Can community interactions mediate mountain pine beetle responses to fire? 1Crisia
Tabacaru, 2Jane Park, and 1Nadir Erbilgin 1Renewable Resources, University of Alberta; 2Parks Canada
INTRODUCTION
RESULTS and DISCUSSION
Figure 1: A mountain pine beetle. denimpine.com/documents/45.html
1) Although MPB colonized burned trees more often than un-
3) Curculionids (direct competitors) are the most important
burned ones, colonization decreased within in the burned areas over time (Fig. 6).
variable predicting MPB immediately after and 1 year post-fire (Random Forest; Fig. 8).
Proportion of New Trees Colonized
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). 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.
0.7 Unburned
0.6
Low Moderate
0.5 0.4 0.3 0.2 0.1 0 2009
2010
2011
2012
Figure 6: MPB colonization immediately and 1-3 years post-burn (means +/- SE).
Our main objectives, therefore, are:
1) To determine MPB colonization patterns within forests
Figure 8: Variables in order of importance in predicting MPB for Random Forest analyses immediately post-fire (L) and 1 year post-fire (R).
2) The bark community is associated with the burned area
burned by prescribed fire, and
(NMDS; Fig, 7).
MPB may prefer burned trees but a more intense fire may attract more beetles than a light fire (Fig. 6).
2) To explore the mechanisms behind these responses, specifically with respect to the bark community.
Although MPB prefer burned trees, the increase in natural enemies may mediate their response (Fig. 8).
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 2: The Saskatchewan Crossing prescribed burn after 1 year.
METHODS
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.
FUTURE WORK and IMPLICATIONS
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).
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.
We counted MPB attacks in the fall, following the flight period and new colonization (Fig. 4).
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.
We used flight intercept, landing rate, and emergence traps (Fig. 5) to quantify MPB and the bark community.
Figure 4: The authors with an MPB gallery in a burned tree. Photo: Kurt Illerbrun; http://www.ext. colostate. edu/pubs/insect/05528.html
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 9: Heading into the burn at the Y. H. T. Ranch. Photo: Kyle Vaughan
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.