Dynamics of beetle-killed snags following mountain pine beetle outbreaks in lodgepole pine forests

Snags (standing dead trees) are important components of forest ecosystems that, among other benefits, provide critical habitat for many species wildlife, but also represent safety concerns to firefighters, workers, and the public. We identified factors that influence fall rates lodgepole pines, Pinus contorta Dougl. ex Loud., killed by bark beetles during a severe regional-scale outbreak mountain pine beetle, Dendroctonus ponderosae Hopkins, occurred in 2004–2012. Data were obtained annual assessments (2010–2019) network 107 0.081-ha circular plots installed P. forests Colorado, Idaho, Montana, Utah Wyoming, U.S. A total 3789 snags monitored, each case we recorded, variables, year snag was created fell floor. Among age classes (i.e., number years since tree death), highest (1046) 12 death (YSD), those 13 14 YSD exhibited lowest date (<10%) despite being oldest our study. largest diameter. Snag every class from 1 YSD, with greatest proportion events occurring 4–8 YSD. By 2019, 24.7% (937) modeled using Cox’s proportional-hazards model included six covariates interest: elevation (m), slope aspect (categorical, cardinal direction), (%), canopy cover height height:dbh (m, diameter at 1.37 m height). Slope had strongest on rates. Northern aspects, increased cover, taller heights decreased probability fall. Conversely, southern aspects ratios taller, skinner snags) The predicted half-life amount time required 50% population floor) ~16 after which function linear, ~0.04/year decline survival 15–30 observed longevity confers ecological benefits some may offer opportunities extended periods salvage. However, checking (cracks) rapidly occurred, 6 older least one check 5.5 height, can negatively impact lumber recovery. relatively slow study lengthen regarding hazard trees, human safety, protection infrastructure. implications these results management discussed.