed, a cutting, a gemma, a spore, a fragment, etc.) that can produce a new individual one detached from the parent plant.
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Figure 2. Change in plant cover over time
on plots that received (treated) and did
not receive (control) plant propagules
and mulch at the onset of the experiment
in 2004. Mary’s Harbour, Labrador.
establish vegetation on mined peatlands
(Rochefort et al., 2003).
Plant fragments were collected from a
local donor site that was characterized by
a cover of lichens, mosses and low shrubs
on a very shallow peat soil. As we hypothesized that hair cap mosses should play a
key role in vegetation establishment and
surface stabilization, the fragment mixture
collected from the barrens was enriched by
including mosses taken from Polytrichum
dominated mats. Plant fragments were
spread thinly and evenly on the plot surface at a 1:10 density ratio (i.e. surface area
of donor plot: surface area of destination
plot = 1:10) (Figure 1). The plots were
then covered with mulch made of freshly
harvested green Calamagrostis canadensis
stems and leaves, and bone meal fertilizer
was hand-spread on the surface at a rate
of 20 g/m2. Plant cover in all plots was
recorded in September 2005, July 2006
and September 2009.
Even though plant cover remained
low in our experimental plots for the first
A
two years after propagule introduction
(Figure 2), it was lower in controls plots
than in treated plots, where a diverse plant
community was slowly taking hold.
Five years after propagule introduction, differences between control and treated plots were even clearer: plant cover was
higher and much more diverse in treated
plots (Figure 3). Lichens, for example,
were nearly absent from control plots
while in the experimental plots small colonies of Cladina and Stereocaulon lichens
had developed from the fragments initially
introduced. Based on cover data only, vascular plant establishment was comparable
between treated plots and controls, but in
terms of species distribution and diversity
the plots were strikingly different. In control plots, only a few species of grasses and
shrubs were represented. Plots that had
received propagules, in contrast, showed
many small individuals of a variety of species dispersed throughout the plot and
growing among the mosses. In the case
of woody species, for example, the num-
ber of individuals per meter square was
nearly double on treated plots than on
controls. Mosses remained more abundant
and diverse in treated plots compared
with controls, although the difference in
Polytrichaceae cover remained the same
through time after the second year as hair
cap mosses also started to establish in the
control plots, possibly from spores produced in the adjacent treated plots.
Establishing Alvar Mosses
on Quarry floors
Limestone quarry floors present a
number of challenges to revegetation, the
major ones being very shallow or nonexistent soils and harsh environmental
conditions. Starting in 2003, researchers
from the University of Guelph conducted
the Quarry to Alvar Initiative (Larson et
al., 2006), an innovative research project
aimed at assessing the potential for restoring abandoned limestone quarry floors
to alvars, which are naturally occurring
limestone pavement ecosystems of sig-
B
Figure 3. One of the Labrador treated plots after five years (A; same plot as in Figure 1) and a close up taken on the same plot showing mosses,
lichens and shrub seedlings (B).
canadian reclamation | issue 1 | volume 12 | spring/summer 2012
49
A
B
Figure 4. Can species of mosses that grow in alvars be established on limestone quarry floor? (A) Mosses, low grasses, forbs and shrubs
and stunted trees of an alvar on the Bruce Peninsula, Ontario. (B) Nearly bare limestone floor at Fletcher Creek Quarry, on the Fletcher
Creek Ecological Preserve, near Guelph, Ontario. Extraction at this site ceased 80 years ago.
nificant conservation value. A summary
of the project findings was published in
the Fall/Winter 2009 Issue of Canadian
Reclamation (Matthes et al., 2009). The
project presented here complements the
work conducted earlier by the University
of Guelph researchers and concentrates on
mosses, an important component of the
alvar flora. Both projects were funded by
the Management of Abandoned Aggregate
Properties (MAAP) Program of the
Ontario Aggregate Resources Corporation
(TOARC).
Alvars are flat, relatively open areas
of calcareous bedrock with a sporadic,
thin soil cover. Plant communities on
these bedrock outcrops are a unique mixture of stunted trees, herbs, forbs, mosses
and lichens (Schaefer and Larson, 1997).
Despite the low plant biomass, the vascular plant flora of Ontario alvars is highly diverse and contains some unusual,
rare and even endangered native species
(Catling and Brownell, 1995). The advantages of restoring quarries to alvars would
be two-fold. Firstly, rehabilitated quarry
floors could become habitat extensions
for alvar species. Secondly, the development of a simple but effective method to
establish alvar communities on limestone
quarries would reduce the need for more
costly rehabilitation alternatives, such as
the importation and placement of large
Figure 5. View of some experimental plots
that were part of a trial on the effect of
substrate and straw mulch on moss establishment; (A) before the experiment, in June 2008
(B) Same area in November 2010, after three
growing seasons, with newly established moss
colonies well visible on limestone.
50
quantities of topsoil, while still resulting in
the restoration of a highly valuable natural
habitat (Figure 4).
Surveys conducted on old depleted
quarries by University of Guelph researchers showed that quarry floors resemble
alvars with respect to many environmental
conditions, and that a number of plants
characteristic of alvars are also present in
old quarries (Tomlinson et al., 2008). Old
quarry floors and alvars are therefore sufficiently similar to justify the use of alvars
as a restoration target for abandoned quarries. Richardson (2009) showed that a
number of alvar vascular plant species can
be established in quarries by seeding and
simple soil amendments, which suggests
that simple, inexpensive restoration techniques could be developed to speed up the
transition from quarry floors to alvars.
Of all the groups of plants – vascular
plants, bryophytes and lichens – that are
characteristic of alvar vegetation, bryophytes were shown by the University of
Guelph research team to be the least
successful at establishing on their own
on abandoned quarry floors. The overall
objective of this project was therefore to
determine if and how alvar moss species
can be successfully introduced to quarry
floors. The goal is to provide recommendations for simple and affordable methods
that, in combination with seeding of alvar
A
vascular plants, will promote and accelerate the establishment of functional alvar
plant communities on depleted quarry
floors.
Starting in 2008 and through 2010,
a series of alvar moss introduction experiments were conducted in four quarries
located across southern Ontario. In order
to ensure that our conclusions could be
extrapolated to a variety of sites and field
conditions, experiments were replicated
among quarries and in different years and
seasons. Several species of alvar mosses
were used. Mosses were collected from
old, naturally revegetated quarries or from
areas surrounding quarries. They were
introduced to the experimental plots at
a 1:8 density ratio (surface area of donor
plot: surface area of destination plot = 1:8).
Trials were monitored over a one to four
year period. Field experiments were conducted on a small scale due to limitations
in source material (propagules). Special
attention was nonetheless given to largescale applicability and to compatibility
with the methods suggested by Larson et
al. (2006) for the establishment of alvar
vascular plants in quarries.
The results of these experiments
showed that species of mosses naturally found on alvar limestone pavement
can be successfully established on quarry
floors starting from propagules (Figure 5).
B
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Figure 6. Effect of straw mulch and propagule introduction on the establishement and evolution of moss cover on a limestone quarry floor.
The experiment was conducted in an old, depleted quarry located in Leeds and Grenville County, southeastern Ontario.
November 2008
November 2009
November 2010
November 2011
Figure 7. Change in moss cover in a plot (50 cm x 50 cm) over the course of the experiment. This plot was on thin soil over rock and was covered
with straw mulch at the onset of the experiment. Most of the remaining straw mulch was removed prior to taking pictures, then replaced. The pale
green moss is Tortella tortuosa; Schistidium rivulare is a darker green. The lower right quadrat did not receive moss propagules.
52
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in order to apply the approach tested here
at a larger scale, these projects both indicate the need and suggest the feasibility of
developing revegetation techniques that
encompass a greater diversity of plant
groups. ■
References
Figure 8. Effect of substrate type on the establishment of introduced alvar mosses on limestone quarry floor. Same experiment and quarry as in Figure 6.
With appropriate methods (see results
below) a certain amount of success
was obtained in all the experiments we
conducted, with the exception of those
cases where our experimental plots were
completely washed out by flooding.
The use of straw mulch greatly
improved moss establishment and was a
key factor contributing to success at all
sites and for most species tested (Figures 6
and 7). Straw mulch may act in two ways.
By retaining moisture and reducing substrate temperature, straw mulch creates a
sheltered environment with a microclimate more favorable for the mosses. It
also reduces the probability of propagules
getting dispersed by water or wind. The
latter effect appeared particularly important at one site where the experimental
plots were located on a gentle slope.
Our experiments also demonstrated
that the presence of a thin layer of mineral soil on the bare limestone improved
moss establishment, but to a lesser extent
than mulch. This was true for plots
where the substrate was naturally present
(Figure 8) as well as for those where a thin
layer of sand or sand and organic matter
was experimentally added to a bare rock
surface. Like mulch, this thin layer of
material may act both to retain moisture
and to reduce the probability of moss
propagules being dispersed.
Conclusions
Mosses and lichens contribute significantly to the flora as well as the
functioning of many ecosystems. These
groups were too often overlooked in the
past when it came to restoration, even in
environments where they are naturally
abundant or where they play a significant
ecological role.
The two projects presented here
demonstrate that it is possible to establish species of mosses and lichens, starting
from propagules, for restoration purposes.
Although further work is clearly needed
Catling, P.M. and V.R. Brownell. 1995. A review
of the alvars of the Great Lakes region: distribution, floristic composition, biogeography
and protection. Canadian Field Naturalist
109:143-171.
Larson, D.W., U. Matthes, P. Richardson
and S. Tomlinson. 2006. The Quarry to
Alvar Initiative. Final report to the Ontario
Aggregate Resources Corporation (TOARC).
University of Guelph, Guelph, Ontario.
79 pp.
Matthes. U., P.J. Richardson, S. Catton,, C.D.
Stabler, and D.W. Larson. 2009. The Quarry
to Alvar Initiative: Creating new alvar habitat
from abandoned limestone quarries. Canadian
Reclamation 2009(2):10-15.
Quinty, F. and L. Rochefort. 2003. Peatland
Restoration Guide, 2nd ed. Canadian
Sphagnum Peat Moss Association et New
Brunswick Department of Natural Resources
and Energy. Québec, QC, 106 pp.
Richardson, P.J. 2009. Causes and consequences
of biodiversity in the reconstruction of ecosystems. Ph.D. Thesis, University of Guelph,
Ontario.
Rochefort, L., F. Quinty, S. Campeau, K. Johnson
and T. Malterer. 2003. North American
approach to the restoration of Sphagnum
dominated peatlands. Wetlands Ecology and
Management 11: 3-20.
Schaefer, C.A. and D.W. Larson.1997. Vegetation,
environmental characteristics and ideas on the
maintenance of alvars on the Bruce Peninsula,
Canada. Journal of Vegetation Science 8:797819.
Tomlinson, S. U. Matthes, P.J. Richardson, and
D.W. Larson. 2008. The ecological equivalence
of quarry floors to alvars. Applied Vegetation
Science 11:73-82.
For more information on these
projects, please contact Suzanne Campeau
at Bryophyta Technologies: suzanne.
[email protected];
(418) 486-2060.
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