The Ecology of Snow and Snow-covered Systems: Summary and Relevance to Wolf Creek, Yukon

Abstract

There is an increasing perception that northern ecosystems should be studied in a more integrative manner, in which individual studies make use of principles and results from related environmental disciplines. A recent addition to the integrative fields of study, snow ecology, is the science of the relationships between organisms and their environment whether it be in snow cover or snow- covered regions. Wolf Creek Research Basin is unequivocally qualified as a subject for the study of snow ecology because of its long snow-covered period >7 months, cold climate, largely intact ecosystem and representation of several northern Canadian biomes. In this paper, we discuss the role of snow as a factor in global climate and as a habitat for organisms with relation to its physical and chemical properties. The interactions between snow and micro-organisms, vegetation, and animals is also presented with emphasis on the capacity of individuals and communities to adapt to the cold. Finally we consider the role of snow and soil in the nutrient cycling of snow-covered ecosystems and the net losses and/or gains of nutrients by these systems during spring runoff. In doing so we hope to demonstrate how environmental science can be conducted and improved using a framework of habitat, environment and rigorous application of physical, chemical and biological principles. The potential applications of snow ecology to Wolf Creek are identified and promoted as a demonstration of multi- disciplinary, integrative science.

Full text

The Ecology of Snow and Snow-covered Systems:
Summary and Relevance to Wolf Creek, Yukon
H.G. Jones
Institut National de la Recherche Scientifique-Eau, Université du Québec,
Ste-Foy, Québec, G1V 4C7
J.W. Pomeroy
National Hydrology Research Centre,
11 Innovation Blvd., Saskatoon, Saskatchewan, S7N 3H5
Abstract
There is an increasing perception that northern ecosystems should be studied in
a more integrative manner, in which individual studies make use of principles
and results from related environmental disciplines. A recent addition to the
integrative fields of study, snow ecology, is the science of the relationships
between organisms and their environment whether it be in snow cover or snow-
covered regions. Wolf Creek Research Basin is unequivocally qualified as a
subject for the study of snow ecology because of its long snow-covered period
>7 months, cold climate, largely intact ecosystem and representation of several
northern Canadian biomes. In this paper, we discuss the role of snow as a factor
in global climate and as a habitat for organisms with relation to its physical and
chemical properties. The interactions between snow and micro-organisms,
vegetation, and animals is also presented with emphasis on the capacity of
individuals and communities to adapt to the cold. Finally we consider the role of
snow and soil in the nutrient cycling of snow-covered ecosystems and the net
losses and/or gains of nutrients by these systems during spring runoff. In doing
so we hope to demonstrate how environmental science can be conducted and
improved using a framework of habitat, environment and rigorous application of
physical, chemical and biological principles. The potential applications of snow
ecology to Wolf Creek are identified and promoted as a demonstration of multi-
disciplinary, integrative science.
The Role of Snow Cover in Ecology: Scalar Considerations
Although snow has long been the subject of scientific investigation, the vast
majority of the studies have been limited to various disciplines in the physical
and biological sciences. As a result, very few works permit a full appreciation of
snow cover and/or snow-covered regions as functional ecosystems. An
ecosystem, or ecological system, is a set of interacting, interdependent living and
non-living components or sub-systems (Tivy and O’Hare, 1982); the system or
sub-systems functioning over different scales - from the global biosphere to
microbiological communities. Even at the global scale, climate, cryosphere and
Wolf Creek Research Basin: Hydrology, Ecology, Environment
1

terrestrial ecology are intimately related and, although snow and ice may cover
lesser areas of the Earth than non-snow areas at any one time, strong feedback
mechanisms between snow, ice and the atmosphere can influence the whole
biosphere. Thus snow and ice can be considered to play a role in the dynamics
of all ecosystems (Groisman and Davies, 1999). An example of the large-scale
effects of snow-cover climate interactions is the influence of snow cover in
Eurasia on the global climate. An above-normal snow cover in Eurasia and/or the
Tibetan plateau will delay or weaken the Indian monsoon giving lower-than-
normal precipitation, and also effect the climate in the tropical Pacific and North
America (Barnett et al., 1989). Hence the climate of Wolf Creek is
interconnected with the climate of other snow-covered regions, being influenced
by those in Alaska and Asia and in turn influencing those to the south and east
in North America.
At the biome-continental scale, the duration of snow cover is one of the key
factors in determining biological productivity (Hammond, 1972). The increase in
recent knowledge on relationships between climate, snow cover and biome
ecology has been facilitated by techniques of remote sensing and the modelling
of the Earth’s atmosphere with Global Circulation Models (GCMs; Groisman
and Davies, 1999). However, snow also plays a more direct role in the ecology
of organisms at much smaller scales. In the following sections we discuss some
of the basic physical and chemical properties of snow that allow it to be a habitat
for different snow communities and the types of organisms that are found in,
under and on snow during the winter.
Snow as a Habitat and Habitat Cover:
Physical and Chemical Properties
Seasonal snow cover may be considered as an atmospheric sediment of short
duration. In a snowy environment such as Wolf Creek, it is a sedimentary layer
of fundamental importance to almost all forms of life in the basin. The snow
cover is a dynamic system, subjected to physical metamorphism, phase changes
and chemical transformations that make it a habitat for certain forms of life. Life
can continue in and under snow due to the unique physical texture of the milieu.
In the subnivean world, organisms and soil rely on the insulating capacity of
snow cover for heat retention so that extreme thermal fluctuations in the
atmosphere are dampened at the soil surface (Pomeroy and Brun, 1999).
However, snow not only mediates heat but also light between the atmosphere and
the ground and many micro-organisms and plants have adapted to light levels in
snow that are optimal for photosynthesis particularly during the spring melt. The
structure and heat exchange of snow with the atmosphere, above-snow
vegetation and the soil are key elements in the timing of runoff in spring
(Pomeroy and Brun,1999). This is the time when many ecosystems receive the
majority of their water resource of the year. Snow cover, however, acts not only
as a hydrological reservoir for whole ecosystems but also as a source of nutrients
Jones & Pomeroy - Snow Ecology
2

(e.g. N, S,) on which true nival and subnival organisms rely for growth and
reproduction (Tranter and Jones, 1999). Snow acquires these nutrients by various
processes during formation in the atmosphere (Barrie,1991), by atmosphere-
snow exchange (Cadle, 1991) snow-soil transfer and by fallout from forest
canopies (Jones, 1991). In snow-covered soils, nutrient cycling continues
throughout the winter, and, in particular, gives rise to gaseous emissions (e.g.
CO
2
, N
2
O) at the snow-soil interface (Sommerfeld et al., 1993). Gaseous
emissions under snow may represent a significant part of the annual flux of C
fixed by photosynthesis (see below Nutrient cycling in snow-covered soils;
Zimov et al., 1993). In the melt period, water soluble inorganic species of
nutrients such as NH
4
and NO
3
allow microbial communities to flourish; much
of the nutrient content is transformed by microbiological activity into organic
matter within the snow cover while the rest is discharged to the soil and streams
(see below Nutrient cycling in snow-covered soils; Jones, 1991). The
disappearance of the snow habitat at the end of winter drives a marked change in
organism behaviour: spring comes to the North. Physical snow studies in Wolf
Creek are summarized later in this volume by Pomeroy et al. (1999) where the
accumulation of snow as a habitat in various vegetation/elevation zones is
described. Our snow chemistry studies of the basin have found the snows to be
dilute, (Cl
-
< 0.14; NO
3
-
< 1.4; SO
4
2
-
< 0.87; Ca
+
< 0.48 µg/ml) with
concentrations of major geochemical anions and cations near to “remote-
location” baseline levels. Wolf Creek is not yet subject to acid snow, however as
shown in this volume by Gregor et al. (1999) there is an organic contaminant
input.
True Snow Microbial Communities
The microbial community is made up largely of snow algae, bacteria, yeasts and
snow fungi. True snow algal populations grow and reproduce wholly within the
water retained by snow during snowmelt. The algae possess structural and
reproductive adaptations that permit them to successfully complete these
essential phases of their life cycle during the relatively short melt season. These
include the algae from mountainous and continental snow cover (Hoham, 1980),
the ice algae and cyanobacteria from dry valley lakes in Antarctica (Parker et al.,
1982) and the algae from permanent glaciers (Ling & Seppelt, 1993). Studies on
other organisms such as snow fungi (Hoham et al., 1993; Stein and Amundsen,
1967), ice fungi (Abyzov, 1993), and eubacteria have also been reported
(Margesin & Schinner, 1994). Before the mid 1960s, research emphasized the
systematics, taxonomy and distribution of snow and ice algae; however, since the
1960’s the life histories, biochemistry, physiology and ecology have now been
added as some of the principal subjects of study (Hoham and Duval, 1999).
Cell structures allow microbes to adapt to snow cover characteristics. Many of
the snow algae are flagellates and they move to sites of nutrients and optimal
light levels through meltwater in the pack. Physiological changes include
Wolf Creek Research Basin: Hydrology, Ecology, Environment
3

enzymes that permit optimal growth at low temperatures (Hoham, 1980),
resistance to freeze-thaw cycles (Morris et al., 1979) and, in the case of snow
covers in open areas, the production of pigments which protect the cell and
impede the photoinhibition of photosynthesis by light of short wavelengths e.g.
carotenoids in Chloromonas nivalis (Hoham and Mullet, 1978) and astaxanthin
esters in Chlymadomonas (Bidigare et al., 1993). Particular interest is now being
shown in the capacity of snow micro-organisms to support nival food webs
which allow communities in snow-covered regions to survive over winter
(Hoham and Duval, 1999; Aitchison-Benell, 1999; Walker et al., 1999). No
studies of micro-organisms in snow nor of nival food webs have been reported
for the Yukon Territory. The results of any future studies in Wolf Creek should
prove of general interest because of the paucity of data for this region of the
world.
Animals and Snow
Animals that are active throughout the winter live in, under and on snow. Some
small animals such as invertebrate grazers like ciliates, rotifers and collembola,
can feed on snow microbe populations (Aitchison, 1989, Hoham et al., 1993)
which live in and under snow. The microbial productivity thus serves as a base
for a part of the energy transfer through the higher invertebrate levels e.g. mites
and spiders and the vertebrates such as voles, shrews, birds, etc. (Aitchison-
Benell, 1999) thus extending the food chain in the cold season.
Both invertebrates and vertebrates, have had to adapt physiologically to the cold
temperatures in order to move, find and devour prey on, in and under snow. In
many north-temperate and deep mountainous snow covers the subnivean
temperatures are close to 0°C and the freezing of bodily fluids does not pose a
major problem for invertebrates inhabiting this ecological niche as it does
vertebrates which are active on the snow surface or in subarctic or arctic
subnivean space. Aitchison-Benell (1999) discussed the way active nival and
subnival invertebrates succeed in overcoming freezing by lowering the freezing
point of the haemolymph by anti-freeze agents such as thermal-hysteris-proteins
and low molecular weight cryoprotective alcohols (e.g. glycerol; Lee, 1991). For
example, the winter-active spider Bolyphantes index can maintain normal
activity down to -5°C. However, at -9.3°C it becomes comatized (chill coma) and
below the supercooling point of -15.3°C will freeze solid (Hågvar, 1973). The
springtail Isotoma hiemalis can remain active down to -6°C, experiences chill-
coma at -8°C and has a supercooling point of -15°C. Isotoma hiemalis is also an
example of an invertebrate which undergoes a morphological change of the
locomotory appendages from summer to winter called cyclomorphosis which
allows the organism to move to the snow surface; the change then reverses in the
spring with the disappearance of snow cover (Zettel, 1984). Springtails and mites
are the arthropods most tolerant of cold (Sømme, 1993).
Jones & Pomeroy - Snow Ecology
4

Vertebrates may be active on, in or under the snow cover. The majority of
subnivean vertebrates are small mammals such as the microtines and insectivores
(Cranford, 1984; Pruitt, 1984). These usually weigh less than 250 g and serve as
prey for larger mammals e.g. weasels, foxes, birds. To survive the cold,
insectivores possess high metabolic rates and have to feed almost continuously.
Shrews will favour habitats with litter, deep humus or snow cover where they
construct nests to conserve heat (Aitchison-Benell, 1999). As in the case of the
invertebrates, vertebrates will undergo physiological and morphological change
in winter. The thyroid, pituitary, adrenals and parathyroid glands of soricine
shrews become inactive, and changes in the salivary glands occur; brown adipose
tissue is also converted to heat, all of which reduce metabolism and activity
(Aitchison, 1987). Shrews also show morphological changes which include
reductions in brain volume and weights of the kidneys, liver and spleen, and
shortened body length (Merritt, 1986). The reduced size increases the hair
density, giving greater insulation per unit surface area (Mezhzherin, 1964).
However, even these methods fail to enable the animals to survive continuous
cold and the northern limit of shrew distribution is the -30°C mean January
isotherm in the Former Soviet Union (F.S.U.), the coldest areas being inhabited
by the smallest Sorex species, e.g. S. minutissimus (mean weight of about 4 g)
(Mezhzherin, 1964).
Shrews and other small mammals such as lemmings are an integral part of the
winter food web being the prey for weasels, foxes, birds and larger mammals.
Formazov (1946) published a comprehensive review on the importance of snow
cover in the ecology of both small and large mammals which drew heavily both
on the knowledge of indigenous hunters and his own observations of animals and
snow cover relationships in different regions of the F.S.U. In his classic work
‘Snow cover as an integral factor of the environment and its importance in the
ecology of mammals and birds’ the author extended the concept of climatic and
edaphic factors in ecology to cover ‘chionic’ factors (Formazov, 1946). These
represent snow cover characteristics such as distribution, longevity, depth,
density, and hardness which are determinant in the success or failure of
populations to survive in snow-covered regions. Species were classified as either
chionophiles (well adapted to snow cover), chioneuphores (partially adapted to
snow cover), or chionophobes (having great difficulty to function in snow
covered environments). Following Formazov, studies on large mammals and
birds have been numerous and have contributed greatly to our knowledge of
snow ecology e.g. wolves (Huggard, 1993), muskoxen (Nellemenn, 1997),
caribou (Ouellet et al., 1993), goshawks (Tornberg, 1997). The scope of the
research has been expanded to include physiological, biochemical, and other
more fundamental biological attributes of species snow interactions e.g. ungulate
feeding and excretory metabolism in snow-covered terrain (DelGiudice et al.,
1989; White et al., 1997).). In the northern Yukon, several studies by the
Canadian Wildlife Service have clearly demonstrated the linkage between snow
cover conditions and caribou herd behaviour. As elsewhere, the caribou of Wolf
Wolf Creek Research Basin: Hydrology, Ecology, Environment
5

Creek are observed to use wind-blown snow-free ridges for winter travel and
feeding and summer snowpatches for escape from insects and heat.
Vegetation and Snow
The whole basic vegetative mosaic of certain biomes (e.g. the boreal forest and
tundra) depends on snow-vegetation interactions. Regional vegetation patterns in
alpine, arctic and cool temperate landscapes are strongly dependent on the
distribution and physical characteristics of the snowpack (Walker et al., 1993).
In the boreal forest, wind and snow accumulation are two of the most important
factors in the dynamics of soil temperature, soil moisture, depth of freezing, and
heat flux and the subsequent growth and distribution of plant communities.
Tundra regions are extensively influenced by snow and wind. Snow has long
been recognized as a strong factor in the make-up of mountain vegetative
communities. Many plants in cold regions will survive under deep snow cover
due to the high thermal insulation capacity of the snow (Pomeroy and Brun,
1999; Walker et al., 1999). Others adapt to shallow or intermittent cold snow
cover by retaining a large amount of dead tissue which can trap snow for
insulation, by storing large amounts of high-energy reserves (sugars, starches,
lipids) for frost hardiness (Bell and Bliss, 1979) and by developing growth forms
resistant to desiccation (Bliss, 1966). Many plants show rapid spring growth and
flowering even under snow from over-wintering buds (Galen and Stanton, 1995).
International Tundra Experiment studies that are being initiated in Wolf Creek
will help to elucidate the relationships between vegetation and snow that help to
govern vegetation patterns in the basin.
In forest areas trees intercept snow and play a major role in soil moisture
dynamics and forest hydrology (Pomeroy and Brun,1999). Sublimation of the
intercepted snow will consume considerable amounts of energy from the forest
environment and reduce the transfer of moisture from the atmosphere to the soil
(Harding and Pomeroy, 1996). As forests become more open, the abrasive nature
of wind-blown snow crystals is a key factor in tree survival. The damage and kill
to trees above the snow surface due to wind-blown snow is a common sight in
high-alpine and taiga regions. Pockets of mostly deformed trees (krummholz)
survive only where the topography is favourable to obtain a foothold (Daly,
1984; Begin and Boivin, 1999). Due to the combined influence of wind-induced
drought stress, freezing and snow drifting, these islands of trees gradually die off
on the windward side and advance through the drift on the leeward side thus
gradually moving in line with the wind (e.g. 0.02 m year
-1
; Benedict, 1984).
These krummholz are extremely important for the survival of plant communities
in the immediate area as the protected downwind side will provide a microsite
for a more luxuriant and diverse vegetation than the upwind area (Walker et al.,
1999). These types of snow-vegetation relationships are used in paleoecological
studies e.g. the reconstruction of past snow regimes by the study of tree
morphology (Begin and Boivin, 1999).
Jones & Pomeroy - Snow Ecology
6

In addition to these severe physical stresses on vegetation, nutrient distribution
is also a key factor in plant distribution and productivity. Soil nutrient content
may vary widely due to atmospheric deposition, aeolian erosion, temperature
regimes and snow depth. In some cases subnival animal activity will also
influence nutrient availability. For example, lemmings can reduce the standing
crops of vegetation (live and dead above-ground biomass) by 50% of the annual
above-ground production and 20% of the total annual production and redistribute
nutrients through the excretion of faeces and urine (Walker et al., 1999).
Nutrient Cycling in Snow-covered Soils
Thus plants, animals, micro-organisms are all tightly bound in the transfer of
nutrients throughout snow-covered systems from snow to soil to the atmosphere
(Jones, 1991; Williams, 1996). An important source of nutrient loss from soil is
by gas emissions to the atmosphere. Respiration and allied microbiological
processes such as denitrification and nitrification continue to produce CO
2
, CH
4
,
N
2
, NO, N
2
O and other gases throughout the winter. The extent to which
seasonal snow cover will influence gaseous emissions from soil will vary with
the duration and depth of snow during the cold, dry accumulation period, and
with the discharge rates and chemical composition of meltwaters during the melt
season (van Bochove et al., 1996). Due to the porous nature of snow, gases
released from the soil will give rise to either consistent gaseous concentration
profiles in the snow cover (Sommerfeld et al., 1993) or ephemeral localized gas-
rich pockets of air within the snow cover (Zimov et al., 1993). The distribution
of gases in snow cover depends on soil temperature and texture, and the physical
structure of the snow cover and its interaction with the atmosphere (Massmann
et al., 1995). Ice lenses are impermeable to gaseous diffusion and considerably
reduce gaseous fluxes between soils and the atmosphere (Winston et al., 1995).
Gaseous emissions under snow may represent a significant part of the annual
Carbon cycle. Sommerfeld et al. (1993) estimated that CO
2
emissions from an
Alpine soil under snow constituted approximately 25% of the total annual
amount of C fixed by photosynthesis. Zimov et al. (1993) reported that emissions
of CO
2
under snow cover in the open taiga of Siberia could theoretically
represent the respiration of over 60% of the annual organic C production. In the
case of N
2
O, Brooks et al. (1996) estimated that the winter/spring N losses by
denitrification (N
2
, N
2
O) represented 50% of the annual gaseous N loss and van
Bochove et al. (1996) have shown that the rates of N
2
O emissions from snow-
covered agricultural soil represented 25% of the annual emissions. Emissions
were very high during the spring snowmelt period.
The spring melt period is also a time of both gains and losses of nutrients for soil
by hydrological input and output respectively. The soil will gain the nutrient
loads of discharged meltwaters by infiltration and biological assimilation but can
also lose nutrients by gaseous emissions and runoff (Williams et al., 1993). Jones
Wolf Creek Research Basin: Hydrology, Ecology, Environment
7

and Roberge (1992) found that the export of NO
3
in a boreal forest was greatest
during the meltwater runoff period. This has also been found to be true for other
ecosystems such as hardwood forests (Rascher et al., 1987) and high-altitude
alpine sites (Williams et al., 1993). NH
4
discharged by meltwaters is generally
fixed or assimilated by the soil and practically no loss of N occurs by direct
transfer of this species through the soil by meltwater to surface waters (Williams
et al., 1996). As NO
3
is far more mobile than NH
4
in soils, the export of NO
3
by
surface waters may originate both from the solute in the meltwaters (Williams et
al., 1993) and/or from the leaching of the species from soil after over-wintering
mineralization of organic matter (Rascher et al., 1987). However, it is extremely
difficult to distinguish between the two sources of NO
3
in conventional studies.
Williams et al. (1996) used K
15
NO
3
as a tracer in a study to elucidate the relative
importance of the two sources. Their results suggested that soil mineralization
under the seasonal snow, rather than snowmelt release of NO
3
, may be the main
control on the concentrations of NO
3
in surface waters and the export of N in
spring. However, the difference between regional snow covers, soils and spring
precipitation, may cause the relative importance of the sources to change from
year to year and export pathways may depend on many factors including the
amount of snow, the rate of melt, soil texture, and soil microbiological activity.
The result can either be a net loss or gain of nutrients. Jones and Bedard (1987)
showed that variations in inter-annual hydrologic exports of N during snowmelt
in a boreal forest can give rise to total spring exports which are either greater or
less than the amounts of the nutrient discharged from the snow cover. The
nutrient cycling between snow, terrestrial and aquatic systems is unknown for
Wolf Creek but considered to be of the utmost importance for primary
productivity in the respective systems. It is hoped that future studies will focus
on this topic.
Concluding Remarks
This brief overview of the functioning of snow and snow-covered systems has
covered some of the principal aspects of snow ecology. Life in snow and in the
cold represents how adaptable life is to survive in harsh natural environments.
Wolf Creek Basin provides an example to the world of a particularly well-
understood snow ecosystem in a northern environment. In the case of Humanity,
technology now facilitates our existence in cold regions but the impact of human
activity on these fragile systems is considerable. Wolf Creek is particularly
vulnerable as it lies partly within the urban boundary of the largest Canadian city
north of the 60th parallel. Human impacts on Wolf Creek have changed
dramatically in the last century as mining, subdivisions and motorized transport
proliferate. We need knowledge on how cold ecosystems function so that
technological and natural communities can co-exist while maintaining the
diversity and quality of life in such severe and spectacular environments.
Jones & Pomeroy - Snow Ecology
8

References
Abyzov, S.S., 1993. ‘Micro-organisms in the Antarctic ice’. In: Antarctic
Microbiology, Editor, Friedmann, E. I., Wiley-Liss, New York, p. 265-295.
Aitchison, C.W., 1987. ‘Review of winter trophic relations of soricine shrews’,
Mammal Rev., 17, 1-24.
Aitchison, C.W., 1989. ‘The ecology of winter-active collembolans and spiders’,
Aquilo Ser. Zoologica, 24, 83-89.
Aitchison-Benell, C.W., 1999. ‘The effect of snow cover on small animals’. In: Snow
Ecology, editors Jones, H.G., Pomeroy, J.W., Walker, D.A. and Hoham, R.,
Cambridge University Press, Cambridge, UK.
Barrie, L., 1991. ‘Dry deposition to snowpacks’. In: Seasonal snowpacks: Processes
for compositional change. Proceedings of the NATO Advanced Research
Workshop on processes of chemical change in snowpacks, Maratea, Italy, July
1990. Editors, Davies, T.D., Tranter, M. and Jones, H.G., Springer-Verlag,
Berlin. Series G, Ecological Sciences, 28, 1-20.
Barnett, T.P., Dumenil, L., Schlese, U., Roeckner, E. and Latif, M., 1989. ‘The effect
of Eurasian snow cover on regional and global climate variations’, J. Atmos.
Sci., 46, 661-685.
Begin, Y. and Boivin, S., 1999. ‘Tree-ring dating of past snow levels in Northern
Québec’, In: Snow Ecology, editors Jones, H.G., Pomeroy, J.W., Walker, D.A.
and Hoham, R., Cambridge University Press, Cambridge, UK.
Bell, K.L. and Bliss, L.C., 1979. ‘Autoecology of Kobresia bellardii: why winter
snow accumulation limits local distribution’, Ecological Monographs, 49,
377-402.
Benedict, J.B., 1984. ‘Rates of tree-island migration, Colorado Rocky Mountains
USA’, Ecology, 65, 820-823.
Bidigare, R.R., Ondrusek, M.E., Kennicutt II, M.C., Iturriaga, R., Harvey, H.R.,
Hoham R.W. and Macko, S.A.,. 1993. ‘Evidence for a photoprotective function
for secondary carotenoids of snow algae’, J. Phycol., 29, 427-434.
Bliss, L.C., 1966. ‘Plant productivity in alpine microenvironments on Mount
Washington, New Hampshire’, Ecological Monographs, 36, 136-155.
Brooks, P.D., Williams, M.W. and Schmidt, S.K., 1996. ‘Microbial activity under
alpine snowpacks, Niwot Ridge, Colorado’, Biogeochemistry, 32, 93-113.
Cranford, J.A., 1984. ‘Population ecology and home range utilization of two
subalpine meadow rodents (Microtus longicaudus and Peromyscus
maniculatus)’. In: Winter Ecology of Small Mammals, Editor, Merritt, J.E.,
Carnegie Museum of Natural History, Pittsburg, Special Publication No. 10,
ISBN 0-935868-10-0, p. 285-292.
Wolf Creek Research Basin: Hydrology, Ecology, Environment
9

Daly, C., 1984. ‘Snow distribution patterns in the alpine krummholz zone’, Progress
in Physical Geography, 8, 157-175.
DelGiudice, G.D., Mech, L.D. and Seal, U.S., 1989. ‘Physiological assessment of
deer populations by analysis of urine in snow’, J. Wildl. Manage., 53, 284-291.
Formazov, A.N., 1946. Snow cover as an integral factor of the environment and its
importance in the ecology of mammals and birds. Moscow Soc. Naturalists,
Materials for Fauna and Flora U.S.S.R. Zool. Section, New Ser. 5, 1-152.
English translation: Prychodko, W., and Pruitt, W. O., (1963). Occasional Paper
1, Boreal Inst. Univ. Alberta, Edmonton.
Galen, C. and Stanton, M.L., 1995. ‘Responses of snowmelt species to changes in
growing season length’, Ecology, 75, 1546-1557.
Groisman, P.Ya. and Davies, T., 1999. ‘Snow cover and the Climate system’. In:
Snow Ecology, editors Jones, H. G., Pomeroy, J. W., Walker, D. A. and Hoham,
R., Cambridge University Press, Cambridge, UK.
Hågvar, S., 1973. ‘Ecological studies on a winter-active spider Bolyphantes index
(Thorell) (Araneida, Linyphiidae)’, Norsk ent. Tiddskr., 20, 309-314.
Hammond, A.L., 1972. ‘Ecosystem analysis: Biome approach to ecosystem
research’, Science, 175, 46-48.
Harding, R.J. and Pomeroy, J.W., 1996. ‘The energy balance of the winter boreal
landscape’, J. of Climate, 9, 2778-2787.
Hoham, R.W., 1980. ‘Unicellular Chlorophytes - Snow algae’. In: Phytoflagellates.
Editor Cox, E., Elsevier North Holland, Inc. p. 61-84.
Hoham, R.W. and Mullet J.E., 1978. ‘Chloromonas nivalis (Chod.) Hoh. & Mull.
comb. nov., and additional comments on the snow alga Scotiella’, Phycologia,
17, 106-107.
Hoham, R.W., Laursen, A.E., Clive, S.O. and Duval, B., 1993. ‘Snow algae and other
microbes in several alpine areas in New England’. In: Proceedings of the Fiftieth
Annual Eastern Snow Conference, Québec City, Québec, Canada, June 8-10,
p. 165-173.
Hoham, R.W. and Duval, B., 1999. ‘Microbial ecology of snow and fresh-water ice
with emphasis on snow algae’. In: Snow Ecology, Editors Jones, H.G.,
Pomeroy, J.W., Walker, D.A. and Hoham, R., Cambridge University Press,
Cambridge, UK.
Huggard, D.J., 1993. ‘The effect of snow depth on predation and scavenging by Gray
Wolves’, J. Wildlife Manage., 57, 382-388.
Jones & Pomeroy - Snow Ecology
10

Jones, H.G., 1991. ‘Snow chemistry and biological activity: a particular perspective
of nutrient cycling’. In: Seasonal snowpacks: Processes for compositional
change. Proceedings of the NATO Advanced Research Workshop on processes
of chemical change in snowpacks, Maratea, Italy, July 1990. Eds., Davies, T.D.,
Tranter, M, and Jones, H.G. Springer-Verlag, Berlin. Series G, Ecological
Sciences 28, 21-66.
Jones, H.G. and Bedard, Y., 1987. ‘The dynamics and mass balances of NO
3
and SO
4
in meltwater and surface runoff during springmelt in a boreal forest’. In: Forest
Hydrology and Watershed Management. IAHS Publication 167, 19-31.
Jones, H.G. and Roberge, J., 1992. ‘Nitrogen dynamics and sub-ice meltwater patters
in a small boreal lake during snowmelt’, In: Proceedings of the 49th annual
meeting of the Eastern Snow Conference. Editors, Ferrick, M. and Pangburn, T.,
p. 169-180.
Lee, R.E., Jr,. 1991. ‘Principles of insect low temperature tolerance’. In: Lee, R.E.,
Jr., & D.L. Denlinger (eds.), Insects at Low Temperature. Chapman & Hall, New
York and London, p. 17-46.
Ling, H.U. and Seppelt, R.D., 1993. ‘Snow algae of the Windmill Islands, continental
Antarctica. 2. Chloromonas rubroleosa sp. nov. (Volvocales, Chlorophyta), an
alga of red snow’, Eur. J. Phycol. 28, 77-84.
Margesin, R. and Schinner, F., 1994. ‘Properties of cold-adapted microorganisms and
their potential role in biotechnology’, J. Biotech. 33, 1-14.
Massman, W., Sommerfeld, R., Zeller, K., Hehn, T., Hudnell, L. and Rochelle, S.,
1995. ‘CO
2
flux through a Wyoming seasonal snowpack: diffusional and
pressure pumping effects’. In: Biogeochemistry of seasonally snow-covered
catchments, Editors. Tonnessen, K.A., Williams, M.W. and Tranter, M., IAHS
Publication 228, 71-80.
Merritt, J.F., 1986. ‘Winter survival adaptations of the short-tailed shrew (Blarina
brevicauda) in an Appalachian montane forest’, J. Mamm., 67, 450-464.
Mezhzherin, V.A., 1964. ‘Dehnel’s Phenomenon and its possible explanation’, Acta
theriologica, 8, 95-114.
Morris, G.J., Coulson, G. and Clarke, A., 1979. ‘The cryopreservation of
Chlamydomonas.’ Cryobiology, 16, 401-410.
Nellemenn, C., 1997. ‘Grazing strategies of muskoxen (Ovibus moschatus) during
winter in Angujaartorfiup Nunaa in western Greenland’, Can. J. Zoology, 75,
1129-1134.
Ouellet, J.P., Heard, D.C. and Boutin, S., 1993. ‘Range impacts following the
introduction of Caribou on Southampton Island, Northwest Territories, Canada’,
Arctic and Alpine Research, 25, 136-141.
Wolf Creek Research Basin: Hydrology, Ecology, Environment
11

Parker, B.C., Simmons, G.M., Jr., Seaburg, K.G., Cathey, D.D. and Allnut, F.C.T.,
1982. ‘Comparative ecology of planktonic communities in seven Antarctic oasis
lakes’, J. Plankton Res. 4, 271-286.
Pomeroy, J.W. and Brun, E., 1999. Physical properties of snow. In: Snow Ecology,
Editors Jones, H.G., Pomeroy, J.W., Walker, D.A. and Hoham, R., Cambridge
University Press, Cambridge, UK.
Pruitt, W.O. Jr., 1984. ‘Snow and small mammals’ In: Winter Ecology of Small
Mammals, Editor, Merritt, J.E., Carnegie Museum of Natural History, Pittsburg,
Special Publication No. 10, ISBN 0-935868-10-0, p. 1-8.
Rascher, C.M., Driscoll, C.T. and Peters, N.E., 1987. ‘Concentration and flow of
solutes from snow and forest floor during snowmelt in the West-Central
Adirondack region of New York’, Biogeochemistry, 3, 209-224.
Sommerfeld, R.A., Mosier, A.R. and Musselman, R.C., 1993. ‘CO
2
, CH
4
and N
2
O
flux through a Wyoming snowpack and implications for global budgets’, Nature,
361, 140-142.
Sømme, L., 1993. ‘Living in the cold’, Biologist, 40, 14-17.
Stein, J. and Amundsen, C.C., 1967. ‘Studies on snow algae and snow fungi from the
Front Range of Colorado’, Can. J. Bot., 45, 2033-2045.
Tivy, J. and O’Hare, G., 1982. Human impact on the Ecosystem. Oliver and Boyd,
Edinburgh, 243 pp.
Tornberg, R., 1997. ‘Prey selection of the goshawk Accipter gentilis during the
breeding season: The role of prey profitability and vulnerability’, Ornis
Fennica, 74, 15-28.
Tranter, M. and Jones, H.G., 1999. ‘The chemistry of snow: processes and nutrient
cycling’. In: Snow Ecology, Editors Jones, H.G., Pomeroy, J.W., Walker, D.A.
and Hoham, R., Cambridge University Press, Cambridge, UK.
van Bochove, E., Jones, H.G., Pelletier, F. and Prêvost, D., 1996. ‘Emissions of N
2
O
from agricultural soils under snow cover: a significant part of N budgets’,
Hydrological Processes, 10, 1545-1550.
Walker, D.A., Billings, W.D. and De Molenaar, J.D., 1999. ‘Snow-vegetation
interactions in tundra environments’. In: Snow Ecology, Editors Jones, H.G.,
Pomeroy, J.W., Walker, D.A. and Hoham, R., Cambridge University Press,
Cambridge, UK.
Walker, D.A., Halfpenny, J.C., Walker, M.D. and Wessman, C., 1993. ‘Long-term
studies of snow-vegetation interactions’, BioScience, 43, 287-301.
White, P.J., Garrolf, R.A. and Heisey, D.M., 1997. ‘An evaluation of snow-urine
ratios as indices of ungulate nutritional status’, Can. J. Zoology, 75, 1687-1694.
Jones & Pomeroy - Snow Ecology
12

Williams, M.W., Brown, A. and Melack, J.M., 1993. ‘Geochemical and hydrological
controls on the composition of surface waters in a high-elevation basin, Sierra
Nevada’, Limnol. Oceanogr. 38, 775-797.
Williams, M.W., Brooks, P.D., Mosier, A. and Tonnessen, K.A., 1996. ‘Mineral
transformations in and under seasonal snow in a high-elevation cathment in the
Rocky Mountains, United States’, Water Resour. Res., 32, 3161-3171.
Winston, G.C., Stephens, B.B., Sunquist, E.T., Hardy, J.P. and Davis, R.E., 1995.
‘Seasonal variability in CO
2
transport through snow in a boreal forest’.
In: Biogeochemistry of seasonally snow-covered catchments, Editors,
Tonnessen, K.A., Williams, M.W. and Tranter, M. IAHS Publication 228, 61-70.
Zettel, J,. 1984. ‘The significance of temperature and barometric pressure changes for
the snow surface activity of Isotoma hiemalis (Collembola)’, Experientia, 40,
1369-1372.
Zimov, S.A., Zimova, G.M., Daviodov, S.P., Davidova, A.I., Voropaev, Y.V.,
Voropaeva, Z.V., Prosiannikov, S.F., Prosianikova, O.V., Semiletova, I.V., and
Semiletov, I.P., 1993. ‘Winter biotic activity and production of CO
2
in Siberian
soils: a factor in the Greenhouse Effect’, J. Geophys. Res., 98, 5017-5023.
Wolf Creek Research Basin: Hydrology, Ecology, Environment
13

Jones & Pomeroy - Snow Ecology
14