Abstract:

【Objective】 Xanthoceras sorbifolium Bunge is a light-loving species and adapts well to low temperatures and drought conditions, but it is susceptible to waterlogging. This species is naturally distributed in northeastern, northwestern and northern China. It is an ideal species for afforestation, wind and sand fixation, and conversion of cropland to forest. This study aimed to clarify the comprehensive effects of various environmental factors in different distribution areas on the phenophases ofX. sorbifolium Bunge and analyze the related variation pattern to provide a scientific basis for resource protection and development of this species. 【Method】 Six X. sorbifolium Bunge seedling populations from its main distribution areas, including Kundu, Tianshan and Wudan in Inner Mongolia Autonomons Region, Chengde and Yuxian in Hebei Province, and Shaanxian in Henan Province, were considered for this study. In 2016, 30 individual plants with consistent growth vigor were selected from each seedling population to systematically observe nine phenophases, including the early flowering stage, leaf bud germination stage, full flowering stage, late flowering stage, leaf expansion stage, fruit fast-growing stage, fruit maturing stage, fruit dropping stage and deciduous stage. Correlation and regression analyses were performed to reveal the dominant environmental factors that affected phenophase and function rules.【Result】 Significant differences were observed in the phenophases among the plants from the different distribution areas. The maximum and minimum differences were observed in the full flowering stage (42 days) and fruit fast-growing stage (29 days), respectively. Most of the phenophases of the plants from the Shaanxian population occurred earlier than those of the plants from the other populations, although the deciduous stage was the longest in the Shaanxian population, which led to the longest total growth period (221 days). In the Kundu population, the deciduous stage occurred early and the other phenophases occurred late; as a result, this population had the shortest total growth period (146 days). Most of the phenophases were positively correlated with longitude, latitude, and annual sunshine hours and negatively correlated with altitude, annual average temperature, absolutely highest temperature, absolutely lowest temperature, ≥10 ℃ annual accumulated temperature, annual rainfall, annual evaporation and frostless period. Annual average temperature was the main factor that influenced the early flowering stage, full flowering stage, late flowering stage, leaf expansion stage, fruit fast-growing stage, deciduous stage and total growth period. Frost-free period had a significant effect on the leaf bud germination stage and fruit dropping stage. The fruit maturing stage was mainly affected by the annual sunshine hours. The absolute maximum temperature was the main factor that affected the total flowering period.【Conclusion】 There is an obvious geographical variation pattern in the phenophases ofX. sorbifolium Bunge, and environmental factors significantly affect these phenophases. Higher latitude and longitude decrease the temperature and postpone the critical growth period of X. sorbifolium Bunge. Correspondingly, its florescence, bud bursting, and fruiting stage are postponed and the species stops growing and defoliates earlier in autumn. As a result, the total growth period ofX. sorbifolium is shortened.

Key words: Xanthoceras sorbifolium Bunge, population, phenophase, environmental factor