不同林龄樟子松人工林径向生长对气候及地下水位变化的响应

全球气候变化导致森林生态系统的结构与功能发生改变，甚至出现树木死亡与林分衰退的现象，研究林分生长对气候变化尤其是干旱事件的响应有助于预测未来气候变化下生态系统的稳定性。以辽宁章古台5个林龄的樟子松人工林为研究对象，分析了树木径向生长对气候因子与地下水位的响应，结果表明：秋季气温，尤其是最低气温显著影响樟子松林的生长（44年生林分除外）；低林龄樟子松林（36、39年）生长与当年夏季及生长季内的降水显著正相关，而高林龄樟子松林（52年）生长则与当年春季尤其是当年2月与5月降水显著正相关；36、39、52年生樟子松人工林年表与当年夏季的Palmer干旱指数（PDSI）显著正相关，44、58年生樟子松人工林年表则与地下水位显著正相关。应对早期干旱（即1997年）时，樟子松人工林表现为随林龄增加，其抵抗力增加而恢复力降低；在随后的两个干旱事件中，高林龄樟子松林的抵抗力不再明显高于低林龄，可能是由于地下水位显著降低影响根系吸水；受累积干旱的影响，所有林龄樟子松人工林对2007-2008干旱事件的弹性力均小于1，径向生长量明显降低。地下水位是影响不同林龄樟子松人工林生长及对干旱抵抗力的重要因子，考虑地下水位有助于进一步提升森林生态系统对气候变化响应研究的准确性。

Radial growth responses of Mongolian pine (pinus sylvestris var. mongolica) plantations at different ages to climate and groundwater level changes

Global climate change has caused changes in the structure and function of forest ecosystems, and even tree mortality and forest decline. Studying the response of forest growth to climate change, especially to extremely drought events, will help predict the stability of the ecosystem under future climate change. In this study, five Mongolian pine (pinus sylvestris var. mongolica) plantations of different ages were selected in Zhanggutai town, Liaoning Province. We analyzed the response of radial growth of trees to climate factors and groundwater level dynamics. The results showed that the autumn temperature, especially the minimum temperature, significantly affected the growth of Mongolian pine forests (except the 44-year-old stand); The growth of Mongolian pine forest with lower ages (i.e., 36 and 39 years) was significantly positively correlated with the precipitation in current summer or growing season, while that with greater ages (i.e., 52 years) was significantly positively correlated to the precipitation in current spring, especially in current February and current May; The chronologies of 36, 39 and 52 year-old Mongolian pine forests were significantly positively correlated to Palmer Drought Severity Index (PDSI) in current summer, while the chronologies of 44 and 58 year-old stands were significantly negatively correlated to groundwater level. In response to the early drought event occurred in 1997, the growth resistance of Mongolian pine increased with increasing stand age, while the recovery decreased. In the subsequent two drought events, the resistance of Mongolian pine forests with greater age was no longer significantly higher than that with lower age. It might due to the obvious decrease in groundwater level, which affected root the water absorption. Affected by cumulative drought, the resilience of Mongolian pine plantations with five ages to the 2007-2008 drought event was less than 1, and the radial growth was significantly reduced. Groundwater level is an important factor affecting the growth and drought resistance of Mongolian pine plantations at different ages. Considering the effect of groundwater level can further improve the accuracy of research on forest ecosystem response to climate change.