نوع مقاله : مقاله کامل علمی پژوهشی
نویسندگان
1 استادیار پژوهش، مؤسسۀ تحقیقات جنگلها و مراتع کشور، سازمان تحقیقات، آموزش و ترویج کشاورزی، تهران، ایران
2 دانشیار پژوهش، مؤسسۀ تحقیقات جنگلها و مراتع کشور، سازمان تحقیقات، آموزش و ترویج کشاورزی، تهران، ایران
چکیده
کلیدواژهها
موضوعات
عنوان مقاله [English]
نویسندگان [English]
Background and objectives: The objective of the present study is to investigate the effect of site origin on the growth traits of P. euphratica trees using cluster and regression analyses in order to clarify differences in site performance and to identify more suitable sites for cutting collection and seedling production for use in afforestation programs and the restoration of natural stands.
Materials and methods: During the leaf-fall season, one-year-old branches were collected from natural bases of selected P. euphratica trees in sites of Markazi Province, and cuttings were prepared from these branches. All collected cuttings were planted in the nursery of the Markazi Natural Resources and Watershed Administration, where one-year-old seedlings were produced. After seedling production in the nursery and land preparation in February 2021, the one-year-old seedlings originating from the 10 studied sites were planted in the Arak nursery field. The experiment was conducted using a randomized complete block design (RCBD) with three replications (blocks), and nine seedlings from each site were planted in each replication. At the end of the third year after planting, DBH and total tree height were measured and recorded, and the standing tree volume was calculated. After calculating tree volume and considering the survival rate, volume per treatment was estimated based on planting spacing and converted to m3 ha-1. Data on quantitative growth traits were analyzed using two-way analysis of variance (Two-Way ANOVA), considering the main effects of site and block as well as their interaction. Furthermore, in order to examine the pattern of similarity and differences among sites, hierarchical cluster analysis (Cluster Analysis) was performed based on the data obtained from the combination of site and block (as replications) using JMP software and Ward’s method. In addition, descriptive statistical indices of growth traits, including mean, standard deviation, standard error, and coefficient of variation, were calculated using the Distribution platform in JMP software. Moreover, to investigate the relationships among growth traits, regression analysis (Regression Analysis) was conducted in JMP software, considering tree volume as the dependent variable and diameter at breast height (DBH) and tree height as independent variables.
Results: In the third year after planting of seedlings in the Shahid Rajaei nursery field in Arak, the highest values for DBH, height, and total volume were observed for the Bazarjan site in Tafresh in block 3. The total volume ranged from a minimum of 5.95 m³ ha-1 in block 3- Joftan site (Tafresh) to a maximum of 20.48 m³ ha-1 in block 3- Bazarjan site (Tafresh). Hierarchical cluster analysis of the growth traits of P. euphratica trees was performed using Ward’s method based on standardized data of DBH, height, and total volume. Cluster 1 comprised the Bazarjan site in Tafresh (blocks 1, 2, and 3), Mahallat (blocks 1 and 2), and Arjrud in Saveh (blocks 2 and 3). Cluster 5 included the Dezful site (block 1), Ghalatein in Saveh and Jelmajerd in Khomein (block 2), Gotvand (blocks 2 and 3), Isfahan (block 2), and Joftan in Tafresh and Kerman (block 3). Clusters 2, 3, and 4 showed intermediate growth performance. The results of multiple linear regression indicated that the regression model for estimating tree volume based on DBH and height was significant at the 0.05 level. The coefficient of determination (R2) was 0.956, indicating that approximately 96% of the variance in tree volume was jointly explained by DBH and height. Based on the estimated coefficients, the multiple regression equation for estimating tree volume was derived as: V=−20.016+4.605×D+2.328×H.
Conclusion: The results of this study showed that the site origin of cuttings has a significant effect on the growth traits of P. euphratica trees.
کلیدواژهها [English]
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