Bandurko V.V., Ph.D. Safonov A.I.
Donetsk National University , Ukraine
REALIZATIONOFSTRATEGICPOTENTIAL
ANDSTRATEGIES
OFSPECIES OF STEPPE PHYTOCENOSESSURVIVAL
The research of some ecological questions (ecological and cenotic niches, potentials; steadiness and dynamism of ecosystems; ontogenetic and phytocenologic strategy) is important for balanced development of typical ecosystems of Ukraine .
Modern economic activity of man leaves its mark on quantitative and qualitative state of biological diversity. The ecosystems with steppe types of vegetation are considerably vulnerable. Their steady exploitation led to radical changes in biotic structure that couldn't but affected their diversity
Steppe type of vegetation in our country is regarded as priority protected units as it recovers very slowly when superficial layer of soil is disturbed, can change ontogenetic and phytocenologic strategy, and it quickly reduces its territories under anthropogenic pressure.
Object of researches was a species of genus Stipa L. and their populations. The species of genus Stipa are ediphicators , often being dominants and indicators of steppe ecosystems, systems of disturbed vegetable cover and evaluation of anthropogenic pressure level onto natural systems. They play an integral role in normal functioning of the unique fertile steppes of Donbass .
Methods of research: field geobotanic (reconnaissance and itinerary, detail and itinerary and stationary), populational , ecological, morphological and methods of statistical processing of results.
The research was conducted on the territory of the RLP " Kleban - Byk " ( Kostyantynivskyi district of the Donetsk region in Ukraine ). The overall territory of the experimental areas made 273 m 2 . As the species of genus Stipa L. are in The Red Book of Ukraine, the research was conducted at the same areas with minimal removal of individuals from the population.
As the result of the research aiming at investigation of the list of species of Stipa populations, we identified 13 species of Stipa L.
It is stated that in spite of homogeneity of growing conditions of Stipa, it is represented by more than forty stable ecological states – econiches , that have different level of overlap between them and form five ecological tendency rows (according to natural changes of ecological indices).
Econiches that are characterized by average value of factors are also typical with the smallest hiatus between adjacent niches. An indicator of such biotops is S. zalesskіі and partially S. lessіngіana , S . dasyphylla , S. tіrsa .
The biggest hiatus belongs to econiches of S. borystenіca that are very specific. For other species, especially such as S. pennata and S. pulcherrima ecological amplitude, first of all of humidity and carbon soils, is realized on a whole range of econiches , sometimes embracing a large diapason of factors. These very factors condition differentiation of ecological niches, as they are limiting even with their value.
Ecological space, even being changeable, is organized by the states of different energetic level, including high one, such as ecological niches that are distinguished by discreteness, specificity and mutual dependence of indices of ecological factors.
Thus, amplitude of species tolerance to each factor is realized through participation in ecological niches. And on the contrary, in the absence of the whole range of this or that factor it can be unrealized. But it can serve as certain potential for forming ecological adaptations, which approximately coincides with the available data on Stipa studying of other authors and on other steppe areas of Ukraine .
During formation and differentiation of plant niches we considered biotic transformation of places of growing. Thus, for patients realized niches are formed under the influence of violents which coincides with the scientific publications.
We discovered that each type in an association is able to change its positions in the limits of amplitude of ecological factors depending on its ontogenesis and peculiarities of cenotically conditioned functioning.
We determined that species of Stipa are able to change cardinal points of factors value in multidimensional space of a niche against the background of its ontogenesis and dynamics of conditions. It's especially true for the conditions of increased anthropogenic pressure: direct – trampling down and indirect – changes of chemical-toxicological balance. The species of Stipa survive on the verge of the lowest and the highest thresholds (critical points) of their existence according to all the factors and resources.
The lowest threshold in this case is soil humidity and mineral balance, the highest – temperature factor and light.
Such data are necessary for populations sustainability forecast. We conducted research in different conditions of S. pennata growing. In protected areas S. pennata passes all the stages of development.
With cattle pasture S. pennata ceases being a competitive plant and shows signs of stress-sustainable species.
When analyzing age structure of S. pennata it was determined that under favourable conditions of growing the age structure is normal, generative individuals prevailing.
A clear ecotopic differentiation of ecospaces (" ordinational fields") of agglomeration groups of steppes, formed on the chernozem , was traced. In the cenomorphic structure of the territories under analysis megathermophytes and heliophytes are prevailing. On the particular local background the most determinant for the vegetation structure-forming ecological factors are soil fertility and humidity.
It is proved, that balance ecosystem structure of steppe territories of RLP is defined by progressive need of complete presence of typical phytocenoses , representatives of genus Stipa playing the determinant role.