Conference publications

Abstracts

XXIII conference

Signs of stochastic determinancy of forest ecosystem succession in the Markov model

Nemchinova A.V.

nemanvic@rambler.ru

The proposed method for estimation of the course of forest ecosystem succession to the climax state used a discrete Markov chain model [1]. In an oriented graph of model there are 32 vertices, identified with the succession stages, allocated on the basis of the vertical layering structure of forest communities and the positions of trees in their composition [2]. Course of succession from stage to stage can be identified by the mutual transition of growing trees to the upper sublayers. Predicting of the next state of the vertical structure of each individual described the community is a difficult task because it is conditioned by stochastic processes internal cenotic relationships of populations and by the influence of external factors. In this approach the retention time in any step of the succession is time interval with indefinite length from duration of the whole succession accepted as unit. The probabilities of random transitions by stages during 1 step are reflected in the transition probabilities matrix calibrated by the frequency of forest communities in each of the 32 stages within research area (555 descriptions on the area of approx. 500.000 Ha). The credibility of alternative transitions we take as proportional to the frequency of occurrence of the communities in the stage where the transition occurred to. Duration succession we set as the average number of steps before reaching the climax by means of the Markov-chain fundamental matrix [1]. Correlated with the maximum value, they predict the relative time of reach a climax. Several models are constructed in different sampling of communities by volume, by stages and allocated in different landscapes. It turned out that the duration of the succession courses an average in 2-3 times shorter than durations calculated on a theoretical model with the assumption equal probability of alternative transitions. Thus it shows the level of stochastic determinancy of autogenous succession. The trajectories of succession in different versions of models in general coincide with the course of succession in the theoretical model. In the mosaic of mutual transitions several stages stand out, which restrain the temp of succession. They can be named by temporarily absorbing states or subterminal stages in the blocks of elements of transition matrix, the size of which in the course of succession from the first stage is increased exponentially.

References.

1. Logofet D.O. Markov chain as a model of succession: a new perspective of the classical paradigm // Lesovedenie, № 2, 2010. Pp. 46-59.

2. A Nemchinova A.V. Evaluation of structural degradation and restoration potential in forest ecosystems by means of a Markov succession model // Vestnik of Nekrasov KSU. №7 (20) 2014. Pp. 70-75.

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