Responses of radial growth of Larix principis-rupprechtii to abrupt warming

Abstract

To investigate the impacts of abrupt warming on tree growth, we collected tree ring cores from larch (Larix principis-rupprechtii) in three different sites, including Saihanba National Nature Reserve, Pangquangou National Nature Reserve, and Fengning Qiansongba National Forest Park. Based on the tree ring method, Mann-Kendall test was used to examine the occurrence time of temperature rise mutation. We further analyzed the radial growth law of larch before and after the temperature mutation and its correlation with the monthly climate data. The results showed that the sudden temperature rise occurred in the Saihanba area in 1987, the Fengning area in 1989, and the Pangquangou area 1994. Before the sudden warming, there was no significant trend for the radial growth in all the three regions. After the sudden warming, however, it decreased significantly (with a decrease rate of 0.08·10 a-1) in Saihanba area. The radial growth of larch increased significantly in Pangquangou area (with an increase rate of 0.10·10 a-1), while no significant change was observed in the Fengning area. Before the sudden warming, there was a significant positive correlation between the radial growth of larch in the Saihanba area and the highest temperature in May and June. After the sudden warming, there was a significant positive correlation with precipita-tion in July, and a highly significant positive correlation with the standardized precipitation evapotranspiration index(SPEI) from September of the previous year to July. Prior to the sudden warming, there was no significant relationship between the radial growth of larch in the Pangquangou area and monthly climate factors. However, after the sudden warming, a significant positive correlation was found with the lowest temperature in September of the pre-vious year. Before the sudden warming, the radial growth of larch in Fengning area was significantly negatively correlated with the lowest average temperature in July. After the sudden warming, it showed a significant negative correlation with the average and highest temperatures in June. Accordingly, the radial growth of larch in the Saihanba area experienced drought stress following a sudden temperature change. If temperature continues to rise in the future, larch in the Fengning area would also face drought stress. Conversely, warming conditions would be beneficial for the radial growth of larch in the Pangquangou area.