Relative size and stand age determine Pinus banksiana mortality |
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| Authors: | Han YH Chen Songling Fu Robert A Monserud Ian C Gillies |
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| Institution: | aFaculty of Forestry and the Forest Environment, Lakehead University, 955 Oliver Road, Thunder Bay, Ontario, Canada P7B 5E1;bEcologically Sustainable Production of Forest Resources, PNW Research Station, USDA Forest Service, 620 SW Main Street, Suite 400, Portland, OR 97205, USA |
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| Abstract: | Tree mortality is a poorly understood process in the boreal forest. While large disturbances reset succession by killing all or most trees, background tree mortality was hypothesized to be affected by competition, ageing, and stand composition. We tested these hypotheses on jack pine (Pinus banksiana Lamb.) mortality using data from long-term repeatedly measured permanent sample plots collected between 1952 and 1989 in Ontario, Canada. The probability of mortality over a 5-year period was modeled using logistic regression with the maximum likelihood estimation employed for parameter estimation. Relative competitiveness measured as the ratio of individual tree diameter at breast height (DBH) to mean stand DBH explained more variation in mortality than stand age did. Mortality increased rapidly with decreasing DBH ratio. A U-shaped mortality pattern with stand age was found while stand composition had no effect on mortality. Developed by using a residual sequential regression approach, our final mixed-effects model with a 81% model correctness of mortality prediction conclusively demonstrated that relative competitiveness is the key determinant for jack pine mortality. |
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| Keywords: | Relative competitiveness Stand composition Logistic model Boreal forest Jack pine |
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