Assessment of Quercus robur L., Acer plantanoides L., Ulmus glabra Huds. allelopathic activity in natural and artificial phytocenoses of the Southern Urals using multivariate analysis

The Quercus robur, Acer plantanoides, Ulmus glabra allelopathic activity in natural relict communities and forest plantations of the Southern Urals was studied. We also examined the contribution of factors affecting the variance of allelopathic transfer indicators. Among them are transfer agents (extracts from leaves, leaf fall, root zone soil), habitat type (natural/artificial), concentration of water extracts (1:100, 1:50, 1:25, 1:10), and type of donor plant species (Q. rour, A. platanoides, U. glabra). Various combinations of species pairs in the donor–acceptor system were studied in classical laboratory experiments. Allelopathic activity was evaluated by growth responses (germination and root length) of classical test subjects Lepidium sativum L., Linum usitatissimum L., Viola tricolor L. The exposure time was 120 h, under illumination with a photoperiod of 15 h of daylight and temperature 21±1 °C. An array of primary morphometric measurements (720 indicators) was obtained. Multivariate statistical technique – Redundancy analysis – was used to evaluate the contribution of factors determining allelopathic activity of donor plants. Statistical significance of the effects was confirmed by randomisation procedure at p≤0.05. The effect of each factor in the variation of allelopathic activity values is explained based on primary indicators. The hierarchy of regressors (factors) by contribution to the variance of allelopathic activity indicators was established. The impact of transfer agents is statistically significant (F(2/69)=18.91; p<0.001) and demonstrates a contribution to the variance of germination and root length indices of acceptor plants by 35.4%. Regressor – donor species – determines less variability (16.0%) of the above indicators of acceptor plants at statistical significance (F(2/69)=6.58; p<0.001). Multivariate analysis confirmed a statistically significant inverse relationship between the concentration of aqueous extracts of all donor species and the inhibitory effect on seed germination of the biotests. The minimum contribution to the variance was found for the regressor, habitat type. In the gradient between natural and artificial communities, the contribution to variance is 1.95% and is not statistically significant. Thus, the feasibility of using multivariate statistical analysis to compare allelopathic effect is shown.