Reproduction in plants of grass and subshrub layer as a factor of the forest ecosystem stabilization

Abstract

Reproduction in a broad sense is the process by which female parents generate some or other germs (diasporas) able to form new individuals that are genetically similar to the female parents. The two main types of reproduction are found in forest grasses and subshrubs: seed (or by spores in spore-bearing plants) and vegetative. The establishment of features of plan reproduction of grass and subshrub layer is an important scientific issue in the context of the preservation and restoration of forest ecosystems, because plants of grass and subshrub layer have a significant impact on the initial stages of natural regeneration of plants of the first layer. Some features of reproduction of plants of different layers of forest ecosystems – from grass to woody – have been studied on the basis of our own observations and literature data. The observations were carried out on the territory of Desnyansko-Starogutsky National Nature Park and the adjacent territories. Forest ecosystems of the north-east of Ukraine have been in active use for a long time. Currently, these forests, in part, have obtained conservation status, and the volume of logging has been sharply reduced. Therefore, the majority of forests are characterized by the progressive succession, during which the proportion of plant silvan species increases and, consequently, the number of motile vegetative plant species increases in the lower layers of forest. The eight plant species of grass and subshrub layer, such as Aegopodium podagraria L., Asarum europaeum L., Calluna vulgaris (L.) Hull, Carex pilosa Scop., Molinia caerulea (L.) Moench., Stellaria holostea L. Vaccinium myrtillus L., Vaccinium vitis-idaea L., have been selected as models. It is established that the capacity for vegetative propagation and clone formation is an important feature of reproduction of most forest grasses. The key parameters of generative reproduction of clone forming plants of grass and subshrub layer and their dependence on the ecological and coenotic factors have been shown as well. To establish the level of reproduction the following morphometric parameters were determined: weight of generative organs (g), number of generative shoots (pieces), reproductive effort (%), share of generative individuals in the population (%). In case of generative reproduction, an important biological characteristic is the so-called reproductive effort, which characterizes the contribution of organic matters and energy in the reproductive process. It is typically shown as the percentage of phytomass of the reproductive structures of the total phytomass. In general, generativity of the investigated plants of grass and subshrub layer was determined by the ecological and cenotic conditions, and therefore varied from association to association. Forest grasses and subshrubs, in turn, are an important factor for regeneration of all types of woody species in forest ecosystems. Depending on the composition and abundance of plants of grass and subshrub layer, the number of seedlings and little undergrowth of all woody species of trees is reduced in varying degrees, and the indicators of their growth are getting worse. The impact of the live ground cover on undergrowth of woody species is ultimately determined by the specificity of the ecological and coenotic situation in the areas of regeneration and the specific ecological and phytocoenotic properties of undergrowth of certain woody species. The main environmental problems of recreational zones from the perspective of possibilities of natural regeneration of woody species are the effect of mechanical actions on the soil. Grass and subshrub layer as a sensitive indicator of the increase in anthropogenic load is the first to undergo such transformation in recreational forests. Under its influence its species composition varies and is depleted, distribution of certain species as well as their phytomass and projective cover decrease. Many forest species disappear from the cover, and weeds begin to grow. Protection of forests as holistic ecosystems is an important issue, being developed during the XX century, and not having lost its significance even today. The main directions of its solution are connected with the development of the ecological network of Ukraine and the proper use of all forest resources.