Phenology and Morphometric Parameters of Spiraea cantoniensis Lour. as Indicators of Climate Change in Urban Ecosystems

Abstract The identification of phenological patterns and morphological changes in Spiraea cantoniensis Lour. in urban ecosystems is essential for the optimal selection of taxa. Given that changes in vegetation dynamics are strongly associated with variability in climatic patterns, this study employed the extended BBCH scale, accumulated heat sums, and circular statistical methods to analyse phenological patterns, together with morphometric analyses of inflorescences, flowers, and fruits. The results indicate that extreme climatic events influenced the flowering and fruiting phenophases, with the accumulated heat sums emerging as a more significant predictor than the day of the year. In this research, the year factor affected the occurrence of secondary and tertiary flowering at the end of May and at the end of July 2024. It is noteworthy that in urban landscape phenology, Spiraea cantoniensis exerts a dominant influence at the beginning of April, while from mid-April Spiraea × vanhouttei (Briot) Carrière assumes dominance within the same composition. For the first time, this study defines the diameters of inflorescences, the number of flowers per inflorescence, the occurrence of flowers with six petals (38%), the diameters of individual fruits, the number of fruits per infructescence, and the number of seeds per fruit. Our study confirms that the phenological and morphological changes of Reeve’s spiraea are influenced by the year factor, i.e. climatic conditions, and highlights the need for continued research in the coming years. Monitoring and documenting the phenological and morphological characteristics of Spiraea cantoniensis are essential for assessing the impacts of climate change on its ecological functioning and the potential risks to the sustainable development of urban ecosystems, as well as for evaluating its potential as an indicator of climate change.