Study of Phenological Changes in Black Locust using Descriptive Methods and Quantitative Analysis

    Studying the phenological stages and determining their occurrence in different biological conditions is useful instrumental in restoring and selecting the bases in forestry. Therefore, descriptive method and quantitative analysis were used to study the phenology of Black Locust (Robinia pesudoacacia L.). In descriptive method, the phenomenological observations were recorded during the specified intervals and of the plant components were photographed during the growth season using color channels for the quantitative method. The color of the components of the plant was uniform using the Photoshop software, color channel digit and then the percentage of each color channel was determined. Pearson correlation coefficient was used to examine the correlation between temperature and precipitation with 2G-RB index in SPSS 22.0 software. The climatic characteristics were used to study the growing day-degree (GDD). The results showed that the vegetative growth of the plant begins early April and continues until early August. The leaves of the tree shed in late December, and goes to dormancy in three months of winter. The emergence of the bud was observed in late June and the flowering in mid- July. The fruits of the tree were formed at the end of August, and arrived mid-September until early November. The seeds of this tree were scattered from early September to early May. The significant correlation was only observed between the mean monthly temperature and color change of the plant stem and the tree required 3180, 5569.5, 629.7, 1153.7, 569.60, 1474.40, 5951.90, 653.30, 282.70 and 830.90 GDD for vegetative growth, leaf emergence, bud appearance, flowering, fruit formation, fruit ripening, seed loss, leaf fall, leaf loss and dormancy, respectively. Since the R. pesudoacacia is a suitable tree for cultivation in temperate cold and semi-arid regions, understanding its phenology will assist in biological restoration and green space development.