Effects of Snowpack on Vegetation Composition

Andrea DixonWinter Ecology

Spring 2009

Silene acaulis

Geum rossii

Mountain Research Station, University of Colorado, Boulder

Question

Does differential snowpack affect alpine plant community composition?

Snowpack

1. Snowpack varies across the landscape due to local variables such as topography, wind and climatic factors

2. Snowmelt is controlled by the quality of snow, the thickness of the snowpack, air temperatures and solar radiation

3. Snowpack, and thus snowmelt, affects growing season length

Photo: Williams, et al.

Snowpack and Vegetation

LESS SNOWPACK = LONGER GROWING SEASON

Focus on 2 studies:

RESPONSES OF SNOWBED PLANT-SPECIES TO CHANGES IN GROWING-SEASON LENGTH (Galen & Stanton, 995)

SMALL-SCALE PLANT SPECIES DISTRIBUTION IN SNOWBEDS AND ITS SENSITIVITY

TO CLIMATE CHANGE (Schob, et al. 2009)

Results- Study #1

RESPONSES OF SNOWBED PLANT-SPECIES TO CHANGES IN GROWING-SEASON LENGTH (GALEN & STANTON, 995)

Leaf expansion occurs at snowmelt -w/in 3 days

Leaf expansion occurs at snowmelt -w/in 6days

Leaf expansion occurs at snowmelt -w/in 9 days

These 2 plants had a 2-3 fold increase in cover with long growing seasons. These plants also have longer periods of shoot growth.

Results- Study #1

RESPONSES OF SNOWBED PLANT-SPECIES TO CHANGES IN GROWING-SEASON LENGTH (GALEN & STANTON, 995)

Growing season length had the most pronounced affect on those plants that begin their leaf expansion (growth) at snowmelt.

Plants that delay their leaf expansion by 1-2 weeks, were not as affected by changes in growing season length.

R. adoneus

T. parryi G. rossii

S. procumbens

Results- Study #2

SMALL-SCALE PLANT SPECIES DISTRIBUTION IN SNOWBEDS AND ITS SENSITIVITY TO CLIMATE CHANGE (SCHOB, ET AL. 2009)

5 Categories of Plants

1. Dominants (make up most of the vegetation) – Increased with later snowmelt dates

2. Subordinate species (making up less of the % cover than dominants):2a. Indifferents to snowmelt dates – no change to later snowmelt dates2b. Snowbed specialists – increased significantly with later snowmelt

dates (delayed leaf expansion plants)2c. Avoiders of late-snowmelt sites – significantly decreased with later

snowmelt dates (immediate leaf expansion plants)3. Transients – almost completely disappeared with later snowmelt dates

SNOWMELT DATE

Fig. 1 Number of species along the snowmelt gradient for the five categories :

Dominants D (-□-)

Indifferents to snowmelt dates I (- · - - · -)■

Snowbed specialists S (- -○- -)

Avoiders of late-snowmelt sites A (- · · -+- · · -)

Transients T (- -×- -).

Results- Study #2

Results- Study #2

SMALL-SCALE PLANT SPECIES DISTRIBUTION IN SNOWBEDS AND ITS SENSITIVITY TO CLIMATE CHANGE (SCHOB, ET AL. 2009)

Plant species richness was reduced by approximately 50% in snowbeds with late melt dates.

Total cover by vascular species was not reduced- only the number of species making up the cover.

Conclusions

Plants have species specific responses to snowpack variation (Galen & Stanton, 1995)

Longer growing season will lead to loss of species that area adapted to and thrive on a short growing season (late snowmelt) as their habitat disappears (Schob et al., 2008)

Growing season length had a significant impact on the plants that have leaf growth that is synchronized with snowmelt (snowbed specialists) (Galen & Stanton, 1995)

This becomes a disadvantage during years of late snowmelt (Galen & Stanton, 1995)

Conclusions

If temps increase and snowmelt occurs earlier, plants that avoid late snowmelt sites will increase their area of cover, comprising a greater percentage of the cover species as their suitable habitat increases in area (Schob et al., 2008)

Transient plants may increase in amount of cover, as well as number of overall species of transients with longer growing season- this needs more study (Schob et al., 2008)

Works Cited

Galen, C. and M. L. Stanton, 1995. Responses of snowbed-plant species to changes in growing-season length. Ecology 76:1546-1557.

Monson, R.K., D.L. Lipson, S.P. Burns, A.A. Turnipseed, A.C. Delaney, M.W. Williams and S.K. Schmidt, 2006. Winter forest soil respiration controlled by climate and microbial community composition. Nature 439:711-714.

Raible, C.C., C Casty, J. Luterbacher, A. Pauling, J. Esper, D.C. Frank, U. Buntagen, A.C. Roesch, P Tschuck, M. Wild, P.L. Vidale and C Schar, 2006. Climate variability- observations, reconstructions and model simulations for the Antlantic-European and Alpine region from 1500-2100 AD. Climate Change 79:9-29.

Schob C. , P.M. Kammer, P. Choler, H. Veit, 2008. Small-scale plant species distribution in snowbeds and its sensitivity to climate change. Plant Ecology 200:91-104

Seastedt, T.R. and L. Vacarro, 2001. Plant species richness, productivity, and nitrogen and phosphorus limitations across a snowpack gradient in Alpine Tundra, Colorado, USA. Arctic, Antarctic and Alpine Research 33:100-106.

Summary

Conclusion:

Plants responses to snowpack (growing season length) are species specific based on their adaptations to the environment- such as how/when they begin leaf expansion

Warming and cooling trends seen in the Alpine will lead to decreases in some plants and increases in others, which could lead to plant community compositions that are ‘novel’ for the Alpine

Question: Does differential snowpack affect alpine plant community composition?