Survival of Subnivean vs. Supranivean Plants

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Transcript Survival of Subnivean vs. Supranivean Plants

Survival of Subnivean
vs. Supranivean Plants
*The Snow Buttercup and
Engelmann Spruce*
Arden Piland
Winter Ecology – Spring 2005
Mountain Research Station – University of Colorado, Boulder
Two Environments
• Subnivean: The environment below the
snow (Snow buttercup)
• Supranivean: The environment above the
snow (Engelmann Spruce)
Survival
• Living through the winter:
-most plants well adapted to these
stresses
• Reproduction and success of offspring:
-directly related to winter conditions
leading into growing season
Question(s):
• What factors affect the reproductive
success and the survival of seedlings
of the two species?
• How do the species help to ensure the
survival of progeny?
Effects of Snowdepth
• Growing season length
-outer regions of snowpack= earlier melt=longer
growing season
-30% decrease in growing season from shallow
to deep parts
• Soil fertility
-shallower depths more fertile (more nutrients)
*overtime, more vegetation and microbial
activity (Galen and Stanton, 1999)
• Water availability
-more snow in winter = more available moisture
Snow Buttercup (Ranunculus
adoneus)
• Hemicryptophytes
• Store starch in roots to
overwinter
• Start to grow under snowpack
• Emerge with established
flowers and photosynthesizing
(Stanton et al, 1997)
Effects of growing season length
• Seeds
-fewer seeds produced in late
melt sites (G&S,1991)
-33% decrease in seed mass
in late melt sites
*Larger seeds 6 times more
likely to germinate (G&S,
1993)
Effects cont…
• Seedlings
*30% increase in production of true
leaves in early melt sites
*22% decrease in winter survival if
didn’t produce true leaves in first
season
Effects of soil fertility
• Higher nutrient content= more conducive
to infection by mycorrhizae
• Higher starch content in roots
• More resistant to yearly differences in
growing season length (Scherff et al, 1994)
Some things they do….
• Habitat affinity: more
abundant in early
melting sites (G&S, 1999)
• Symbioses with
mycorrhizae
-Vesicular arbuscular
mycorrhizae (VAM)
(Mullen & Schmidt, 1993)
-Dark-septate
endophytic (DSE) fungi
(Mullen et al, 1998)
• Photosynthetic seeds
(G&S, 1997)
Disscusion/Conclusions
• Main stresses:
-growing season length
*affects time for production-less
seeds, less viable seeds, weaker
seedlings
-soil fertility
*less nutrient gain, less starch
storage, slower growth from snow
(problems of growing season), less
resistant
Engelmann Spruce (Picea Engelmanni)
• Not limited by snowpack determined
growing season..
-water? Yes, but can still set seeds..
• Greatest mortality occurs during
seedling life stage
• Survival of seedling critical
Stress factors for seedlings
• Water availability
-in unusually dry year (not much winter
snowfall) no seedlings emerged-1st time in 16
years (Johnson et al, 2004)
-multiyear study-most seedlings emerged in
wettest year (Germino et al, 2001)
-measure of seedling water potentials
*lowest levels of photosynthesis when
lowest water potentials (Johnson et al,
2004)
Stress cont…
The problem of low temperature photoinhibition
• Photoinhibition= low levels of photosynthesis
Low night temperatures + high light exposure
• High sky exposure= lots of heat lost to night sky=low leaf
temperature=frost formation=stomate damage.
• Next day high light=rapid warming, can’t adjust=respiration
>>photosynthesis (Germino & Smith 1999)
• Coupling of effects means reduced photosynthesis.
-restricted carbohydrate and energy gain, don’t form good
roots=more water stress=chance of survival decreases
(Johnson et al, 2004)
Seedling survival tactics
• Tree islands
-seedling density decreases farther from
tree islands
*reduces sky exposure (insulation/less
light), convective heat gain = less
photoinhibition (Germino et al, 2001)
• Grass cover
-90% survival rate
*same protection as from trees
(Germino et al, 2001)
Survival cont..
• Crown architecture
-needles inclined from horizontal
*decreases sky exposure
* heat dissipation between needlesgradual warming in day, slower cooling at night
(Germino & Smith, 1999)
• Habitats with water retention
-high % new seedlings found on moss layers
and fallen logs (Johnson et al, 2004)
Yep, still goin’…..
• Ribbon forests
-Seedlings establish selves on leeward side
*more water available
*protection from high light and low
temps. (Marchand, 1996)
Conclusions of ES seedlings
• Stresses-#1 water availablity (if low, extremely low levels of
photosynthesis, dessication, death)
-High sky exposure=low night temps & high day light
levels=photoinhibition= plant growth decreased (bad
roots)
• Cope methods
- “choose” sheltered habitat (Tree islands/ribbon forests,
grass cover)
-alter crown structure to reduce photoinhibition
- “choose” site with more water (mosses, logs,
leeward side of ribbon forest)
SURVIVE!!!
SUMMARY
• Snow buttercup
-survival restricted by growing
season length and soil fertility
-Survive by:
*habitat selection (longer
growing season, more fertile soilmore/better seeds)
*mycorrhizae symbioses
(more nutrient acquistion, more
explosive growth, longer grow
season, more resilient)
*photosynthetic seeds (more
carbohydrate production, better
reserves, better survival )
Engelmann Spruce (seedlings)
• Survival restricted by:
-low temps/high light
(photoinhibition, bad roots)
-water (less photosynthesis,
dessication, death)
• Ensure survival by:
-Increasing cover (tree islands,
grass, alter crown structure)
-moister habitat selection
(leeward of ribbons, mosses,
logs)
Message:
• Subnivean (snow buttercup) and
Supranivean (Engelmann Spruce) both
affected by winter conditions but in different
ways:
-Subnivean: snowpack restricts length of
growing season and alters nutrient
availability
-Supranivean: snowpack restricts amount of
water available but also restricted by poor
plant health (reduced roots) from
photoinhibition
*Plants from both environments developed
behavioral and morphological adaptations to
ensure their survival.
REFERENCES
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Galen, C, Stanton M.L. 1991. Consequences of emergence phenology for reproductive
success in Ranunculus adoneus. American Journal of Botany. 78(7):978-988.
Galen, C, Stanton M.L. 1993. Short term responses of alpine buttercups to experimental
manipulations of growing season length. Ecology 74(4):1052-1058.
Galen, C., Stanton, M.L. 1999. Seedling establishment in alpine buttercups under experimental
manipulations
of growing season length. Ecology. 80(6):2033-2053.
Germino, M.J., Smith, W.K. 1999. Sky exposure, crown architecture, and low-temperature
photoinhibition in conifer seedlings at alpine treeline. Plant, Cell and Environment.
22:407-415.
Germino, M.J., Smith, W.K., Resor, A.C. 2001. Conifer seedling distribution and
survival in alpine-treeline ecotone. Plant Ecology. 162:157-168.
Johnson, D.M., Germino, M.J, Smith, W.K. 2004. Abiotic factors limiting
photosynthesis in Abeis lasiocarpa and Picea engelmannii. Tree Physiology.
24:377386.
Marchand, P.J. 1996. University Press of New England. Life in the Cold. Pg:75-91.
Mullen, R.B., Schmidt, S.K. 1993. Mycorrhizal infection, phosphorus uptake, and phenology in
Ranunculus adoneus- implications for the functioning of mycorrhizae in alpine systems.
Oecologia. 94(2):229-234
Mullen, R.B., Schmidt, S.K., Jaeger, C.H. 1998. Nitrogen uptake during snowmelt by the
snow buttercup, Ranunculus adoneus. Arctic and Alpine Research. 30(2):121-125.
Scherff, E.J., Galen, C., Stanton, M.L. 1994. Seed dispersal, seedling survival and habitat
affinity in a snowbed plant-limits to the distribution of the snow buttercup, Ranunculus
adoneus. 1994. Oikos. 69(3):405-413.
Stanton, M.L., Galen C. 1997. Life on the edge: adaptation versus environmentally
mediated gene flow in the snow buttercup, Ranunculus adoneus. The American
Nauturalist. 150(2):143-178.
Stanton, M.L, Galen, C, Shore, J. 1997. Population structure along a steep environmental
gradient: consequences of flowering time and habitat variation in the snow
buttercup, Ranunculus adoneus. Evolution. 51(1):79-94.
Cont…
Survival Strategies
• Habitat affinity, mycorrhizae and
photosynthetic seeds =
-more carbohydrate production
-more reserves
-faster growth from snow (longer grow
season)
-more seeds/ better seeds
INCREASED SURVIVAL! YAY!