Stand-level factors associated with resurging mortality from eastern larch beetle (Dendroctonus simplex LeConte)

Anomalous outbreaks of an invasive defoliator and native bark beetle facilitated by warm temperatures, changes in precipitation and interspecific interactions

“…Beneficial relationships between precipitation and insect outbreaks by understudied species or feeding guilds may be an area of concern as precipitation regimes shift with a changing climate (Trenberth , Jamieson et al ). Likewise, the relationship between drought and eastern larch beetle outbreaks is not well understood (Crocker et al ), although the initiation and spread of outbreaks by spruce beetle, a congener that also attacks trees early in spring, are facilitated by drought (Hart et al , ). Total annual precipitation in the previous three years is negatively correlated with mortality by eastern larch beetle (Table 4b), indicating that drought may indeed facilitate outbreaks of eastern larch beetle in Minnesota.…”

“…Since then, eastern larch beetle has killed between 519 and 85 444 ha of mature tamarack annually in Minnesota (Fig. 1), totaling more than 426 000 m 3 in tree volume (Crocker et al ). This outbreak is the longest and most destructive documented by eastern larch beetle (McKee and Aukema ).…”

“…Descriptions of covariates considered in statistical models predicting the activity (presence, absence) of larch casebearer and eastern larch beetle on tamarack across 4 × 4 km grid cells inMinnesota, USA (2000-2016. First-order neighborhood; total number of cells out of the nearest four (i.e.…”

“…Best fit multiple logistic regression models for activity of (a) larch casebearer and (b) eastern larch beetle on tamarack inMinnesota, USA, 2003-2016. An explanation of predictors is provided inTable 1.…”

Reconstructing past forest composition and abundance by using archived Landsat and national forest inventory data

“…A unique aspect of insect outbreaks as a forest disturbance agent is that damage is generally limited to a restricted taxonomy defined by the range of susceptible hosts for a given herbivore (Sturtevant et al 2004;Koricheva, Klapwijk, and Björkman 2012), in many cases restricted to a particular genus or family (Jactel and Brockerhoff 2007). Broad-scaled risk assessments quantifying forest susceptibility to specific herbivores therefore requires detailed compositional information (e.g., Crocker et al 2016). Evidence suggests that outbreak dynamics (i.e., outbreak duration, frequency, intensity, or spatial synchrony) can be related to the landscape concentration or arrangement of host (Volney and McCullough 1994;Roland 2005;Wesołowski and Patryk 2006;Haynes, Liebhold, and Johnson 2009;Robert et al 2018) and the relative proportion of associated non-host species (e.g., Cappuccino et al 1998;Raffa, Powell, and Townsend 2013).…”