How do snowpack depth and proximity to trees affect subnivean plant growth

Robin Reibold

Winter Ecology: Spring 2014Mountain Research Station,

University of Colorado, Boulder

Background

• Plant requirements for growth– Temp above freezing– Light for photosynthesis– Nutrients

• Light snow has the highest insulative value[1]

• Deep/Dense snow has lower light penetrance[2]

Hypothesis

• Being closer to trees will increase subnivean plant growth– Being near trees will increase snow depth over

clear areas[3]– Longwave radiation from tree

• Deeper snowpack will increase subnivean plant growth– Insulative value– Not too deep, still

need light getting through

Methods

• Three types of site– Meadow– Tree in Meadow– Tree in Forest

• 5 samples at each• Measured– Temp, depth,

amount of growth

W S N E

1

2

Observations

• Many tree sites had a thin layer (1-4cm) of snow on top of a thin layer of ice

• Despite the ice, some green shoots were still growing under and through

• Dominant species were grasses– Small number of forbs and mosses

• The bottom half of the meadow was very wind scoured meaning lower snowpacks

Comparison of sites

• The clear sites all had higher snowpack depths• Temperature was seemingly unaffected by proximity to trees• T depended on snowpack depth

P=0.4758, not significant

How snowpack affected the amount of plant growth

# shoots compared to % shoots at each site

Conclusions

• Snow depth is a more important factor for subnivean plant growth than proximity to trees

• Clear areas have higher productivity but trees seem to increase chance of success in a meadow

• Hypothesis is refuted– Being close to trees has negative effect on growth

• When combined with deep snow see no growth

– Deeper snowpack is best indicator

Citations

• [1]http://www.sciencepartners.info/?page_id=595• [2]Bohren C, Colors of snow, frozen waterfalls and icebergs,

JOSA, 23:12:p1646-52, 1983• [3]Lawrence D, Slater A, Contribution of snow condition

trends to future ground climate, Climate dynamics, 34:7-8:p969-81, 2010

• [4]Kappen L, Plant activity under snow and ice, with particular reference to lichens, Arctic, 46:4:p297-302, 1993

• [5]Olofsson J, Ericson L, Torp M, Stark S, Baxter R, Carbon balance of arctic tundra under increased snow cover mediated by a plant pathogen, Nature climate change, 1:p 220-23, 2011