升温突变对川西道孚林线川西云杉和鳞皮冷杉生长的影响

高山林线作为理想的全球气候变化监测器，是研究植被与气候变化关系的重要场所。利用川西道孚县高山林线川西云杉（Picea likiangensis var.balfouriana）和鳞皮冷杉（Abies squamata）的年轮宽度资料，基于树木年代学的方法，构建差值年表并通过升温突变前后（1995年前后）年轮指数与气候要素的相关分析，探讨了该区林线主要针叶树种的年轮响应变化，为研究青藏高原地区树木与气候响应关系提供研究基础。结果表明：（1）年尺度上，1995年气温突变前后川西云杉和鳞皮冷杉年轮指数和生长弹性时间变化趋势均不显著，没有发生显著的响应分歧现象。（2）月尺度上，升温突变前川西云杉年轮指数与前一年11月月均最高温、5-7月月均温、6月月均最高温、7月月均最低温呈显著正相关；鳞皮冷杉则与前一年11月月均温、11月月均最高温和12月月均温呈显著正相关；表明升温突变前林线树木生长分别受夏季和冬季温度控制；升温突变后川西云杉年轮指数与前一年11月月均温呈显著负相关，和当年2月降水量及7月月均最低温呈显著正相关；而鳞皮冷杉则与当年5月月均温和5月月均最低温呈显著负相关，与5月降水的正相关性达到最大；表明升温突变后林线川西云杉生长依然受夏季温度控制，而鳞皮冷杉生长则受到春季干旱胁迫的影响。未来气候若随着升温出现干暖化，则林线鳞皮冷杉可能会发生明显的响应分歧现象。

Effects of abrupt warming on Picea likiangensis var. balfouriana and Abies squamata growth at tree line in Dafu, Sichuan, China

Alpine tree line is the key area to study the relationship between vegetation and climate change. Used the tree ring width data of Picea likiangensis var. balfouriana and Abies squamata at tree line in Dafu, Sichuan, China, based on the method of dendrochronology, the residual chronologies was devoloped. Through the correlation analysis between tree ring index and climatic factors before and after abrupt warming (1995), we anaylazed the changes in the tree ring response of the main coniferous tree species at tree line. The results show that:(1) on the annual scale, the temporal trend of tree ring index and tree resilience of P. likiangensis var. balfouriana and A. squamata before and after abrupt warming was not significant, and there was no obvious divergence phenomenon. (2) On the monthly scale, tree ring index of P. likiangensis var. balfouriana before abrupt warming was significantly positively correlated with the average maximum temperature in December of the previous year, the monthly average temperature from May to July, the average maximum temperature in June, and the average minimum temperature in July; tree ring index of A. squamata was significantly positively correlated with the average temperature in November, the maximum temperature in November, and the average temperature in December of the previous year. Both indicated that tree growth at tree line before abrupt warming was controlled by summer and winter temperature. After abrupt warming, tree ring index of P. likiangensis var. balfouriana was significantly negatively correlated with the average tempreture in November of the previous year, and was significantly positively correlated with the precipitation in February and the average minimum temperature in July; while the A. squamata was significantly negatively correlated with the average temperature in May and the average minimum temperature in May. The correlation coefficient between fir growth and the precipitation in May reached the maximum. All indicated that the growth of P. likiangensis var. balfouriana was still controlled by summer temperature, while the growth of A. squamata was affected by spring drought stress after abrupt warming. If it becomes dry with continuous warming in the future, divergence phenomena of A. squamata maybe appear.