1. Facilitative effects of Cushion Plants in the
Hudson Bay Lowlands of Churchill, Manitoba
Melissa Antoniadis
MSc. Candidate, Physical Geography
York University , Department of Geography
Supervisory Committee – Richard Bello & Christopher Lortie
March 26, 2013

2. Facilitation
• Interactions between organisms that are beneficial to at least one
organism & harmful to none of them (Lortie & Turkington, 2008)
Nurse effect
• One species provides microclimatic conditions that improves
the establishment, survival & growth of other species
Padilla and Pugnaire, 2006. Retama
sphaerocarpa shrub in the Tabernas desert

3. Cushion Plants
Protect other plants by providing
•Shade
•Moderated soil & air temperature
•Soil moisture
•Protection from wind & herbivores
•Increased soil quantity & nutrients
Vaccinium uliginosum (Alpine Blueberry)
shrub arctic/subarctic alpine species

4. Why is facilitation relevant?
• Nurse plants act as keystone species for many trophic levels &
maintain biodiversity
• Restoration technique for disturbed plant communities
•Mitigate impacts of global environmental change

5. Why Churchill, Manitoba?
• Global warming is expected to be most
apparent in arctic ecosystems
• where 3 ecosystems meet
• Facilitation may play an important role
in treeline advancement, especially
after forest fires
• 2 studies in recent years found Alpine
Blueberry facilitated tree seedlings

6. Geographic distribution of cushion plant research
Reid, 2011

7. Trophic Interactions
• Cushion plants have been
found to facilitate other
trophic levels ie insects
Molenda et al (2012), Reid (2011)

8. Stress Gradient Hypothesis
• Positive interactions increase
with increasing stress in the
environment

9. Twin Lakes Study Site
3 sites (100x100m) minimum 50 cushion plants per site
Town of Churchill
Site 1. White Twin Lakes
spruce (high
elevation)
Site 2. Burned area
(medium elevation)
Twin Lakes
Fire
Site 3. Black
spruce (low
elevation)

10. Research Questions
1) Are Alpine Blueberry cushion plants acting as
facilitators to other plant & arthropod species,
& specifically spruce tree seedlings?
2) Does facilitation increase with increasing
environmental stress
3) Is facilitation greater in the disturbed burned
area compared to the relatively undisturbed
areas?

11. Measuring Facilitation
• Parallel linear transects to select cushion plants & paired adjacent
non-cushion microsites
• Measure area of each cushion plant microsite & use same
dimensions for each paired non-cushion microsites
• Record plant species richness
& density in each microsite
• Record spruce seedling height,
stem diameter & number of whirls
• 9 Ipod nanos to record insect
visitations to flowers & leaves
(3/site)
Reid (2011)

12. What’s Creating the Stress?
Measuring Environmental Variables
• Latitude/longitude, elevation & slope (GPS)
• Sunlight - PAR sensors above & below cushions
(30 paired microsites per site)
• Water table position - 3 wells (1 per site)
• Nutrients – surface soil samples for pH & N,P,K, from each site
& lab analysis (30 paired microsites per site)
• Surface soil moisture (6 cm) - theta probe in moist,
intermediate & dry conditions (30 paire microsites per site)
• Temperature/humidity - data loggers one minute intervals
for duration of study (3 paired microsites per site)
• Infrared thermometer different times of day to control for other
elements ie wind (30 paired microsites per site)

13. Data Analysis
• Two-way ANOVA of plant species richness & density vs
cushion & non-cushion microsites & same for spruce
seedlings for density & health measures
• Regression analysis of temperature, sunlight, moisture, &
nutrients vs 1)elevation, 2)plant species richness, 3)density
• Chi-square test of frequency of pollinator visits in cushion
vs non-cushion microsites

14. References
Acuna-Rodrigues, I.S., Cavieres, L.A., and Gianoli, E. 2006. Nurse effect in seedling establishment: Facilitation and
tolerance to damage in the Andes of central Chile. Revista Chilena de Historia Natural, 79, 329-336.
Antonsson, H., Bjork, R.G., and Molau, U. 2009. Nurse plant effect of the cushion plant Silene acaulis (L.) Jacq. in an
alpine environment in the subarctic Scandes, Sweden. Plant Ecology and Diversity, 2, 17-25.
Arredondo-Nunez, A., Badano, E.I., and Bustamante, R.O. 2009. How beneficial are nurse plants? A meta-analysis of
the effects of cushion plants on high-Andean plant communities. Community Ecology, 10, 1-6.
Badano, E.I., and Marquet, P.A. 2008. Ecosystem engineering affects ecosystem functioning in high-Andean
landscapes. Oecologia, 155, 821-829.
Brooker, R.W., Maestre, F.T., Callaway, R.M., Lortie, C.L., and Cavieres, L.A. 2008. Facilitation in plant communities:
The past, the present, and the future. Journal of Ecology, 96, 8-34.
Chapin, F.S., Shaver, G.R., Giblin, A.E., Nadelhoffer, K.J. & Laundre, J.A. 1995. Response of Arctic tundra to
experimental and observed change in climate. Ecology, 76, 694-711.
Chrimes, D., Lundqvist, L., and Atlegrim, O. 2004, Picea abies sapling height growth after cutting Vaccinium myrtillus
in an uneven-aged forest in northern Sweden. Forestry, 77(1),.
Grau, O., Ninor, J.M., Blanco-Moreno, J.M., van Logtestijn, R.S.P., Cornellisen, J.H.C., and Callaghan, T.V. 2012. Shrub-
tree interactions and environmental changes drive treeline dynamics in the subarctic. Oikos, 001-011.
Molenda, O., Reid, A., and Lortie, C.J. 2012. The alpine cushion plant silene acaulis as foundation species: A bug's-eye
view to facilitation and microclimate. Plos One, 7(5), e37223.
Padilla, F., and Pugnaire, F. 2006. The role of nurse plants in the restoration of degraded environments. Frontiers in
Ecology and the Environment, 4(4), 196-202.
Reid, A. 2011. Cushion plants in the alpine of British Columbia, Canada: Systematic review, trophic facilitation, and
pollen limitation. A thesis submitted to the Faculty of Graduate Studies in partial fulfillment of the requirements
for the degree of Master of Science. York University.

15. Thank you,
Questions?