Lesovedenie

Whatever level of recurrent plus breeding cycle is achieved there is a need of additional supplement of breeding population by new elite tree specimens. Due to this fact investigations concerning the confluence of ecological, genetics and intracoenotic factors facilitating their appearance is evermore actual. In 2021—2023 5 elite and 3 normal stands which included 71 elite trees growing within the northern taiga subzone were studied. Most of the stands were conditionally even-aged because of their arising after total catastrophic events such as clear cuts, windfalls and so on. The “elite” phenomena for new pine stand became possible precisely because of some kind of catastrophic event accompanied by fire (slash fire or natural fire), which cleared space, and was followed soon by abundant crop of pine seeds from surrounding stands. Specimens belonging to the leading group of trees which germinated in the first phase (0—15 years) of pine self-regeneration had the maximum probability to evolve into the elite ones. The genetic proximity of trees of all selection categories can be explained by the fact that all of them belong to the same generation period (about 30 years). At the same time actual genetic features of elite trees most commonly stay unrevealed and special trials with vegetative and seed progenies are needed to bring them to light.

The article presents data on the study of the drought resilience limits of Scots pine trees (Pinus sylvestris L.) in the south of the East European Plain in connection with changes in the forest-steppe climate and an increase in the number and intensity of droughts. It was shown that the rate of the global warming in the 20th century was 0.11°C/10 years, while in the 21st century it became 0.35°C/10 years. The objective of the study was to determine the drought resilience limits of the Scots pine trees on different life cycle stages in the forest-steppe zone of the East European Plain. The object of the study was the northern Kaluga and Ryazan, central Voronezh and southern Belgorod pine populations growing in the ecologically favourable territory of the forest-steppe zone of the Russian Plain. As a result of studying the pine response to 6 severe droughts (early 1991 and 2007, summer 2010 and 2020, late 2014 and 2020) and an 8-year heat wave (2007—2014), the threshold of resistance of the stages was determined, which, according to the descending vector, represent the following series: ontogenesis, sporogenesis, embryogenesis, gametogenesis. The cause for the poor harvest in 2012 was the cumulative effect of two droughts on the megasporogenesis processes (2010 — in the year of the megasporogenesis initiation, 2012 — in the year of fertilisation). The impact of the 1991 drought on early embryogenesis led to a 5-fold decrease in pine yield and overall lower seed viability. The weather stress of 2010 during late embryogenesis affected such vital indicators of the future plants as growth rate, phenotypic variability, and seasonal development rhythms. It caused mass death of 1-year-old seedlings and the appearance of many morphoses and developmental deviations in 2-year-old plants. Severe droughts in 2007, 2010, 2012, 2014 during the heat wave of 2007—2014 caused destabilization and transition of pine forests to a state of semi-nonequilibrium systems. The return of pine stands to a state of equilibrium continued for three optimal years.

The geometric morphometry of leaf blades was evaluated for five families under the conditions of the Kirsanovsky forestry in the Tambov region based on 17 indicators that reflect metric and structural characteristics. A comprehensive assessment of correlations in all groups revealed a direct relationship between indicators that determine morphological features of leaves. Considering the signs that characterise the length and width of blades, it should be noted that a change in any feature alters the configuration of the whole leaf, necessitating the use of a set of important features rather than a single one. Among these features, LSP, LB2-LB6, and WCB2-WCB6 are the most informative. Values that imply measurements in degrees are unable to produce statistically significant results, so the angle of deviation of blade veins of different orders is not practical for use as an indicator for evaluating intra- and inter-family variability. The main contribution to the total dispersion (80%) is made by the blades of the fifth, sixth, and seventh orders.

In the context of climate change and increasing soil salinization, research on adaptive breeding is becoming especially relevant. In vitro stress modelling is a promising biotechnological approach to plant selection for resistance to negative environmental factors. The effect of sodium chloride salinization (to simulate salt and osmotic stress) in vitro on the survival, growth, callusogenesis, and morphogenesis of 12 collection clones of Betula pendula L., B. pubescens Ehrh., B. pendula Roth var. carelica (Mercklin) Hämet-Ahti, B. pendula “dalekarlica” (L.f.) was studied. A significant influence of genotype on the survival of explants and their ability to regenerate under salt exposure was demonstrated. It has been established that the use of a 4-fold stepwise (from 0.2 to 1 %) increase in NaCl exposure on a selective nutrient medium without hormones allows differentiating clones by salinity resistance. The highest adaptive capabilities under NaCl-induced salinity were shown by the clones of downy birch, the lowest — by the clones of silver birch. Informative and relatively simple indicators for differentiating clones are the frequency of callus formation and the viability of callus cultures, which characterise the initial and final phases of callus formation and depend on the genotypic characteristics of the original plants. A selective in vitro system is presented, based on the genetic diversity of collection clones (species, varieties, polyploids, mixoploids) and induced cellular heterogeneity of stem callus cultures obtained from the clones most resilient against salinity. The results of the studies confirm the potential of using genetic variability of the initial material under conditions of simulated NaCl stress for selection of birch clones (and lines) adapted to salinity. Three regenerated birch lines selected using selective nutrient media in vitro are promising initial material for adaptive selection.

For the first time, a variability analysis of phenological dates of woody plant development in connection with climate change was conducted for the conditions of Primorsky Krai. The study is based on a continuous (from 1987 to 2022) series of phenological observations for five tree species from the Nature Chronicle of the Sikhote-Alin Reserve. According to data from the Terney weather station, a trend for warming by 0.29°С/10 years was revealed. The best predictor for the shift in phenological dates and changes in the duration of the growing season turned out to be the average spring air temperature (R² = 0.30—0.69). Another good predictor for phenological shifts was the average annual temperature and the sum of active temperatures on May 1 (temperature threshold 0°С). Temperature sensitivity for the dates of spring phenophases, calculated based on the average spring temperature for the studied tree species, was 3—6 days/°С. The flowering phase is the most sensitive to air temperature. The best ability to indicate climate changes among the species under consideration was found in the common bird cherry (Padus avium Mill.). No significant trends in the change of autumn phenological data have been identified over the years of observation. Over 35 years of observation, plants have not shown any clear signs of phenological development adaptation to increasing temperatures.