INTRODUCTION

Can community interactions mediate mountain pine beetle responses to fire?

1) Although MPB colonized burned trees more often than un-burned ones, colonization decreased within in the burned areas over time (Fig. 6).

1Crisia Tabacaru, 2Jane Park, and 1Nadir Erbilgin 1Renewable Resources, University of Alberta; 2Parks Canada

Our main objectives, therefore, are:

1) To determine MPB colonization patterns within forests burned by prescribed fire, and

2) To explore the mechanisms behind these responses, specifically with respect to the bark community.

However, stressed trees may be more susceptible to MPB1 and fire leaves live, yet partially burned—and thus stressed—trees in its wake2. However, the change in the bark insect community associated with MPB may mediate MPB-fire interactions. Figure 1: A mountain pine

beetle. denimpine.com/documents/45.html

Figure 2: The Saskatchewan Crossing prescribed burn after 1 year.

We established a total of 135 plots at 3 burned and unburned stands in Alberta: Mt. Nestor, Saskatchewan Crossing, and the Ya Ha Tinda Ranch. Plots were divided between 3 burn severity classes: moderate, low, and unburned (Fig. 3).

We counted MPB attacks in the fall, following the flight period and new colonization (Fig. 4).

We used flight intercept, landing rate, and emergence traps (Fig. 5) to quantify MPB and the bark community.

Figure 3: An example of a burn gradient at Saskatchewan Crossing. Figure 5: A hanging passive flight intercept trap and a landing rate trap on the left and an emergence trap on the right.

Figure 4: The authors with an MPB gallery in a burned tree. Photo: Kurt Illerbrun;

http://www.ext. colostate. edu/pubs/insect/05528.html

Fire (Fig. 1) is used to break up even-aged lodgepole pine stands in Alberta and to remove potential host trees of mountain pine beetles (MPB) (Fig. 2).

Figure 6: MPB colonization immediately and 1-3 years post-burn (means +/- SE).

Figure 7: Bark insect families are more associated with burned plots (low=red, green=moderate) than unburned plots (blue=unburned) (L); and Curculionids (direct competitors) are later arrivals in to a burn (green=1 year post-fire, red=year of fire) (R).

Figure 8: Variables in order of importance in predicting MPB for Random Forest analyses immediately post-fire (L) and 1 year post-fire (R).

Thanks to K. Vaughan, G. Belanger, K. Andressen, K. Illerbrun, C. Meijndert, S. Cousineau, M. Zurawell, C. Andressen, G. Woodman, B. Smerekova, AB Sustainable Resource Development (ASRD), and Parks Canada for field assistance. Thanks to B. Jones (ASRD) for design advice. Research is supported by the Foothills Research Institute, ASRD, Parks Canada, Alberta Sports, Recreation, Parks, and Wildlife, Alberta Conservation Associations, Department of Renewable Resources, and NSERC

References: (1) Waring and Pitman 1983. J. Appl. Entomol. 96: 265-270. (2) Arno 1980. J. Forest 78: 460-465.

METHODS

RESULTS and DISCUSSION

FUTURE WORK and IMPLICATIONS

Although MPB may prefer burned stands, it is necessary to determine whether they reproduce more or less successfully in these areas. We introduced MPB into bark from burned trees in the lab to assess reproduction. Ultimately, this study will help determine whether burned stands can be sinks or sources for MPB in Alberta. This will inform managers regarding the unique challenges of prescribing fire where MPB are prevalent.

Figure 9: Heading into the burn at the Y. H. T. Ranch. Photo: Kyle Vaughan

3) Curculionids (direct competitors) are the most important variable predicting MPB immediately after and 1 year post-fire (Random Forest; Fig. 8).

2) The bark community is associated with the burned area (NMDS; Fig, 7).

MPB may prefer burned trees but a more intense fire may attract more beetles than a light fire (Fig. 6). Although MPB prefer burned trees, the increase in natural enemies may mediate their response (Fig. 8).

Specifically, Curculionids (direct competitors) may outcompete MPB in the years following a fire, and may ultimately suppress them to a low population level, potentially preventing outbreaks.

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