4). The sub-regional chronologies highlight the strong fidelity between chronologies within group (i.e., BEC unit) and the synchronous WSB outbreak events across the study area, while also emphasizing the unique

outbreak history at smaller spatial scales (Fig. 4 and Fig. 5). For example, chronologies in the very dry-mild BEC unit (FC and FR) are located on south facing slopes of the Fraser or Chilcotin Rivers and were characterized by a pronounced high amplitude signal when compared to the other sub-regional chronologies (Fig. 4). Chronologies from the dry-cool Fraser BEC unit (S1–S2, S5–S6) (Fig. 4), which is characterized by wetter and cooler conditions, have a notable quiescent phase from the early-1700s to early-1800s (Fig. 4 and Fig. 5) that also corresponds to decreased power in the wavelet spectrum (Fig. 6). This suggests that site and/or stand conditions play an important GSI-IX chemical structure role in mediating tree response click here to WSB outbreaks. For the very dry-mild sites conditions such as steep slopes, thin soils, and availability of

soil moisture all likely contribute to increasing the sensitivity of these chronologies to negative (e.g., WSB defoliation) and positive (e.g., growing season moisture) stimulus. Conversely, the dry-cool Fraser sites, which were sampled at higher elevation (Table 1) and not from steep slopes, have a dampened sensitivity to environmental factors (Fig. 4). Site factors in combination with cooler and wetter climatic conditions (Table 2) are likely resulting in a more average growth response over time where tree grow is less responsive to events like budworm feeding (Fig. 4). The stand level to

sub-regional scale WSB outbreak dynamics across the study area highlight the complex interactions between: site characteristics, canopy structure and composition, host plant quality, bud phenology, growth Osimertinib molecular weight rates, tree resistance and climate, which to some extent all play a role in determining the intensity of individual outbreaks and tree growth responses across an area (Kozlowski, 1969, Clancy, 1992, Swetnam and Lynch, 1993, Chen et al., 2001, Maclauchlan and Brooks, 2009 and Nealis, 2012). Synchronous outbreak periods in the Cariboo Forest Region in the 1720s, late-1700s, 1870s and 1930s (Fig. 5) were also present in the reconstructions from locations south of our study area (Campbell et al., 2005, Campbell et al., 2006, Alfaro et al., 2008, Alfaro et al., 2014 and Flower et al., 2014). Notably, the outbreak from 1898 to 1909 was a widespread event that appears in reconstructions in the area directly south of the Cariboo Forest Region (Campbell et al., 2006 and Alfaro et al., 2014), the southern Okanagan (Alfaro et al., 2008 and Alfaro et al., 2014), southern Vancouver Island (Harris et al., 1985), as well as in northeastern Oregon (Swetnam et al., 1995) and in stands found from central Oregon to western Montana (Flower et al., 2014).