祁连山东部青杄年内径向生长动态对气候的响应

树木径向生长对气候因子的响应是树轮气候学的基础。在我国西北地区,虽然已有大量的树轮-气候响应研究,但是响应分析多基于数理统计结果,缺乏对树木生长过程的理解。基于此,于2013年到2015年在祁连山东部吐鲁沟国家森林公园内通过Dendrometer连续监测了树轮气候重建中常用树种青杄的径向生长,通过平均值法提取2013到2015年生长季内不同时间尺度(1天、7天、10天)的平均径向生长量及对应时间段的平均气候状况。不同时间尺度径向生长量和气候因子的相关分析结果表明,时间尺度的延长削弱了树干水分昼夜变化的干扰,但水分仍然是青杄径向生长的限制因子。为了进一步分析青杄径向生长与气候关系随时间的变化情况,以31天为窗口将日径向生长量与气候要素每隔一天进行滑动相关,结果显示:5、7月青杄的径向生长与降水的关系稳定,都呈显著正相关,但是6月降水的年际变率较大,导致树木可利用水分的变幅也较大,因而树木径向生长与6月水分的响应关系不稳定,存在较大的年际差异,而这可能是一些树轮-气候响应研究中轮宽与6月降水关系不显著的原因。

Intra-annual stem radial growth dynamics of Picea wilsorii in response to climate in the eastern Qilian Mountains

The responses of stem radial growth to climate are the basis of dendroclimatology. There is much research on the tree radial growth response to climate change in northwest China. However, most studies are based on statistical analysis, lacking an understanding of tree growth processes. Therefore, two Picea wilsorii trees were continuously monitored with a dendrometer in the Tulugou National Forest Reserve in the eastern Qilian Mountains from 2013 to 2015 in this study. We extracted the stem radial increment at different time scales (1 day, 7 days, 10 days) and mean climate factors. Our studies have shown that the extension of the time scale weakens the disturbance of diurnal variation in the trunk water, but the available water status is still a major limiting factor for stem radial growth. To further understand the major climatic factors affecting radial growth, we calculated the moving correlation coefficient between the daily radial growth and the daily meteorological data (temperature, precipitation, VPD) within a window of 31 days. We found that the stem radial growth was significantly positively correlated with precipitation in May and July during the three years, but the change of available water was large to the radial growth of Picea wilsorii during the three years. Thus, the relationship between the stem radial growth and precipitation in June was unstable. This may be the reason why the relationship between tree-rings and precipitation in June is not significant in some studies on the climate response of tree-rings.