西安4种落叶乔木物候期对气候变化的响应

以西安1979—2018年的气候资料和植物物候观测资料为基础，采用分段回归和趋势倾向率等方法，分析了毛白杨(Populus tomentosa)、杜梨(Pyrus betulifolia)、七叶树(Aesculus chinensis)和灯台树(Bothrocaryum controversum)4种落叶乔木展叶盛期和叶全变色期的生长趋势，使用偏相关分析探讨了气温、降水和日照时数与物候期的关系并通过偏最小二乘回归(Partial Least Squares, PLS)判断气候变量对物候期的综合影响。结果表明：(1)1979—2018年，4种乔木的生长季长度延长，整体表现为春季物候期提前，秋季物候期推迟；(2)展叶盛期物候指标与叶全变色期物候指标，转折均发生在1982年；转折后，物候特征变化显著，春季物候的提前速率和秋季物候的推迟速率加快，展叶盛期平均提前3.8d/10a,叶全变色期平均推迟4.7d/10a;(3)展叶盛期与春季气温表现为极显著负相关，叶变色期与秋季气温表现为显著正相关；降水对植物物候的影响不显著；春季物候与日照时数呈现极显著负相关关系，秋季物候期与日照时数呈不显著正相关...

Response of phenology phases of four deciduous trees to climate change in Xi'an

Based on the climatic data and plant phenology observation data of Xi''an from 1979 to 2018, we analyzed the growth trends of four species of deciduous tree during the full leaf development period as well as the full leaf discoloration period using methods of segmented regression and trend tendency rate. We studied the relationship between plant phenology variation and climate change through correlation and Partial Least Squares (PLS) regression analysis. The analyses generated four primary results. First, from 1979 to 2018, the spring phenological periods of four kinds of trees were advanced while the autumn phenological periods were postponed. The length of the growing seasons was extended as a whole. Second, the spring and autumn phenological periods of Xi''an area had abrupt changes in 1982. After the abrupt change, plant phenological characteristics changed dramatically compared with the overall trend, showing that the spring advance rate and autumn postponement rate were faster. The spring phenological period has advanced at a rate of 3.8 days per decade, while the autumn phenophase has delayed at a rate of 4.7 days per decade. Third, the significantly negative correlation existed between the blooming leaf period and the air temperature. The leaf discoloration period positively correlated with the air temperature. However, the influence of precipitation on plant phenology was not significant. The spring phenology and sunshine hours showed very significantly negative correlation. Insignificant positive correlation was observed between the autumn phenology period and sunshine hours. Finally, both the spring and the autumn phenophase were jointly affected by the climatic factors, with air temperature as the predominant factor. The order of the explanatory power of the influence factors on the phenological period is temperature > sunshine hours > precipitation. The rise of the temperature during the same period plays the dominant role in advancing the tree leaf blooming period and the postponement of the leaf color change period.