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Due to the widespread use of products based on silver nanoparticles, the risk of contamination of the soil cover and surface water increases, since an element in this form can leach out of the material. The amount of silver emissions into the environment is increasing every year. There is growing evidence of silver toxicity for living organisms of not only aquatic, but also terrestrial ecosystems. Silver, accumulating in soil in large quantities, like other heavy metals, can have a toxic effect on the physical, chemical and biological properties of the soil.High doses of the element can have a significant effect on the biological properties and ecological condition of soils. The study of enzyme activity can be used to identify major changes in the soil under the influence of silver. In this regard, it is relevant to study the effect of silver on catalase activity, since this enzyme is an indicator of the potential biological activity of the soil and reflects the intensity of mineralization processes in it. The aim of the work was to study the effect of silver pollution on the activity of soil catalase most characteristic of the southern regions of Russia. The object of the study identified soils characteristic of southern Russia: ordinary chernozems, seropesks and brown forest soils. For model studies, soil samples were taken from the upper arable layer (0‑10 cm), since silver accumulates in the surface soil layers. Silver pollution was modeled in a laboratory. Used silver nitrate at a concentration of 1 mg / kg, 10 mg / kg and 100 mg / kg, the experiment was 3 times biological repetition. The choice of biological indicators is due to the fact that oxidoreductases are most sensitive to chemical pollution among enzymes. This enzyme is an indicator of the biological activity of the soil and reflects the intensity of the mineralization processes in it. Laboratory and analytical studies were carried out using generally accepted methods in biology, soil science and ecology. Catalase activity was determined by the volumetric method according to A.Sh. Galstyan. As a result of the study of the effect of silver on three types of soils, the most characteristic of the southern regions of Russia, a decrease in catalase activity was noted. The degree of reduction of this indicator depended on the dose of the element introduced into the soil. The degree of resistance to silver contamination has the following sequence: common chernozem> sulfur sands ≥ brown forest soil. This is probably due to the light particle size distribution of sulfur sand and the acidic reaction of the environment of brown forest soils (pH = 5.8), as well as a low content of organic matter (1.8 % and 2.3 %, respectively), which contributes to high mobility, and therefore and high ecotoxicity of silver in these soils. A decrease in the activity of catalase of ordinary chernozem was observed for 90 days. At 1 UDC on the 30th and 90th day of the experiment, the same decrease in the studied parameter was observed. A similar pattern was observed at 10 UDC at the same experimental time. At 100 UDC (100 mg / kg) on the 90th day after contamination, a tendency toward restoration of catalase activity was observed, however, control values before silver contamination were not achieved. Chernozems have a high number of microorganisms and their high activity, and pollution tolerance mechanisms provide detoxification of soils from exposure to silver.

Ngoc Linh mountain range with Ngoc Linh peak of 2598m.a.s.l is an important part of forest ecosystems in Central – Highlands, Vietnam. Located on the complex terrain with stable and long-term geological components, the plant communities here contain the diversity and originality of the high mountains and contiguous areas between Central and Central Highlands Vietnam. The study area covers 65571 hectares, of which Ngoc Linh Nature Reserve covers about 40500 hectares, spread over medium and high mountain terrain. Strongly divided terrain has created the richness, diversity, and originality of ecosystems, especially the structure of natural vegetation. The article presents characteristics and differentiation of forest plantations in Ngoc Linh mountain area; study diversity, and conservation value of regional plant diversity resources; analyzing the characteristics and relationships of plants with geographical factors, especially the rules of elevation, slope, terrain direction, soil and drainage capacity of forest land. Comparison of similarities and differences with some other areas of the Central Highlands, especially the communities with the participation of coniferous plants. To implement the scientific content, various methods have been used. Among them are the main methods: Mapping method and Geographic Information Systems, Field survey methods and Phytogeography (Plant Geography) methods. The study results recorded 1128 species of vascular plants, belong to 627 genera, 175 families, 59 orders, 10 classes, 6 divisions. The flora of Ngoc Linh mountainous area fully converges the vascular plants of the plants in Vietnam, in which the species mainly focus on Magnoliophyta. This is the most diverse division with a total of 145 families, 571 genera and 1032 species, accounting for 82,39 % of families, 91,07 % of genera, and 91,48 % of species. The comparison results show that the proportion between sectors in the plants of Ngoc Linh and the plants of Vietnam has the same structure, with quite similar proportions of dominant species group. Accordingly, the absolute advantage of the Magnoliophyta is from 91.48 % and 92.62 % respectively. 80 rare and precious species have been identified in the IUCN Red List and Vietnam’s Red Data Book 2007. There are 189 endemic species of 135 genera of 66 families. In which there are 107 endemic species of Central Vietnam, the rest belong to Vietnam endemic. Some endemic species with high conservation significance is: Panax vietnamense, P. dalatensis, Quercus langbianensis. The rules of distribution according to elevation are shown in the structure of plant communities through species composition and canopy structure of the forest. Accordingly, plant communities have a high diversity with complex structures, including 3–4 layers. At 900 m.a.s.l elevation, in mixed forests, broadleaf trees form multi-dominant and diverse species. From 1000–1500 m.a.s.l, on the mountainside terrain, the dominant vegetation with P. kesiya in the emergent layer. High diversity in forest structure clearly manifests at 2000–2300 m.a.s.l. Plants are strongly differentiated; some places are multi-dominant, and some places are dominant with P. dalatensis. The most diversity of plants is concentrated at an elevation of 2000–2300 m.a.s.l and the number of the most canopy spread from 1500–2000 m.a.s.l. Gymnosperms, especially P. kesiya and P. dalatensis, participate in single dominant and codominance roles in mixed forest communities. There are differences in the distribution of major conifer species forming plant communities in Ngoc Linh mountain range compared to Chu Yang Sin National Park and Bidoup – Nui Ba National Park in Central and South – Central Highlands. Accordingly, in Ngoc Linh, P. dalatensis has a wider distribution area, higher dominance with a clear role in the formation of plant communities at elevations above 2000 m.a.s.l.