We investigated relationships between the flowering phenology of Prunus yedoensis

以82个观赏海棠品种为研究对象，进行了始花期（S₁）—盛花期（S₂）—末花期（S₃）3个阶段的花期物候观测，系统地研究了品种群的花期物候特征，旨在为海棠专类园建设及海棠花期物候性状特异种质挖掘与定向育种提供参考。结果表明：根据始花期的候区分布，可将82个品种划分为最早（VE）、早（E）、中（M）、晚（L）和极晚（EL）5大花期时序品种群；最早与最晚开花品种的始花期间隔22 d。根据S₁ ~ S₃花期持续时间长短，以3 d为级差，可将82个品种划分为超短（VS）、短（S）、中等（M）、长（L）和超长（VL）5大花期长短类群；82个品种平均花期长度为（11.4 ± 2.8）d。基于花期物候频率统计，构建了始花期（S₁）、盛花期（S₂）和末花期（S₃）的品种频度指数动态分布函数（CFI），其动态函数的直线斜率存在显著差异（k₁ = 6.312 < k₂ = 6.821 < k₃ = 9.1557），反应了3个花期阶段物候节奏由慢而快的变化趋势。还构建了观赏多度指数函数（CDI），为品种群花期整体观赏性评价提供了新的参考依据；基于CDI，将品种群的群体观赏期划分为6个阶段，即启动期（P₀）、指数快速上升期（P₁）、指数高位稳定期（P₂）、指数快速下降期（P₃）、窗口期（P₄）和指数低位持续期（P₅）；P₁ ~ P₃期间CDI值 ≥ 13.6%，时间长达21 d；P₂时段的CDI值高达75.3% ~ 80.3%，时间达3 d。基于82个观赏海棠品种S₁ ~ S₃的花期长度（L）和开花期间每日最高气温均值（T）的二维源数据，以T = 23 ℃和T = 27 ℃为分界点，拟合了L与T之间的分段耦合函数，不同温度区间耦合度（R²）差异显著：52个品种分布于A区（T = 19.2 ~ 22.9 ℃），21个品种分布于B区（T = 23.0 ~ 26.9 ℃），9个品种分布于C区（T = 27.0 ~ 32.0 ℃）；这反应了花期长短的相对性，当T ≤ 23 ℃时，花期长短的主导因子为遗传因素，T ≥ 27 ℃时，花期长短的主导因子为日最高气温，T = 23.0 ~ 26.9 ℃时，花期长短由遗传因素和日最高气温共同主导。

With 82 ornamental crabapple cultivars as the research object，the flowering phenology at initial flowering stage（S₁），full blooming stage（S₂）and end flowering stage（S₃）was observed and studied systemly to provide references for the building and maintenance of crabapple gardens，for the excavation and development of special crabapple traits，and for the oriented breeding of crabapple with special flowering phenology. The results were as follows：According to the‘Hou’area distribution（five days is a‘Hou’in Chinese）of S₁，82 ornamental crabapple cultivars were divided into five major flowering sequence groups：Very early group（VE），early group（E），medium group（M），late group（L），and extremely late group（EL），and flowering days interval between the earliest and the latest flowering variety was as long as 22days. According to flowering days from S₁ to S₃，with three days as level differential，82 crabapple cultivars，of which average flowering days was（11.4 ± 2.8）d，were divided into five major groups：Very short group（VS），short group（S），medium group（M），long group（L）and very long group（VL）. Based on flowering phenology frequency statistics，cumulative cultivar frequency index（CFI）functions at S₁，S₂ and S₃ were constructed respectively. It is found that the function linear slope values（i.e. k values）of S₁，S₂ and S₃ were different significantly–k₁（6.312）< k₂（6.821）< k₃（9.1557），which reflected a slow to fast rhythm changing trend in flowering phenology from S₁ to S₂ to S₃. Also，Ornamental cultivar diversity index（CDI）function was constructed，which provided a new reference frame for evaluating the whole flowering appreciation value of the 82 cultivars. Based on CDI function，the whole flowering appreciation period of 82 cultivars were divided into six typical phases：start-up period（P₀），fast rising period（P₁），high and stable period（P₂），fast falling period（P₃），window period（P₄）and low index period（P₅）. It is worth mentioning that in P₁–P₃，CDI ≥ 12.4% and the lasting time was up to 21 days，and in P₂，CDI ranges from 75.4% to 80.2%，and the lasting time was 3 days.Based on the two-dimensional data of flowering days（L）of 82 cultivars and its respective mean daily maximum air temperature（T）during the flowering period（S₁–S₃），and with T = 23 ℃ and T = 27 ℃ as critical air temperature points，the three piecewise coupling functions between L and T were fitted respectively. It is found that the coupling coefficient（R²）between L and T were different significantly for the three cultivar groups distributed in different air temperature zones. Fifty-two cultivars distributed in air temperature zone A（T = 19.2–22.9 ℃），21 cultivars distributed in air temperature zone B（T = 23.0–26.9 ℃），and 9 cultivars distributed in temperature zone C（T = 27.0–32.0 ℃）. That indicated the relativity of flowering days，which depends on both genetic and air temperature factors. When T ≤ 23 ℃，the genetic base was the dominant factor for flowering days，whereas when T ≥ 27 ℃，the daily maximum air temperature turned into the dominant factor. Also，when T = 23.0–26.9 ℃，the genetic base and the daily maximum air temperature both were the dominant factors for flowering days.

Many temperate and boreal tree species have a chilling requirement, that is, they need to experience cold temperatures during fall and winter to burst bud normally in the spring. Results from trials with 11 Pacific Northwest tree species are consistent with the concept that plants can accumulate both chilling and forcing units simultaneously during the dormant season and they exhibit a tradeoff between amount of forcing and chilling. That is, the parallel model of chilling and forcing was effective in predicting budburst and well chilled plants require less forcing for bud burst than plants which have received less chilling. Genotypes differed in the shape of the possibility line which describes the quantitative tradeoff between chilling and forcing units. Plants which have an obligate chilling requirement (Douglas-fir, western hemlock, western larch, pines, and true firs) and received no or very low levels of chilling did not burst bud normally even with long photoperiods. Pacific madrone and western redcedar benefited from chilling in terms of requiring less forcing to promote bud burst but many plants burst bud normally without chilling. Equations predicting budburst were developed for each species in our trials for a portion of western North America under current climatic conditions and for 2080. Mean winter temperature was predicted to increase 3.2-5.5 degrees C and this change resulted in earlier predicted budburst for Douglas-fir throughout much of our study area (up to 74 days earlier) but later budburst in some southern portions of its current range (up to 48 days later) as insufficient chilling is predicted to occur. Other species all had earlier predicted dates of budburst by 2080 than currently. Recent warming trends have resulted in earlier budburst for some woody plant species; however, the substantial winter warming predicted by some climate models will reduce future chilling in some locations such that budburst will not consistently occur earlier.