Survival of Subnivean vs. Supranivean Plants

1. 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

2. Two Environments • Subnivean: The environment below the snow (Snow buttercup) • Supranivean: The environment above the snow (Engelmann Spruce)

3. 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

4. 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?

5. 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

6. 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)

7. 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)

8. 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

9. 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)

10. 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)

11. 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

12. 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

13. 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)

14. 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)

15. 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)

16. 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)

17. Yep, still goin’….. • Ribbon forests -Seedlings establish selves on leeward side *more water available *protection from high light and low temps. (Marchand, 1996)

18. 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!!!

19. 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 )

20. 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)

21. 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.

22. REFERENCES • 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. 24:377- 386. • 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.

23. 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!