Причини и следствия экологического замещения сосны в рамках процесса естественного возобновления пристепных боров

Abstract

The processes of natural renewal in coniferous forests growing near steppes are very time and space dynamic and conforming to the laws of nature. The results of our researches carried out in the river basin of the Seversk Donets in 2003-2013 confirm this fact. The splash of renewal wave is observed on the whole territory of the research object and is a reaction in return of pine population concerning the entry to the zone of optimum hydrothermal conditions.As a rule, the shoots and self-sown plants occurring everywhere are followed by renewal wave fading and spatial localization of breeding grounds containing viable rising shoots in the gaps of parent plantation canopy. The results of our researches allow to affirm that probably there is the possibility to observe three process realization versions which are the most widely spread : adaptation to gaps by rising shoots, the marked appropriateness of rising shoots to midday shadow cone and pine substitution by ecologically close species. As a rule, the probability of ecological substitution in the general amount of possible versions is appreciably higher. Our ten year observations concerning rising and young pine shoots allow to suppose that renewal processes take place successfully if pine rising shoots emerged just after fire or when farming ceased on farm lands. In this case cenopopulations of flourishing species fill the „windows“ and are often appropriate to the southern expositions of outward contour in the forest tract where there is no place for the cone of the midday shadow. If there is a time barrier of one and more years between a forest fire or farming ceasing on farm lands and fruiting of parent forest stands, the appropriateness of rising pine shoots tothe cones of midday shadow and “windows” in the parent plantation canopy becomes an inevitable and appropriate occurrence. It is significant that the unshaded part of the gap in the plantation canopy is assimilated actively by cereals and steppe motley grass with ground smallreed (Calamagrostis epigeios Roth) dominating. As a result, beyond the cone of midday shadow pines are substituted by ecologically analogical plants. Finally, if the cenopopulation of ground smallreed was in time to adapt to an ecological niche during a certain period, the abundant fruiting does not leave signs within the probable “windows” of invasion. As a result, even during the years of abundant fruiting in the “windows” of forest stand canopy and in the cleared spaces where smallreed cenopopulation dominates one does not have to reckon on activization of renewal processes. The emerged shoots, self – sown plants and rising shoots die during the first years of their life. While observing the changes of ecological factors in abiotic and biotic order, we can note that the realization of pine forest reproduction potential into the category of self-sown plants and further rising shoots occurs in an appointed succession. So, the version of the successful occurrences progress from the position of renewal process realization as well as a negative version are more than predetermined occurrences. The ecological niche as a complimentary pair concerning the process is a significant condition within the process. In the end it permits to forecast some possible versions to realize the renewal process in coniferous forests growing near steppes.

Досить часто навіть при сприятливому збігу комплексу екологічних чинників спостерігається загасання хвилі відновлення або відбувається локалізація осередків відновлення в просторі. Одній з причин є заміщення сосни на рослини екологічні аналоги в межах існуючих екологічних ниш. На підставі експериментального матеріалу, який було одержано під час досліджень за 2003 – 2013 рр., встановлюються умови успішної реалізації процесу відновлення, а також вказуються причини та особливості процесу заміщення сосни на етапі формування ценопопуляції підросту.

Довольно часто даже при благоприятном сочетании комплекса экологических факторов наблюдается затухание волны возобновления или же локализация очагов возобновления в пространстве. Одной из причин является замещение сосны на растения экологические аналоги в границах существующих ниш. На основании експериментального материала, полученного в течение исследований 2003 – 2013 гг., раскрываются условия успешной реализации процесса возобновления, а также указываются причины и особенности процесса замещения сосны на этапе формирования ценопопуляции подроста