, 2004). Peltonen et al. (2002) studied spatial synchrony of forest insect outbreaks found that the Moran effect was likely the dominant mechanism causing spatial synchrony in outbreaks across regional scales and that dispersal

was of lesser importance. This finding was supported by Swetnam and Lynch (1993) who also found that exogenous factors (e.g., climatic variability) played a significant role in regulating regional-scale WSB outbreaks in northern New Mexico. More recently, Flower et al. (2014) found that warm-dry climate preceded outbreaks by up to three years, but during outbreaks conditions

tended to be cooler and wetter. Selumetinib clinical trial The comparison of regionally synchronous WSB outbreaks and climatic proxies from the western portion of the study area suggest that the influence of climate on outbreak dynamics is highly complex (Fig. 5). From the late-1600s to early-1700s and from the 1940s to the end of the record, synchronous outbreaks coincide with positive summer temperature and negative SWE anomalies indicative of warmer and drier climatic conditions (Fig. 5). However, from the Erastin ic50 late-1700s to the around the 1920s synchronous outbreaks coincide with negative temperature and positive SWE anomalies that are indicative of cooler and wetter climatic conditions (Fig. 5). During this same time period (with the exception of the 1920s) extensive wet periods prevailed across the southern Canadian Cordillera (Watson and Luckman, 2004) and there were numerous episodes of glacial expansion in Mt. Waddington range west of the study area (Larocque and Smith, 2003). During

periods when warmer Oxalosuccinic acid and drier conditions were associated with WSB outbreaks (Fig. 5), Starheim et al. (2012) found that the low-frequency signals associated ocean-atmospheric forcing, i.e., Pacific Decadal Oscillation and the Pacific North America Index were prominent in their hydroclimatic reconstructions. Previous research in the western US shows that WSB outbreaks are associated with wetter conditions in the spring and summer, while years leading up to outbreaks are associated with drought conditions (Swetnam and Lynch, 1989, Swetnam and Lynch, 1993, Ryerson et al., 2003 and Flower et al., 2014). In southern BC, outbreaks have been found to be associated with average air temperatures and drier winters (Campbell et al., 2006).