Возможность использования почвенных беспозвоночных для индикации градаций увлажнения аренных лесных экосистем

УДК 592:504.53 + 574.21

OPPORTUNITY OF USING SOIL INVERTEBRATES
FOR GRADATIONS INDICATION OF HUMIDIFICATION EDAPHOTOPES IN SANDY FOREST ECOSYSTEMS

I. M. Loza*, V. V. Brigadirenko**

*Dnipropetrovsk State Agrarian University, Dnipropetrovsk, Ukraine
**Dnipropetrovsk National University, Dnipropetrovsk, Ukraine, E-mail: brigad@ua.fm

Key words: sandy forest ecosystems, soil invertebrates

И. М. Лоза*, В. В. Бригадиренко**

*Днепропетровский государственный аграрный университет, г. Днепропетровск, Украина
**Днепропетровский национальный университет, г. Днепропетровск, Украина,
E-mail: brigad@ua.fm

Ключевые слова: аренные лесные экосистемы, почвенные беспозвоночные

Under conditions of Ukraine’s Steppe on sandy terraces of the rivers in saucer-shaped valleys there are naturally formed unique plant associations, aspen-and-birch separated forest stand. They are adapted for their existence under the conditions of instable water relationships. The investigation of structural and functional organization features of the natural complexes is rather perspective, because it allows upon the basis of received data to form their artificial analogues on the sites which have experienced the underflooding influence by mine waters.

Under such conditions are formed unique psammophyte meadow and wood ecosystems, not characteristic of the Steppe area. In 2002–2005 the authors of this paper investigated arena wood biogeocenoses. Especially interesting was the revelation in the formation of aspen separated forest stands, as a result of a subsidence of the earth surface within the limits of artificial pine plantations on sands. In the center of a small pine-tree forest area there were formed significant depression deepening (with a dimension diameter of 50 meters).

Here the terrestrial surface has lowered into a depth of 2 meters and the landscape had changed considerably. There are two principal reasons of trees destruction on the investigated territory: the first one is an underflooding and a loss of rootlets assemblages as a result of the lack for oxygen. The second one is the inability of plants to realize water and mineral nutrition in connection with sharp fluctuations of the groundwater mineralization.

Changes in the flora structure in such cases are characterized as total-catastrophic successions. The formation of a new ecotope and the establishing of a new ecosystem are carried out under the conditions of a hard disruption of all the ecosystem components.

The research of grassy phytocenoses of technogenic wetlands have allowed to reveal vegetational groupings, which in the ratio of the plant life-form, the structural organization of herbage almost have not any differences from those similar natural. The majority of species that are comprised in such groupings have rather a wide range of tolerance in respect of such leading ecological factors as the fertility (mineralization) of the soil and its humidifying.

With a level of subsoil waters 120 centimeters from the surface and deeper tree assemblages of rootlets get almost the optimal amount of moisture: owing to that the dropout of woody species occurs selectively, due to the weaken and old trees. With a rise of level waters up to
70–80 centimeters there begins a mass destruction of the wood. In the vegetable blanket there occur abrupt changes and there develop mesophilic meadowy elements. Instability in the level of subsoil waters has substantially influenced the vegetation formation of the sandy terrace. Thus, mass pine plantations often have a central tree stem, which died away at a young age; that suggests the underflooding which took place here 30 years ago. Then the hydrological situation has been stabilized, and the trees kept on their growth and development. At that the pine system is regularly in an air hunger, the trees have dry tops of trees, they are died off and replaced intensively by more moisture-loving species of wood, such as aspen and birch.

As a consequence of subsoil waters coming within 3 meters of the surface (including subsidence areas), the soil genesis changes. In the lower part of the soil profile, the abundant moisture activates reduction processes and starves the pine roots of oxygen. In the upper part of soil profile, the litter decomposing processes are intensified and the organic matter content increases. When subsoil waters reach 1.5 meter below the surface, there is abundant moisture in the upper part of the soil profile and the soil regime changes from flushing to exudative. The oxidizing processes take place in the dry summer period in the upper part of topsoil. During rainy periods or after snowmelt the subsoil waters outcrop and form temporary ponds.

On the soils of a new type there form new primitive plant aggregations, which are adapted for an instable hydrological mode. The studying of features in the structural and functional organization of these natural complexes is perspective enough as far as it allows upon the basis of received data to form their artificial analogues on the areas, which have experienced an influence of the underflooding by mine waters.

The purpose of zoological researches was the conclusion of an opportunity to use separate taxonomic groups of ground invertebrates for the indication of humidification. For this purpose it has been researched how unevenly are distributed separate groups of ground invertebrates in various hygrotopes of steppe woods. We have investigated 29 wood ecosystems and 20 taxonomic groups of ground invertebrates, which are most often found in wood ecosystems of Ukraine’s Steppe.

As a result of the researches it is established that optimal conditions for the existence of the majority of investigated ground groups of invertebrates are those of humidifying hygro-mesophytic. The least number of invertebrates is registered under mesoxerophytic conditions. Groups of Formicidae and Hemiptera have the largest population.

As a result of the distribution analysis for dominant taxonomic groups herpetobia, it is established that the population in the majority of groups in separate hygrotopes differs inauthentically in the humidification gradient. Only for small families Scarabaeidae and Noctuidae and group Hemiptera presented by 1–7 species of Fisher criterion value have exceeded critical values for 95 % of the significance level. It testifies a regular change of dominant species inside the majority of considered taxons, and leads to more or less constant values of the average number of separate groups in various hygrotopes.

To formulate authentic conclusions about the distribution of the species (taxonomic or ecological groups of species or values of any characteristic herpetobia) in the gradient of the studied factor, it is necessary to collect invertebrates simultaneously in several dozens of ecosystems. To minimize an error arising because of a significant mobility of herpetobia components, it is necessary to make some consecutive collections in each of the investigated ecosystems, and when carrying out the analysis there should be used the averaged data.

 


Zoocenosis — 2005
 Біорізноманіття та роль зооценозу в природних і антропогенних екосистемах: Матеріали ІІІ Міжнародної наукової конференції. – Д.: Вид-во ДНУ, 2005. – C. 198-200.

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