【Abstract】Aims Seasonality is the typical characteristic of plant landscape in Beijing, including seasonal dynamics of plant phenology. We analyzed the seasonal changes in phenology of 120 deciduous trees in Beijing Botanical Garden, with additional efforts on an innovative methodology in studying plant phenology. Methods Based on the standards of the Chinese Phenological Observation Method, three-level Phenological Code (a, b, and c) was used to recode the phenology data. Our data analysis was performed with “pentad” (5-day period) in 24 Solar Terms. The analytical methods include a frequency distribution method were employed to explore the division of phenophases and their dynamic constitution. The frequency distribution statistics in SPSS 20.0 were applied to explore the temporal dynamics in occurrence time and duration for different types of phenophases. Important findings The division of phenological seasons and their phenological constitution: the 6th–19th pentad for Spring, with 54.03% of the whole phenophases that are featured with sprouting, leaf spreading and flowering; the 20th–45th pentad for Summer, with 12.95% of phenophases that include complete leaf spreading for all trees, intensive fruiting, few flowering, and autumn-leaf scenery in late summer; 46th–59th pentad for Autumn, with 27.19% of the phenophases that are characterized with leaf discoloration and defoliation, some fruiting, and very few flowering; and the 60th pentad for Winter, with 0.6% of phenophases that are all constituted with defoliation. The temporal distribution patterns of different kinds of phenophases are as follows. The leaf development phenophases span from the 3rd to 23rd pentad and averagely last for 3.27 pentads, with Sorbaria kirilowii as one of the earliest leaf-unfolding species. The leaf coloration phenophases happen between the 40th and 63rd pentad, with Tilia mongolica and Armeniaca sibirica as the earliest species to show fall-color leaf. The autumn-leaf duration lasts for 8.2 pentads in average, with Euonymus alatus and Sambucus williamsii as the typical species that show longer leaf duration. The leaf period averagely lasts for 44.2 pentads, with Abelia chinensis, Salix matsudana, and Kerria japonica holding the longest leaf time. The flowering phenophases happen during the 1st–53rd pentad, with the 8th–23rd pentad as the best ornamental period, and three species (Chimonanthus praecox, Jasminum nudiflorum, and Ulmus pumila) as the earliest blooming species and Elsholtzia stauntoni as the last one to bloom. The flowering period lasts for 6.7 pentads in average, with Sorbaria kirilowii, Hibiscus syriacus, and Lagerstroemia indica showing the longest flowering time. The fruiting phenophases happen between the 8th and 59th pentad, with U. pumila and Lonicera fragrantissima as the earliest species for fruit maturation. The fruiting duration averagely lasts for 29.0 pentads, and those species that do not lose fruits during the winter and some other species with longer fruit holding period though falling fruits completely in winter such as Viburnum melanocarpum and Physocarpus opulifolius ‘Luteus’ have longer ornamental time of fruit scenery. Compared with a counterpart research in the 1980s, this study revealed that the spring in 2017 came earlier by a pentad than that 30 years ago while autumn came later by 3 pentads. Additionally, the autumn duration shortened by 2 pentads while the summer duration prolonged by 4 pentads, resulting in larger differences in the duration among the four seasons.

【Keywords】 plant phenology; seasonal division; phenological dynamics;

【DOI】