Survival functions for boreal tree species in northwestern North America Francesco Cortini a,⇑ , Philip G. Comeau a , Vlad C. Strimbu a , E.H. (Ted) Hogg b , Mike Bokalo a , Shongming Huang c a Department of Renewable Resources, University of Alberta, 751 General Services Building, Edmonton, AB T6G 2H1, Canada b Canadian Forest Service, Natural Resources Canada, Northern Forestry Centre, 5320-122nd Street, Edmonton, AB T6H 3S5, Canada c Governament of Alberta, Agriculture and Forestry, 8th floor Great West Life Building 9920-108 Street, Edmonton, AB T5K 2M4, Canada article info Article history: Received 28 February 2017 Received in revised form 15 June 2017 Accepted 16 June 2017 Keywords: Tree survival Mortality Logistic models Estimates of competition Climate variables abstract Logistic survival probability models were developed for seven tree species in northwestern North America using Permanent Sample Plot (PSP) data from: six Canadian provincial and territorial govern- ments, the government of Alaska (USA), and four forestry companies; for a total of 1,250,257 trees within 11,673 PSPs. The survival probability of: white/Engelmann spruce (Picea glauca (Moench) Voss/Picea engelmannii Parry ex Engelm.), black spruce (Picea mariana (Mill.) BSP.), lodgepole pine (Pinus contorta Douglas ex Loudon), jack pine (Pinus banksiana Lamb.), trembling aspen (Populus tremuloides Michx.), bal- sam poplar (Populus balsamifera L.), and balsam fir (Abies balsamea (L.) Mill.) was modeled using tree size (dbh), competition estimates (basal area of the larger trees by species group), climate normal, tagging limits and the time elapsed between consecutive measurements. Survival increased nonlinearly with tree size and the effect of competition on tree survival was related to the shade-tolerance of the species and to stand composition, with shade intolerant conifer species (i.e. lodgepole and jack pine) being more nega- tively affected by competition compared to shade intolerant deciduous species (trembling aspen and bal- sam poplar) and shade tolerant spruce species (white and black spruce). Competition from larger spruce (Picea spp.), fir (Abies spp.) and deciduous species (e.g. Populus spp. and Betula spp.) had stronger influ- ences on survival than pine species (Pinus spp.). Intraspecific competition also had significant effects on survival of the majority of the species. Climate Moisture Index provided better results than other climate variables for most species and survival probability increased with increasing values of CMI (i.e. relatively cooler and wetter climate), while for pine species survival probability decreased with increasing CMI and showed higher levels of survival on warmer and drier sites for the range of conditions included in our data. The predictive equations developed in this study could be used to improve the predictive ability of existing growth and yield models such as the Mixedwood Growth Model. Ó 2017 Elsevier B.V. All rights reserved. 1. Introduction Tree mortality reduces stand density and affects competition and understory conditions which will influence growth of remain- ing trees and regeneration, and can have major impacts on stand yield. A substantial body of literature in boreal forests has already demonstrated the strong effects of competition, tree size, and tree age on survival probability (e.g. Yao et al., 2001; Yang et al., 2003; Luo and Chen, 2011; Reyes-Hernandez and Comeau, 2014). This is particularly evident in trembling aspen (Populus tremuloides Michx.) and balsam poplar (Populus balsamifera L.) mixed stands with white spruce (Picea glauca (Moench) Voss). Climate, site, and genetics also influence the probability of sur- vival of trees (Caspersen and Kobe, 2001). Climate has been shown to influence survival probabilities of aspen, spruce and pine in the boreal forest (Peng et al., 2011; Luo and Chen, 2013; Dawson, 2013). Bell et al. (2014) reported that stand conditions, such as density, influence the effects of drought on aspen decline. Luo and Chen (2013) suggest that mortality in young stands is highly sensitive to climate induced drought stress, and that late succes- sional species such as white and black spruce or moist site species such as balsam poplar are even more sensitive than trembling aspen or jack pine. In contrast, in their analysis of data for pine and spruce stands in the Hinton area of Alberta, Thorpe and Daniels (2012) found that climate did not significantly affect tree http://dx.doi.org/10.1016/j.foreco.2017.06.036 0378-1127/Ó 2017 Elsevier B.V. All rights reserved. ⇑ Corresponding author. E-mail addresses: fcortini@gmail.com (F. Cortini), Phil.Comeau@ualberta.ca (P.G. Comeau), strimbu@ualberta.ca (V.C. Strimbu), ted.hogg@canada.ca (E.H. (Ted) Hogg), mike.bokalo@ualberta.ca (M. Bokalo), shongming.huang@gov. ab.ca (S. Huang). Forest Ecology and Management 402 (2017) 177–185 Contents lists available at ScienceDirect Forest Ecology and Management journal homepage: www.elsevier.com/locate/foreco