Survival of Subnivean vs. Supranivean Plants

*The Snow Buttercup and *The Snow Buttercup and Engelmann Spruce*Engelmann Spruce*

Winter Ecology – Spring 2005

Mountain Research Station – University of Colorado, Boulder

Arden Arden PilandPiland

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 ButtercupSnow Buttercup (Ranunculus (Ranunculus adoneus)adoneus)

• HemicryptophytesHemicryptophytes• Store starch in roots to Store starch in roots to

overwinteroverwinter• Start to grow under snowpackStart to grow under snowpack• Emerge with established Emerge with established

flowers and photosynthesizing flowers and photosynthesizing (Stanton et al, 1997)(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: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 Engelmann Spruce (Picea Engelmanni)(Picea Engelmanni)

• Not limited by snowpack determined Not limited by snowpack determined growing season..growing season..

-water? Yes, but can still set seeds.. -water? Yes, but can still set seeds..

• Greatest mortality occurs during Greatest mortality occurs during seedling life stageseedling life stage

• Survival of seedling criticalSurvival 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 needles-gradual 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-Stresses-

-#1 water availablity (if low, extremely low levels of -#1 water availablity (if low, extremely low levels of photosynthesis, dessication, death)photosynthesis, dessication, death)-High sky exposure=low night temps & high day light -High sky exposure=low night temps & high day light levels=photoinhibition= plant growth decreased (bad levels=photoinhibition= plant growth decreased (bad roots)roots)

• Cope methodsCope methods- “choose” sheltered habitat (Tree islands/ribbon forests, - “choose” sheltered habitat (Tree islands/ribbon forests, grass cover)grass cover)-alter crown structure to reduce photoinhibition-alter crown structure to reduce photoinhibition- “choose” site with more water (mosses, logs, - “choose” site with more water (mosses, logs, leeward side of ribbon forest)leeward side of ribbon forest)

SURVIVE!!!SURVIVE!!!

SUMMARY• Snow buttercup

-survival restricted by growing season length and soil fertility-Survive by:

*habitat selection (longer growing season, more fertile soil-more/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• Galen, C, Stanton M.L. Galen, C, Stanton M.L. 1991. Consequences of emergence phenology for reproductive 1991. Consequences of emergence phenology for reproductive

success in success in Ranunculus adoneusRanunculus adoneus. American Journal of Botany. 78(7):978-988.. American Journal of Botany. 78(7):978-988.• Galen, C, Stanton M.L. Galen, C, Stanton M.L. 1993. Short term responses of alpine buttercups to experimental1993. Short term responses of alpine buttercups to experimental

manipulations of growing season length. Ecology 74(4):1052-1058.manipulations of growing season length. Ecology 74(4):1052-1058.• Galen, C., Stanton, M.L. 1999. Galen, C., Stanton, M.L. 1999. Seedling establishment in alpine buttercups under experimental Seedling establishment in alpine buttercups under experimental

manipulations manipulations of growing season length. Ecology. 80(6):2033-2053.of growing season length. Ecology. 80(6):2033-2053.• Germino, M.J., Smith, W.K. 1999. Sky exposure, crown architecture, and low-temperature 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. photoinhibition in conifer seedlings at alpine treeline. Plant, Cell and Environment. 22:407-415.22:407-415.

• Germino, M.J., Smith, W.K., Resor, A.C. 2001. Conifer seedling distribution andGermino, M.J., Smith, W.K., Resor, A.C. 2001. Conifer seedling distribution andsurvival in alpine-treeline ecotone. Plant Ecology. 162:157-168.survival in alpine-treeline ecotone. Plant Ecology. 162:157-168.

• Johnson, D.M., Germino, M.J, Smith, W.K. 2004. Abiotic factors limitingJohnson, D.M., Germino, M.J, Smith, W.K. 2004. Abiotic factors limiting photosynthesis in photosynthesis in Abeis lasiocarpa Abeis lasiocarpa and and Picea engelmanniiPicea engelmannii. Tree Physiology.. Tree Physiology.

24:377-24:377- 386.386.• Marchand, P.J. 1996. University Press of New England. Marchand, P.J. 1996. University Press of New England. Life in the ColdLife in the Cold. Pg:75-91.. Pg:75-91.• Mullen, R.B., Schmidt, S.K. 1993. Mycorrhizal infection, phosphorus uptake, and phenology in Mullen, R.B., Schmidt, S.K. 1993. Mycorrhizal infection, phosphorus uptake, and phenology in

Ranunculus adoneus-Ranunculus adoneus- implications for the functioning of mycorrhizae in alpine implications for the functioning of mycorrhizae in alpine systems. systems. Oecologia. 94(2):229-234Oecologia. 94(2):229-234

• Mullen, R.B., Schmidt, S.K., Jaeger, C.H. 1998. Nitrogen uptake during snowmelt by the Mullen, R.B., Schmidt, S.K., Jaeger, C.H. 1998. Nitrogen uptake during snowmelt by the snow buttercup, snow buttercup, Ranunculus adoneusRanunculus adoneus. Arctic and Alpine Research. 30(2):121-125.. Arctic and Alpine Research. 30(2):121-125.

• Scherff, E.J., Galen, C., Stanton, M.L. 1994. Seed dispersal, seedling survival and habitat 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, affinity in a snowbed plant-limits to the distribution of the snow buttercup, Ranunculus Ranunculus adoneusadoneus. 1994. Oikos. 69(3):405-413.. 1994. Oikos. 69(3):405-413.

• Stanton, M.L., Galen C. 1997. Life on the edge: adaptation versus environmentallyStanton, M.L., Galen C. 1997. Life on the edge: adaptation versus environmentally mediated gene flow in the snow buttercup, mediated gene flow in the snow buttercup, Ranunculus adoneusRanunculus adoneus. The American. The American Nauturalist. 150(2):143-178. Nauturalist. 150(2):143-178.

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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!