Responses of Pinus sylvestris var. mongolica tree ring width to climate factors at different elevations in the northern Greater Khingan Mountains

This study used dendroclimatology to examine the effect of climate factors on tree-ring widths of Pinus sylvestris var. mongolica at various altitudes in the northern Greater Khingan Mountains under the background of climate change. Standardized tree-ring width chronologies of Pinus sylvestris var. mongolica were developed at three altitudinal gradients (1150 m, 900 m, 700 m), and relationships between the climate factors and tree-ring width were examined at various time scales. The study found the following: (1) The tree-ring width chronology at high altitudes contained more climate information. (2) Differences were observed in the response of Pinus sylvestris var. mongolica to climate factors at different altitudes. Significant positive (negative) correlations existed between tree-ring width and temperature at high and intermediate (low) elevations. Significant positive (negative) correlations were observed between tree-ring width and precipitation at intermediate and low (high) elevations. (3) Similarities and variations were observed in the trend of the tree-ring width at the three altitudes after an abrupt temperature change. The growth trend increased significantly at high and intermediate altitudes and decreased at low altitudes. The response of high-altitude trees to precipitation weakened, and the response to temperature strengthened. The response of intermediate-altitude trees to temperature increased, and that of low-altitude trees to precipitation weakened. (4) As the temperature increased, the sensitivity of trees to temperature increased (decreased) at high and intermediate (low) altitudes, and the sensitivity to precipitation increased. This study reveals the complex relationships between climate factors and tree-ring width of Pinus sylvestris var. mongolica at different altitudes in the northern Greater Khingan Mountains and provides a scientific basis for evaluating the adaptation capacity of forest ecosystems to future climate change.