构树叶物候持续时间的纬度格局

Latitudinal patterns of leaf phenology duration in Broussonetia papyrifera

利用中国物候观测网9个站点记录的构树(Broussonetia papyrifera)叶物候近半个世纪的数据,使用线性回归模型分析构树叶物候持续时间的纬度差异。结果显示,构树叶物候持续时间随纬度增加有明显逐渐缩短的趋势。具体表现为:随着纬度增加,展叶期逐渐提前,落叶期逐渐延迟。对环境因子的重要性进行随机森林回归分析,结果表明,展叶季前的温度是控制构树展叶期和叶持续时间最关键的环境因子,而落叶季前的降水量是落叶期最关键的环境因子,这表明叶物候持续时间的纬度格局是由温度和降水量共同塑造的。结果表明,广布种植物物候存在明显的纬度梯度,以此适应不同的当地环境条件,提高了自身适应性。从地理格局视角,评估纬度对同一物种不同种群叶物候的影响,有助于评估物种未来的分布范围变化及灭绝风险。

In the Northern Hemisphere,leaf phenology is often reported to have a high spatial variability due to environmental differences at different latitudes.The duration of plant leaf phenology has an important impact not only on the carbon sequestration capacity of plants,but also on their reproductive success and ability to adapt to climate change.However,previous studies on population differences in leaf phenology often were only focused on the differences in leaf unfolding or leaf discoloration stages among different populations,and less attention was paid to the duration of leaf phenology and its driving mechanism.In this study,linear regression models were established by using the phenological data of the leaves of paper mulberry(Broussonetia papyrifera).recorded by China Phenology Observation Network to analyze the latitudinal differences in the duration of phenology of the leaves.The analysis showed that with the increase of latitude,the leaf-unfolding stage for paper mulberry gradually advances and the leaf-falling period gradually delays,indicating that the leaf phenology duration for paper mulberry tended to be shortened with the increase in latitude.The analysis of the importance of environmental factors by using random forest regression showed that the temperature before the leaf-unfolding stage was the most critical environmental factor controlling the leaf-unfolding stage and leaf duration of paper mulberry,and that the precipitation prior to leaf fall was the most critical environmental factor at the leaf fall season,indicating that the latitudinal patterns in leaf phenology duration are jointly shaped by temperature and precipitation.All these results show that the phenology of widely distributed plants has obvious latitudinal gradients in different populations,so as to adapt to different local environmental conditions and improve their own adaptability.Studying the phenological differentiation of different populations of the same species from the perspective of latitudinal differences is helpful to assess the changes in the distribution range and extinction risk of species in the future.