The Value of Meristem States, as Estimated by a Discrete-Time Markov Chain

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Abstract
I used a discrete Marko chain to model the dynamics of meristem states of mountain white birches (Betula cordifolia Regel) at their elevational limit. Meristems could enter different states from summer to summer (summer dormancy, short-shoot production, long-shoot production, death), according to sets of transition probabilities. First, I verified the Markovity of meristem states. Than I used a Markov chain to estimate the life-expectancy of each meristem state and to compute the life-time rewards (number of meristems produced) brought to the host plant by each meristem state. The simulation demonstrated that summer-dormant buds ultimately made a greater contribution to growth than other states because of the increased longevity of summer-dormant meristems combined with their ability to change state. Summer-dormant were crucial for repairs after damage caused by unfavourable climatic episodes at the tree line. By accumulating summer-dormant meristems, tundra birches could thus survive periodic crown destruction and ''wait'' for climatic improvements that would allow them to reach the threshold height needed for sexual reproduction.