Vìsnik Dnìpropetrovsʹkogo Unìversitetu: Serìâ Bìologìâ, Ekologìâ (Jul 2015)
Quercus robur vitality structure and its dynamics at the initial stages of ontogeny
Abstract
We present the results of evaluation of vitality structure of ontogenetic subcenopopulations of juvenile and immature (im1 and im2) plants Quercus robur L. in seven aggregations of forest vegetation of Krolevets-Hlukhiv Geobotanical Region. It is found that ontogenetic subcenopopulations of Q. robur young generation, formed under canopy of deciduous forests of the region under study, are noted for high level of vitality structure diversity and for having three qualitative types: blooming, balanced and depressive ones. It is observed that dynamics of Q quality index values in ontogenetic subcenopopulations Q. robur in the aggregations under study fits three variants of changes. In the first one we can see stable decrease of Q quality index values in the line j → im1 → im2. Three of seven aggregations under study have dynamics of Q index values fitting the variant where increase of values takes place in the phase j → im1, and their decrease occurs in the phase im1 → im2. Q index values also decrease in the phase j → im1 and their increase in the phase im1 → im2 is established in three more phytocenoces. It is proved that change to every next phase of development (from j to im1, and also from im1 to im2) is accompanied by the appearance of vitality plasticity in Q. robur young generation (i.e. Q quality index value changes) and vitality variability (changes of share of individuals of various vitality classes), respectively. Quantitative as well as qualitative aspects of vitality plasticity realization are evaluated based on the original factor – index of vitality dynamics – IVD. It is found that at the initial stages of ontogenetic development negative changes of vitality structure in Q. robur happen more often then positive ones. Decrease in the individuals’ vitality and worsening of vitality structure are mainly accompanied by the reduction of cohort quality status. Ascertained facts as for vitality structure of ontogenetic subcenopopulations of juvenile and immature (im1 and im2) plants fairly prove the complicated nature of formation of continuous flow of Q. robur generations in phytocenoses with the appearance of this species and assurance of stable and lasting existence of its cenopopulations, respectively. From the peculiarities of vitality structure and its dynamics, we assume that considerable transformation of species composition of forest stands as a result of Q. robur reduction in their composition may happen in forests Tilieto (cordatae)–Acereto (platanoiditis)–Quercetum (roboris) stellariosum (holosteae) and Quercetum (roboris) acereto (tatarici)–urticosum (dioicae) in the studied region in future.
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