Abstract: Background, aim, and scope Diameter structure plays a decisive role in the future development of a forest. Using tree-ring data and survey data in a climate change background, we explore changes in the relationships between fire disturbance, the growth of Larix gmelinii (larch), and climate change by reconstructing the historical diameter structure. Materials and methods In this study, we investigate L. gmelinii in areas disturbed by fire in 1987, 2003, and 2015 in the Greater Khingan Mountains. Nearby areas not disturbed by fire are selected as control sites. Results (1) Fire disturbance caused the diameter structure of L. gmelinii to be positively deviated and the kurtosis value increased. After 15 years of recovery from moderate fire disturbance, there was a negative bias and the kurtosis value decreased. Fifteen years after recovery from severe fire disturbance, it remained positive and reached the peak of kurtosis but then showed a tendency to negative bias, and the kurtosis value decreased. (2) Fire disturbance changed the response relationship between the diameter growth of L. gmelinii and climate. Under moderate fire disturbance, the growth of L. gmelinii was steadily and significantly negatively correlated with the winter temperature of the previous year (p < 0.05). The positive correlation with the temperature in the growing season changed from positive in the initial stage of fire disturbance to a negative correlation in the mid-term (15 years of recovery) (p < 0.05), while the relationship with precipitation in the growing season of the previous year was positively correlated (p < 0.05). Under severe fire disturbance, the diameter growth of L. gmelinii was significantly negatively correlated with precipitation in the current growing season (May—August), the previous year’s growing season (July—September), and winter of the previous year (November—December) (p < 0.05). The negative correlation with the winter temperature of the previous year changed from the initial period of recovery to a positive correlation (p < 0.05) in the later period (31 years of recovery), and a negative correlation with a change in precipitation in the current growing season (p < 0.05). Discussion Different fire disturbances can change the diameter structure of L. gmelinii by changing the forest’s light intensity, degree of competition, and soil composition. With increased recovery time, the distribution of the diameter of L.gmelinii forest is difficult to restore to the original ecological state. Under global warming, the growth of L. gmelinii in the Greater Khingan Mountains will be more sensitive to climatic factors, with increased temperatures increasing the respiration of L. gmelinii, promoting growth and development. Transpiration led to a change in the water distribution pattern of larch in the Greater Khingan Mountains and a decrease in environmental water content, which hindered growth. Fire disturbance can also change the diameter structure of the forest stand, which in turn can change the response of larch growth in the Greater Khingan Mountains to climate change. Conclusions (1) Increased fire intensity has a suppressive effect on diameter growth. Prolonged fire disturbance recovery time promotes diameter growth, and forest restoration time is shorter under moderate fire disturbance conditions than under severe fire disturbance conditions. (2) Fire disturbance changed the response relationship between the diameter growth of L. gmelinii and the climate in the Greater Khingan Mountains. The diameter growth showed an obvious lag response to temperature and precipitation. Under future climate warming conditions, the diameter distribution of L. gmelinii may move to a small and medium diameter level. Simultaneously, the diameter growth rate after fire disturbance will slow significantly, the recovery process from fire disturbance will be longer, and it will be difficult to restore the larch to its original natural state. Recommendations and perspectives Under the trend of increasing global warming and increasing fire disturbance events, the response relationship between the diameter structure of L. gmelinii in the Greater Khingan Mountains and the climate may change significantly under the influence of fire disturbance. This warrants further research and scrutiny.
Keywords: diameter structure; fire disturbance intensity; climatic factors; Larix gmelinii