Impact of snow molds on conifers of the ribbon forest

Impact of snow molds on conifers of

the ribbon forestMax Owens

EBIO 4100, Spring 2013

Winter EcologyMountain Research Station

University of Colorado-Boulder

IntroductionStructure of the ribbon forest: snow

accumulation has multiple effects on trees (Knight

1994)

Snow molds are specialized fungi that attack dormant plants under cover of snow (Pokorny 2009)

Many different species of cold-tolerant fungi are present under the snow during winter and disappear quickly after snowmelt (Schmidt et al. 2008)

IntroductionThese psychrophilic (cold-loving) fungi produce

mycelia during the severe conditions of winter. (Hoshino et al. 2009)

How?Spruce sapling growth is strongly inhibited by

presence of snow mold. (Cunningham et al. 2006)

IntroductionOpportunistic snow molds are insulated from

harsh climate of winter by the snowpack, and antagonists are practically absent (Matsumoto 2009)

For phytopathogenic fungi adapted to the cold, the subnivean environment is the perfect place to parasitize young trees

Question: How does the depth of snow contribute to the maintenance of the structure of the ribbon forest, as related to the presence of phytopathogenic snow mold?

Why it matters: Important factor in limiting growth of subalpine

trees?Maintenance of ribbon forest, a common structure in

subalpine forests near tree lineClimate change—precipitation on the rise at higher

elevations (Kittel 2013)

Hypothesis: The added insulative value of deeper snow creates a better environment for snow molds to parasitize trees.

 Prediction: We would expect to see a greater incidence of snow mold in the glades of the ribbon forest, where snow is deeper.

SiteSubalpine ribbon forest above Mountain

Research Station at ~3,330m (10,930 ft.)

[Google 2013]

Methods 2 x 40m transect

crossing glade from ribbon to ribbon

Snow depth, tree heights, DBHs, and snow mold evidence were measured.

Snow was removed along transect to expose small trees, and snow was removed to base of each tree to expose any snow mold damage

MethodsIf present, height of snow mold/snow mold

damage extent was measuredTrees with a DBH of 8 cm or greater were

excluded, since trees this large generally did not have branches beneath the snowpack

Only one transect due to time constraintsUsed Excel and R to create plots, regressions

and t-tests

Results

Physical appearance of infected trees

• 2 main categories• Bundled needles with black

mold in between• Brown/black needles, not

bundled• Several trees with healthy

needles below snowpackBundled needles

Discolored needles, not bundled

Results

p-value: 0.268R2: 0.292

Regression

Resultsp-value: 0.0302

Bundled needles

Discolored, not bundled

Healthy needles

1 Engelmann spruce

1 Engelmann spruce

4 subalpine firs

2 subalpine firs

2 subalpine firs

T-test

Results

p-value: 0.326 T-test

ResultsRegression of snow depth and height of snow mold

was not significant, but trended towards higher extent of snow mold with greater snow depths

Significant difference in snow depths between trees with and without snow mold

Not enough data to differentiate snow mold presence/appearance between different tree species

No significant difference in tree size between trees with and without snow mold

DiscussionDeeper snow creates favorable environmental

conditions (insulation, moisture) for snow mold to infect treesPersistence of snow is critical (Matsumoto 2009)

Snow mold infection inhibits spruce growth, and one of the primary drivers of snow mold infection of saplings was snow duration (Cunningham et al. 2006)

Snow mold-tree interactions play at least some part in the complex maintenance of ribbon forest structure

DiscussionFurther research

Replicates of this study to create an accurate profile of snow mold height extent with snow depth (is there an optimal depth for infection?)A direct correlation between snow mold and snow

depth has implications for climate change.Snow depth and the maintenance of the ribbon

forest to determine the relative impacts of physical damage, shorter growing seasons, and infection by snow molds on trees

How much snow mold damage is too much for a conifer to survive?

ConclusionRibbon forest structure controlled by several

factors, including snow moldsFungi that infect plants underneath the snow; limits

growthDeeper snow makes snow mold infection more

likely InsulationAbundant moisture

Not enough data to determine pattern of snow mold damage extent in ribbon forest

Acknowledgements

Thanks to Tim Kittel for support and analysis help, and to Sebastian Baily, Jake Delfin, and Atty

Phleger for data collection help.

Literature Cited Cunningham, C., N.E. Zimmermann, V. Stoeckli, and H.

Bugmann. 2006. Growth response of Norway spruce saplings in two forest gaps in the Swiss Alps to artificial browsing, infection with black snow mold, and competition by ground vegetation. Canadian Journal of Forest Research. 36(11): 2782-2793.

DOI: 10.1139/x06-156

Hoshino, T., N. Xiao, O.B. Tkachenko. 2009. Cold adaptation in the phytopathogenic fungi causing snow molds.

Mycoscience. 50: 26–38. DOI: 10.1007/s10267-008-0452-2

Kittel, Timothy. 2013. Historical Climate Change on Niwot Ridge. http://culter.colorado.edu/~kittel/WEcol_GuestLec/NiwotRidgeClimateChange_TKittel213.pdf. Accessed 21 February 2013.

Knight, D.H. 1994. Mountains and Plains: the Ecology of Wyoming Landscapes. Yale University, New

Haven. Matsumoto, N. 2009. Snow molds: a group of fungi that

prevail under snow. Microbes and Environments. 24(1): 14-20.

DOI: 10.1264/jsme2.ME09101 

Pokorny, J.D. 2012. Snow Molds of Conifers. http://www.rngr.net/publications/forest-nursery-pests/ conifer-diseases/snow-molds-of-conifers/?searchterm=snow%20molds%20of%20conifers. Accessed 5 February 2013.

Schadt, C.W., A.P. Martin, D.A. Lipson, S.K. Schmidt. 2003. Seasonal dynamics of previously unknown fungal

lineages in tundra soils. Science. 301 (5638): 1359-1361.

DOI: 10.1126/science.1086940

Schmidt, S.K., K.L. Wilson, A.F. Meyer, M.M. Gebauer, A.J. King. 2008. Phylogeny and ecophysiology of opportunistic “snow molds” from a subalpine forest ecosystem. Microbial Ecology.

56 (4): 681-687. DOI: 10.1007/s00248-008-9387-6