Mycorrhizae, Gesundheit

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Mycorrhizae, Gesundheit

• Definition
• Mycorrhizal types
• What do they look like?
• What do they do?
• Ecological Significance
• Mycorrhizal Research

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Definition of Mycorrhizae

• Myco fungus
• rhiza root
• Mycorrhizae symbiosis between fungi and plant
  roots

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Mycorrhizal Types

• Ectomycorrhizae
• Endomycorrhizae or Vesicular Arbuscular
  Mycorrhizae (VAM)
• Ectendomycorrhizae or Ericoid
• Orchid Mycorrhizae (parasitic)

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What do they look like?

• Ectomycorrhizal Families Pinaceae, Fagaceae,
  Betulaceae, Salicaceae
• Mantle made of hyphae
• Hartig net
• Septate hyphae D. Ascomycota and D.
  Basidiomycota (clamp connections)
• Photos from Masters Thesis UAF

40 Power
1000 Power
250 Power
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Cartoon from Masters Thesis UAF
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What do they NOT look like?
Uninfected salicaceous fine roots
40 Power
250 Power
Photos from Masters Thesis UAF
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What do they look like?

• Endomycorrhizae
• Vesicles
• Arbuscules
• Non-septate hyphae
• D. Zygomycota

Photos from Masters Thesis UAF
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Cartoon from Masters Thesis UAF
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How Do Mycorrhizae Function?

• Fungal hyphae release enzymes (chitinase,
  peroxidase, cellulase, protease) which allows
  them to digest and penetrate substrates.
• Secretion of enzymes breaks down tough organic
  substrates that can then be absorbed and used by
  the fungus and/or host plant as energy and
  nutrient sources for growth and reproduction.
• (Laursen 1985)

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Function of Mycorrhizae Benefits to Plants

• Hyphae increase surface area of roots for
  increased absorption of soil nutrients Nitrogen,
  Phosphorus

10 -85 photosynthates made (Finlay and
Söderström 1992)
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Function of Mycorrhizae Benefits to Plants

• Increase water uptake and aid drought resistance
  to plants
• Resistance to some root pathogens due to thick
  hyphal mantle
• Increase plant tolerance to soil temperature
  extremes, pH extremes, toxic heavy metals, and
  transplant shock

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Function of Mycorrhizae Benefits to World
Agriculture

• Aid in plant establishment on nutrient poor soils
  (mining reclamation and revegetation projects)
• Increase plant size in short time period
  (forestry)
• Reduce fertilizer requirements
• Cut down production costs
• Decrease fertilizer contamination of the
  environment

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Ecological Significance

• Plants of different families or genera can share
  the same mycorrhizal connection.
• Cheating potentials
• Tripartite associations ectomycorrhizae,
  endomycorrhyzae, AND nitrogen fixing nodules on
  the same root (Forest Soils Lab, Corvallis)
• Holistic ecology linking Northern Spotted Owl
  to Old Growth Forests to their flying squirrel
  prey who feed on the mushrooms from the
  mycorrhizae that form specifically on Old Growth
  tree roots. Take one out of the link, and the
  other three in the system fail owl, squirrel,
  mycorrhizae, tree

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Mycorrhizal Research at University of Alaska,
Fairbanks

• Testing Gehring and Whithams hypothesis (1991)
  that herbivory reduces aboveground photosynthetic
  tissue which in turn reduces the sugars available
  for maintaining mycorrhizae.

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Hypotheses

• Does browsing affect
• The total dry Salicaceous (Cottonwoods willow,
  poplar, aspen) fine root mass
• The quantity of ectomycorrhizae on Salicaceous
  fine roots
• Does the depth affect
• The total dry Salicaceous fine root mass
• The quantity of ectomycorrhizae on Salicaceous
  fine roots
• Does the combination of browsing and depth affect
• The total dry Salicaceous fine root mass
• The quantity of ectomycorrhizae on Salicaceous
  fine roots

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Study Site

• 17 km segment of the Tanana River floodplain
  within the Bonanza Creek Experimental Forest
  Long-Term Ecological Research (BNZ LTER) site
  located 28 km south-west of Fairbanks Alaska
• Primary succession begins with colonization of
  nitrogen and phosphorus deficient glacial silt by
  wind blown willows and balsam poplar.
• Soils later in succession, after thinleaf alder,
  a nitrogen fixer, are not as limited

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Study Site
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Study Site
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Study Site
Courtesy of John P. Bryant
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Study Site
Courtesy of Keith Van Cleve
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Study Site
Courtesy of Keith Van Cleve
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Exclosures

• Seven pairs of permanent exclosures and their
  respective control plots established in 1988,
  along the 17-km reach of the Tanana River in the
  BNZ LTER site
• High tensile strength steel wire and 2.5-cm mesh
  fence wire were hung on 5-m fungicide treated
  fence posts to prevent moose and snowshoe hare
  from entering the exclosures throughout the year

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Exclosures
Courtesy of John P. Bryant
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Animals Omitted from Exclosures
Moose (Alces alces), left Snowshoe hare (Lepus
americanus), below
Courtesy of John P. Bryant
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Data Gathering
Five soil cores were taken randomly from each
treatment Soil cores were preserved in
Formaldehyde, acetic acid and ethanol (FAA Sass
1958) Cores where cut into 3 depths (0-5cm,
5-10cm, 10-15cm) Willow, aspen, and balsam poplar
roots (salicaceous species) were lumped together
because they could not be isolated from one
another
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Data Gathering
Fine roots were washed, sorted, weighed, and
stored in 50 ethanol (210 samples) Stored fine
roots were randomly subsampled 2x per sample 10
KOH was added to each slide to view
ectomycorrhizae Counts of ecto infection per
total root numbers were recorded for each
subsample
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Data Gathering
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Data Gathering
Courtesy of John P. Bryant
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Data Gathering
Essentially all browsing of willow and balsam
poplar shoots occurs in the winter season, so
will be called winter browsing by moose and
snowshoe hare
Courtesy of John P. Bryant
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Results
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Results
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Results
ANOVA of browsing effects on ectomycorrhizal
infection () and fine root biomass (g/m2)
Mean Browsing BNZ LTER Floodplain (Kielland
1996)_________________
1988-89 60 1989-90 60 1990-91 50 1991-9
2 25 (Deep snow)
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Discussion

• Ectomycorrhizal infection of fine roots of willow
  and balsam poplar growing outside exclosures was
  reduced by about 16 in comparison to
  ectomycorrhizal infection of willow and balsam
  poplar that had been protected from browsing by
  moose and snowshoe hare for the previous 4
  winters.
• 16 reduction in ectomycorrhizae compares
  favorably to the results of Gehring and Whitham
  (1995) following simulated herbivory on pinyon
  pines growing in infertile cinder soil and
  fertile sandy loam soil.
• Bryant (1987) demonstrated that pruning of shoots
  in one winter reduced the soluble carbohydrate
  concentration of current-year shoots in the next
  winter.

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Discussion

• Thus, browsing by moose and snowshoe hare could
  reduce the supply of soluble carbohydrate to
  roots, thereby reducing the supply of
  carbohydrate available to ectomycorrhizae, and as
  a consequence, reduce ectomycorrhizal infection
  of salicaceous fine root.
• Successful infection of fine roots by
  ectomycorrhizae is very important to the
  competitive ability of woody plants (Allen and
  Allen 1990), and especially woody plants growing
  in nutrient deficient soils (Allen 1991), such as
  the recently deposited glacial silt that formed
  our sites on the floodplain of the Tanana River
  (Van Cleve et al. 1991)

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Discussion

• By reducing ectomycorrhizal infection of willow
  and balsam poplar fine roots, winter browsing by
  snowshoe hare and moose are likely to reduce the
  ability of these species to compete for nutrients
  with thinleaf alder (Alnus tenuifolia), a species
  that is mycorrhizal and rarely browsed by
  snowshoe hare and moose (Wolff and Zasada 1979
  McAvinchy 1991).

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Discussion

• This shift from willow to alder is an extremely
  important event in ecosystem development because
  the nitrogen fixed by alder in the alder stage of
  primary succession provides most of the nitrogen
  annually accumulated by the Tanana River
  Floodplain ecosystem (Klingensmith and Van Cleve
  1993 Van Cleve et al. 1993)
• Thus the willow stage of succession will be brief
  with browsing, and the alder stage will take
  over, giving less food to sustain moose and
  snowshoe hare. (implications for hunting)

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Mycorrhizal Research at University of Alaska,
Fairbanks

• Testing Gehring and Whithams hypothesis that
  herbivory reduces aboveground photosynthetic
  tissue which in turn reduces the sugars available
  for maintaining mycorrhizae.
• Results support the hypothesis by finding that
  moose and hare browsing on willows and poplars
  decreases the photosynthetic biomass the sugars
  made, and thus fewer mycorrhizae are supported

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Bibliography

• Allen, M.F. 1991. The ecology of mycorrhizae.
  Cambridge University Press, New York.
• Allen and Allen 1990. The mediation of
  competition by mycorrhizae in successional and
  patchy environments. In Grace, J.B., Tilman,
  G.D. (eds). Perspectives on plant competition.
  Academic Press, New York, pp 367-389.
• Bryant, J.P. 1987. Feltleaf willow-snowshoe
  hare interactions plant carbon/nutrient balance
  and flood plain succession. Ecology 681319-1327
• Finlay, R and Söderström, B. 1992. Mycorrhiza
  and carbon flow to the soil. In Allen, M.F.
  (ed) Mycorrhizal functioning. Routledge Chapman
  and Hall, New York, pp 134-160.
• Gehring, C.A. and Whitham, T.G. 1991. Herbivore
  driven mycorrhizal mutualism in insect
  susceptible pinyon pine. Nature 353556-557.
• Gehring, C.A. and Whitham, T.G. 1995. Duration
  of herbivore removal and environmental stress
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  Ecology 762118-2123
• Kielland, K. 1996. Role of free amino acids in
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  Ecoscience, in press.
• Laursen, G.A. 1985. Mycorrhizae A review of
  the importance of fungi from high-latitude
  forests of Alaska. Agroborealis 17(2)58-66.
• McAvinchy, R.J.P. 1991. Winter herbivory by
  snowshoe hares and moose as a process affecting
  primary succession on an Alaskan floodplain.
  M.S. Thesis, Universiyt of Alaska, Fairbanks.
• Sass, J.E. 1958. Botanical microtechnique, 3rd
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• Wolff, J.O. and Zasada, J.C. 1979. Moose
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• Van Cleve, K., Chapin, F.S. III, Dyrness, C.T.,
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