Determining the Natural Establishment Pattern of Quercus Persica Generative Regeneration in Different Site Conditions to Restore Zagros Forests

Recognizing the establishment pattern of natural regeneration to imitate it in reforestation is an important step towards the restoration of Zagros forests. In this regard, the present study was conducted to investigate the status of natural establishment of generative regeneration of Quercus persica in three stands of Dalab protected forests, Ilam province, with different topographic conditions during spring and summer of 2016. In each stand a basic transect was established perpendicularly to the slope in which the regeneration establishment positions including "under the tree crown", "under the shrub", "under the bush", "next to the rock" and "bare space" were selected. For each regeneration establishment position three replications were selected and for each of them a circular permanent plot with area of 15m2was established. In each plot the number of seedlings and their heights were measured. Results showed that most amount of Q. persica regeneration is in north aspect and the height of 1400 m above sea level, under the crown of Q. persica and P. atlantica trees, in northern side of tree crowns and at a distance of the first third of tree crown radius. The lowest amount of oak regeneration depending on site conditions was at under the bushes, next to the rocks and in bare spaces. There was no oak regeneration under the crown of A. cineracens trees. The most density of tall seedlings was at a distance of the third third of tree crown radius and the lowest amount of that was at a distance of first third of tree crown radius. It was concluded that the tree crown has the most important role in seedling establishment and it is nursing in comparison with other regeneration establishment positions in the forest. Given the remarkable establishment of regeneration under the shrubs and bushes, to their effective roles in supporting of seedlings and their growing can be mentioned. Based on the above results, the natural regeneration establishment pattern of oak for restoration of Zagros forests can be proposed.
Extended Abstract
1- Regeneration is a valuable natural process through which plants can be reestablished and this strategy helps plants to sustain and preserve their diversity and genetic identity. Nowadays, natural regeneration in Zagros forests has faced fundamental problems and the regeneration amount of tree and shrub species has reduced quantitatively and qualitatively. Performed seeding in forested areas could not be yet effective contributing to improve the regeneration of these forests. It seems that one of the contributing ways to overcome this problem is to find out how to establish natural regeneration in different site conditions of these forests and to imitate its pattern during seeding in the field. In this regard, it was attempted to investigate some of the effective factors on regeneration such as the site topography and the seedling establishment position under the canopy cover or in uncovered area which are responsive to some needs of the seedling. So, the aim of this study is to investigate the quantitative and qualitative status of Persian oak generative regeneration in different topographic conditions and various regeneration establishment positions and determine its regeneration establishment pattern in Dalab protected forests, Ilam province.
2- In this research, three forest sites were selected in Dalab region of Ilam province based on different site conditions (two northern and southern aspects and two classes of altitude, 1400-1450 m and 1500-1550 m above sea level). In each stand, one basic transect was established perpendicular to the slope and on it the regeneration establishment positions were selected and marked. The regeneration establishment positions were included "under the trees", "under the shrubs", "under the bushes", "next to the rocks" and "bare space". For each regeneration establishment position three replications was considered and for each of them a 15m2circular permanent plot was established. Inside the plots counting the number of seedlings and measuring their heights was done during the spring and summer of 2016. The present study was carried out in an experimental design of split plot. Collecting the data of two seasons spring and summer and their initial analysis, site conditions and regeneration establishment position on the amount of generative regeneration, analysis of data variance was performed by GLM test in SPSS software to study the effect of sampling season,. Also, the amount of regeneration and height of seedlings in different sides of tree crowns and in different parts of the crown with different distances from tree trunk were analyzed by one-way ANOVA.
3- The most amount of Persian oak regeneration was found in the north aspect and height of 1400 m above sea level, under the crown of Persian oak and Wild pistachio trees, in north side of tree crowns and at a distance of first third of tree crown radius. The reason for this referred to the more favorable and cooler microclimate conditions of the northern slopes and the presence of more shadows and moisture in them and also the better micro-climatic conditions under the crown of trees than the other regeneration establishment positions and the more favorable and cooler conditions of the northern side of their crowns. The least amount of regeneration depending on site conditions was under the bushes, next to the rocks and in bare space and under the crown of maple trees was not found oak regeneration. This result suggests that, despite the light demanding nature of the Persian oak species, seedlings of this species need some shade in the early ages and should be sheltered by seed trees. The most density of tall seedlings was at a distance of third third of tree crown radius which is due to the light demanding of oak species that gradually with growing of its seedlings their optical needs is increased.
4- In all studied cases, the tree crown has the most important role in seedling establishment and its nursing compared to the other regeneration establishment positions in the forest. Also, given the remarkable frequency of regeneration under shrubs and bushes after the option of under the tree crowns, it can be mentioned to the effective role of these biological agents in supporting the seedlings, growing and protecting them from the risk of environmental factors, wildlife and particularly domestic animal grazing which could give us a model for reforestation. Therefore, it can be said that doing seeding or seedling planting to enrich and rehabilitate of western forests in straight and regular lines which are usually carried out by the executive organs, are not conclusive and to improve it successfully, reforestation should be done irregularly and in accordance with the natural establishment pattern of regeneration.