MOOSE WINTER DIET AND HEIGHTENED VULNERABILITY OF QUAKING ASPEN TO FUNGAL CANKERS Lesley Seale CU Boulder EBIO 4100 Spring 2012

Quaking Aspen (Populus Tremuloides) Keystone species (Kaye et al. 2005)

Provides habitat Stabilizes erosion

Tolerant Disturbance site species Thin, soft bark

vulnerability SW Colorado is

experiencing aspen dieback/decline (St.Clair et al. 2010)

Cankers specific to Aspen in the Rockies

Cryptosphaeria/Snake Canker

Hypoxylon Canker

Cytospora Canker

Sooty Bark Canker Black

Canker

(Hinds, 1981)

Cervid Winter Diet

Elk (Cervus elaphus)and Moose (Alces alces) in the montane/subalpine Moose near MRS

Aspen bark provides protein

During winter, range concentrated near feeding grounds (Hart and Hart, 2001)

Elk browsing decreases the vigor of mature stems; harming cambium, increasing mortality and pathogen infection. (Kaye et al. 2005, 1284)

Reduced aspen stand size and habitats (Hart and Hart, 2001)

Do aspens with moose gnawing have fungal canker infections?

The question….

Methods Study design – Sample aspen in moose habitats

to determine if there is a relation between infected trees and wounds from browsing.

Implementation of design Two 30m x 30m plots: Rainbow Lakes trailhead and

near C-1. Sample all aspens within the plot and record

Limitations—time, sample size, breadth of data

1

2

Data Collection Measurements

DBH Canker symptoms Browsing evidence

1: this season 2: callus not formed by dry and teeth marks still

seen 3: callusing, some teeth grooves still seen 4: fully healed, all teeth marks gone

FRESH GNAW

1

OLD HEALE

D GNAW

4

Results 211 tree sampled Classified as:

Only gnawed (10) Only cankered (20) Gnaw and

cankered (31) No gnaws or

cankers (150)

Test for Independence

Freshness Distribution

Gnaw DBH proportions

Data

060

120180

Aspen Cankering relative to Moose Gnawing

Num

ber

of A

spen

Tre

es

Χ2 Test of Independence H0: Canker and moose gnawing are

independent of each other. HA: Cankers are related to moose

gnawing. Χ2 : 73.5 P(Χ2 > 73.5)= 0.0039

P-value (0.0039) is less than the significance level (0.05), H0 is rejected.

Supports that there is an association

Freshness (1-4)15%

17%

20%

49%4

1

2

3

FRESH GNAW

1

OLD HEALE

D GNAW

4

Gnawed DBH

0 to 7

14 to 21

28 to 35

0 0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4 0.45

Proportion of DBH Distribution Gnawed

Percent

DBH

(cm

)0 to 7

14 to 21

28 to 35

0 0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4 0.45

Population DBH Dis-tribution

Percent

DBH

(cm

)

Discussion Elk browsing does create a wound in the bark for fungi to infect. Injured stems usually succumbed to invasions by pathogenic fungi

rather than from mechanical injury alone. (Hart et al. 2001, 197) Studies by Thomas Hinds prove that discoloration is actual

precenence of the fungi in tree tissue, proved by floresent properties of the fungi. It is likely that fluorescence is the oxidizing of acids and phenols to be

more toxic quinines, which are then polymerized to insoluble nontoxic melanin causing the discoloration around the perimeter of infection. (Hinds 1981)

More fires and/or fewer cervids would favor the growth of aspen. (Hart et al. 2001, 197)

Other damages harm Falling trees Carvings Burrowing insects Other fungus

Further Questions Presence of predators?(Weisberg et al. 2003, 152)

Do elk/moose avoid canker trees? Could some of the trees already have fungus inhabitants prior to elk feasting?

Photosynthesis in the trunk decreased?

How is the fungus transporting?

Does cambium damage in the winter create cavitation that is more damaging to the tree than in other seasons, increasing vulnerabilty? Angiosperms in general, and aspen specifically, show greater sensitivity to

freeze–thaw induced cavitation than conifers (St. Clair et al. 2010, 371)

In riparian zones that aspens are highly browsed will willows threaten to take over, instead of conifers?

Aspens are a keystone species, important to the biodiversity in the forest.

Winter ranges of cervids heavily depend on the presence of aspens as a source of protien.

Decline in aspen stands can be in part attributed to the joint devastation of trees by cervids and fungi.

Loss of aspen stands means loss of habitat for more than just moose.

Literature Cited Hart, John H. and D.L. Hart. " Interaction Among Cervids, Fungi, and Aspen in Northwest

Wyoming." USDA Forest Proceddings RMRS-18 (2001): 197-205.

Hendreyx, Jessica. "Pests and Environmental Problems at High Altitude Landscapes." Montana State University. http://plantsciences.montana.edu/horticulture/HighAltitudeLandscapes/Aspencanker.htm (accessed February 10, 2012).

Hinds, Thomas. "Cryptosphaeria Canker and Libertella Decay of Aspen." Phytopathology 71 (1981),

Kaye, Margot, Dan Binkley and Thomas Stohlgren. "Effects of Conifer and Elk Browsing on the Quaking Aspen Forests in the Central Rocky Mountains, USA. ." Ecological Applications 15 (2005): 1284- 1295.

St. Clair, Samuel B., John Guyon and Jack Donaldson. "Quaking Aspen’s Current and Future Status in Western North America: The Role of Succession, Climate, Biotic Agents, and Its Clonal Nature." Progress in Botany 71 (2010): 371-400.

Weisberg, Peter J. and Michael B. Coughenour. "Model-Based Assessment of Aspen Responses to Elk Herbivory in Rocky Mountain National Park, USA." Environmental Management 32 (2003): 152-169.