Interactions Between Fire and Spruce Beetles in a Subalpine Rocky Mountain Forest Landscape

Abstract

Interactions between natural disturbances are widely recognized as important determinants of vegetation patterns in forested landscapes but have only rarely been investigated quantitatively. In a subalpine forest landscape in northwestern Colorado, we quantified spatial associations of fire and spruce beetle (Dendroctonus rufipennis) outbreaks over more than a century and developed a multivariate logistic model of probability of occurrence of spruce beetle outbreaks. The study area, an ∼2800 km2 landscape in White River National Forest, was affected by severe widespread fires around 1879 and by a spruce beetle outbreak in the 1940s, which affected most of the forests that were dominated by Picea engelmannii (Engelmann spruce) and Abies lasiocarpa (subalpine fir). The boundaries of the fires ca. 1879 and of the 1940s spruce beetle outbreaks were digitized based on an 1898 vegetation map and modern aerial photograph interpretation, and overlaid in a Geographic Information System. The areas disturbed by the ca. 1879 fires and the 1940s beetle outbreak were also overlaid with 303 fires recorded after 1950 as well as with topographic and forest structural variables. Forests that had burned in 1879 were less affected by the 1940s outbreak than older stands. On the other hand, areas affected by the 1940s spruce beetle outbreak showed no higher susceptibility to subsequent fires. A multivariate logistic model indicated that, although fire history had the greatest effect on stand susceptibility to spruce beetle outbreak, dominance of neighboring stands by spruce as well as elevation were also important predictors of outbreaks. Predictive modeling of spatial interactions between fire and spruce beetle disturbances needs to consider the high degree of variability in the nature of these interactions related to contingencies such as time since last major disturbance, topographic position, and weather during windows of potential interaction. Corresponding Editor: F. W. Davis.

Do mountain pine beetle outbreaks change the probability of active crown fire in lodgepole pine forests?

“…Colorado (Bebi et al 2003, Kulakowski andVeblen 2007) and in conifer forests of California (Bond et al 2009), which generally do not support the hypothesis of increased probability of stand-replacing crown fire following bark beetle outbreak. Similarly, in lodgepole pine forests, Kulakowski and Veblen (2007) did not find higher occurrence or severity of fire in 5-year post-beetle stands.…”

“…These studies, which were carried out in different forest types (lodgepole pine [ (Simard et al 2008), with some analyses suggesting slightly increased probability or severity of fire following beetle outbreak (Bigler et al 2005), and others showing no evidence for such a relationship (Bebi et al 2003). In this study, we employ a prospective approach to quantify fuel dynamics and predict potential fire behavior during and for several decades after bark beetle outbreak.…”

Ecological importance of intermediate windstorms rivals large, infrequent disturbances in the northern Great Lakes

“…Fires , hurricanes (Boose et al 1994), and blowdowns (Canham and Loucks 1984, Foster and Boose 1992, Rich et al 2007) have garnered widespread attention, but ice storms, floods, volcanic eruptions, tornados, and insects are stimulating increased interest (cf. Foster et al 1998, Bebi et al 2003, Stueve et al 2007.…”

Modelling natural disturbances in forest ecosystems: a review

“…Models of such interactions mainly focused on descriptive, statistical approaches, including various logistic regression models (Bebi et al, 2003;Bigler et al, 2005;Breece et al, 2008), generalized linear models with different link functions (Peltonen, 1999;Eriksson et al, 2005;Hood and Bentz, 2007) and classification tree models (Kulakowski and Veblen, 2007). As an alternative approach for evaluating hypotheses and conceptual understanding about fire-bark beetle interactions, Youngblood et al (2009) demonstrated the utility of structural equation modelling.…”