Том 85, № 2 (2024)

Plant functional traits are important for the formation of plant communities and for plants’ ability to dominate there. The comparison of mean trait values of organisms within community with that for the random samples of the local biota allows estimating the importance of the trait for the formation of the community composition. The comparison of mean and community weighted mean values allow estimating their role for the dominance in any given community. We studied leaf functional traits (leaf area, mass, specific leaf area — SLA, leaf dry matter content — LDMC), as well as the contribution of Grime’s CSR strategies scores (competitors — stress-tolerators — ruderals) in two subalpine communities at the Teberda National Reserve (the North-Western Caucasus, Russia). Many leaf functional traits and plant strategies differ significantly in the fens and tall-herb communities from the random set of the species belonging to the local high mountain flora. The tall-herb community species have larger size (area and mass) of leaves, higher SLA and lower LDMC, as well as higher contribution of C and lower contribution of S and R strategies. The dominants of this community differ from the subordinate species by even larger leave size, lower SLA, higher LDMC higher C and lower R strategy scores. The plants of subalpine fens, in compare with random set of species, have smaller leaf size, lower SLA and higher LDMC, higher contribution of stress-tolerancy (S) and lower contribution of C and R strategies scores. In compare with subordinate species, the dominants of subalpine fens have even lower SLA and higher LDMC, higher S and lower R strategy scores. Thus, under the same climate conditions in depressions of mesorelief, but under the different hydrological conditions, in the subalpine belt of mountains there are plant communities with the contrasting functional structure. This underpins the important role of moisture conditions for the establishment of the spatial pattern of high mountain communities.

Siberian fir (Abies sibirica Ledeb.) is one of the main forest-forming species of northeastern European Russia. Compared to other forest-forming species, Siberian fir is poorly studied and there are no integral models describing the dynamics of fir photosynthesis depending on environmental factors and growing conditions. Modeling of intensity of fir photosynthesis depending on vertical gradients of environmental factors and anatomo-morphological structure of Siberian fir needles varying from the location within the vegetation canopy by height is the purpose of the present study. The study was conducted in the middle taiga subzone of the Komi Republic in a bilberry-sphagnum spruce forest at two altitudinal levels. The objects of the study are represented by two Siberian fir trees occupying different positions in the stand structure, one being a part of the main tier, the other being a part of the second tier. The CO₂ assimilation rate of fir needles, the intensity of incident photosynthetically active radiation, air temperature, relative air humidity, and atmospheric CO₂ concentration were measured in the crowns of selected trees on uncut shoots; the anatomical and morphological structure of fir needles depending on their height position in the stand structure was studied. A regression equation modeling the dependence of CO₂ assimilation rate by Siberian fir needles on environmental factors was obtained on the basis of experimental data. Validation showed the adequacy and statistical significance of the model. Specificity of the model and anatomo-morphological features of Siberian fir needles depending on their height in the stand was revealed.

Based on the original data on the fractionation of stomach and excrements contents, the effectiveness of the masticatory apparatus and post-gastric transformation of food particles in representatives of small herbivorous mammals is considered. It was found out that in the group of small animals with a body mass from 20 to 200 g the effectiveness of chewing does not depend on the body size but is due to the specifics of the functioning of the chewing apparatus. Particle reduction in this group is masked by a rapid change in digestion regimes, the intensity of nonspecific or specialized coprophagy, and the development of the fiber separation mechanism in the large intestine, which leads to high variability of results. The influence of body size is realized when larger herbivores with a body mass of up to 3–5 kg (hares) and up to 20 kg (beavers) are introduced into the comparison. In this case the influence of body size on the effectiveness of chewing is clearly manifested. In this interaction between the groups of animals, effects similar to those previously established in a wide comparative series of large herbivores with a body mass of up to 3000 kg were revealed. Thus, chewing can be considered as a function of body size, when comparing animals that differ significantly in body mass. Special attention is paid to the fraction of the finest particles, as containing not only fragments of fibers, but also non-food inclusions.