大兴安岭不同纬度兴安落叶松生长对干旱适应性及生长衰退的差异

Distinctions in drought adaptability and growth decline of Larix gmelinii at different latitudes in Greater Khingan Mountains

气候变暖引起干旱事件发生频率和强度增加,由此导致全球部分森林出现衰退和死亡的现象已被广泛报道。然而由于不同地区森林对水分亏缺适应性不同,需要从区域尺度对森林适应干旱事件的特征进行详细研究。在中国东北的森林地区中,大兴安岭在过去几十年中变暖速度最快。以落叶松为主的大兴安岭森林,作为中国唯一的北方森林,具有重要的生态意义。尤其是在全球变暖极大地影响水条件的情况下,了解其对缺水的适应非常重要。通过树木年轮学方法分析比较不同纬度(47°17′—51°17′N)兴安落叶松(Larix gmelinii)径向生长变化率和树木生长对极端干旱的适应性特征(抵抗力(Rt)、恢复力(Rc)和恢复弹力(Rs))。结果表明:不同纬度兴安落叶松对干旱的应对策略呈现共同特征表现为:(1)研究区不同纬度的兴安落叶松生长均与当年生长季7和8月PDSI显著正相关(P<0.05);(2)大径级树木对干旱的抵抗力和恢复弹力更低,对干旱的适应能力更弱。不同纬度兴安落叶松对干旱的应对策略呈现差异性表现:(1)兴安落叶松对干旱的抵抗力和恢复弹力随纬度升高而降低,恢复力随纬度升高而增加;(2)研究区范围内较高纬度的兴安落叶松对干旱的适应能力较弱导致出现生长衰退的频率和强度最高,处于中间、较低纬度地区兴安落叶松对干旱的适应能力较强出现生长衰退较少。基于这些结果,我们可以推断,在一年中的快速生长期,落叶松的径向生长对缺水更为敏感,某些生物因素对调节适应很重要。气候条件影响适应性:在高纬度或高海拔地区,当干旱发生时,可能更易使得落叶松径向生长下降。我们可以预测,当缺水伴随着温度升高时,落叶松的适应性可能会增强,但随着水分条件的持续变化,干旱强度或频率的进一步增加可能会使结果复杂化。

It has been widely reported that the frequency and intensity of drought events caused by climate warming have increased,resulting in the decline and death of some forests in the world.However,due to the different adaptability of forests to deficit in different regions,the characteristics of forest adaptation to drought events should be carefully studied at the regional scale.Among the forested regions of Northeast China,the Greater Khingan Mountains have seen the fastest rate of warming during the past several decades.The Greater Khingan Mountains forest,dominated by Larix gmelini,has important ecological significance as the only boreal forest in China.Understanding its adaption to water deficits is important,especially as global warming greatly affects water conditions.In this study,we analyzed and compared the radial growth rate and adaptability to extreme drought(resistance(Rt),recovery(Rc)and resilience(Rs))of Larix gmelini at different latitudes(47°17′—51°17′).The results showed that the coping strategies of Larix gmelini to drought in different latitudes had common characteristics:(1)the growth of Larix gmelini at different latitudes in the study area was significantly positive correlation with Palmer Drought Severity Index(PDSI)in July and August of current growing season(P<0.05);(2)Large size trees had lower resistance and resilience to drought,and weaker adaptability to drought.The coping strategies of Larix gmelinii to drought in different latitudes were distinct:(1)the resistance and resilience of Larix gmelinii to drought decreased with the increase of latitude,while the recovery was on the contrary;(2)the adaptability of Larix gmelinii in higher latitudes to drought was weak,resulting in the highest frequency and intensity of growth decline,while those in middle and lower latitudes were on the contrary.Based on these results,we can infer that radial growth of Larix gmelinii is more sensitive to water deficit during the rapid growth period of the year and certain biological factors are important to regulating adaptation.Climatology conditions affect adaptation:at higher latitudes or higher altitudes,Larix gmelinii may be more susceptible to declines in radial growth when droughts occur.We can predict that the adaptability of Larix gmelinii could be enhanced when to water deficits are accompanied by temperature increases,but as water conditions continue to change,further increases in drought intensity or frequency may complicate the outcomes.