川西米亚罗林区不同海拔岷江冷杉生长对气候变化的响应

为分析青藏高原东缘半湿润区树木生长与气候关系随海拔变化的规律,于川西米亚罗林区分别在高、中、低海拔选取3个采样点,共采集132棵岷江冷杉年轮样芯,建立了最长达170a(1842-2011年)3个海拔高度的差值年表.岷江冷杉年轮指数与气候因子的相关分析表明:随海拔高度降低,温度与生长的负相关呈增加趋势.高海拔岷江冷杉径向生长与前—年冬季最低温呈显著正相关,中低海拔与当年春季均温、最高温和年均最高温呈显著负相关.低海拔岷江冷杉与当年4月降水呈显著正相关,随海拔升高降水与岷江冷杉生长的相关性降低.中低海拔岷江冷杉年表与4、5月帕尔默干旱指数(P DSI)呈显著正相关,表明在中低海拔存在春季干旱胁迫,抑制了岷江冷杉的生长.另外,大龄树木比小龄树木对气候变化的响应更敏感.

Climate-growth relationships of Abies faxoniana from different elevations at Miyaluo, western Sichuan, China

Tree rings which can record the past climatic events allows for retrospective analyses of climate-growth relationship. Generally, it is assumed that the relationships between tree growth and climate are elevation-independent and age-independent if the biological growth trend related to elevation and age is removed from the tree-ring data. However, if tree growth of different elevations or ages responds differently to climatic conditions, a dendroclimatic analysis based on samples at different elevations or with different ages may be biased in capturing climatic variability throughout the length of the chronology.In our study, tree cores of Abies faxoniana were taken from three different elevations (High altitude; Middle altitude; Low altitude) to represent the trees growth in Miyaluo of western Sichuan, China (total 132 cores, 37 at Low altitude; 51 at Middle altitude and 44 at High altitude). Three residual chronologies were developed from the cross-dated ring width series using the program ARSTAN, the longest was 170 years (1842-2011). Response analysis showed that the correlation between temperature and chronologies was almost negative, at low altitude there was the highest correlation coefficient. The positive correlation between PDSI (April and May of the current year) and the chronologies of Middle altitude and Low altitude showed that drought stresses inhibited the tree growth. In addition, a significantly positive response to precipitation (April of the current year) found at Low altitude explained that the precipitation was quite important for the tree growth.Furthermore, analysis of different age classes (old or young) showed that the response of old tree growth to climate change were more obvious than that of the young tree growth. It revealed that climate conditions would affect tree growth differently between different ages. Physiological processes and hydraulic constraints related to tree ages could possibly be the main causes of these age-dependent responses, so the relative sampling strategies should be considered.