Modeling the effects of temperature on growth and persistence of tree species: A critical review of tree population models

Global climatic change is expected to affect growth and survival of trees and will likely change the geographical distribution of many temperate and boreal tree species. Models that calculate the effects of environmental factors, as well as biotic factors, such as intra- and interspecific competition, on growth and survival of trees have been widely used to calculate the potential effects of temperature changes on tree populations. The methods to calculate thermal effects in such models are described and analyzed for the soundness and consistency of underlying assumptions. They are compared to the evidence from studies of tree physiology, growth, and biogeography. The use of thermal indices, especially temperature sums, in studies of tree growth and development is discussed. It is concluded that the majority of modeling studies to date have been based on faulty and internally inconsistent assumptions and/or do not utilize basic findings from more than a century of tree research. Only a small number of recent studies are based on assumptions that are consistent with such findings. Because of a lack of mechanistic explanations for many observations regarding tree growth and development, only empirical modeling approaches are currently available for these aspects of tree ecology. Hybrid approaches, partly mechanistic, partly empirical, are a promising alternative to purely empirical models, as long as the different aspects are well defined in the models. Several aspects of modeling studies remain problematic. Future studies will have to find methods of parameterization that do not infer fundamental growth and survival limits from the geographical distribution of tree species. A consideration of intraspecific genetic variation in trees will greatly improve models of tree growth and survival.