SNOW AND INVERTEBRATES

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SNOW AND INVERTEBRATES

• Group  ALBRIGHT Aaron
• HÄMÄLÄINEN Julia
• HEIM Caleah
• KAUNISTO Sirpa
• KAUPPINEN Elsi
• LOENS Juliette
• RIQUIER Florence
• Instructor  Pohjola Pekka

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Introduction

• Our topics were snow temperature, density and
  insulative quality, the effect of snow in the
  survival of scale insect eggs in willows,
  intranivean and subnivean invertebrates and
  distribution of Rhabdophaga rosaria.

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I. Snow temperature, density and insulative
quality
The physical properties of snow and the affect
they have on nival organisms.
Caleah Heim Aaron Albright
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Life Under the Snow

• Physical Properties of Snow
• Subnivean Organisms
• Vegetation
• Nutirent Cycling

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Structure of Ice (I)
At 0C and normal atmospheric pressure
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Changes in Structure if Ice(Snow)

• Snow undergoes certain physical metamorphism in
  varying conditions
• Temperature
• Humidity
• Wind
• Solar Radiation
• Ground Temperature

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Snow Properties

• Density and depth of snow pack are regulating
  factors of snows thermal insulation capacity

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Invertebrates - Microbial

• Deep snow packs allow not only for larger
  organisms to live but also microbial communities
• Ex. snow algae, bacteria, yeast, and fungi
• These communities are essential to the survial of
  species of higher trophic levels (ex. rotifers
  feeds on fungi eaten by collembola eaten by
  spider eaten by shrew- and so on)

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Invertebrates

• Subzero temps do not mean death to arctic species
• Under snow temp up to 0.01C
• Anti-freeze agents (HSP, thermal-hysteris-proteins
  , cryoprotectants)

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Vegetation

• Green vegetation can exist under deep snow cover.
• Food
• Plants can survive due to high thermal insulation
  of snow or retention of dead organic matter

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Nutrient Cycling

• Respiration and allied microbiological processes
  such as denitrification and nitrification
  continue to produce CO2, CH4, N2, NO, N20, and
  other gases throughout the winter

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II. Willow scale
The effect of snow to the survival of scale
insect eggs in willows
HÄMÄLÄINEN Julia KAUNISTO Sirpa KAUPPINEN Elsi
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• Snow is necessary for most invertebrates
  survival in winter
• Preparing for winter is determined mainly by
  photoperiod

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• Most of the invertebrates overwinter in certain
  stage of development (egg, larva, pupa or adult)
• Some of the invertebrates are active in winter.
• They move mostly in the space between snow and
  ground and in the cavities in the bottom layer of
  snow.

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Data and methods

• We studied the willow scale insects (Chionaspis
  salicis) overwintering on willow stems (Salix
  sp.).
• willow scale insects belong to family Coccidae.

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• The willow scale insect is polyphagous and live
  for example on blueberry (Vaccinium myrtillus)
  and willow species phylicifolia, myrsinifolia,
  caprea, pentandra, lapponum, cinerea
• Only Chionaspis salicis eggs survive over
  winter.

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• The females attach to the willow stems

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• and lay their eggs on the bark

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• Willow scale insects are parthenogenetic
• Females are 1,5 2,5 mm long and 1 1,5 mm
  wide.

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• Females scale is almost shaped like a perry,
  flattish and scaly

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• In Finland males are rare, but in southern parts
  of Europe males are more common
• Adult males are with or without wings

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• Often individuals aggregate so that the trunk
  becomes white

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• We collected some willow stems near research
  station and counted dead and alive eggs from
  different heights from the snow surface. Empty
  scales were also counted.

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Results
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Conclusion

• the number of dead eggs was highest between 10
  centimetres below and above snow cover
• There was no statistical variation in the number
  of dead eggs at different highs.
• The number of scales increased almost linearly
  from the snow cover to deeper under the snow.

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Error probability increased, because...

• Difficulty of identification of dead eggs from
  alive ones
• There was confusion about filling the forms

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III. Intranivean and Subnivean InverterbratesThe
distribution of Rhabdophaga Rosaria
LOENS Juliette RIQUIER Florence
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• Winter ? outside conditions more and more strong
  ? temperature decreases ? number of invertebrates
  decreases
• Some survive by different ways of over wintering
• vertical migration in snow
• winter activity
• Invertebrates move toward warmer place, from the
  top to the bottom of snow cover

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1. Intranivean invertabrates

• Insects present in snow cover during winter time

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• Method
• snow samples taken everyday
• two sites
• ? old field site
• ? pine forest
• layers between 0 cm and 70 cm
• 6 litres per each 10cm layer of snow
• different snow samples were melted and sieved
  through a plankton-net
• invertebrates were identified and counted in
  order to evaluate their density

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• Results and discussion
• ? Individuals found per m3 of snow in both sites
  (average)

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Collembola
Homoptera
Araneae
Acari
Diptera
Oligochaeta
Nematoda
Mecoptera
Psocoptera
Coleoptera
Tardigrada
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• Results and discussion
• ? Distribution of invertebrates in different
  snow layers

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• Results and discussion
• ? Distribution of the 4 main species in the
  different snow layers

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• Conclusion
• Collembola is the most abundant invertebrate
  specially in old field site
• importance of Araneae in this area
• Acari was the most common invertebrate group in
  pine forest

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2. Subnivean invertabrates

• Subnivean invertebrate invertebrates that move
  on snowpack
• None found during the trip
• some scale insects (Chionaspis salicis) and
  specimens of insect pupae, galls and nests were
  found.

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3. Distribution of Rhabdophaga rosaria

• Class Insecta
• Order Diptera
• Family Cecidomyidae
• Genus Rhabdophaga
• Specie Rhabdophaga rosaria

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Rhabdophaga rosaria

• Called gall-midge ? larvae cause and live in bud
  galls (rosette)
• Usually found in the willow trees (salix)

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Abundance of Rhabdophaga rosaria

• ? Number of infected bushes and non-infected
  bushes collected everyday in two areas a wetland
  and an old field site

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• Questions