近30年快速升温对两种典型小地形上兴安落叶松径向生长的影响

沟谷和低海拔坡地是大兴安岭地区典型的微地形,这2种微地形的冻土对全球变暖极为敏感.本文在内蒙古大兴安岭北部地区进行树木年轮采样,建立了树轮宽度年表,对比2种小地形上兴安落叶松径向生长对近30年快速升温响应的差异.结果表明: 汗马和莫尔道嘎采样点分别在2000和1980年左右出现树木径向生长与温度的分异现象,之后树木的生长均为沟谷湿地大于山坡立地.1984—2008年2种地形年表t检验均达到显著水平,年表间欧氏距离在1980年以后为0.937～2.742,远大于平均值(0.809～1.304).快速升温使得兴安落叶松径向生长对水热条件的响应发生改变,山坡上兴安落叶松主要受温度限制生长减慢,而沟谷冻土退化中兴安落叶松在短期内生长加快.随着气候变暖,兴安落叶松将经历一个受温度调控的复杂的环境——生长胁迫与气候响应模式,如果气候持续变暖,冻土退化,兴安落叶松可能在我国境内消失.

Impacts of rapid warming on radial growth of Larix gmelinii on two typical micro-topographies in the recent 30 years

Ravine and slope are the two typical micro-topographies in the Great Xing’an Mountains. Permafrost in the two micro-topographies is extremely sensitive to global warming. To compare the differences in responses of Larix gmelinii radial growth to rapid warming in the recent 30 years, tree-ring samples were collected from northern part of Great Xing’an Mountains in Inner Mongolia and tree ring-width chronologies were developed. The results showed that the divergence between tree growth and temperature occurred in 1980 in Mo’erdaoga and in 2000 in Hanma, respectively. Since 2000, tree growth on ravine sites was greater than that on the slope stands. Chronology of two topographies reached significant level by t test in 1984-2008, the Euclidean distance was 0.937-2.742 between chronologies, and far greater than the average (0.809-1.304). The rapid warming caused a significant radial growth response in L. gmelinii to hydrothermal conditions. On the slope sites, tree growth was mainly controlled by temperature and declined gradually in recent years, while the trees growing in ravines showed an accelerating growth rate with permafrost degeneration. L. gmelinii was undergoing profound environmental pressures caused by rapid warming, and it would experience a complex growth and development process. More seriously, L. gmelinii might disappear in China with a warming climate and permafrost degeneration.