Dynamics Of Diameter Structure Of Larix Gmelinii Forest Under Fire Disturbance

The diameter structure plays a decisive role in the future development of the forest.In this paper,the Larix gmelinii in the Greater Xing'an Mountains area is taken as the research object,and the fire disturbed areas in 1987,2003 and 2015 and the unfire disturbed areas in the vicinity are selected as typical plots Based on the tree-ring data and survey data,the historical diameter structure was reconstructed,combined with the climate change background,to explore the effect of fire disturbance on the relationship between stand diameter structure and stand productivity,and to provide a theoretical basis for the restoration of vegetation productivity in the Daxinganling fire disturbance plot.the result shows: 1)Increasing fire disturbance intensity inhibits the growth of the diameter,and prolonged fire disturbance recovery time promotes the growth of the diameter,and the forest restoration time is shorter in the case of moderate fire disturbance than in the case of severe fire disturbance.Moderate fire disturbance promotes the growth of larch diameter in Xing'an,and the diameter structure of larch in Xing'an moves to large and medium diameter levels(12-24cm).As the intensity of fire disturbance increases,the diameter structure of larch in Xing'an moves from a large-diameter grade(20-24cm)to a small-diameter grade(4-10cm).With the increase of fire disturbance recovery time,the diameter structure of Larix gmelinii forest gradually moved from the large diameter level(20-24cm)to the small diameter level(4-10cm).2)Fire disturbance changed the response relationship between the diameter growth of larch and the climate in Xing'an.The diameter growth of larch in Xing'an showed an obvious "lag response" to temperature and precipitation.The response relationship between the growth of Larix gmelinii and the winter temperature in the previous year(November-January)under moderate fire disturbance changed from a significant positive correlation to a significant negative correlation(P <0.05);severe fire disturbance and the growing season of the year(May-August),the previous year's growing season(JulySeptember)and last year's winter(November-December),the response relationship of precipitation changed to a significant negative correlation(P <0.05).With the prolonged recovery time,the temperature in the growing season(June-August)of the year and the precipitation in the growing season(MaySeptember)of the previous year strengthened the growth promotion of larch.The winter temperature(November-December)last year Winter(December-January)precipitation more significantly inhibited the growth of larch in Xing'an.In the future climate warming,the diameter distribution of Larix gmelinii may move to the small and medium diameter level.At the same time,the diameter growth rate after fire disturbance will be greatly slowed down,and the recovery process of fire disturbance will be lengthened and it is difficult to restore to the original nature status.3)The relationship between diameter structure and stand productivity under different fire disturbances is different,and it varies with the recovery period.After 3 years of short-term recovery,the internal diameter and productivity of the control and moderate fire disturbance plots are positively correlated,but the internal diameter structure and productivity of the severe fire disturbance plots are non-linearly related.There is a downward trend in productivity,and the average diameter of the forest stand recovers to over 14 cm with time,and the two show a positive correlation;after 15 years of recovery,the restoration diameter of the severe and moderate fire disturbance plots are positively correlated with productivity;After 31 years of recovery,the diameter and productivity of severe fire disturbance plots turned into a negative correlation.