¹³⁷Cs circulation in forest eco systems on the territory of the Chornobyl exclusion zone (Plant)

Seasonal changes in the content of ¹³⁷Cs in plants of the forest ecosystems on the territory of the Chornobyl exclusion zone have been studied. Samples were selected from 2013 till 2015 once per two weeks. The studied objects were one- and two-year-old needles and branches of the Scots pine (P. sy...

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spelling Zarubina, N.Ye.
2022-08-27T11:23:37Z
2022-08-27T11:23:37Z
2022
¹³⁷Cs circulation in forest eco systems on the territory of the Chornobyl exclusion zone (Plant) / N.Ye. Zarubina // Доповіді Національної академії наук України. — 2022. — № 2. — С. 92-98. — Бібліогр.: 11 назв. — англ.
1025-6415
DOI: doi.org/10.15407/dopovidi2022.02.092
https://nasplib.isofts.kiev.ua/handle/123456789/184961
582.287, 539.16, 546.36
Seasonal changes in the content of ¹³⁷Cs in plants of the forest ecosystems on the territory of the Chornobyl exclusion zone have been studied. Samples were selected from 2013 till 2015 once per two weeks. The studied objects were one- and two-year-old needles and branches of the Scots pine (P. sylvestris). The ¹³⁷Cs content was measured by the gamma spectrometry. In the needles and branches of P. sylvestris, the maximum values of ¹³⁷Cs concentration are noted in the summer. The minimum values of ¹³⁷Cs content in the studied organs of P. sylvestris are characteristic of the autumn-winter period. Probably, the annual fluctuations in the content of this radionuclide in various organs of the studied plants are a consequence of the existence of the constant circulation of ¹³⁷Cs in the forest ecosystems, as a result of which this radionuclide not only gets from the soil into P. sylvestris, but is also excreted from its living tissues.
Досліджено сезонні зміни вмісту ¹³⁷Cs у рослинах лісових екосистем на території Чорнобильської зони відчуження. Зразки відбиралися у 2013, 2014 та 2015 рр. із періодичністю один раз на два тижні. Досліджено одно- та дворічні хвоя і пагони сосни звичайної (P. sylvestris). Вміст ¹³⁷Cs визначено за допомогою методів гамма-спектрометрії. У хвої та пагонах P. sylvestris максимальні концентрації цього радіонукліда відмічено влітку. Мінімальні значення питомої активності ¹³⁷Cs у досліджених органах сосни звичайної є характерними для осені та зими. Ймовірно, щорічні коливання вмісту цього радіонукліда в різних органах P. sylvestris є наслідком існування постійного кругообігу ¹³⁷Cs у лісових екосистемах, під час якого цей радіонуклід не тільки потрапляє з ґрунту до рослини, але й виводиться з її живих тканин.
This work was financed by the STCU 5954 project.
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Видавничий дім "Академперіодика" НАН України
Доповіді НАН України
Екологія
¹³⁷Cs circulation in forest eco systems on the territory of the Chornobyl exclusion zone (Plant)
Циркуляція ¹³⁷Cs у лісових екосистемах на території Чорнобильської зони відчуження (рослина)
Article
published earlier
institution Digital Library of Periodicals of National Academy of Sciences of Ukraine
collection DSpace DC
title ¹³⁷Cs circulation in forest eco systems on the territory of the Chornobyl exclusion zone (Plant)
spellingShingle ¹³⁷Cs circulation in forest eco systems on the territory of the Chornobyl exclusion zone (Plant)
Zarubina, N.Ye.
Екологія
title_short ¹³⁷Cs circulation in forest eco systems on the territory of the Chornobyl exclusion zone (Plant)
title_full ¹³⁷Cs circulation in forest eco systems on the territory of the Chornobyl exclusion zone (Plant)
title_fullStr ¹³⁷Cs circulation in forest eco systems on the territory of the Chornobyl exclusion zone (Plant)
title_full_unstemmed ¹³⁷Cs circulation in forest eco systems on the territory of the Chornobyl exclusion zone (Plant)
title_sort ¹³⁷cs circulation in forest eco systems on the territory of the chornobyl exclusion zone (plant)
author Zarubina, N.Ye.
author_facet Zarubina, N.Ye.
topic Екологія
topic_facet Екологія
publishDate 2022
language English
container_title Доповіді НАН України
publisher Видавничий дім "Академперіодика" НАН України
format Article
title_alt Циркуляція ¹³⁷Cs у лісових екосистемах на території Чорнобильської зони відчуження (рослина)
description Seasonal changes in the content of ¹³⁷Cs in plants of the forest ecosystems on the territory of the Chornobyl exclusion zone have been studied. Samples were selected from 2013 till 2015 once per two weeks. The studied objects were one- and two-year-old needles and branches of the Scots pine (P. sylvestris). The ¹³⁷Cs content was measured by the gamma spectrometry. In the needles and branches of P. sylvestris, the maximum values of ¹³⁷Cs concentration are noted in the summer. The minimum values of ¹³⁷Cs content in the studied organs of P. sylvestris are characteristic of the autumn-winter period. Probably, the annual fluctuations in the content of this radionuclide in various organs of the studied plants are a consequence of the existence of the constant circulation of ¹³⁷Cs in the forest ecosystems, as a result of which this radionuclide not only gets from the soil into P. sylvestris, but is also excreted from its living tissues. Досліджено сезонні зміни вмісту ¹³⁷Cs у рослинах лісових екосистем на території Чорнобильської зони відчуження. Зразки відбиралися у 2013, 2014 та 2015 рр. із періодичністю один раз на два тижні. Досліджено одно- та дворічні хвоя і пагони сосни звичайної (P. sylvestris). Вміст ¹³⁷Cs визначено за допомогою методів гамма-спектрометрії. У хвої та пагонах P. sylvestris максимальні концентрації цього радіонукліда відмічено влітку. Мінімальні значення питомої активності ¹³⁷Cs у досліджених органах сосни звичайної є характерними для осені та зими. Ймовірно, щорічні коливання вмісту цього радіонукліда в різних органах P. sylvestris є наслідком існування постійного кругообігу ¹³⁷Cs у лісових екосистемах, під час якого цей радіонуклід не тільки потрапляє з ґрунту до рослини, але й виводиться з її живих тканин.
issn 1025-6415
url https://nasplib.isofts.kiev.ua/handle/123456789/184961
citation_txt ¹³⁷Cs circulation in forest eco systems on the territory of the Chornobyl exclusion zone (Plant) / N.Ye. Zarubina // Доповіді Національної академії наук України. — 2022. — № 2. — С. 92-98. — Бібліогр.: 11 назв. — англ.
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fulltext 92 ОПОВІДІ НАЦІОНАЛЬНОЇ АКАДЕМІЇ НАУК УКРАЇНИ ISSN 1025-6415. Dopov. Nac. akad. nauk Ukr. 2022. № 2: 92—98 ЕКОЛОГІЯ ECOLOGY Ц и т у в а н н я: Zarubina N.Ye. 137Cs circulation in forest eco sys tems on the territory of the Chornobyl ex clu sion zone (Plant). Допов. Нац. акад. наук Укр. 2022. № 2. С. 92—98. https://doi.org/10.15407/dopovidi2022.02.092 https://doi.org/10.15407/dopovidi2022.02.092 UDC 582.287, 539.16, 546.36 N.Ye. Zarubina, https://orcid.org/0000-0003-1630-7667 Institute for Nuclear Research of the NAS of Ukraine, Kyiv E-mail: nataliia.zarubina@gmail.com, zarubina@kinr.kiev.ua 137Cs circulation in forest ecosystems on the territory of the Chornobyl exclusion zone (Plant) Presented by Academician of the NAS of Ukraine V.I. Slisenko Seasonal changes in the content of 137Cs in plants of the forest ecosystems on the territory of the Chornobyl exclu- sion zone have been studied. Samples were selected from 2013 till 2015 once per two weeks. The studied objects were one- and two-year-old needles and branches of the Scots pine (P. sylvestris). The 137Cs content was measured by the gamma spectrometry. In the needles and branches of P. sylvestris, the maximum values of 137Cs concentration are noted in the summer. The minimum values of 137Cs content in the studied organs of P. sylvestris are characteristic of the autumn-winter period. Probably, the annual fluctuations in the content of this radionuclide in various organs of the studied plants are a consequence of the existence of the constant circulation of 137Cs in the forest ecosystems, as a result of which this radionuclide not only gets from the soil into P. sylvestris, but is also excreted from its living tissues. Keywords: 137Cs, circulation, Chornobyl NPP, plant, forest ecosystems. Studies of the dynamics and redistribution of 137Cs along the vertical profile of soils, forest lay- ers, fungi, and other objects indicate a gradual decrease in the levels of the specific activity of this radionuclide in various objects of the forest ecosystems over time after the accident. The results of studies of the seasonal dynamics of the 137Cs content are not so unambiguous and often contain contradictory data. In [1], it was indicated that there is an internal cycle of the annual seasonal redistribution of 137Cs between the aboveground and underground phytomasses on the territory of the Ukrainian Polissia. By the beginning of the growing season in May, the content of this radionuclide in the aboveground phytomass is lower than in June. By the end of the growing season, 137Cs is trans- ferred from the aboveground part of the mosses to the underground one. Studies [2] carried out during the growing season on the territory of Ukrainian Polissia made it possible to assert that the contents of 137Cs in plants of different species (blueberry, lingonberry, male fern, and bracken) are subject to seasonal changes characteristic of each species and phy sio- logical features associated with them. 93ISSN 1025-6415. Допов. Нац. акад. наук Укр. 2022. № 2 137Cs circulation in forest ecosystems on the territory of the Chornobyl exclusion zone (Plant) In [3], it was indicated that, in blueberries on the territory of the Ukrainian Polissia, the maximum content of 137Cs was found in the ground phytomass during the period of mass fruit- ing in July. It was also noticed that beginning from March, the specific activity of this radio- nuclide in the terrestrial phytomass almost steadily increases. After the berries ripen, there is an intensive outflow of 137Cs from the aboveground phytomass to the rhizomes till October- November. In fungi-macromycetes of the forest ecosystems on the territory of the Ukrainian Polissia, the seasonal dynamics of the 137Cs content was recorded — the maximum levels of specific acti- vity of this radionuclide are registered in their fruit bodies in October, the minimum levels are found in June [4]. The authors of [5] determined that the levels of the specific activity of 137Cs in the above- ground phytomass of the forest ecosystems in winter increases by 10 times compared to that of May. In [6], it is indicated that the seasonal dynamics of 137Cs accumulation in the growth of Scots pine (a pollution indicating organ of the standing timber as a whole) is characterized by an almost unidirectional change in the 137Cs concentration downward from spring to autumn. In [7], seasonal changes in the assimilation apparatus of the Scots pine are taken into consi- deration. The author showed that sharp decreases in the 137Cs concentration (by 2-3 times) from spring to autumn are characteristic of physiologically active needles of the current year. The sta- bilization begins around September. The same patterns were observed for two-year-old needles. But, at the same time, no clearly marked changes in the content of this radionuclide in two- and three-year-old needles are observed during the growing season. The aim of the work was to study the seasonal variations in the content of 137Cs in various objects of the forest ecosystems during the calendar year at a remote stage of the development of the accidental situation. The changes in the concentration of this radionuclide in the plant (Scotch pine) of the forest ecosystems in the exclusion zone of the Chornobyl nuclear power plant are discussed in. what follows. Materials and methods. Sampling sites. We studied the 137Cs circulation in different organs of the Scotch pine on the territory of the exclusion zone of Chornobyl NPP (ChNPP). The sam- pling sites are located at different distances and directions from Chornobyl NPP (Fig. 1). The sampling sites within the Chornobyl exclusion zone are located at the following coor- dinates: Dytiatky (30˚07’21.83’’E, 51˚07’13.37’’N), Paryshiv (51˚17’57.54’’E, 30˚18’17.43’’N), Leliv (30˚09’36.63’’E, 51˚19’19.74’’N). The sampling was carried out during 3 years between 2013 and 2015. The size of the sampling sites is approximately 10 m by 10 m. The soil at the sampling sites belong to the sod-podzolic type. The Scots pine (Pinus sylvestris L.) prevails among the wood vegetation on the territory of the studied sampling sites. Sampling of organs of P. sylvestris. Samples were taken once every two weeks. The objects of research were one- and two-year needles and branches of P. sylvestris. P. sylvestris was used as the main research object for several reasons: this species is the predominant species of the forested areas on the territory of the Chorno- byl exclusion zone — 91565.0 hectares (pine forests occupy almost 60 % of the forested area) [8]; sampling of photosynthesis’ organs of this plant species is available throughout the year; the ability to carry out the simultaneous sampling of needles and branches of different ages. 94 ISSN 1025-6415. Dopov. Nac. akad. nauk Ukr. 2022. № 2 N.Ye. Zarubina To study the dynamics of the 137Cs content, samples of branches with needles were taken us- ing a pruner without felling a tree. Each sampling was taken from 7 out of the specified 15 model trees. The sample consisted of 15 annual and 15 two-year-old branches with needles. Under laboratory conditions, the needles were separated from the branches, and the resulting 4 samples (one- and two-year-old needles and branches) were dried separately at room tempera- ture for 1-1.5 months. The obtained samples after the drying were ground using a laboratory mill and placed in dis- posable calibrated plastic dishes for the following gamma-spectrometric studies [9]. Radiometry. 137Cs specific activity measurements were performed employing a CANBERRA gam- ma-spectrometric unit based on the coaxial high-purity HPGe semiconductor detector, model GC6020. The detection unit was covered with 100-mm lead protection allowing effective measure- ments of samples with comparatively low radionuclide specific activity. The measurement time was from 600 to 14,400 seconds depending on the specific activity of radionuclides. The measurement errors of this series of samples did not exceed 10 % and, as a rule, were within the limits of 3-5 % of the radionuclide activity. When carrying on the research of the content of radiocaesium (137Cs with a half-life of about 30 years in this work) in the same object, it is necessary to exclude the influence of the physical decay of this element in it. The recalculation of the results was carried out on the “zero” date of the event (for 1986/04/26) according to the formula of radioactive decay. The data obtained in this way excluded the influence of that part of the radionuclide that had decayed on the date of each specific sampling. In the study, the values of 137Cs activity concentrations in different organs of P. sylvestris are shown, being recalculated using the radioactive decay formula. In this article, the 137Cs specific activity in samples (dry weight) is given in Bq/kg. Fig. 1. The sampling sites within the Chornobyl exclusion zone: 1 — Leliv; 2 — Paryshiv; 3 — Dytiatky 95ISSN 1025-6415. Допов. Нац. акад. наук Укр. 2022. № 2 137Cs circulation in forest ecosystems on the territory of the Chornobyl exclusion zone (Plant) Results and discussion. As a result of the studies, it was found that the content of 137Cs in annual needles is, on average, higher than in other studied organs of P. sylvestris at all sampling sites. The lowest levels of specific activity of 137Cs are characteristic of 2-year-old branches. An exception is the Paryshiv sampling site, where the content of 137Cs in this organ is slightly higher than in 2-year-old needles (Table 1). Needles and branches show seasonal changes in 137Cs specific activity levels, unlike soil (Fig. 2-4). The maximum content of this radionuclide is typical of annual needles and branches from the beginning of the growing season (from May till autumn). By the end of the growing season, the concentration of 137Cs in young needles and branches in some years decreases by almost an order of magnitude smaller. Increases in the levels of specific activity of 137Cs during the season of vegetation in needles and branches are observed during the second year of their lives, which correlate well with similar changes in the content of this radionuclide in annual needles and branches (Table 2). An increase in the levels of the specific activity of 137Cs is observed with the onset of the in- tensive growth of young needles and branches. During this period, the plant requires significantly larger amounts of nutrients and water. Additional amounts of radionuclide may come with water, which leads to an increase in the content of 137Cs in growing needles and branches. The pine is an obligate mycotroph. Probably, the indicated additional intake of 137Cs into the plant during the period of intensive growth of young branches and needles is associated not only with its intake in the dissolved form with water, but is also the result of the existing symbiosis: an additional amount of 137Cs can come from the long-term depot of this radionuclide — mushroom mycelium at the high pumping of water through the Gartig network into the root system of the plant and further into the growing organs. The annual decrease in the 137Cs content in all the studied organs of P. sylvestris by autumn may indicate the existence of the circulation of this radionuclide in forest ecosystems in the soil–plant chain. Thus, 137Cs enters into the soil not only with litter, but also its outflow from living plant tis- sues can occur. The literature indicates that potassium constantly circulates in plants [9]. It can be assumed that cesium, being a chemical analog of potassium, can also constantly circulate in the plant. Peaks and drops in the specific activity of 137Cs in different organs of P. sylvestris, not related in time to the growing season, can be caused by short-term changes in weather conditions. The latter can cause the drying out or moistening of the forest litter, which is reflected in changes in the number of soil microflora and active mycelium of fungi, as well as in the intensity of their vital Table 1. Average contents of 137Cs in various organs of P. sylvestris on the territory of sampling sites from 2013 till 2015, Bq/kg dry weight Organ Leliv Paryshiv Dytiatky 1st needles 811 ± 587 194 ± 160 1292 ± 582 1st branches 531 ± 418 142 ± 103 871 ± 580 2nd needles 280 ± 184 75 ± 49 464 ± 190 2nd branches 258 ± 142 80 ± 41 374 ± 165 Table 2. Spearman correlation coefficients between the contents of 137Cs in different organs of P. sylvetsris on the territory of sampling sites Organ Leliv Paryshiv Dytiatky 1st needles – 1st branches 0.888 0.852 0.828 1st needles – 2nd needles 0.821 0.661 0.762 1st needles – 2nd branches 0.807 0.665 0.653 1st branches – 2nd needles 0.736 0.642 0.620 1st branches – 2nd branches 0.782 0.777 0.705 2nd needles – 2nd branches 0.847 0.681 0.680 96 ISSN 1025-6415. Dopov. Nac. akad. nauk Ukr. 2022. № 2 N.Ye. Zarubina Fig. 2. Specific activity of 137Cs in different organs of P. sylvestris, sampling site Leliv, Bq/kg dry weight Fig. 3. Specific activity of 137Cs in different organs of P. sylvestris, sampling site Paryshiv, Bq/kg dry weight Fig. 4. Specific activity of 137Cs in different organs of P. sylvestris, sampling site Dytiatky, Bq/kg dry weight 97ISSN 1025-6415. Допов. Нац. акад. наук Укр. 2022. № 2 137Cs circulation in forest ecosystems on the territory of the Chornobyl exclusion zone (Plant) activity. This, in turn, can lead to abrupt changes in the value of the specific activity of 137Cs in various organs of the Scots pine [10]. As a result of the executed studies, an abnormally high content of 137Cs in the pine needles and branches at the Dytiatky sampling site was detected (see Fig. 4 and Table 1). The relatively low content of this radionuclide in the soil of this sampling site cannot be the cause for the no- ticed phenomenon [11]. The specific activity of 137Cs in the pine organs at this sampling site is approximately 1.5 times higher than at the Leliv sampling site (10-km zone) and 2 times higher than at the Paryshiv sampling site. The high content of 137Cs in the needles and branches may be due to the structural features of the forest litter at this sampling site. The thickness of the litter at the Dytiatky sampling site differs significantly from the thickness of the litter at other sampling sites. If, at the Leliv and Paryshiv sampling sites, the average thickness of the soil layer A0f + A0h is 7 cm, at the Dytiatky sampling site, it is only 1.5 cm. The low volume of the litter layer contains a smaller amount of soil biota and fungi, which are a barrier to the entry of 137Cs into the plant. This, probably, leads to the relatively high 137Cs content in the pine needles and branches at the Dytiatky sampling site. Conclusions. The levels of the specific activity of 137Cs in needles and branches of P. sylvestris vary depending on the season. This process occurs almost simultaneously for one- and two-year- old branches and needles. The maximum values of the 137Cs content in the studied organs of P. sylvestris are observed in summer. From the beginning of autumn till the end of the year, slight spikes in the values of the 137Cs content are observed against the general background of low con- centrations of this radionuclide. Based on the data obtained, it can be argued that the 137Cs content in the needles and branch- es of the Scots pine is not a constant value, but is subjected to seasonal changes. The redistribu- tion of this radionuclide in forest ecosystems has a complex multidirectional character. Probably, in forest ecosystems, there is a constant circulation of 137Cs in the soil-plant chain. This work was financed by the STCU 5954 project. REFERENCES 1. Orlov, O. O. & Dolin, V. V. (2010). Biogeochemistry of 137Cs for forest-swamp ecosystems of the Ukrainian Polissia. Kyiv: Naukova Dumka (in Ukrainian). 2. Grabovskyi, V. & Dzendzelyuk, O. (2012). Seasonal changes of 137Cs content in some medical herbs and berry plants from Western Ukraine. Visnyk of the Lviv University. Ser. Biol., Iss. 58, pp. 175-184 (in Ukrainian). 3. Krasnov, V. P. & Orlov, A. A. (2004). Radioecology of berry plants. Zhytomyr: Volyn (in Ukrainian). 4. Zarubina, N. (2016). The influence of biotic and abiotic factors on 137Cs accumulation in higher fungi after the accident at Chornobyl NPP. J. Environ. Radioact., 161, pp. 66-72. https://doi.org/10.1016/j.jenvrad.2015.11.014 5. Mukhamedshin, K. D., Chilimov, A. I., Bezuglov, V. K. & Snytkin, G. V. (2000). Certification of forest resources based on radiation characteristics, as the basis for obtaining normative-clean forestry products in the territory contaminated with radionuclides. In Questions of forest radioecology (pp. 7-46). Moscow: MGUL (in Russian). 6. Shcheglov, A. I. (1999). Biogeochemistry of technogenic radionuclides in forest ecosystems. Moscow: Nauka (in Russian). 7. Perevolotsky, A. N. (2006). Distribution of 137Cs and 90Sr in forest biogeocenoses. Gomel: RRUE “Institute of Radiology” (in Russian). 8. Project of organization and development of forestry of the State specialized enterprise “Northern Pushcha”. (2017). Irpin: Ukrainian State Project Forest Management Production Association (in Ukrainian). 98 ISSN 1025-6415. Dopov. Nac. akad. nauk Ukr. 2022. № 2 N.Ye. Zarubina 9. Zarubina, N. Ye. (2019). 137Cs and 40K in the needles and branches of scotch pine (Pinus sylvetris L.) on the territory of Chornobyl exclusion zone. Nucl. Phys. At. Energy, 20, No. 1, pp. 51-59 (in Russian). https://doi.org/10.15407/jnpae2019.01.051 10. Zarubina, N. Ye. & Zarubin, O. L. (2018). Seasonal variation in the content of 137Cs in different objects of forest ecosystems in Chornobyl exclusion zone. Nucl. Phys. At. Energy, 19, No. 1, pp. 48-55 (in Russian). https://doi.org/10.15407/jnpae2018.01.048 11. Zarubina, N. Ye. (2020). 137Cs circulation in forest ecosystems on the territory of the Chernobyl exclusion zone (Soil). Dopov. Nac. akad. nauk Ukr., No. 10, pp. 85-92. https://doi.org/10.15407/dopovidi2020.10.085 Received 18.11.2021 Н.Є. Зарубіна, https://orcid.org/0000-0003-1630-7667 Інститут ядерних досліджень НАН України, Київ E-mail: nataliia.zarubina@gmail.com, zarubina@kinr.kiev.ua ЦИРКУЛЯЦІЯ 137Cs У ЛІСОВИХ ЕКОСИСТЕМАХ НА ТЕРИТОРІЇ ЧОРНОБИЛЬСЬКОЇ ЗОНИ ВІДЧУЖЕННЯ (РОСЛИНА) Досліджено сезонні зміни вмісту 137Cs у рослинах лісових екосистем на території Чорнобильської зони відчуження. Зразки відбиралися у 2013, 2014 та 2015 рр. із періодичністю один раз на два тижні. Дослідже- но одно- та дворічні хвоя і пагони сосни звичайної (P. sylvestris). Вміст 137Cs визначено за допомогою мето- дів гамма-спектрометрії. У хвої та пагонах P. sylvestris максимальні концентрації цього радіонукліда від- мічено влітку. Мінімальні значення питомої активності 137Cs у досліджених органах сосни звичайної є характерними для осені та зими. Ймовірно, щорічні коливання вмісту цього радіонукліда в різних органах P. sylvestris є наслідком існування постійного кругообігу 137Cs у лісових екосистемах, під час якого цей ра- діонуклід не тільки потрапляє з ґрунту до рослини, але й виводиться з її живих тканин. Ключові слова: 137Cs, циркуляція, Чорнобильська АЕС, рослина, лісові екосистеми.