祁连山青海云杉物候表型的空间分异及其内在机制

Spatial variability of phenological phenotype of Picea crassifolia in Qilian Mountains and its internal mechanism

量化种群水平植物物候空间分异的遗传表达与表型可塑性,对于合理预测气候变化对植物动态的影响具有重要实践意义。该研究以祁连山广泛分布的优势常绿针叶树种——青海云杉(Picea crassifolia)为研究对象,通过对排露沟流域5个海拔带20个样地的156株样树进行连续两年的物候过程监测,研究了物候表型的空间分异规律,结合同质园移植实验,解析了物候空间分异的遗传分化成分,并借助岭回归和Lasso回归分析,探讨了环境因子对非遗传分化部分(即表型可塑性)的调控作用。研究发现:青海云杉表观物候期均随海拔升高而呈现推迟的趋势(每100 m 0.57–1.36 d),这种空间分异体现了一定程度的种源效应(即遗传分化现象),其所占比例平均为20.8%,且年际之间基本维持在相对稳定的水平;同时,研究发现同质园内来自高海拔的种群的春季物候期要明显早于低海拔种群,这可能与高海拔种源的芽分化需要较低的季前热量积累阈值有关;物候格局与环境因子关系的分析结果显示,除海拔影响外,季前热量积累、季前降水量、冻害发生频率对于解释物候动态起到了关键的指示作用。

Aims The aim of this study is to address how the spatial variability of phenological phenotype is characterized in natural populations, and what drives such spatial variability(genetic variation or phenotype plasticity).Methods The phenological process of 156 sample trees in 20 plots of five altitudes in Pailugou watershed was monitored for two consecutive years, and the saplings selected at different altitudes were transplanted in common garden. The investigation data were analyzed using ridge regression and lasso regression.Important findings All phenological stages of Picea crassifolia were delayed with altitude(0.57–1.36 d per 100 m). This spatial variability reflected a certain degree of provenance effect(i.e. genetic variation), with an average contribution rate of 20.8% that maintained at a relatively stable level between years. An interesting finding is that the spring phenology timing of high-altitude populations in the common garden was significantly earlier than low-altitude populations, which may be related to the lower threshold of pre-season heat accumulation required for bud differentiation of high-altitude populations. In addition, we found that pre-season heat accumulation,altitude, pre-season precipitation and freezing injury frequency played key roles in explaining phenological dynamics at the population level.