Snow and Invertebrates Winter Ecology Field Course 21'24'02'2005

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Snow and Invertebrates(Winter Ecology Field
Course 21.-24.02.2005 )

• Suvi Järvinen
• Hannnele Valkama
• Taina Oinonen
• Jenna Toivanen
• Niina Ihatsu
• Sanna Leppänen
• Martin Wehrhausen
• Jan Tvrdý

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Introduction

• Why Winter Ecology Field Course? Because snow and
  low temperatures are some of the most important
  phenomenas in ecology.
• Samples and other data were collected close to
  Mekrijärvi Research Station, located in eastern
  Finland near municipality of Ilomantsi.

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Questions and Themes

• Snow Temperature, Density and Insulative
  Quality.
• Intranivean and Supranivean Invertebrates.
• Does the Plant Age Effects Oviposition Preference
  of Pine Aphid (Lachnnus pineti)?
• The effect of plant vigor (shoot length) to
  birch aphids (Euceraphis betulae) oviposition
  preference.

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1, Snow Temperature, Density and Insulative
Quality.

• Suvi Järvinen, Jan Tvrdý

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Snow Temperature, Density and Insulative Quality
Introduction

• Distribution of organisms are dictated primarily
  by temperature, wind and precipitation.
• At present ca. 5 of the annual precipitation on
  our planet comes in the form of snow.
• In February worldwide as much as 39 of land
  areas are covered by snow (Holopainen 1994).

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Temperature

• Snow temperature is a dominant variable in many
  physical processes in the seasonal snowpack.
• The temperature profile reveals much about both
  the current physical state of the snowpack.

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TemperatureResults And Conclusions

• Difference between one day air and snow surface
  temperatures at both stands is caused by
  different time of measuring.
• Snow temperature is increasing with snow depth.
• From collected data we can estimate that
  temperatures of snow under depth around 50 cm are
  not dramatically changing (accoding to air
  temperatures changes).
• Ground temperatures at both stands were all the
  time close to O C, so the insulative quality of
  snow cover was proved and it is significant.

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Density

• Once snow falls it begins to change,
  metamorphose.
• The crystalline structures and the loosely packed
  emulsion begin to degenerate almost immediately.

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DensityThree types of changes

• Destructive metamorphism
• Deterioration of snowflakes and formation more or
  less rounded ice grains.
• Caused by wind, weight of snow.
• Constructive metamorphism
• When ground heated water vapour starts migrate
  upward within snowpack.
• Condensation of water vapour results a growth of
  the grains.
• Melt metamorphism
• The temperature is above freezing point.
• After wormer weather periods ice layers and
  formation can be foun in the snowpack.

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DensityResults And Conclusions

• Snow density is increasing with snow depth,
  except the two deepest layers.
• Can be caused by ground layer flora such as plant
  residues or evergreen plants, shrubs.

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Insulative Quality

• Accumulation of snow provides protection from
  wind serving as a "roof" over the subnivean
  spaces.
• Snow is an effective insulator, especially when
  newly fallen, because it forms an emulsion of
  crystals and air.
• It S (z/G)i
• where z is thickness (cm) and G is density
  (g/cm3) of each layer i (Marchand 1996).

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References

• Gray, D. M. and D. H. Male, 1981. Handbook of
  Snow Principles, Processes, Management andUse.
  Willowdale, Ontario, Canada, Pergamon Press,
  776p.
• Holopainen, I. J et all, 1994. Northern Winter
  as an Ecological Factor, University of Joensuu,
  Finland, 22p.
• Marchan, P. J., 1996. Life in The Cold,
  University Press of New England.
• McClung, D. and P. Schaerer, 1993. The Avalanche
  Handbook. The Mountaineers, Seattle, WA.
• http//realscience.breckschool.org/upper/eb_book/w
  inter/snow.html
• http//www.fsavalanche.org/NAC/techPages/articles/
  02_WSC_Deems.pdf
• http//www.joensuu.fi/mekri/

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2, Intranivean and supranivean invertebrates
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Intranivean and supranivean invertebrates

• Results
• - Supranivean invertebrates could not be found
  because weather was too cold (under -5 C).
• - There was more invertebrates in the pine forest
  and in the lower snow layers, because there is
  warmer and lots of air spaces for invertebrates
  to move.

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Comparing the old field site and the pine forest

• In the pine forest the most common invertebrates
  belonged to Acari and Collembola.
• - In the old field site the most common
  invertebrates belonged to Araneae and Collembola.

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References

• Holopainen I. (toim.). 1990. Eliöiden
  sopeutuminen Suomen talveen.
• Viramo J. 1980. Liikettä lumellahämähäkkejä ja
  hyönteisiä. Suomen Luonto 2/80 s. 84-85.

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3, Does the plant age effect oviposition
preference of pine aphid (Lachnnus pineti)?
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Introduction

• Pine aphids lives in pines making bad infections
  to the needles and even to the whole tree.
• Aphids stay over-wintering as eggs.
• Our interest was to know is there differences
  between the number of the eggs in 1st and 2nd
  annual and is the length of the annual linked to
  the number of the eggs.

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Pine aphid alive eggs are black, round and full
while the dead eggs are also black but dried out.
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Results
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Distribution of pine aphid eggs between annuals
shoots.
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Regression between annual length and number of
eggs in the first annual.
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Regression between annual length and number of
eggs in the second annual.
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Discussion

• In the first annual there are more alive eggs
  than in the second annual, but the number of dead
  eggs is quite similar.
• Female prefers more the second annual than the
  first one because the density in the second
  annual is higher than the first annual.
• There are no regression between the annual length
  and the number of the eggs.
• Females prefer the annual length between 3 10
  cm.

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References

• Uunio Saalas 1949 Suomen metsähyönteiset sekä
  muut metsälle vahingolliset ja hyödylliset
  eläimet, p. 173
• Huttunen, M.A. (ed.) 2002 Field Course in Winter
  Ecology 2002.
• http//bio.joensuu.fi/winter/w2002
• Holopainen I.J. (ed.) 1990 Eliöiden sopeutuminen
  Suomen talveen.

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4, The effect of plant vigor (shoot length) to
birch aphids (Euceraphis betulae)oviposition
preference

• Niina Ihatsu, Martin Wehrhausen

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Introduction

• Euceraphis betulae (Homoptera)
• Soft-bodied, thin-skinned insects with long feet
• E. betulae is most common of the 300 E. species
  in Finland
• Imaginae are 1,5 7 mm large and bright green
• Females lay their eggs on the bark of birches
  near to the buds in autumn

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Introduction
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Introduction
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Methods

• Trees
• Twigs taken from
• 5 B. pendula and 5 B. pubescens randomly around
  the Mekrijärvi Station
• Trees with heights of 1,5 ... 2 m
• No age classes considered
• Trees from open sites

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Methods

• Counting of eggs
• About 20 twigs from each tree
• Only the annual sprouts examined
• Eggs on buds counted under microscope
• Measurments
• Lenght of sprout
• Number of buds per sprout
• Number of eggs at each sample

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Results and discussion
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Results and discussion
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Results and discussion
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Results and discussion
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References

• Huhta, V. (ed.) 1998 Selkärangattomat. Suomen
  luonto. Weilin Göös.
• Huttunen, M.A. (ed.) 2002 Field course in Winter
  Ecology 2002.
• - http//bio.joensuu.fi/winter/w2002.pdf
• Nuorteva, M. 1999 Metsähyönteisten maailmasta.
  Tremex.
• Poteri, M. (ed.) 2002 Taimituho-opas.
  Metsäntutkimuslaitoksen tiedonantoja 843.
• Price, P.W. 1997 Insect ecology. Northern
  Arizona University. USA.

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Thank you for your attention

• Questions, comments?