Altitude-belt zonality of forest vegetation in mountainous regions of the Sayan Mountains: A model of ecological second-order phase transitions

Abstract

A model of ecological second-order transitions has been proposed as a description of altitude-belt zonality of wood vegetation. The objects of the study are forest cenoses on the northern slope of Kulumyss Ridge (the Sayan Mauntains), while the results include the altitude profiles of forest vegetation. Ecological phase transition can be considered as a transition of cenoses at different altitudes from the state of the presence of certain tree species within the studied territory to the state of their absence. By analogy with the physical model of second-order phase transitions, the order parameter has been introduced (i.e., the area occupied by a single tree species at a certain altitude), as well as the control variable (i.e., the altitude of the forest vegetation belt). As the formal relation between them, an analog of Landau’s equation for phase transitions in physical systems has been obtained. The model is in good accordance with the empirical data. Thus, it can be used for estimation of upper and lower boundaries of altitude belts in individual tree species (such as birch, aspen, Siberian fir, and Siberian pine), as well as of the width of their ecological niches with regard to altitude. The model also includes the parameters that describe numerically the interactions between different species of wood vegetation. The approach versatility allows simplification of the description and modeling of forest vegetation altitude zonality and enables assessment of vegetation cenose response to climatic changes.