فرهاد جهانپور

Botanical gardens are a collection of plants in a closed space used for education, research, preserving species outside the habitat, and introducing people to a nature-friendly environment. Zagros Botanical Garden has been built northwest of Khorramabad city with an area of 12 hectares. The collection of wild and native fruit is one of the collections in Zagros Botanical Garden, which is carried out on 1.3 hectares. Seedlings of species were obtained from the General Department of Natural Resources of Lorestan, Kermanshah, Kurdistan, and Ilam provinces. By going to different urban or rural areas, seeds or cuttings of local fruit species were collected, propagated, and planted. The planting plan was divided into two sections (wild and native) for project implementation. In each section, trees were planted in smaller rectangular and longitudinal pieces. Variable planting distances were considered based on each species' number, type, and specific ecological conditions. Six local fruit species, including 13 varieties and ten species of wild fruit, were successfully established and adapted to the conditions in Zagros Botanical Garden.

Several research projects have been implemented in the direction of planting and growth status of poplar trees in the Lorestan region, the most important of which was examining the final stage of compatibility of different poplar clones. In this research, 20 poplar clones (10 closed-crown and 10 open-crown) were cultivated for five years in the agricultural garden station (14 ha of land) in Khorramabad city and experimented in the climatic and ecological conditions of the province. Finally, among the closed crown clones that were cultivated at a planting spacing of 3 × 3 m during the years (2010-2014), clones of P. nigra 63/135 and P. nigra 56/72 with the highest diameter growth of 8.142 and 6.8 cm, respectively, and the height growth rate of 6.62 and 6.49 m, respectively and the average wood production of 19.495 and 13.79 m3 ha-1yr-1, they are among the best clones. Among the open crown clones planted at 4 4 m spacing, Populus euramericana 455 and P. euramericana BL.costanzo, which were respectively 9.95 and 9.54 cm in diameter, 8.32 and 7.51 m in height, and in terms of average wood production per ha, they had 20.59 and 17.04 m3, which were introduced as superior clones. Of course, in the research that was done on three densities of planting spacing between 6 different clones of poplar during the years 2018-2023, the clone of P.n. 62/154 was much more successful and with higher performance than other clones, which can be suggested for introduction and planting in the fields of Lorestan province along with P.nigra 62/167 clone.

One of the major problems in poplar cultivation is the existence of low-yielding poplar species and their traditional cultivation, which reduce wood production per unit area. To identify the most productive and adaptable clones to local climate and introduce them for mass wood production, ten clones of open-crown poplar based on the Randomized Complete Block Design (RCBD) with three replicates and planting spacing (4m × 4m), were selected and evaluated in Khorramabad Agricultural Garden Station for five years (2012-2015). Analysis of variance showed that the year and clone factors had a significant effect on height, diameter and volume increment. The mean comparisons showed that the highest (1.56 m) and lowest (0.77 m) of height increment belonged to Populus euramericana455 clone and Populus x interamericanes clone respectively. Also, the Populus euramericana455 clone had the maximum diameter increment (9.95cm) and Populus x interamericanes clone had the minimum (6/95) diameter increment. The Populus euramericana455 and Populus x interamericanes clones had the highest (8.85 cm) and lowest (1.16 cm) of volume increment in the fifth year respectively. In terms of pest resistance and wood production, Populus deltoides 63/10, Populus deltoids and Populus x costanzo had a better conditions.

The growth of forest trees is controlled by various components. One of the main factors determining the structure and composition of the forest is the competition between the trees and competition involves complex relationships that depend on the pattern of tree distribution, the availability of resources, and the efficiency of resource utilization. Therefore, knowledge of tree competition mechanisms is ecologically and economically important. The purpose of this study was to determine the correlation between competition index and some characteristics of Persian oak (Quercus brantii Lindl var.persica) in Hashtad-Pahlu, Khorramabad.

A total of 30 Oak trees were selected randomly in different aspects. Height, DBH and crown diameter were measured. Beneath their crown in two aspects (north-south) at a distance of one meter from trunk, fine roots sampling (60 samples) was performed at 0-30 cm depth.

The result of analysis of variance showed that there was a significant difference between the value of competition index for Iranian oak species in different ranges (Sig = 0.000) so that the highest average value of this index was related to the northern exposition. Significant difference was observed for competition index in diameter class but no difference in height class. With increasing crown diameter, DBH and decreasing height/DBH ratio as well as crown diameter / DBH, competition index values ​​increased and decreased respectively. Correlation showed that with increasing crown diameter and DBH, competition index value increased and with decreasing height / DBH ratio as well as crown diameter / DBH index value decreased. Results revealed the significant differences for trees in terms of crown diameter, DBH, height / DBH ratio and crown diameter/DBH ratio in aspects. Pearson correlation coefficients showed that there was a significant negative correlation between competition index and carbon biomass of Persian oak fine roots.

The difference between the competition index in the height and diameter classes of Persian oak trees indicates the importance and role of these two important characteristics in estimating it and also the difference in the competitiveness of trees in different stages of forest stand development. The results showed that light-demanding Oak trees based on various site conditions differ in terms of competitiveness and some characteristics in different positions.