Bilberry vs. cowberry in a Scots pine boreal forest: III. Another forest, another method, and similar conclusions

摘要

Markov chain formalism developed formerly for the joint dynamics of cowberry (Vaccinium vitis-idaea) and bilberry (V. myrtillus) in the course of post-fire succession (Logofet, Maslov, 2019) is applied here to a similar set of empirical data, namely, the rooted presence/absence of these species on a great number of small (20 x 20 cm) quadrats laid down in a protected sub-xeric Cladina-Vaccinium pine forest (boreo-nemoral zone) and re-examined each 5 years during 25. As before, a discrete Markov chain describes the 5-year transitions between the four quadrate states: species-free, V. myrtillus alone, V. vitis-idaea alone, and both species present. In contrast to the former study, we summarize the total observation period by weighted averaging the frequencies of each kind of transition, thus getting a single mean-frequency transition matrix, P-mf, rather than the pattern-multiplicative average, G, of the 5 one-step transition matrices. We have verified the correctness of the mean frequencies (i.e., the strata homogeneity) by a statistical (Mantel-Haenszel) test and obtain the standard spatial and temporal characteristics of the observed dynamics from the fundamental matrix of the Markov chain. The conclusion for ecology is that there is a unidirectional trend revealed in temporal changes for three of the four chain states: the share of V. myrtillus quadrats and that of both species quadrats are permanently increasing, while the share of species-free quadrats decreases. The fourth (V. vitis-idaea alone) state has a local maximum at the middle stages of succession, after which its share decreases. The terminal stable outcome of species dynamics is expected to be a distribution where 29.1% of quadrats are occupied by the Vaccinium myrtillus alone, 15.2% by V. vitis-idaea alone, 44.4% by the both species, and 11.3% be species-free. The results confirm that the coexistence of V. myrtillus and V. vitis-idaea can be stable at the final stages of succession. The total time of post-fire succession is estimated at approximately 140 years. From the forest typology point of view, we have a gradual transformation of Cladina-Vaccinium pine forest into Vaccinium and further into Vaccinium-Myrtillus pine forest.