The content of labile, especially water extractable organic carbon (WEOC) is a sensible indicator of soil organic matter quality. The main objectives of this study were: i) to investigate the profile changes of cold and hot water extractable organic carbon in forest and arable soils; ii) to evaluate the correlation between these labile fractions of soil organic matter and total organic carbon content. The experiments were carried out on a Gleyic Albeluvisol (ABg) in the upper part of Dniester basin, Western Ukraine. The soil samples were taken from 50-cm depth soil profile with 5-cm step. Total organic carbon (TOC), cold water extractable organic carbon (CWEOC) and hot water extractable organic carbon (HWEOC) contents in soil were determined as well as pH (H 2 O) and electrical conductivity of soil:water suspensions. The results of this study showed that in 0-50 cm layer of arable soil TOC content decreased by 32%, CWEOC -by 23% and HWEOC -by 74% compared to forest soil that confirmed a high informative role of HWEOC fraction. The profile changes of WEOC percentage were analysed. They also show that HWEOC is much more informative indicator of soil organic matter quality than CWEOC. The most prominent changes of soil chemical properties, TOC, CWEOC and HWEOC contents in response to deforestation were observed in the top 5-cm soil layer. We suggested this thin soil layer to be defined as soil stress-sensitive zone.

No abstract

Реферат. Щучка антарктическая Desсhampsia antarctica (Poaceae) является важным эдификатором в экосистемах прибрежной Антарктики и оказывает существенное влияние на состав органического вещества почвы. Целью этого исследования является определение состава низкомолекулярных органических соединений в гумусово-дерновом горизонте лептосоли под D. antarctica и зональной серой лесной почвы под D. cespitosa. Необходимость сравнения состава и свойств почв под этими родственными видами растений обусловлена поиском маркеров, свойственных именно антарктическим почвам. В работе применены методы высокоэффективной жидкостной хроматографии для определения фенолов, фенолкарбоновых, фенилкарбоновых гидроксибензойных кислот, кумариновых производных и флавоноидов. Результаты исследований показали, что образцы гумусово-дернового горизонта Нd почвы под D. antarctica и D. cespitosa характеризуются близкими значениями рН (H 2 O), рН (CaCl 2) и удельной электропроводности. Содержание органического углерода в почвах под растениями этих видов также отличается незначительно и изменяется в пределах 101-114 мг•г-1. В исследованных почвах содержится примерно одинаковое количество фенолов и фенолкарбоновых кислот, а также гидроксибензойной кислоты. В то же время в почве под D. cespitosa выявлено на порядок меньше фенилкарбоновых кислот и в 5 раз меньше флавоноидов. Кроме того, обнаруженных в антарктической почве кумариновых производных (около 50 мкг•г-1) под D. cespitosa не было вообще. Учитывая значительную биологическую активность упомянутых выше классов органических веществ, можно сделать вывод, что обнаруженные различия обусловлены не столько условиями среды, сколько особенностями жизненного цикла щучки дернистой, а высокое содержание фенилкарбоновых кислот и кумариновых производных в почве под D. antarctica свидетельствует об особых процессах трансформации органического вещества почвы, требующих дальнейших исследований. Ключевые слова: Desсhampsia antarctica, Desсhampsia cespitosa, низкомолекулярные органические соединения, фенолы, водорастворимое органическое вещество.

The decision making in forestry and choosing the appropriate silvicultural practices are based on the knowledge about forest development. Usually, forest development is described as a cycle or sequence of phases similar to the development cycles of organisms. The information about the development cycle of unmanaged forest ecosystems is applied and adapted to managed stands to refine the managerial approaches and decision making. Moreover, natural forests are more stable and resist pests and diseases better. Thus, knowing the mechanisms that lie behind this self-sustainability could help in forest management. Assigning a patch of a stand a specific development phase makes it possible to evaluate its productivity and make decisions about necessary silvicultural operations. Yet there is no single opinion among scientists about how many phases the forest’s life cycle has, not to mention that different classifications offer different and sometimes even contradictory criteria to define the current forest development phase for a given subplot. The confusion in terminology for stand structures and stand development phases is also an issue to be considered. Additionally, the most popular approaches to assigning forest development phases are compared. A short overview of the algorithms used to define the forest development phases is given. There is a lack of a complex approach in the offered algorithms of assigning a subplot to a certain development phase. In particular, soil properties, as well as belowground biomass, are entirely ignored. It is necessary to develop a more comprehensive and detailed approach to defining forest development phases and arranging the diagnostic criteria in a clear and easy-to-use system that could enhance decision making in forestry. Only a few studies are currently focused on soil properties and belowground biomass in temperate deciduous forests under different development phases. Although there is still little information on this issue, the data are insufficient and/or controversial. Our study offers several possible directions to make the classifications of forest development phases more elaborate by considering the soil and belowground parameters. They include, but are not limited to, the quantity, density, humidity, and acidity of the forest floor, soil respiration, and content of water-extractable organic matter in the soil.

The Antarctic hairgrass (Deschampsia antarctica É. Desv.) is one of two flowering plants native to the Antarctic and therefore it was intensively studied for decades. However, there is still limited information available about the content of biogenic and toxic elements in the leaves of this plant. While being an important component of the Antarctic terrestrial ecosystems, the content of nutrients like K, P, and S in the plants of D. antarctica may significantly affect soil properties, especially in such hot spots like rhizosphere and detritosphere. Moreover, the content of toxic elements and trace metals in particular in the plant is an important criterion to evaluate its indicative role, whether or not D. antarctica may be used as a bio-indicator to monitor the Antarctica environmental state. In this study, we report the preliminary results about the content of K, P, Ca, S, Mg, Na, Si, Fe, Zn, Al, Sr, Mn, Cu, B, Cr, Ba, V, Pb, Cd, and Co in the leaves of D. antarctica from the natural habitats of the maritime Antarctіс. Dry leaves were digested in nitric acid (closed-vessel microwave digestion). Elemental concentration was measured by ICP-OES technique. It was found that differences between the samples taken from one location were far less notable than between samples from different locations. Among the biogenic elements, the content of potassium was the most variable – from 12.2 mg·g-1 on Galindez Island to 28.7 mg·g-1 on the Cape Tuxen (Antarctic Peninsula). The content of trace metals also varied greatly between the samples from different locations. The results of this preliminary study suggest that due to the high content of nutrients, leaves of D. antarctica should be considered as an important precursor of soil organic matter, as well as a possible bioindicator. However, future studies are needed to confirm these preliminary results and hypotheses.