Antarctic Science 25(2), 318–328 (2013) &Antarctic Science Ltd 2013 doi:10.1017/S095410201200082X
Rapid denudation processes in cryptogamic communities from
Maritime Antarctica subjected to human trampling
, F. LARA
, P. TEJEDO
, A. QUESADA
and J. BENAYAS
´a, Universidad Auto
´noma de Madrid, c/ Darwin 2, 28049 Madrid, Spain
´a, Universidad Auto
´noma de Madrid, c/ Darwin 2, 28049 Madrid, Spain
*Corresponding author: firstname.lastname@example.org
Abstract: This study explores the impact of human trampling on moss and lichen dominated communities of
Maritime Antarctica. A simulation of trampling was performed on previously unaffected plots of different
terricolous cryptogamic assemblages at Byers Peninsula, Livingston Island. The communities studied were:
1) a uniform moss carpet, 2) a heterogeneous moss assemblage composed of hummocks and turfs, and
3) a fellﬁeld lichen community. All communities analysed were extremely sensitive but different denudation
processes were observed. None of the plots maintained 50% of initial coverage after 200 pedestrian transits.
Even very low trampling intensity resulted in disturbance at all plots. Sensitivities of the different
communities were identiﬁed in order to formulate recommendations for minimizing the trampling impacts. In
our study the lichen dominated community on dry exposed soils exhibited the lowest resistance to trampling.
For moss communities, lower resistance was found in peat soils with higher water content and biomass. With
the current trend of increasing human presence in Antarctica, we predict that the cumulative impacts of
trampling over future decades will adversely affect all types of moss and lichen communities.
Received 27 January 2012, accepted 11 July 2012
Key words: fellﬁeld soils, human impact, management, moss and lichen communities, recreation ecology,
Bryophyte and lichen communities constitute one of the
few types of terricolous vegetation in Maritime Antarctica,
being especially developed in favourable coastal locations.
Ice-free areas of coastal sites experience most of the human
impact from ship-borne tourism and scientiﬁc research on
the Antarctic Peninsula and offshore islands (Lynch et al.
2010, Hughes et al. 2011). Therefore terrestrial vegetation
is especially vulnerable to human foot trafﬁc. The increase
of visitors to the Antarctic has been exponential during
the last twenty years with cumulative trampling impacts
detected at or near tourist landing sites (Bastmeijer &
Roura 2004) and around scientiﬁc ﬁeld camps (Tejedo
et al. 2009). Increased human presence is relatively well
documented. Data on national research programmes
activities are available on the Antarctic Treaty Secretariat
(ATS) website (http://www.ats.aq/e/ie.htm). Information on
tourist visits is published on the International Association
of Antarctica Tour Operators (IAATO) website (http://
iaato.org/es/tourism-statistics). Tourist visits are largely
concentrated in the Antarctic Peninsula region. Tourists
arrive on cruise ships and make shore visits on the ice-free
coastal zones of two to three hours each, one to three times
daily (Bertram 2007). Scientiﬁc expeditions are far more
widespread along the Antarctic Peninsula, as personnel can
work out of stations, ships or ﬁeld camps (Hughes et al.
2011). As a result, both diffuse and concentrated trampling
patterns can be expected to result from human activities on
the Antarctic Peninsula.
Other factors, such as climate change (Vaughan et al.
2003, Turner et al. 2005) and human induced biological
invasions (Frenot et al. 2005, Hughes & Convey 2010),
could act in synergy with the deterioration of terrestrial
ecosystems resulting from trampling (Smith 1994, Olech
1996, Smith & Richardson 2011). Moreover, other human
activities could also have indirect effects. For example, in
the case of the South Orkney Islands, sealing activities
in the 18th century may have indirectly led to the severe
damage to vegetation caused by expanding fur seal
populations (Smith 1988). Available knowledge on the
effects of trampling in the Antarctic is currently rather
sparse (Tin et al. 2009, Convey 2010).
This study offers a ﬁrst attempt to assess the sensitivity
of bryophyte and lichen terricolous communities under
experimental trampling conditions in Antarctica. Previous
studies of trampling on bare soils conducted by Ayres et al.
(2008) in the McMurdo Dry Valleys showed that even low
levels of human trafﬁc could produce impacts on soil biota.
Tejedo et al. (2005, 2009) developed indicators and measured
the effects of experimental trampling on bare soils on Byers
Peninsula. On Cuverville Island, de Leeuw (1994) and Beyer
&Bo¨lter (2002) reported that low trampling intensities
rapidly led to disturbances to terrestrial vegetation. Thor
(1997) and Johansson & Thor (2008) studied the possible
impacts of human activities on terrestrial vegetation around
research stations in Dronning Maud Land and reported
no severe damage but a decline in the number of lichen
species. In our study area, the South Shetland Islands,
signiﬁcant damage to terrestrial vegetation has already been
documented at sites with a high concentration of scientiﬁc
stations, such Fildes Peninsula, King George Island (ASOC
2004), or tourist visited sites such Barrientos Island, Aitcho
Archipelago (Ecuador & Spain 2012).On a larger scale,
Scott & Kirkpatrick (1994) conducted studies of the effects
of trampling on the biodiversity of sub-Antarctic Macquarie
Island. Also in the sub-Antarctic, Gremmen et al. (2003)
examined the different habitats crossed by paths on Marion
Island. In the Arctic, West & Maxted (2000) examined the
effects of trampling around ﬁeld camps in Svalbard. To our
knowledge, no experimental trampling studies focused on
the sensitivity of cryptogamic formations have been
performed in the Antarctic Peninsula.
Experimental trampling studies of vegetation have been
frequently conducted in more temperate areas (Cole &
Bayﬁeld 1993, Cole 1995a, 1995b, Marion & Cole 1996,
Marion & Leung 2001, Farrell & Marion 2001, 2002),
providing an extensive framework of procedures. The speciﬁc
aim of the current study is to measure the resistance capacity
of different Antarctic terricolous cryptogamic communities
to human trampling. The resistance of vegetation to
trampling is deﬁned by the amount of damage in terms of
cover loss caused by a given trampling intensity (Cole &
Bayﬁeld 1993). To this end, we used a linked set of
indicators and ﬁeld observations. Our objectives were to
identify effective indicators for assessing the consequences
of trampling on cryptogamic vegetation, and to estimate
the magnitude of this impact on different bryophyte and
lichen communities. With this study, we hope to advance
our baseline knowledge on crytogamic formations in the
Antarctic Peninsula, contribute towards minimizing the
environmental impacts of scientiﬁc expeditions, and alert
the scientiﬁc community to the challenges faced by these
most sensitive plant formations in the context of increased
human activity in the Antarctic.
Material and methods
Description of the study area
Byers Peninsula is situated on the western side of Livingston
Island (62834'35''–62840'35''S, 60854'14''–61813'07''W) and is
Fig. 1. Study site at Byers Peninsula ASPA No. 126 topographic map (modiﬁed). Inset: the location of the three cryptogamic
communities in the South Beaches of Byers Peninsula. Source: ASPA 126 Management Plan, Byers Peninsula (Map 2).
TRAMPLING EFFECTS ON CRYPTOGAMIC COMMUNITIES 319
the largest ice-free area in the South Shetland Islands
(Lo´pez-Martinez et al. 1996). Its numerous freshwater
bodies are of interest for limnological studies (Quesada
et al. 2009). The periglacial landscape comprises tens of
lakes and streams with diverse biological conditions (Toro
et al. 2007). The landforms and deposits with various origins
support varied types of vegetation. The cryptogamic ﬂora of
Byers Peninsula is remarkably rich, including 42 species
of mosses (Ochyra et al. 2008, ATCM 2011), similar to that
of South Bay, another important ice-free area on Livingston
Island (Sancho et al.1999).
Although lichen communities can be found throughout
Byers Peninsula, bryophyte vegetation is more developed
on the south coast (Lindsay 1971), and especially in
areas at low altitudes that beneﬁt from nearby meltwater.
We analysed three terricolous cryptogamic communities
situated inland and on the southern beaches (Fig. 1)
which have different appearances and ecological afﬁnities
(Fig. 2). Community A (‘‘moss carpet community’’)
comprises uniform moss carpets of highly hydrophilous
pleurocarpous mosses growing on wet coastal plains,
permanently bathed by melting snowpacks. Community B
(‘‘moss hummock community’’) corresponds to heterogeneous
moss assemblages dominated by large hummocks of
pleurocarpous mosses, irregularly patched with turfs and
cushions of acrocarpous mosses, developed on seepages
areas of raised beach terraces not permanently wetted.
Community C (‘‘lichen fellﬁeld community’’) is an
example of a fellﬁeld cryptogamic community dominated
by small foliose lichens accompanied by different mosses,
growing on seepage areas of exposed upland slopes that
dry out after the spring melt. Following the classiﬁcation
by Smith (1996) and Ochyra et al. (2008) the three
communities can be related to three different types of
sub-formations within the non-vascular cryptogam tundra
formation. Community A corresponds to the bryophyte
carpet and mat sub-formation, Community B the tall moss
cushion (hummock) sub-formation, whereas Community C
is placed in the crustaceous and foliaceous lichen sub-
Fig. 2. Diagram of cryptogamic communities in South Beaches. Main image: large moss covered lowland area containing communities
A and B. Author: L.R. Pertierra. January 2010. Top left-hand image (1): highland containing Community C. Top right-hand image
(2): detail of fellﬁeld lichen community (C) on exposed upland slopes. Bottom left-hand image (3): detail of a moss hummock
community (B) on a raised beach terrace. Bottom right-hand image (4): detail of a uniform moss carpet community (A) on
a coastal plane.
320 L.R. PERTIERRA et al.
Determination of baseline conditions
At the start of each experiment, before any trampling has
been initiated, the baseline conditions of each cryptogam
community were referred to as 'Level Zero' (0). In order to
conduct initial descriptions of the bryophyte and lichen
composition of each community, experimental plots of 6 m
that were representative of each community were selected.
Species composition was determined in the laboratory from
samples from the plots, following established procedures
(Sancho et al. 1999, Bednarek-Ochyra et al. 2000, Øvstedal
& Smith 2001, Putzke & Pereira 2001, Ochyra et al. 2008).
Specimens are stored in the MAUAM herbarium.
Edaphic parameters were determined in the laboratory
from triplicate core samples of each community. Soil organic
matter was quantiﬁed by the Walkley & Black wet oxidation
method (Nelson & Sommers 1982). Total nitrogen (N)
content was determined by the Kjeldahl method (Bremner
& Mulvaney 1982). Exchangeable potassium (K) was
determined by atomic absorption spectrometry using an
ammonium acetate extraction method (Thomas 1982). The
method of Olsen et al. (1954) was used to estimate available
phosphorus (P). Soil acidity (pH) was measured in water and
in 0.1 M potassium chloride (KCl) using a 1:2.5 soil/solution
ratio. Electrical conductivity was measured in a 1:5 soil:
water extract. General geomorphological information was
extracted from local cartography (Lo´pez-Martinez et al. 1996,
Navas et al. 2008).
Procedures for trampling experiments
Trampling was measured as the number of pedestrian
transits. For the purpose of standardization (Cole 1995a,
1995b), experiments were performed by a person 1.80 m
tall, weighing 85 kg and wearing rubber boots. Transects
followed the dimensions suggested by Cole & Bayﬁeld
(1993). Dimensions of 6 m x 1 m were selected in order that
three random plots, each 25 cm x 25 cm, could be sampled
at each of ﬁve semi-quantitative stages. The ﬁve sampling
stages were deﬁned by the resistance of the cryptogam
communities to trampling. The ﬁrst sampling stage took
place when the ﬁrst evidence of damage as a result of
trampling could be seen, or when 95% of the vegetation cover
remained intact. This stage was labelled as 'Level One' (1).
Trampling would continue and measurements were made at
subsequent levels of degradation including: 'Level Two' (2),
where c. 75% of the vegetation cover remained intact,
'Level Three' (3), where c. 50% of the vegetation cover
remained intact, 'Level Four' (4), where c. 25% of the
vegetation cover remained intact and 'Level Five' (5),
where less than 5% of the initial vegetation cover remained
intact. This approach was selected in order to fully cover
the dynamics of vegetation denudation. Since it represents
50% of vegetation denudation, 'Level Three' serves as an
indicator of resistance of the moss and lichen communities
that can be used for comparing with other studies. In the
remainder of this paper, we will refer to the various states
of the cryptogam communities by means of a code
combining the letter of the community (A-B-C) with the
level of degradation (0 to 5).
For the purpose of monitoring when the next sampling
stage was reached, the amount of vegetation cover was
estimated every time trampling intensity was doubled.
A grid of 25 squares was laid over a random plot
of 5 cm x 5 cm and photographically documented. The
percentage of area with complete loss of macroscopic
structure was estimated and used as a measure of the
loss of vegetation cover. Trampling intensity was increased
until total disruption of the crytogamic community was
At each sampling stage, physical and biological indicators
were measured in three random 25 cm x 25 cm sampling
plots. Soil resistance to penetration was used as an indicator
of the effective gradual impact on soil compaction (Tejedo
et al. 2005, 2009). Five measurements were taken at each
sampling stage on the soil of each cryptogam community
with a hand edaphic penetrometer. For total biomass and
water content, core samples were removed from the sampling
plots. In total, 54 circular cores were collected. Core
dimensions ( 7 cm diameter x 7 cm len gth) were s ufﬁcient
to obtain approximately 200 g of wet samples. A core depth
of 7 cm was selected in order that all biomass could be
recovered after trampling. As a result, the measured biomass
and water content need to be considered at these conditions.
Soil fraction from additional samples was sieved in a 2 mm
mesh to measure soil moisture. Cores collected were frozen
at -208C in sealed bags until analysis.
Soil moisture, water content and total organic matter
were respectively quantiﬁed in triplicates through loss-on-
ignition technique with wet & dry weight calculation after
heating in porcelain crucibles in a mufﬂe furnace. Soil
moisture (% soil weight) and water content (% sample weight)
Table I. Chemical properties and nutrient content of the soils from the terrestrial cryptogamic communities from Byers Peninsula.
Community nOrganic matter N C/N K
P pH Electric conductivity
(%) (%) (cmol
/Kg) (ppm) (1:2.5) (dS/m)
Mean SD Mean SD Mean SD Mean SD Mean SD Mean SD Mean SD
A. Moss Carpet 3 1.70 1.21 0.14 0.08 11.53 2.87 0.66 0.19 1.22 0.23 6.33 0.26 0.05 0.00
B. Moss Hummock 3 1.60 0.62 0.15 0.06 12.24 0.97 0.61 0.08 1.27 0.99 6.06 0.16 0.07 0.04
C. Lichen Fellﬁeld 3 2.53 0.90 0.23 0.07 10.98 1.58 0.35 0.03 0.43 0.18 6.99 0.98 0.22 0.06
TRAMPLING EFFECTS ON CRYPTOGAMIC COMMUNITIES 321
Fig. 3. Visual features. Visual status of experimental plots along trampling simulation respectively in A-B-C communities.
Author: L.R. Pertierra. January 2010.
322 L.R. PERTIERRA et al.
were measured after 24 hr at 1058C, while biomass
(mg carbon (C) cm
soil) was measured after 4 hr at 4508C.
Results from soil resistance to penetration, water
content and total biomass were expressed with standard
deviations and represented in graphs. On these graphs the
model ﬁt which best represented the observed trend was
also calculated with its coefﬁcient of determination (r
Vegetation coverage loss trends were also represented.
It was estimated once per stage and thus no standard
deviations were obtained.
Experiments were conducted in the late summer on days
where there had been minimal precipitation on previous
days. Results on soil resistance to penetration and water
content are circumscribed within these conditions and
cannot be easily extrapolated to other studies. Nonetheless
all measurements were performed on the three communities
in parallel and they can therefore be compared.
Community A was made up of dense, uniform and
extensive moss carpets that developed on ﬂat terrain,
and dominated by the hydrophilous pleurocarpous moss
Warnstorﬁa sarmentosa (Wahlenb.) Hedena¨s. Other
large mosses could be occasionally found, particularly
Sanionia georgicouncinata (Mu
¨ll. Hal.) Ochyra & Hedena¨s
and Polytrichastrum alpinum (Hedw.) G.L. Sm. The
community was heavily ﬂooded, with a water content of
87% in core samples and a soil moisture content of 28%
(see Supplemental Table at http://dx.doi.org/10.1017/
Community B comprised heterogeneous, moss dominated
vegetation growing on sandy pebble-rich substrate of raised
terraces, frequently adjacent to Community A but under
drier conditions. It was dominated by the pleurocarpous
Sanionia georgicouncinata and, to a lesser extent, by the
acrocarpous Polytrichastrum alpinum. Depending on
microtopographical conditions, which favoured greater or
lesser water supply, other species could be present, such
as Warnstorﬁa sarmentosa or Polytrichum juniperinum
Hedw. Intermixed with all these large mosses, many very
small species could appear in small proportions, and
we found Bartramia patens Brid., Pohlia wahlenbergii
(F. Weber & D. Mohr) A.L. Andrews, Andreaea regularis
¨ll.Hal., Brachythecium austrosalebrosum (Mu
Kindb., and the leafy liverwort Cephaloziella varians
(Gottsche) Steph. The Antarctic hairgrass Deschampsia
antarctica E. Desv. was also present in small patches.
Samples from this community had a water content of
53% and a soil moisture content of 19% (Supplemental
Table). The substrate was sandier, resulting in moderate
drainage, and bedrock was more evident and was
Community C was a cryptogam assemblage that
developed on upland terrains and was dominated by the
blackish foliose cyanolichen Leptogium puberulum Hue.
The pleurocarpous mosses Brachythecium subpilosum
(Hook. f. & Wilson) A. Jaeger and Sanionia uncinata
(Hedw.) Loeske were also abundant. Other mosses found in
lower proportions were Bartramia patens,Polytrichastrum
alpinum,Schistidium lewis-smithii Ochyra, and Pohlia
cruda (Hedw.) Lindb. This community grew on moraine
soils which were among the driest conditions included in
this study. Water content in the samples was c. 21% and
soil moisture was also around 20%.
Soil characteristics are shown in Table I. Organic matter (OM)
content was very poor for the moss dominated communities
A and B (mineralised soil), and was deﬁcient in the
lichen fellﬁeld Community C (soil mineral-organic).
Results are consistent with the C/N ratios, which indicates
that these nutrients do not act as constraints in the
humidiﬁcation–mineralization process. Nitrogen content
is normal in Communities A and B, whereas it is
comparatively high in Community C which probably has
a higher mineral nitrogen ratio. Soils from all communities
have a low salt content, and hence low electrical
conductivity. All soils have very low values of phosphorus.
Levels of potassium in all soils can also be considered as low
but they lie within normal limits (Thomas et al. 2008).
Physical effects of trampling
The effects of trampling on cryptogamic vegetation are
inﬂuenced by several factors, such as hydrological
conditions, geography and topography. These factors may
inﬂuence the response of the plant communities to human
activity. Visual effects of trampling experiments were
Fig. 4. Physical features. Trampling intensity (passes) and
resistance to penetration (kilogrammes per square centimetre)
for trampling experiments at communities A, B and C.
TRAMPLING EFFECTS ON CRYPTOGAMIC COMMUNITIES 323
photographically documented (Fig. 3). In the case of
the moss carpet community (A), the ﬁrst visible effects
were detected after the ﬁrst 25 passes (A1). Macroscopic
destruction of the vegetation cover was detected after
300 passes (A5). The moss hummock community (B)
exhibited visible effects after 50 passes (B1) and reached
macroscopic destruction after 600 passes (B5). The lichen
fellﬁeld community (C) exhibited visible effects after only
10 passes (C1) and reached macroscopic destruction after
only 160 passes (C5).
Soil characteristics differ between communities
(Table I). Data obtained on resistance to penetration are
shown in Fig. 4. Whereas initial values on soil compaction
were similar (c. 1kgcm
) for communities A, B and C,
ﬁnal values varied. Moss carpet community (A) soils’
compaction reached c. 300 passes without saturation when
the simulation ended due to the total loss of vegetation in
the community. Moss hummock community (B) has an
intermediate compaction on a slow rate up to 600 passes
when the experiment ﬁnished. Finally, lichen fellﬁeld
community (C) has the fastest saturation at 160 passes with
the lowest maximum compaction of the three communities
at the end of the simulation.
The moss carpet community (A) was the richest in water
content. It contained 87% water content prior to the
experiment and at the end of the experiment, water content
fell to 67% (Fig. 5). All of the three communities showed
water loss as a result of trampling. Water content in the
moss hummock community (B) dropped from an initial
value of 55% to 26%. In the lichen fellﬁeld community (C)
water content fell from 24% to 18%.
Biological effects of trampling
Trends of biological parameters are shown in Figs 6 & 7.
For all three communities, loss of vegetation coverage
as a consequence of increased trampling followed a
negative exponential model, although the variation rate was
different for each community (Fig. 6). The lichen fellﬁeld
community (C) exhibited the fastest rate, whereas the moss
hummock community (B) showed the lowest of the three.
The visual details of the denudation process were quite
different for each community (Fig. 3). The moss carpet
community (A) showed an initial resistance. During the
ﬁrst 10–15 passes, while footprints were visible, the
structure of the community was apparently unaffected. At
around 25 passes, ﬁrst scars were observed and, as soon as
the cohesion was damaged, the ﬁssures advanced rapidly.
Due to the high water content of this vegetation the
fragmented portions formed a muddy mass. At c. 300
passes the muddy mass had become sufﬁciently eroded to
reveal bare ground and allow puddles of water to form.
Seventy-eight passes were sufﬁcient to result in loss of 50%
of the vegetation cover (Fig. 6).
Fig. 5. Hydrological features. Trampling intensity (passes) and
water content (percentage in weight) for trampling
experiments at communities A, B and C.
Fig. 6. Biological features (I). Trampling intensity (passes) and
vegetation coverage (percentage) for trampling experiments at
communities A, B and C.
Fig. 7. Biological features (II). Trampling intensity (passes) and
total biomass (milligrams per cm
soil) for trampling
experiments at communities A, B and C.
324 L.R. PERTIERRA et al.
The moss hummock community (B), growing on raised
beach terraces, was drier and easier to walk on. The
vegetation appeared to be ﬁrmer and exhibited a higher
resistance than that of Community A. To disturb the
cohesion required around 50 passes and scars were only
produced in the bigger tufts which were more exposed as
trampling continued and the vegetation was crushed instead
of turning into a muddy mass as in the case of Community A.
Loss of macroscopic moss coverage was not seen even up to
600 passes. One hundred and forty seven passes were needed
to cause a loss of 50% of the vegetation cover (Fig. 6).
Lichen fellﬁeld community (C) was easily fractured with
less than 10 passes, as the dominant lichen had a crunchy
texture when dry. Total loss of plant cover was evident at
160 passes. Thirty-nine passes were sufﬁcient to result in
50% loss of vegetation cover (Fig. 6).
Finally, total biomass per square centimetre of soil on
experimental plots was quantiﬁed to contrast with plant
coverage loss (Fig. 7). The moss carpet community (A)
contained the highest initial biomass of 629 mg C cm
Approximately 74% of the initial biomass was removed
in the experimental process, leaving a ﬁnal 165 mg C cm
soil at the end of the trampling experiment. The moss
hummock community (B) had initially a 52% lower
biomass content than in A. Biomass content in B was at
328 mg C cm
soil prior to trampling and was 121 mg C cm
soil after trampling, corresponding to a 63% loss. The
lichen fellﬁeld community (C) contained the lowest
biomass content. It was slightly lower than in B (60%)
and much lower than in A (31%). Biomass content in C
began at 200 mg C cm
soil before trampling and ended at
72 mg C cm
soil after trampling, corresponding to a 68%
Most of the mosses found in the samples from the
three communities are common on Livingston Island
(Sancho et al. 1999, Putzke & Pereira 2001, Ochyra et al.
2008), but two of them were reported for the ﬁrst time for
the island: Pohlia wahlenbergii, already known from other
islands in the South Shetland Islands, and Brachythecium
subpilosum, a new report for the archipelago (Lara &
Pertierra 2012). Both species have small known Antarctic
populations (Ochyra et al. 2008). Liverworts are not
well represented in Antarctica, and the tiny Cephaloziella
varians is the most common and most widespread
liverwort in Antarctica (Newsham 2010), and is abundant
on Livingston Island (Sancho et al. 1999). The lichen
Leptogium puberulum and the vascular plant Deschampsia
antarctica one of the two phanerogams native to maritime
Antarctica are representative components of the local ﬂora
(Lindsay 1971, Sancho et al. 1999). Communities that are
richer in biodiversity are likely to harbour rare species,
presumably with populations that are easily disturbed,
although further studies will be needed before it could be
determined if these populations are threatened.
Physical effects on soils
The pH ranges from slightly acidic (Communities A and B)
to neutral (Community C), which is consistent with data
obtained for this area by other authors (Navas et al. 2008).
These results correspond to oligotrophic sand soils. Organic
matter and electrical conductivity in Community C were
found to be slightly higher than in the other two sites,
but within the range of values quoted in previous studies
(Roser et al. 1994).
Soil resistance to penetration proves to be a good
indicator for assessing cumulative trampling effects in
soils. It is noteworthy that, after the plant layer is pierced,
the soil surface starts to act in the same way as bare
soils (Fig. 3). The increase in penetration with increased
trampling in Fig. 4 are similar to those found by Tejedo
et al. (2009) for bare soil, and these values could in
themselves be sufﬁcient to disturb the existing edaphic
fauna. Soil characteristics such as texture also differed
among communities (Table I). Therefore the observed
differences can be also explained by the physical properties
of the soils of the different communities soils, such as bulk
density (Tejedo et al. 2009). Our results show that drier
areas with less dense vegetation were more sensitive to
disturbance from trampling. The presence of vegetation
prevented compaction by protecting the soil below.
In all three cryptogamic communities, water loss was
consistently proportional to trampling (Fig. 5). We found
that extreme conditions in water content affected negatively
the plant resistances. As a result the moss hummock
community (B) had in this case the highest resistance
capacities. The moss carpet community (A) had the highest
water content and hence exhibited the least resistance to
trampling. In the lichen fellﬁeld community (C), we also
detected a diminished resistance that could be explained by
the extreme dryness of the vegetation due to the particular
environmental conditions that were present during the
period of our experiments. For this reason it can be argued
that resistance of the communities to trampling can be
severely affected by meteorological conditions. Differences
in resistance to penetration could be also linked to the
initial water content of the community.
In contrast, soil moisture did not change much between
communities nor along the transect (Supplemental Table),
indicating that it was not affected by the trampling process.
Long-term effects of trampling remain to be seen. Lower
water retention due both to compaction increase and
vegetation loss by trampling could lead to shifts in species
composition. This projection can be exempliﬁed by the
results of Gremmen et al. (2003) who found signiﬁcant
differences in species composition and soil moisture between
control plots and frequented paths on Marion Island.
TRAMPLING EFFECTS ON CRYPTOGAMIC COMMUNITIES 325
Damages to vegetation are perhaps the most evident
impacts from trampling (Fig. 3). The continuous and
spongy moss carpets, rich in biomass and with a high water
content, can absorb a small amount of disturbance. But,
as soon as their initial capacity to resist disturbance is
surpassed, the damage grows linearly with the amount of
disturbance. Our results are similar to those of de Leeuw’s
(1994) obtained from moss peat vegetation on Cuverville
Island, Danco Coast. In moss hummock communities
the damage is gradual and is tempered by the physical
characteristics of the community. Drier soils and strong
attachment to the substrate could prevent moss from direct
damage. These communities appear to be more resistant to
trampling, but we must ascertain whether, when certain
levels are surpassed, the damage becomes irreversible due
to extreme loss of water availability or a thinner soil layer.
Finally, lichen fellﬁeld communities show a low degree of
vegetation resistance to trampling due to its extreme
dryness and the morphology of the dominant lichen with
the mixed mosses, which are weakly attached to the
substrate. Direct damage can be observed after a very small
amount of disturbance.
Amount of vegetation cover and visual changes served
as preliminary indicators for assessing degradation status
and resistance capacity of cryptogamic communities in
relation to different intensities of trampling (Figs 3 & 6).
However, vegetation is frequently patchy and circumstantial
disaggregation can be difﬁcult to unequivocally distinguish
from the effects of human trampling. If new species are
found, it might be necessary to monitor small plots in order
to assess the effects of disturbance on plant richness. Thus,
this indicator relies on the existing reference conditions
(Fretwell et al. 2011). Alternatively the technique applied
by Gremmen et al. (2003) involved comparing species
composition along the path against composition on either
side of it. That technique overcomes the need for long time
series in sites without information on possible changes in
species composition when assessing already impacted areas.
With the present results, i.e. 50% cover loss within less
than 200 passes (Fig. 6), we consider all three communities as
extremely sensitive to human trampling (Cole 1995a, 1995b,
Farrell et al. 2001, 2002). Our results are similar to those of
the most sensitive species described by Cole & Bayﬁeld
(1993), although their study was conducted on herbaceous
vascular plants. While our trampling experiments may be
indicating that these three cryptogamic communities in the
Antarctic Peninsula have low short-term resistance to
disturbance, it is possible that these communities possess
high recovery capacities since cryptogams are characterized
by their capacity for vegetative growth from fragmented units
(Smith 1993, Johansson & Thor 2008).
Total biomass decreased as the amount of disturbance
increased (Fig. 7). This was particularly evident in the case
of Community A (moss carpet community), where initial
biomass was the largest. Trampling fragmented the vegetation
which was scattered across the transect or washed away.
A large fraction of the fragmented vegetation (c.50%of
biomass) remained in the transect in a damaged condition
which can potentially act as a propagule bank. A key issue
here involves whether the erosion exceeds the recovery
capacity of the remaining biomass or the growth rate of new
propagules (Smith 1993, Johansson & Thor 2008).
Spatial strategies for minimizing impacts of trampling by
visitors in national parks are discussed in Leung & Marion
(1999) and, for the case of Antarctica, in Tejedo et al.
(in press). Here we detail some lessons learnt from the
present study for the minimization of damages to existing
communities. First, due to the extreme sensitivity of
cryptogamic communities, the best approach should always
be to avoid disturbing them. Alternative routes should be
considered. For instance, bare soils could be more resilient to
low trafﬁc. For this approach Tejedo et al. (2009) contains
more detailed recommendations. Also, stream beds have
traditionally been considered as another alternative route;
however, there is little knowledge about the effects of human
trafﬁc on freshwater ecosystems.
To avoid short-term irreversible damage to moss
carpet communities (A), access should be forbidden to
any large groups. In general, shore visits for tourist groups
are managed so that only 100 people are on shore at any
one time, with one guide for every 20 tourists (IAATO
2011). These numbers are sufﬁcient to cause severe damage
which can easily spread over a large area. If the only
option is to cross over an area covered by moss carpet
communities, a sacriﬁcial path that is precisely deﬁned will
be a more preferable solution than letting the group spread
over a large area. Nonetheless this will not only inevitably
lead to the destruction of the moss community along the
path but will also turn the path into a muddy area. This is
due to the relatively high contents of water and biomass.
These muddy areas are likely to expand as people try to
avoid the existing muddy area by making detours, thereby
increasing the width of the path and creating even more
muddy areas, an idea expressed already in Gremmen et al.
(2003) and recently reported in Barrientos Island (Ecuador
& Spain 2012). Thus, from the perspective of the protection
of these cryptogam communities group leaders should
ensure that members of their group remain on the path. For
small groups of no more than 1–5 people passing through
this area once or twice, such as scientiﬁc expeditions,
our recommendation would be that they spread out, since
the trampling intensity is insufﬁcient to produce direct
impact as long as the trampling pressure is not reproduced.
The impact can be easily spotted by the characteristic
indentations on the moss carpet (Fig. 3).
326 L.R. PERTIERRA et al.
In contrast, damage on moss hummock communities (B)
can become difﬁcult to detect since the visual impact is less
identiﬁable than in A (Fig. 3). Large groups might not
observe any visible damage after their pass and may feel
free to walk there, but the damage is gradual and cumulative,
and visitors should be restricted to the sacriﬁcial path in
order to avoid extended denudation processes. It should be
remembered that, as found in the samples studied, this
community contains a high diversity of bryophytes with rare
The lichen fellﬁeld community (C) shows a high degree
of sensitivity. Each pedestrian transit creates direct impact
and spreading is not an option, not even for small groups.
The impact on this community is not easily visualized due
to the low biomass and cryptic colours, with dominant
black and grey shades (Fig. 3). Elevated zones with
exposed lichen formation should be avoided by groups to
the maximum extent.
The three cryptogam communities studied are all highly
sensitive to trampling. Vegetation cover, soil characteristics,
water content and biomass were identiﬁed as relevant
aspects for the understanding of the denudation process.
High sensitivity was related to extreme hydration and
relatively large biomass in one community and to extreme
dryness and a weak attachment of plants to the substratum
in another community. The three communities behaved
differently in the trampling experiments but they all
exhibited low resistance of the vegetation to trampling.
Different strategies are suggested to minimize the impacts of
trampling; nonetheless the basic recommendation provided
by SCAR (2009) to directly avoid sensitive habitats would
be the ﬁrst measure to apply to all these communities.
The capacity for a sustainable recovery from trampling
disturbances within the context of global change relies on
appropriate management systems addressing the relative
vulnerabilities of terrestrial ecosystems in Maritime
Antarctica (Reid 2007, Tin et al. 2009, Convey 2010).
Thus, a key issue for the future would then involve the study
and monitoring of the resilience of the plant communities.
This paper was contributed to by two projects:
LIMNOPOLAR and EVA-ANTARCTICA. They were
supported by the Spanish Government (POL2006-06635,
CGL2007-28761-E/ANT and CTM2009-06604-E).
Permission to work in the study area for the 2009–10
season was granted by the Spanish Polar Committee.
Logistical support was provided by the UTM (Marine
Technology Unit, CSIC) and the Spanish Navy. We thank
Dr Lars Wormer (University of Bremen, Germany) for his
‘‘trampling’’ ﬁeld support. Thanks also to Dr Jero´ nimo
Lo´pez-Martinez from the Autonomous University of
Madrid, for the provision of Byers cartography. We also
thank two anonymous reviewers for their useful comments.
Finally, we have special thanks to Dr Tina Tin for her
frequent advice that greatly improved the paper.
A supplemental table will be found at http://dx.doi.org/
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