Succession in mixed boreal forest of Russia: Markov models and non-Markov effects

An aggregated scheme is presented for the ideal course of the post-tillage succession (natural overgrowing) among 15 forest types in a mixed (conifero us-broad-leaved) forest in Central Russia. A first, traditional Markov chai n model describes the course of succession leading eventually to the climax state, which is recognised to be a polydominant spruce-broad-leaved forest . The model predicts the average times it would take to reach the climax fr om any other stage of succession, while the current state of the forest is estimated by means of a GIS technology. Present geobotanic knowledge, howev er, assures that the climax state cannot be reached in mixed forest under t he current ecological pressures in general and the lack of sufficient biodi versity in particular. The succession rather terminates at the stage of sub dominant diasporic subclimax-a phenomenon which traditional Markov chain mo dels are unable to reproduce. We suggest a formalisation of the logic why t he subclimax-to-climax transition does not occur under the above conditions , and this results in a non-Markov version of the traditional model. We sho w, by solving a non-linear eigenvalue problem and studying the asymptotic b ehaviour, that the limit vector of state probabilities depends non-triviall y on the initial conditions. Convergence to the climax state takes place on ly for a restricted set of initial vectors representing a sufficient level of biodiversity, while the non-Markov chain absorbs at a subclimax state fo r other initial conditions. (C) 2001 Elsevier Science B.V. All rights reser ved.