Afroalpine plants develop under specific climate with great daily fluctuations and weak seasonal dynamics of temperature. Do leaf functional traits of the plants in Mt. Kenya differ from those of temperate plants in NW Caucasus? To answer this question, we conducted a comparative study at the Teleki valley (4000–4500 m a.s.l.), Mt. Kenya, Kenya, and Teberda national park (2600–2900 m a.s.l.), the Caucasus, Russia. We measured leaf area, fresh and dry mass, C, N, P, δ13C, δ15N and derivative traits (specific leaf area – SLA, leaf dry matter content – LDMC, C:N and N:P ratios) for 48 species at the Teleki valley, and the same traits, except for the δ13C and δ15N, for 141 species in the Teberda national park. The CSR-strategies scores were calculated. We applied the Principal Component Analysis to reveal the main patterns of trait variation. Leaf dry mass of Mt. Kenya alpine plants ranged from 0.27 mg (Sagina afroalpina) to 14.0 g (Dendrosenecio keniodendron). Leaf area, mass and LDMC of alpine plants in both regions did not differ significantly. The SLA of Mt. Kenya’s plants varied about 20-fold: from 2.6 mm2 mg-1 (Festuca pilgeri) to 39.8 mm2 mg-1 (Cineraria deltoidea), and Caucasian plants had higher SLA. N and P leaf concentrations were higher, but C lower in Caucasian plants than in Kenyan. Leaf N:P ratio was similar for both regions, while C:N ratio was higher in Kenyan plants. Species of “rosette” trees (Dendrosenecio spp.) differed from other species by size characteristics (maximal leaf dry mass and area were in Dendrosenecio keniodendron), as well as correspondingly higher investment to mechanical tissues (high C:N ratio, low SLA). By the other functional traits, “rosette” trees were similar to many other alpine plants. Thus, afroalpine plants of Mt. Kenya are close to temperate alpine plants by some leaf functional traits, but possess higher stress-tolerance.

Soils of high mountains significantly differ in the soil organic matter (SOM) content, but the factors of such diversity are still not completely known. We have studied physicochemical and microbiological soil properties and have estimated parameters of standard material decomposition based on the Tea bag index (TBI)—stabilization factor ( S TBI ) and decomposition constant ( k TBI )—in 16 subalpine, alpine, and subnival plant communities of the Teberda National Park (northwestern Caucasus) We tested the following hypotheses: (1) SOM is one of predictors of S TBI and k TBI in the high-mountain zone along with other physicochemical soil properties; (2) the SOM content is greater at high S TBI and low k TBI ; (3) the SOM content correlates with belowground plant productivity. The main gradients of the studied soils include moisture content (automorphic vs. hydromorphic soils) and the concurrent SOM accumulation, as well as the altitudinal gradient (a decrease of soil basal respiration with altitude). The enrichment in nitrogen (e.g. the SOM quality) of the labile fraction is the best predictor of the decomposition rate. The parameter S TBI decreases with the increase in the total carbon content and loss on ignition, while the correlation between k TBI and SOM is positive only in automorphic soils. Thus, the soils rich in organic matter are characterized by low stabilization factor and relatively high decomposition rate. The SOM content in plant communities with herbaceous dominants is in positive correlation with the production of fine roots, which reflects the important role of productivity in organic matter accumulation.

Fires play an important role in structure and function of terrestrial ecosystems, but their long-term impact on the composition and structure of plant communities in humid high mountain regions remains almost not studied. At the most dry alpine grasslands, dominated by a dense-tussock grass Festuca varia, with substantial accumulation of non-decomposed litter, the 23-years long experiment with regular (every two years) litter burning was established. The composition of plant community changed significantly. The mortmass (mass of litter), aboveground vascular plant biomass and relative abundance of dominants decreased substantially. In aboveground biomass the proportion of grasses decreased and that of forbs increased. The shoot numbers of Anthemis cretica, Campanula collina, Deschampsia flexuosa, Festuca ovina, Nardus stricta, and Veronica gentianoides increased after burning. Two-fold increase of alpha-diversity of vascular plants was observed on plots with burning treatment, it was twice as high as initial value, and was significantly higher than the values in the control plots. Long-term burning did not substantially change mean P, Ca and Mg content in the biomass of the most of studied species, only K content decreased in some species, while Mg content increased in Festuca varia and Nardus stricta. The increase of P and Mg content in the mortmass was observed. During long-term burning, weak soil acidification and the decrease of Ca content, as well as strong decrease of nitrogen content and the intensity of nitrogen transformation processes were observed. Generally, the observed patterns were similar to those in other studied herb communities, however, the decrease of K content during the regular burning was not reported earlier.

Contents of C, N, and P and N : P and C : N ratios in plant leaves have been studied in four alpine phytocenoses of the northwestern Caucasus to find out whether the species encountered in these areas differ in chemical composition from random samples from the local flora or not and determine the significance of the values of these traits for dominance, as well as their phylogenetic conservation. The content of nitrogen is lower in the leaves of plants from alpine heaths and Festuca varia grasslands and higher in the leaves of species of Geranium–Hedysarum meadows and alpine snowbeds than in a random sample. Dominants of productive Geranium–Hedysarum meadows contain more nitrogen than nondominant species, while the opposite dependence has been recorded for the other communities. The leaves of the components of all communities except alpine snowbeds contain less phosphorus than a random sample. Dominants of alpine heaths have less phosphorus and Geranium–Hedysarum meadows have more phosphorus in the leaves than nondominant species. The C : N ratio in the leaves is higher than the random value in species of alpine heaths and Festuca varia grasslands and lower in other communities. The dominant species have higher C : N ratios than the other species in all communities except Geranium–Hedysarum meadows. The N : P ratio is higher than the random value in species of all communities except Festuca varia grasslands. All the traits except the C : N ratio have a significant phylogenetic signal.

Forest stand density has been shown to have different, albeit small, effects on soil carbon. We hypothesized that the absence of a density effect on soil carbon (C) storage could be explained by a loss of old soil C. This replacement of old by fresh C could result in zero net C sequestration by soils but could also alter the quality of the soil organic matter. We used one afforestation experiment in Siberia, in which three tree species (spruce, larch and Scots pine) have been grown for the last 30 years at 18 levels of stand density, ranging originally from 500 to 125,000 stems per ha. We selected five density levels and studied the C and nitrogen (N) contents in mineral soils at 0–5 cm depth. The age of the soil C was measured under larch and spruce for three levels of density by radiocarbon (14C) dating. In all soil samples, we determined the stability of the soil organic matter (SOM) by assessing two indices: C decomposability (mineralization of C per unit of soil C) and primability (susceptibility of the SOM to microbial priming). The stand density affected the soil C and N contents differently depending on the tree species. Only under spruce did both the C and N contents increase with density; under larch and pine, the covariation was insignificant and N even tended to decline with a density increase. With the 14C data, we were able to show the strong dilution of old SOM by fresh C derived from the trees; the effect was stronger with a higher density. This provides the first evidence that a density increase increases the fractions of new C versus old C and this can happen without altering the total C contents such as under larch. Although the stand density altered the soil C and N contents only under spruce, it altered C decomposability under all tree species; with a density increase, the C decomposability declined under spruce but increased under larch and pine. This is relevant to predicting C losses from forest soils with different tree species and densities. Higher C losses would occur under larch and pine with higher densities but under spruce, a density increase would reduce the losses of C from the soil. Furthermore, although no significant covariation of stand density with C primability was detected, we first observed strong tree species effects on C primability. Twice as much C was lost from the soil under larch than under spruce or pine by an equal addition of C-glucose. This indicated that elevated C deposition from roots and exudates to the soil as predicted due to an elevated CO2 concentration would most strongly accelerate the soil C turnover and C losses under larch than under spruce and Scots pine. Overall, the tree species altered the susceptibility of the soil C to an elevated C input and the stand density had a strong effect on the decomposability of the SOM, which is an important parameter of C stability. The effect of stand density is, therefore, important to consider even if the stand density does not affect the total soil C.

Partially mycoheterotrophic (mixotrophic) plants are considered to be more common among phylogenetic lineages that include fully mycoheterotrophic plants. Gentianaceae is one such group. Mixotrophy is not well known for alpine plants in contrast to species of tropical and temporal forests. We tested the hypothesis that green alpine species from the Gentianaceae family can be partially mycoheterotrophic. Leaves of nine pairs of species (alpine plants from the Gentianaceae + reference neighboring AM plants from other families) were collected in Tibetan (Sichuan, China) and Caucasian (Karachai-Cherkessian Republic, Russia) mountains. Stable isotope (13C, 15N) natural abundances were determined in fully developed leaves. In each case leaves of Gentianaceae plants were enriched in 15N more than the leaves of other plants which served as comparisons. Except for two species from the section Pneumonanthe (Gentiana asclepiadea and G. septemfida) the studied Gentianaceae plants did not show significant 13C enrichment. We suggest that relative 15N enrichment of leaves may be considered as an indication of partial mycoheterotrophy in alpine Gentianaceae.

An altitudinal gradient in the mountains constitutes a unique 'open-lab' to examine environmental hypotheses and analyse the expected effects of global warming. The distribution of carbon (C)-, nitrogen (N)-, and phosphorus (P)-acquiring enzyme activity, microbial catabolic activity as represented by a community-level physiological profile (CLPP), and microbial functional diversity (HCLPP) within mountainous ecosystems consisting of mixed, fir and deciduous forests, as well as subalpine and alpine meadows (1260-2480 m a.s.l., Mt. Tkachiha, the Northwest Caucasus, Russia) has been studied. Concerning potential drivers, vegetation (plant projective cover, plant functional group composition, plant richness and diversity) and edaphic (soil nutrients: total and available C and N, total P, pH, texture, temperature, microbial biomass C) and topographic (elevation, slope, mean annual temperature calculated using biannual monitoring data) properties have been considered. The distribution patterns of the studied hydrolytic enzymes along an altitudinal gradient cannot be explained solely by elevation change and soil nutrient content. The activity of soil leucine aminopeptidase depends on vegetation type and graminoid abundance. beta-D-glucosidase activity was mainly driven by the quality of soil organic matter (SOM), demonstrating a significant relation with the soil C:N ratio. The chitinase and phosphatase turned out soil temperature-sensitive enzymes. The CLPP depends on the available N content in the soil. The HCLPP distribution with altitude was driven by available N and forbs abundance represented by the widest spectrum of plant families and species. An altitudinal gradient determines the spread of the vegetation zone. In turn, vegetation properties, such as plant functional group composition, species richness and diversity, play a significant role in the distribution of soil microbial activity along an altitudinal gradient that controls the decomposition of SOM and nutrient cycling. Thus, the significant role of vegetation in the distribution of soil microbial activity across a wide range of natural ecosystems and in consideration of topographic and edaphic factors has been demonstrated.

The investigation of belowground plant production and its determining factors is critical for better understanding carbon turnover in the biosphere. The measurement of fine root production is a methodical and difficult task. To reveal factors determining fine root production in mountain ecosystems, we introduced a new modification of ingrowth method with the use of filter balls (tea strainers). We studied root production in 16 communities from upper forest to subnival belts in the range of 2184–3069 m a.s.l. in the Teberda Reserve, Northwestern Caucasus, Russia. The filter balls were filled with sifted soil (without roots or stones) and buried in the soil 7–8 cm deep. The mass of root ingrowth was measured after two months of incubation under natural conditions. Mixed-effect models were applied to test the relationships between root mass, elevation, soil moisture, organic matter content, and pH. The highest root production was observed in an alpine snowbed (247 mg per filter ball in 60 days), the lowest was in forest and subnival communities (3–20 mg per filter ball in 60 days). The communities with woody dominants had lower production than herb communities. It increased with soil moisture, which was the most important factor. In herb communities the production of roots tended to decrease with the elevation. Soil organic matter as a separate factor had a positive relationship with root production in herb communities. There were no links between root ingrowth and soil pH. The method introduced presently both allows for the comparison of plant communities by their root production and reveals factors determining it.

EcologyVolume 102, Issue 3 e03255 The Scientific Naturalist Snow roots: Where are they and what are they for? Vladimir G. Onipchenko, Corresponding Author Vladimir G. Onipchenko vonipchenko@mail.ru orcid.org/0000-0002-1626-1171 Faculty of Biology, Moscow State Lomonosov University, Leninskie Gory 1-12, Moscow, 119234 Russia E-mail: vonipchenko@mail.ruSearch for more papers by this authorAlii M. Kipkeev, Alii M. Kipkeev Faculty of Biology, Moscow State Lomonosov University, Leninskie Gory 1-12, Moscow, 119234 RussiaSearch for more papers by this authorLiesje Mommer, Liesje Mommer Plant Ecology & Nature Conservation Group, Department of Environmental Science, Wageningen University & Research Centre, Wageningen, The NetherlandsSearch for more papers by this authorJan Willem van der Paauw, Jan Willem van der Paauw Plant Ecology & Nature Conservation Group, Department of Environmental Science, Wageningen University & Research Centre, Wageningen, The NetherlandsSearch for more papers by this authorRichard S. P. van Logtestijn, Richard S. P. van Logtestijn Systems Ecology, Department of Ecological Science, Faculty of Science, Vrije Universiteit, De Boelelaan 1085, Amsterdam, 1081 HV The NetherlandsSearch for more papers by this authorDzhamal K. Tekeev, Dzhamal K. Tekeev Teberda State Reserve, Badukskii 1, Karachaevo-Cherkessian Republic, Teberda, 369210 RussiaSearch for more papers by this authorAlexander S. Zernov, Alexander S. Zernov Faculty of Biology, Moscow State Lomonosov University, Leninskie Gory 1-12, Moscow, 119234 RussiaSearch for more papers by this authorAsem A. Akhmetzhanova, Asem A. Akhmetzhanova Faculty of Biology, Moscow State Lomonosov University, Leninskie Gory 1-12, Moscow, 119234 RussiaSearch for more papers by this authorAnna D. Kozhevnikova,, Anna D. Kozhevnikova, Timiryazev Institute of Plant Physiology RAS, Botanicheskaya ul. 35, Moscow, 127276 RussiaSearch for more papers by this authorInga Hiiesalu,, Inga Hiiesalu, Institute of Ecology and Earth Sciences, University of Tartu, Lai 40, Tartu, 51005 EstoniaSearch for more papers by this authorMikhail I. Makarov,, Mikhail I. Makarov, Faculty of Soil Science, Moscow State Lomonosov University, Leninskie Gory 1-12, Moscow, 119234 RussiaSearch for more papers by this authorJohannes H. C. Cornelissen, Johannes H. C. Cornelissen Systems Ecology, Department of Ecological Science, Faculty of Science, Vrije Universiteit, De Boelelaan 1085, Amsterdam, 1081 HV The NetherlandsSearch for more papers by this author Vladimir G. Onipchenko, Corresponding Author Vladimir G. Onipchenko vonipchenko@mail.ru orcid.org/0000-0002-1626-1171 Faculty of Biology, Moscow State Lomonosov University, Leninskie Gory 1-12, Moscow, 119234 Russia E-mail: vonipchenko@mail.ruSearch for more papers by this authorAlii M. Kipkeev, Alii M. Kipkeev Faculty of Biology, Moscow State Lomonosov University, Leninskie Gory 1-12, Moscow, 119234 RussiaSearch for more papers by this authorLiesje Mommer, Liesje Mommer Plant Ecology & Nature Conservation Group, Department of Environmental Science, Wageningen University & Research Centre, Wageningen, The NetherlandsSearch for more papers by this authorJan Willem van der Paauw, Jan Willem van der Paauw Plant Ecology & Nature Conservation Group, Department of Environmental Science, Wageningen University & Research Centre, Wageningen, The NetherlandsSearch for more papers by this authorRichard S. P. van Logtestijn, Richard S. P. van Logtestijn Systems Ecology, Department of Ecological Science, Faculty of Science, Vrije Universiteit, De Boelelaan 1085, Amsterdam, 1081 HV The NetherlandsSearch for more papers by this authorDzhamal K. Tekeev, Dzhamal K. Tekeev Teberda State Reserve, Badukskii 1, Karachaevo-Cherkessian Republic, Teberda, 369210 RussiaSearch for more papers by this authorAlexander S. Zernov, Alexander S. Zernov Faculty of Biology, Moscow State Lomonosov University, Leninskie Gory 1-12, Moscow, 119234 RussiaSearch for more papers by this authorAsem A. Akhmetzhanova, Asem A. Akhmetzhanova Faculty of Biology, Moscow State Lomonosov University, Leninskie Gory 1-12, Moscow, 119234 RussiaSearch for more papers by this authorAnna D. Kozhevnikova,, Anna D. Kozhevnikova, Timiryazev Institute of Plant Physiology RAS, Botanicheskaya ul. 35, Moscow, 127276 RussiaSearch for more papers by this authorInga Hiiesalu,, Inga Hiiesalu, Institute of Ecology and Earth Sciences, University of Tartu, Lai 40, Tartu, 51005 EstoniaSearch for more papers by this authorMikhail I. Makarov,, Mikhail I. Makarov, Faculty of Soil Science, Moscow State Lomonosov University, Leninskie Gory 1-12, Moscow, 119234 RussiaSearch for more papers by this authorJohannes H. C. Cornelissen, Johannes H. C. Cornelissen Systems Ecology, Department of Ecological Science, Faculty of Science, Vrije Universiteit, De Boelelaan 1085, Amsterdam, 1081 HV The NetherlandsSearch for more papers by this author First published: 22 November 2020 https://doi.org/10.1002/ecy.3255 Corresponding Editor: John Pastor. Read the full textAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. 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Isotopic composition of nitrogen in soil microbial biomass (δ 15 N micr ) is connected with the transformation of nitrogen compounds and with the balance of carbon and nitrogen availability for microorganisms. We have studied the dependence of δ 15 N micr on nitrogen isotopic composition in the substrate (δ 15 N of total and extractable nitrogen), as well as the dependence of δ 15 N micr and 15 N-enrichment of microbial biomass (Δ 15 N micr = δ 15 N micr – δ 15 N substr ) on nitrogen availability parameters (the C/N ratio in soil, the N-mineralization activity, the content of extractable nitrogen, and the nitrogen use efficiency) in soils of four alpine ecosystems in the North Caucasus and four tundra ecosystems in the Khibiny Mountains. It has been shown that δ 15 N miсr varies from –0.2 to +8.4‰ and may be characterized by both 15 N-enrichment and depletion (negative Δ 15 N miсr values) relative to the total and extractable soil nitrogen. As a rule, Δ 15 N micr is 1.5–3.1‰ relative to 15 N total and 0.6–4.8‰ relative to 15 N extr . However, under the most N-deficiency conditions in soils of mountain tundra lichen and shrub heaths, N micr does not accumulate an increased amount of 15 N. We have not revealed a close correlation of δ 15 N micr and Δ 15 N micr with the C/N ratio. The accumulation of 15 N in microbial biomass is much stronger related to N-mineralization (positively) and the nitrogen use efficiency (negatively). This testifies to the important role of microbial nitrogen dissimilation in controlling the isotopic composition of soil microbial biomass nitrogen.

The natural nitrogen-15 abundance method does not always make it possible to calculate the rate of symbiotic nitrogen fixation by legumes and needs to be improved. Five legume species typical for the alpine belt of the Teberda Nature Reserve (Anthyllis vulneraria, Astragalus levieri, Hedysarum caucasicum, Oxytropis kubanensis, and Trifolium polyphyllum) have been grown from seeds under conditions of laboratory vegetation experiment. The results show that nodules on the roots of these plants are formed at early stages of their development; Trifolium polyphyllum does not form nodules either under high-mountain conditions or during growth in the laboratory. The natural 15N abundance in the leaves of legume plants in alpine ecosystems makes it possible to calculate the contribution of atmospheric N2 to nitrogen nutrition as early as the first year of their development, while the isotopic nitrogen composition of the roots does not allow this parameter to be determined. The calculation of atmospheric nitrogen fixation rate should take into account isotope fractionation between symbiotic bacteria (nodules) and the host plant; otherwise, the proportion of fixed nitrogen in plant nutrition may be underestimated.

The results of the four-year study of the temperature regime of soils of three common landscapes of northern taiga in Western Siberia, located in the area of discontinuous permafrost, are presented. The soils of lumpy peatlands are characterized by mild permafrost annual regime with very cold summer and moderately cold winter. Temperature regime of the forest soils may be characterized as cold long-time seasonally freezing mild with very cold summer and moderately cold winter. The soils of the investigated region are functioning in conditions of the narrow range of temperatures: at the depth of 20 cm for the soils of all of the landscapes, the temperatures vary within the range of -2.5 to 0°С. This occurs due to their high moisture, low thermal conductivity, specificities of snow cover regime and the freezing effect of permafrost rocks. Annual temperature soil indices are characterized by the weak correlation to the mean annual specificities of air temperature regime. We discovered the direct correlation of annual soil temperature regime and the dynamics of the snow cover (with average and maximal thickness, and thawing date), and with winter N-factor (surface temperature index), and accumulative positive temperatures. Since isolating activity of the vegetation is significantly lower than that of snow (summer N- factors 0.7-0.9), annual fluctuations of summer air temperatures will significantly affect the temperature regime of soils and geo-cryologic situation of the region in general.

Climatic and plant community changes are observed in the alpine belt of the Teberda Reserve (the Northwest Caucasus) in the last decades. Increase of average monthly temperature in the summer months in 2006-2018 was 1.8-2.2 ºC in comparison with 1966-1990. For the last 13 years, the maximum temperature in July and August reached 22.1-23.2 ºC vs. 20.5 ºC in 1966-1990, and minimum temperature during these months did not fall lower than -1.8 ºC whereas in 1966-1990 it fell up to -7.0 ºC. At the same time decrease of summer precipitation, especially in July and August is observed (average 80-100 mm per month vs. 150-160 mm in 1966-1990). Against this climatic background, a significant increase of dwarf shrub with ericoid mycorrhizal symbiosis (Vaccinium vitis-idaea) occurs in plant community of alpine lichen heath. As ericoid mycorrhiza is characterized by high enzymatic activity capable to transform and mobilize soil organic matter, we assume that the appearance of Vaccinium vitis-idaea in grass ecosystems can change soil properties. Simultaneously the observed tendency to decrease the amount of summer atmospheric precipitation in mountain regions can change soil moisture which is also highly important to control soil microbial activity and organic matter transformation. The properties of the mountain-meadow soil of the alpine lichen heath, characterizing labile forms of carbon, nitrogen and phosphorus, as well as biological activity at different soil moisture and in the presence or absence of Vaccinium vitis-idaea in the plant community, have been studied. It has been shown that under V. vitis-idaea soil is characterized by greater acidity and less responsive to changes in soil moisture. Differences in properties in the presence and absence of V. vitis-idaea are predominantly determined by the expressed response of the soil to changes in moisture in the absence of dwarf shrub. Under herbal vegetation, when soil moisture decreases, concentrations of inorganic nitrogen, activity of N-mineralization and nitrification, microbial biomass and soil respiration decrease, but concentrations of labile organic carbon and nitrogen, and enzymatic activity increase. Such changes indicate a shift in organic matter transformation from mineralization to depolymerization, more characteristic of ectomycorrhizal and ericoid mycorrhizal dominated ecosystems. Thus, both factors (soil moisture and invasions of ericoid mycorrhizal plant species) should be taken into account in predicting changes of alpine ecosystems functioning. This study was supported by Russian Science Foundation (16-14-10208).

The study of the effect of plants with different type of mycorrhizal symbiosis on carbon, nitrogen, and phosphorus transformation in soils is important in view of the necessity to predict changes in nutrient cycles upon transformation of the structure of plant communities under changing environmental conditions. The impact of dwarf shrubs ( Empetrum hermaphroditum , Vaccinium myrtillus , Vaccinium uliginosum , and Vaccinium vitis-idaea ) with ericoid mycorrhiza (ERM) and shrub ( Betula nana ) with ectomycorrhiza (ECM) on the properties of Umbric Leptosol of grass meadow in tundra of the Khibiny Mountains has been studied. It is shown that the presence of plants with ERM and ECM causes an increase in the content of labile mineral and organic phosphorus and of extractable organic nitrogen in soil and in the C/N ratio in the microbial biomass and a decrease in the content of nitrates, N-mineralization and nitrification activity, and the C/N and C/P ratios in the extractable organic matter. The increased activity of glucosidase, chitinase, and phosphatase testifies to high activity of exoenzymes of ERM fungi even in soil with high availability of inorganic nitrogen and phosphorus.

An experiment with the enrichment of acid organic-rich mountain-meadow soils (Umbric Leptosols) of alpine ecosystems with mineral nutrients has demonstrated that the contents of organic carbon, total nitrogen, and labile organic compounds are stable and tolerant towards long-term (20 years) application of mineral fertilizers. Only the following direct effects are well pronounced: an increase in the content of inorganic nitrogen and phosphorus after the application of corresponding fertilizers, as well as a rise in pH as a result of liming. Plants are more sensitive indicators of changes in the conditions of nitrogen nutrition. They are characterized by active absorption of additional nitrogen, and the isotopic composition of nitrogen in them becomes heavier. The degree of these effects depends on the initial nitrogen availability. In addition to these direct effects, changes in the nitrogen status of plants also reflect changes in the transformation of nitrogen-containing compounds in soil and in the nitrogen nutrition of plants taking place due to an increased availability of phosphorus and lower acidity under the most phosphorus-depleted and most acid conditions, respectively. These impacts lead to the mobilization of soil organic nitrogen and are likely to reduce the role of mycorrhiza in plant nitrogen nutrition. As a result, a heavier isotopic composition of nitrogen is formed in some plant species.