Global warming significantly affects forest ecosystems in the Northern Hemisphere’s mid-to-high latitudes, altering tree growth, productivity, and spatial distribution. Additionally, spatial and temporal heterogeneity exists in the responses of different tree species to climate change. This research focuses on two key species in China’s Greater Khingan Range: Larix gmelinii (Rupr.) Kuzen. (Pinaceae) and Quercus mongolica Fisch. ex Ledeb. (Fagaceae). We utilized a Maxent model optimized by the kuenm R package to predict the species’ potential habitats under various future climate scenarios (2050s and 2070s) considering three distinct Shared Socioeconomic Pathways: SSP1-2.6, SSP2-4.5, and SSP5-8.5. We analyzed 313 distribution records and 15 environmental variables and employed geospatial analysis to assess habitat requirements and migration strategies. The Maxent model demonstrated high predictive accuracy, with Area Under the Curve (AUC) values of 0.921 for Quercus mongolica and 0.985 for Larix gmelinii. The high accuracy was achieved by adjusting the regularization multipliers and feature combinations. Key factors influencing the habitat of Larix gmelinii included the mean temperature of the coldest season (BIO11), mean temperature of the warmest season (BIO10), and precipitation of the driest quarter (BIO17). Conversely, Quercus mongolica’s habitat suitability was largely affected by annual mean temperature (BIO1), elevation, and annual precipitation (BIO12). These results indicate divergent adaptive responses to climate change. Quercus mongolica’s habitable area generally increased in all scenarios, especially under SSP5-8.5, whereas Larix gmelinii experienced more complex habitat changes. Both species’ distribution centroids are expected to shift northwestward. Our study provides insights into the divergent responses of coniferous and broadleaf species in the Greater Khingan Range to climate change, contributing scientific information vital to conserving and managing the area’s forest ecosystems.

We developed a tree ring width chronology from 1797 to 2020 (224 years) for the northwestern foothills of the Greater Khingan Mountains (GKMs) in northeastern China using 51 tree ring sample cores from 24 Pinus sylvestris var. mongolica (PSM). Pearson’s correlation analysis was used to analyze the relationship between tree ring width and regional climate factors. The standardized chronology was positively associated with the minimum temperature (T_min) in the previous May (r = 0.721, p < 0.01), indicating that this parameter was the main climatic factor limiting PSM growth in the region. We established a secure reconstruction equation for the May T_min from 1797 to 2020. There were 31 warm and 43 cold years in the 224-year reconstructed temperature series, accounting for 13.8% and 19.2% of the total years, respectively. Warm periods were observed in 1820–1829, 1877–1898, 1947–1958, and 1991–2020, whereas cold periods occurred in 1820, 1829–1870, 1899–1927, 1934–1947, and 1960–1988. The observed temperature sequence was highly consistent with the reconstructed sequence from the tree rings, which verified the reliability of the reconstructed results. The spatial correlation analysis indicated that the reconstructed temperature sequence accurately represented the temperature changes in the northwestern foothills of the GKM and surrounding areas. Multi-window spectral analysis and wavelet analysis revealed significant periodic fluctuations from 2 to 6 years, 21.2 years, 48.5 years, and 102.2 years. These periodic variations may be related to the El Niño–Southern Oscillation (ENSO), the Atlantic Multi-Year Intergenerational Oscillation (AMO), the Pacific Decadal Oscillation (PDO), and solar activity. This study expands the existing climate records in the region and provides valuable data support for understanding climate change patterns in the GKM and the scientific predictions of future climate changes.

We established a standardized tree-ring width chronology using 46 Mongolian pine (Pinus sylvestris var. mongolica) tree-ring cores from the Tuqiang Forestry Bureau in the northern Greater Khingan Mountains (GKM). The average minimum temperature from May to July was significantly positively correlated with tree-ring width, indicating that it is the main climatic factor affecting tree growth in the study area. Based on this, the average minimum temperature sequence from May to July for the past 164 years in this region was reconstructed, and its reliability and stability were verified using the leave-one-out method. The reconstruction results revealed four warm periods and two cold periods in the northern GKM over the past 164 years. The four warm periods were from 1891 to 1897, 1902 to 1909, 1923 to 1931, and 2003 to 2023, and the two cold periods were from 1864 to 1880 and 1953 to 1992. The results of multi-window spectrum analysis and wavelet analysis showed that the reconstructed sequence had periodicities of 2.2–5.3 years, 11 years, 39 years, and 52 years, suggesting that the minimum temperature changes may be influenced by El Niño-Southern Oscillation (ENSO), Pacific Decadal Oscillation (PDO), and solar sunspot activities.

To study the radial growth of Mongolian pine (Pinus sylvestris var. mongholica, MP) trees in response to climatic factors against the global warming background in the northeast part of the Greater Khingan Mountains (GKM), 101 tree cores were collected at contrasting altitudes (1100 and 650 m) in the Mordoga area, a tree-ring width chronology of MP was established for that region at both altitudes, and the relation between climatic factors and ring width trends at different time scales was investigated. The results revealed four major findings. (1) The ring width chronology of MP in the low-altitude area has better quality. (2) The growth of MP at high (low) altitude was mainly influenced by temperature (precipitation) factors. (3) Before a sudden change in temperature, there was a decreasing trend in the annual indices of MPs at higher altitudes. The chronological coefficients of MPs at both altitudes showed a significant upward trend after the increase in temperature. (4) The sliding analysis results showed that the stability of the relationship between MP growth and its response to climatic factors at both altitudes was also mostly similar. MP growth is relatively stable and sensitive and to climatic factors as temperatures increase.

Annual density chronologies of Pinus sylvestris var. mongolica L. at high and low elevations in the northern Greater Khingan Range were analyzed, and the responses of earlywood and latewood densities to climatic factors were examined. Significant elevational differentiation was observed in the growth response. At low elevation (630 m), earlywood density was positively correlated with temperatures in c4, c6, and c7 (c, current year) and negatively correlated with precipitation in p11 and c6 (p, previous year). Latewood density was negatively correlated with temperatures in c1–c5 and positively correlated with temperatures in c7–c8. At high elevation (1000 m), earlywood density was significantly negatively correlated with temperatures in p10, p11, c3, and c6, and with precipitation in p11, c2, c3, c5–c7, and c9; latewood density was significantly negatively correlated only with temperature in p11. Following an abrupt temperature shift in 1987, the low-elevation earlywood density chronology shifted from a decreasing to a strongly increasing trend, the low-elevation latewood chronology shifted from a strongly decreasing to a strongly increasing trend, and the high-elevation latewood chronology shifted from a strongly decreasing to an increasing trend. July temperature in the year of the shift drove the trend changes in the low-elevation earlywood and high-elevation latewood chronologies, and May temperature drove the trend change in the latewood density chronology at low-elevation, thereby explaining the shift in the latewood trend. Sliding-window correlation analyses further showed that low-elevation trees are more sensitive to climate fluctuations and exhibit lower growth stability, whereas high-elevation trees are less sensitive to climate fluctuations and show higher growth stability. Thus, the growth of low-elevation P. sylvestris var. mongolica is affected by combined water and heat stress, while the growth of high-elevation trees is primarily limited by temperature. Under ongoing warming, growth potential is likely to increase near the treeline but decline at low-elevation sites. These results provide a robust scientific basis for elucidating the response mechanisms of mountain forests in the Greater Khingan Range to climate change.