Shifts in Ecological Adaptation Strategies of Betula microphylla Based on Phenological Observation, in Xinjiang of China During 2009–2019

Phenology is one of the most obvious biological characteristics for plants affected by external influences. Phenology variations across temperature reflect energy allocation and reproductive strategies, and measures for plants to adapt to seasonal and environmental changes. Previous studies have mainly focused on national and regional vegetation phenology, but endemic vegetation phenology and dynamic variation in Xinjiang remains unclear. Therefore, our study characterized the Betula microphylla phenology in the Xinjiang area of China, over the period of 2009-2019 based on ≥10 ℃ accumulated temperature data and annual precipitation data using phenological data from field observations, explored B.microphylla ecological strategies and drivers. In this study, a total of 18 phenologies of B. microphylla population naturally distributed in the southern margin of the Junggar Basin were observed, divided the climatic year, the relevant climate data and phenological Julian day were used to analyze. Explored the adaptation strategies of B. microphylla to seasonal changes. We found that (1) The phenology of B. microphylla was generally earlier in warmer years and later in colder years, showing a trade-off relationship. (2) The monthly average temperature and acquired accumulated temperature had strong limitation to inflorescence germination in spring, and the monthly average temperature and low temperature accumulation values showed a synergistic relationship when physiological dormancy was broken. The inflorescence has germination strategy of “high low-temperature needs”. (3) In summer, the shallow root system of B. microphylla can replenish the water lost by transpiration. The male inflorescence shows the strategy of quantity victory. (4) From the perspective of autumn, the male inflorescence abscised, and only spread in the top of branches, so as to provide living space for female inflorescences, it is regarded as a "spatial dislocation" strategy. The male inflorescences use a "long dormancy" strategy to cope with the effects of high autumn temperatures. (5) As winter approaches in Xinjiang, all exposed male inflorescence were covered by bud scales.