- A study compared the impacts of graded ski trails, ungraded trails, and trails with artificial snow on alpine vegetation and soil over an 8-year period. Machine-graded trails led to decreased plant cover, productivity, and diversity compared to ungraded trails and control plots. Graded trails also increased soil density and pH while decreasing nitrogen. - The addition of artificial snow on trails increased moisture and nutrient indicator values for vegetation over time. While artificial snow mitigated some impacts, it also delayed plant growth. - The impacts of grading on vegetation and soil generally increased between 2000-2008, rather than recovering as expected, showing long-term effects on the alpine environment.

1. The Impacts Of Ski Trail Management On Alpine Vegetation
And Soil
Emma Olson
University of Wisconsin – River Falls
December 7th, 2015

2. ABSTRACT
Downhill skiing, machine-graded trails, artificial snow, and the use of fertilizer induce
major disturbances to the environment of alpine ski resorts. This paper aims to quantify the
impacts of several ski trail management approaches (graded/ungraded; with/without artificial
snow; fertilizer applications) on the alpine vegetation and soil over time. The impacts of
machine-graded trails were researched by looking at study plots established over an 8 year time
period, which compared vegetation and soil characteristics on different types of ski trails to
adjacent off-trail control plots. Vegetation changes over time were considered as well. Machine-
graded ski trails led to a decreased plant cover, plant productivity, species diversity, and
abundance of early flowering and woody species, and increased indicator values for nutrients,
light, and soil base content compared to control plots. Ungraded trails and the addition of
artificial snow showed increases in vegetation indicator values for nutrients and soil humidity.
Machine-graded trails also had the greatest effects on soil characteristics by increasing soil
density by more than 50%, by increasing pH and C/N ratio, and by decreasing total nitrogen
concentrations. The longer artificial snow had been applied on ski trails, the higher the moisture
and nutrient indicator values. Nutrient leaching from fertilizer applications causes both
environmental impacts and changes in vegetation, and it may pose a greater risk to the alpine
environment than the introduction of nonnative species. Machine grading and fertilization have
the most drastic effects on soils and vegetation, and should be minimized when constructing and
managing ski trails.
Introduction
Every year millions of skiers, snowboarders, outdoor enthusiasts, and tourists visit ski
resorts around the world. Throughout the last 20-30 years the ski industry has grown
significantly, and it now represents a major economic resource in alpine regions. Ski resorts are
not as fun for the environment though as they are for skiers. Kangas et al. (2009) and Rixen
(2013) reported that ski resorts are considered to be among the main causes of environmental
degradation in mountainous regions. Delgado et al. (2007) found this is due to the construction
and use of ski trails, which severely alter landscape aesthetics and potentially threaten the fragile
high-mountain ecosystem, biodiversity, and erosion control. Generally, heavy machinery is used
to dig up and level the terrain, trees and brush are cut down, ground is smoothed and compacted,
artificial snow and snow additives are added, heavy fertilization is applied, and revegetation of
the trails are managed. The result are trails that are maintained as the foundation for a yearly
carpet of snow.
Disturbance of the alpine environment occurs during all ski trail management approaches,
but some are more environmentally friendly than others. For example, cleared ski trails are the
preferred approach, since they cause less damage to the natural ecosystem than graded ski trails.
This approach is more common in the United States where cleared trails are constructed below
the timberline. In Europe, graded ski trails are the more common management approach, where
the trails are located high up in the alpine environment above the timberline. Graded trails cause
more of a disturbance to alpine vegetation and soil because the landscape is bulldozed and
removed of the upper soil layer, leaving little or no vegetation or shrubs. Generally, what
remains after grading is a completely bare, smooth, and compact surface.

3. Research has been done in the sub-alpine region of the United States, comparing graded
and cleared ski trails, but these are below the timberline and do not share the same conditions as
alpine environments. However, these studies are still significant because they emphasize the
importance of using a cleared ski trail approach as opposed to a graded trail. Cleared ski trails do
have some impacts on alpine vegetation and soil, but not as much as a graded trail.
European ski resorts are generally at higher elevations, and are located in areas where
trees do not grow. (New York Times) That’s a very important distinction between U.S. ski
resorts and the European ones. As it was found (New York Times) it is basically a question of
forest or no forest. Several studies on ski trail management in alpine environments have
concluded that cleared runs cause less environmental damage, and offer better growth
opportunities to alpine tundra and other vegetation. This begs the question as to why resorts
choose a graded approach at all. Informal surveys of ski resort managers showed that graded
trails reduces topographical irregularities (depressions, hummocks, and boulders), and graded
trails require less snowfall to open for use than do cleared ski runs. Burt and Rice (2009) found
that managers estimate that approximately 0.5 m additional snowfall is required on average to
open cleared ski runs. Therefore, graded trails can open earlier in the season with an associated
increase in revenue. Also, Burt and Rice (2009) found that the internet-posted status of a set of
paired cleared and graded ski runs in the early part of the 2006-2007 season did open about a
week earlier on average. Managers commented that graded ski trails generally require more
maintenance effort in the summer, due to erosion-control seeding and water-bar repairs, even
though they require less effort for continuous clearing of vegetation.
Ski resorts know the importance of having enough space to accommodate skiers and
snowboarders, so over the years they have been increasing significantly in size. Resorts do not
tend to expand horizontally but rather vertically, higher up into the alpine environment where
trees do not grow. When alpine habitats are graded for trails it causes stress on vegetation and
soil and changes the snow cover characteristics. Rixen et al. (2011) found that these ecosystems
are typically highly sensitive towards changes in environmental conditions and have low
resilience after disturbance. The ski trail management approach used, whether graded or cleared,
will therefore have impacts on species composition, diversity, and productivity of alpine
vegetation, and will negatively affect the alpine ecosystem function and stability.
Ski resorts have implemented artificial snow machines and snow additives on trails for
many years. During the past 20 years their use has increased considerably. The main direct
impacts of ski trail management on vegetation relate to a more compact snow cover (causing soil
frost), the formation of ice layers, machine damage, and a delay in plant development.
Vegetation reacts to these changes in species composition and biodiversity decreasing. The
application of artificial snow modifies some of these impacts: some studies have found that the
formation of ice layers do not change significantly, and machine graded impacts are mitigated
due to a deeper and denser snow cover. However, artificial snow does have negative impacts. A
deep and dense snow cover impacts the vegetation, for example during its developmental stages.
Also, artificial snow does not melt as fast as natural snow. Therefore, man-made snow remains
on the surface longer and significantly lengthens the snowmelt. This enhances the delay in
development of vegetation.
Artificial snow has been found to increase the input of water and ions on ski trails, which
can have a fertilizing effect, and therefore change plant species composition. Snow additives

4. may also be added to artificial snow machines. The additives are made of sterilized
phytopathogenic bacteria and are often used before ski races to harden the surface. The additives,
such as salt, create more preferred icy conditions by their ice nucleation activity (INA). Some lab
experiments have shown that snow additives affected the growth of some alpine plant species.
The application of artificial snow and snow additives can result in environmental impacts, but
the results from studies are inconclusive. More research is needed on the impacts of ice
nucleation activity (INA) and snow hardening products on alpine vegetation and soil.
During and after a ski trail is graded the surface is mostly bare and highly susceptible to
erosion. This is due to the top layer of soil being removed during the grading process. Therefore,
ski resorts will often revegetate the site with nonnative species, mostly grasses, to protect from
any erosion. Grasses are commonly used since they are less expensive than native plants and
have the ability to quickly establish enough vegetative cover required for erosion control.
However, there is a concern for using nonnative grasses in alpine environments due to the risk of
outcompeting native species.
Management approaches for revegetating ski trails also include earth filling with peat and
fertilization, which provide an organic substrate and encourages plant growth. Studies have
found that fertilization has an impact on soil nutrient concentrations and vegetation composition,
and is therefore a cause for concern. This is because runoff and erosion may carry the nutrients
further into the environment or under the ski trails. Nutrient leaching may also affect the water
quality of nearby water bodies in alpine areas.
Some conservationists may argue against any kind of ski trail, and instead recommend
ungraded trails, but skiing nonetheless offers considerable economic benefits and offers millions
of people a way to enjoy the outdoors. That is a difficult thing to take away. However, it may
seem that environmental interests are being sacrificed in favor of financial ones. Some people
may not care waiting a week or two for a resort to open if that’s what it takes to reduce impacts
on the environment, but some may disagree. While graded ski trails, and management activities
in general, continue to be the preferred approach in alpine environments more long-term research
will be needed to better understand their impacts. It is therefore up to scientists and researchers
alike to go into the field, document and make aware of the impacts, so that the alpine soil and
vegetation can be protected and/or restored.
The aim of this paper is to evaluate the impacts of graded ski trails, ungraded ski trails,
and trails with artificial snow on vegetation composition and soil parameters in Europe’s alpine
environment. To help with this I will first give an overview of the impacts that graded trails have
on plant-soil interactions. I will then discuss a study that was conducted which describes in
further detail how ski trails impact the vegetation and soil in alpine environments. The methods
used to obtain the data will be included, along with the results from the study. Second I will get
into how artificial snow and snow supplements impact alpine vegetation and soil, while drawing
conclusions from various sources. Lastly I will discuss the impacts of fertilization on nutrient
concentrations and vegetation composition, and using nonnative grasses to revegetate alpine ski
trails.
Impacts of graded trails on plant-soil interactions
During the summer ski resorts build and maintain graded trails by using heavy
machinery. The machines are used to level, drain, and smooth the surface, and to remove rocks,

5. obstacles, natural vegetation, and upper soil layers. Research has shown that a graded ski trail
results in major disturbances to both plant and soil composition. Burt and Rice (2009) found that
after grading, what remains is usually a mineral substrate with low organic matter content and
poor water holding capacity. On alpine mineral soils plant density and species diversity are a
factor in retaining sediments and nutrients, so a sufficient vegetative cover is necessary for
erosion control. Barni et al. (2007) found that natural re-vegetation processes on these mineral
soils are difficult and slow. This is due to graded trails generally having a decreased plant cover
and plant productivity, and increased indicator values for nutrients, light and soil base content
compared to reference forest plots that were tested.
Removing the upper soil layer from grading can cause vegetation gaps and affects
vegetation in the long-term. Makoto et al. (2014) found this is due to major alterations of soil
biotic, physical and chemical properties, which hinder the establishment and growth of the
original plant species. Moreover, their seed bank is lost, thereby greatly reducing the resilience
of the original species. In response to this, ski resorts will often seed after the grading process
using non-native species. Doing so may result in high proportions of species not native to the
alpine trail area. Makoto et al. (2014) found that some of the non-native species, or
spontaneously established alien plants, may outcompete remaining native species or hamper their
re-establishment. A plant mechanism has been found to exist that gives nonnative species a
competitive advantage over native plant species. It was found (Callaway et al. 2004) that the
vegetation does this by a ‘natural enemy release’; soil-borne pathogens or root herbivores
adapted to the native flora are often not able to infect or consume belowground plant parts.
After the ski trails have been machine graded in the summer, snow-grooming vehicles
and skiers are on the trails throughout the winter. The machines and skiers compact the snow
cover and potentially damage alpine vegetation and soil. Newesely (1997) found that direct
impacts of ski trail preparation on vegetation are primarily caused by the compaction of the snow
cover which results in a denser and less deep snow cover with an increased thermal conductivity
and decreased gas permeability. Cernusca et al. (1990) found that the thermal conductivity in
dense natural snow was found to be about two times higher than in incompact natural snow. The
thermal conductivity, air temperature, and the snow depth are all together responsible for the
cooling (frost damage) of the soil below the surface. Newesely (1997) found that in these
situations severe and long-lasting soil frost occurs.
Methods for measuring machine-graded trails vs. ungraded trails
In 2000, P. Roux-Fouillet, S. Wipf, and C. Rixen conducted a study which chose
permanent plots in pairs consisting of a 4 x 4 m trail plot and an off-trail control plot of the same
area. The trail and off-trail plots were revisited in 2008 for analysis. The areas sampled consisted
of 27 ski trails, with different altitude, aspect, and bedrock material, and were situated in 12
resorts in the Swiss Alps. Vegetation on most sites consisted of alpine grassland and dwarf shrub
heath. For each visited ski trail, one plot was randomly chosen on the trail and one control plot
off the trail. Trails were either machine-graded, or ungraded, and had either natural or artificial
snow resulting in four different types of treatments: natural snow/ungraded; artificial
snow/ungraded; natural snow/graded, and artificial snow/graded. Each control plot was at most
50 m away from the trail plot, and all had the same aspect, slope and altitude, but were not
disturbed by construction or snow treatments. When the researchers returned in 2008, they
analyzed the data consisting of 37 pairs of plots. Between 2000 and 2008, comparisons could

6. only be done with a reduced set of 31 pairs of plots due to treatment changes on six ski trails.
Soil samples were taken on vegetative plots, to be analyzed and used as representing a wider
area.
Data and results
The data shows that ski trails, specifically machine-graded trails, exert disturbance
changes both in vegetation and in soil characteristics. The results of the study includes data for
vegetation on ski trails, soils on ski trails, and vegetation changes on ski trails between 2000-
2008, which will be discussed below.
When a graded management approach was used this was found to decrease total
vegetation cover and the annual productivity. On graded trails the average number of species
present and Shannon diversity were found to be lower, as compared to off-trail plots. Average
number of species decreased by roughly three species. Graded trails showed that indicator values
were significantly affected by favoring light, higher pH and nutrient demanding species and by
delaying humus indicating species. Total cover of graminoids and woody species decreased,
while grading was found to be responsible for the decreased cover of early flowering species.
Ungraded ski trails showed that nutrient availability was higher on ski trails in general.
Adding artificial snow on graded ski trails resulted in conditions that favor plant species who
prefer moist conditions. Roux-Fouillet et al. (2011) found that artificial snow production did not
affect vegetation cover, productivity, species richness or diversity. The cover of snow bed
species was found to decrease significantly due to the interaction of artificial snow and graded
ski trails.
Soil density increased by roughly 50% on graded trails and caused significant changes in
soil total nitrogen concentrations. Lower N concentrations were found on graded trails than on
the control plots. On graded trails the soil pH and C/N ratio were higher. Principal component
analysis (PCA) were used to evaluate the correlation between soil and vegetation characteristics
on ski trails. Roux-Fouillet et al. (2011) found that the PCAs showed a positive correlation
between annual productivity and total vegetation cover, which both were negatively correlated to
soil bulk density. Higher light indicator values were found to be associated with higher soil bulk
density on ski trails, and total N contents of soils were positively correlated with vegetation
cover and productivity. It was also found (Roux-Fouillet et al. 2011) that the soil pH-values were
positively correlated with the indicator values for reactivity and nutrient availability, which in
turn indicated a strong negative correlation with the humus value.
From 2000-2008, the impacts of grading were shown to increase. Roux-Fouillet et al.
(2011) expected the vegetation to recover over time, but instead, the vegetative cover on graded
trails was even lower in 2008 than previously in 2000. This was discovered by the increased
difference between trail and off-trail control plots. The indicator value for reactivity also showed
changes in 2008. This pointed to an increased cover of species preferring high pH-values on ski
trail plots. The cover of graminoids showed a decreased on ski trail plots in 2008, compared to in
2000.

7. Conclusion from the study
Altogether, machine-graded trails, ungraded trails, and artificial snow production were
shown to induce certain stress on alpine vegetation and soil. Roux-Fouillet et al. (2011) found
that the grading of ski slopes implies the use of heavy machinery, radical soil movement,
removal of vegetation and topsoil. The mechanical impacts of skiers and snow-grooming
vehicles were also factors that were shown to cause stress and disturbance on graded and
ungraded trails. All types of disturbances were found to influence the greater proportion of un-
vegetated ground, lower productivity, and decreased species diversity on graded trails. Kammer
and Mohl (2002) found that in alpine environments, plant diversity and richness are rather
limited by climatic conditions than by competition. The findings from Roux-Fouillet et al. (2011)
showed that the suppression of dominant species due to the disturbance caused by snow
compaction may therefore result in decreased vegetation cover and productivity instead of
increased biodiversity.
Machine-graded impacts were reflected in the measure plant indicator values. Plant
species showed a lower soil humus content, higher soil pH, and higher light availability on ski
slopes. Rixen et al. (2011) found this can all be explained by disturbance. Indicator values
showed that plant nutrient availability was higher on ski trails than trails adjacent to them.
Grogan et al. (2004) found that several factors may be responsible for the higher nutrient
availability, such as enhanced soil microbial activity in the less acidic soils, high cover of
legumes, or altered soil nutrient dynamics that are highly influence by the soil temperature
regime during winter. The soil analysis on graded trails also indicated a low biological activity in
the soil. Graded trails showed a lower total N content, composed of up to 95% organic nitrogen,
and an increase ratio of C/N. Roux-Fouillet et al. (2011) found that the combination of negative
disturbances and beneficial factors, such as higher pH, may cause an inconsistent nitrogen
response on graded trails.
Mechanical damage, from snow grooming vehicles, was shown to affect the size and
growth form of many alpine woody species with buds and branches above ground level. Roux-
Fouillet et al. (2011) found the disturbance on ski trails is probably responsible for the decrease
in woody plants. A compact snow cover, decreased thermal insulation, and colder soil
temperatures may be responsible for a decrease in early flowering species on ski trails. These
species usually develop buds under the snow, but their development was shown to be impacted
by the compact and prolonged snow cover. Roux-Fouillet et al. (2011) found that this leads to a
slower and delayed phenological development and thus, a shorter time period for reproduction. A
dense soil on graded ski trails may be harmful for plant growth, due to a negative relationship
between soil density and productivity. A dense soil may also reduce infiltration rates and water-
storage capacity, which in turn could enable soil erosion. Pohl et al. (2009) found the slow re-
vegetation and lack of establishment of a diverse plant cover may cause a positive feed-back
enhancing erosion rates.
Implementing artificial snow on ski trails was shown to cause an increase in moisture
values of the vegetation. The increase of water from artificial snow could exert the risk of soil
erosion on graded ski trails, due to lower vegetation cover and increased soil density. To avoid
long-term damage on ski trails it is therefore recommended that a functioning vegetation cover is
restored as soon as construction of a trail is finished.

8. Roux-Fouillet et al. (2011) found that one of the major findings in the study was that the
vegetation change on graded and ungraded ski trails between 2000 and 2008 indicated
deterioration rather than improvement. This was indicated from the differences in vegetation
cover between trails and control plots. Most of the variables did not change significantly, and
there was no indication of leading to a denser and more productive, or more diverse vegetation.
Roux-Fouillet et al. (2011) found the decrease in vegetation cover was especially pronounced on
machine-graded trails, which indicates that the highly disturbed sites are subject to further
deterioration.
Impacts of artificial snow on vegetation and soil
For a ski resort to have a profitable year, it is essential for resorts in the alpine region to
have sufficient snow cover from early winter to spring. In response to ongoing climatic changes,
many ski resorts for the past few decades have invested in artificial snow machines and snow
supplements, in order to minimize the dependence on natural snowfall. Worldwide climate-
change scenarios have predicted changes in seasonal snowfall patterns, with the snow season
beginning later and ending earlier, and a rise in the snow line to occur. Also, because skiers
request excellent skiing conditions early in the season, i.e. November or early December in the
northern hemisphere, ski resorts must adapt to these changes in snowfall.
However, investing in artificial snow machines and snow supplements are not without
consequences. Artificial snow possesses different physical and chemical properties than natural
snow, and therefore interacts with plant-soil feedbacks differently. Mosimann (1998) and Rixen
(2002) found that due to the additional amount of snow, more water is released during snow melt
in spring, and the postponed snow melt shortens the plant growing season by up to 4 weeks.
Also, because water for artificial snow is taken from lakes, rivers or ground water, it often
contains minerals and other chemical compounds, and thus provides an increased nutrient input.
Changes in vegetation composition have been observed where artificial snow is used, favoring
nutrient- and moisture – demanding species. Additionally, an increase in meltwater is known to
enhance soil erosion rates. As long as climate change continues to affect seasonal snowfall
patterns ski resorts will likely continue to apply artificial snow year round. Long-term
comparative studies are needed to confirm this, but a cumulative effect over time is more than
likely to occur.
Stable snow conditions and snow reliability are very important requirements for ski
resorts. To a certain extent the success of a ski resort depends upon a high quality, deep, and long
lasting snow cover. Therefore, artificial snow machines are used in many ski resorts, and have
been for nearly the past 20 years. The use of artificial snow influences vegetation and soil in
several ways, which will all potentially interact. Man-made snow influences soil-plant
interactions through biological and chemical additives, and also by influencing the snow cover
regimes and the associated microclimates over time. The snow cover also impacts the soil and
vegetation by influencing the temperature, light availability, and the soil moisture content during
the growing season.
Artificial snow is often made by taking water from nearby water bodies, such as lakes,
rivers, reservoirs, and groundwater. Water from these sources is different from natural snow, and
it influences the snow through its nutritional impact. The added snow has shown to contain more
nutrients, such as base cations for plant growth, more salt (together leading to 4 times higher
electrical conductivity) and the pH is often higher.

9. Biological additives, such as ice nucleation activity (INA) products, are sometimes
applied to trails to enhance artificial snow production at temperatures warmer than
approximately -3°C. The INA material consists of sterilized phytopathogenic bacteria (Hirano &
Upper 2000). The most common ice nucleate is ‘Snowmax®’, a product that contains the
sterilized bacteria Pseudomonas syringae. The effects of INA products still remain unclear, but
since 1997, some countries in the Alps have banned them as a precautionary measure, so there is
a concern about using them. Still, studies have been done on INA products, and they have been
shown to influence the alpine ecosystem in different ways. The more significant concerns for
using bacterial products in the alpine environment are from the potential pathogenic effects on
plants, either from surviving bacteria or from toxins in dead bacteria, and an increased INA on
plant tissue. A common example for using INA products is to apply them on trails before a ski
race. Kobayashi et al. (2000) found the salts used on the trails improve the snow quality by
melting the uppermost layer of the snowpack and thus changes the snow quality. The end result
is an icier surface, which is ideal for downhill competitions.
The salts used in INA products are predominantly based on ammonium nitrate (PTX™),
ammonium chloride, ammonium sulphate, potassium chloride, sodium chloride and phosphates.
Nitrate salts are also used in concentrations that are as high as in agricultural fertilization in some
regions. Some research has shown that the salts are more than likely to infiltrate alpine soils and
increase the pH and nutrient availability to plants.
Impacts of fertilization and nonnative seeding on ski trails
At the end of the 1980’s many ski resorts in northern Finland embarked on heavy
construction projects for ski trails in alpine environments. Since then, these same ski resorts have
grown significantly in size, and their impacts on the environment have not been thoroughly
evaluated. That is until a study was done in 2003-2008 at a ski resort in Ruka, Finland. Kangas
et al. (2009) found that, in regards to their research, this is the first time that the impacts of ski
run management on soil and vegetation have been investigated using not only a conventional soil
and vegetation survey, but also an experimental study with each management method as a
separate factor. Their findings will be discussed below.
Kangas et al. (2009) found that results showed intensive fertilization of ski runs may pose
a greater risk to the environment than the spread of nonnative species used in revegetation. The
fertilizer products that are used have shown to leach nutrients into the soil below ski trails. Water
bodies near the resort did show higher temporal variability of nutrient concentrations and
typically higher nutrient levels than control lakes nearby. The impacts of fertilization were also
found to be amplified by artificial snow and a compact snow cover. Artificial snow also showed
an increase on the total snow mass on-site, and therefore intensified the surface runoff due to
additional water. A compact snow cover was shown to affect runoff as well, as it depresses the
water holding capacity of snow. Both artificial snow and a compact snow cover indicated that a
delay in snowmelt resulted in a shorter growing season, therefore impacting vegetation and soil.
After the sowing of nonnative grasses in alpine environments, some seeds may get
washed off to sites under the trails or be carried by the wind into neighboring habitats. However,
forest edges may act as a barrier to wind-dispersed seeds, which could therefore restrict the
invasion of nonnative species to forest interiors. Kangas et al. (2009) found that the invasion of
species from the ski trails to forest interiors is further hindered by the mowing of vegetation in
the summer. Similar results from other studies have shown that nonnative species did not invade

10. the native plant communities, nor did the native species become established on alpine ski trails.
However, it is known that once alien species are introduced to an environment it may take
decades before they become invasive. In fact, it was found (Johnston and Pickering 2001) that
invasive species originating from revegetation practices and amenity planting of ski resorts have
been found to become established in native vegetation in alpine areas. On a side note, some
studies have also shown that horseback riding on alpine trails may introduce alien species on
areas under continuous disturbance.
Kangas et al. (2009) found that revegetating with nonnative grasses and management
approaches resulted in a dense grass and herb-dominated vegetation on the ski trails, compared
to a sparser shrub and moss-dominated vegetation in the forest control plots. Therefore, ski trail
management creates new habitat types, which are maintained by management and the
disturbances caused by skiers and machine-grading. It may also be suggested that a higher
vegetation cover on ski trails is the result of higher light intensity (due to clear-cutting), different
species composition (nonnative and native species), and annual fertilization, which all together
increase nutrient concentrations and pH. Altogether, this showed that the expansion of native
shrub and moss species into the ski trails is delayed by the high pH and nutrient levels and the
disturbances occurring on the trails. In conclusion, the results from this study still emphasize the
importance of monitoring alpine environments for the spread of nonnative species.
Conclusions
This paper demonstrates how ski trail management approaches, particularly trails that are
machine-graded, cause disturbance changes both in vegetation and soil characteristics. The
removal of the top soil layer and compaction of the snow cover during the grading process
causes long-lasting negative impacts on both vegetative cover and soil density, and is by far the
most harmful management approach. A graded ski trail was shown to decrease the total
vegetative cover, annual productivity of soil, average number of species present, and Shannon
diversity. It also showed a lower presence of graminoids, woody species, and early flowering
species in alpine environments. Artificial snow was shown to mitigate some disturbance factors,
but not enough to be considered beneficial. Man-made snow increases the moisture content and
the nutrient load in alpine soils, and it causes a prolonged snow melt in the spring. Seeding with
nonnative vegetation was not shown to cause much of a disturbance to the alpine environment,
but careful monitoring should still be encouraged on ski trails. On the other hand, fertilizing a ski
trail can impact the alpine soil by leaching nutrients during runoff. In summary, machine-graded
ski trails and the fertilization on alpine areas are the two most harmful management approaches.
Therefore, they should be avoided in areas that are sensitive to changes in the environment.

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